Method for transmitting and receiving data in wireless communication system, and device for same

[0001] This application is the National Stage filing under 35 U.S.C. 371 of International Application No. PCT/KR2015/008232, filed on Aug. 6, 2015, which claims the benefit of U.S. Provisional Application No. 62/034,743, filed on Aug. 7, 2014, the contents of which are all hereby incorporated by reference herein in their entirety.

[0002] The present invention relates to a wireless communication system and, more particularly, to a method for transmitting and receiving device to device (D2D) data in a wireless communication system supporting device to device communication.

[0003] Mobile communication systems have been developed to provide voice services while ensuring the activity of a user. However, the mobile communication systems have been expanded to their regions up to data services as well as voice. Today, the shortage of resources is caused due to an explosive increase of traffic, and more advanced mobile communication systems are required due to user's need for higher speed services.

[0004] Requirements for a next-generation mobile communication system basically include the acceptance of explosive data traffic, a significant increase of a transfer rate per user, the acceptance of the number of significantly increased connection devices, very low end-to-end latency, and high energy efficiency. To this end, research is carried out on various technologies, such as dual connectivity, massive Multiple Input Multiple Output (MIMO), in-band full duplex, Non-Orthogonal Multiple Access (NOMA), the support of a super wideband, and device networking.

[0005] An object of the present specification is to define device to device (D2D) control information required for demodulating D2D data in performing direct communication between user equipments.

[0006] Further, another object of the present specification is to provide a method for transmitting and receiving D2D control information and D2D data.

[0007] Further, another object of the present specification is to provide a method for transmitting control information related to a D2D communication resource through a RRC signaling, a D2D grant and the like.

[0008] Further, another object of the present specification is to provide a method for indicating a SA transmission resource and/or a D2D data transmission resource by defining various fields.

[0009] Further, another object of the present specification is to provide a new power control field (or command or control information) for transmission power control of D2D communication.

[0010] Further, another object of the present specification is to provide a method for distinguishing transmission power control information of cellular communication and D2D communication.

[0011] Further, another object of the present specification is to provide a method for distinguishing transmission power control information of SA and D2D data in a D2D communication.

[0012] Further, another object of the present specification is to provide a method for distinguishing and transmitting transmission power control information of SA and D2D data using a D2D grant and DCI format 3/3A.

[0013] Further, another object of the present specification is to define a new DCI format related to D2D communication.

[0014] Further, another object of the present specification is to provide a method of masking a new DCI format related to D2D communication with a separate RNTI which is distinguishable from C-RNTI.

[0015] Further, another object of the present specification is to provide a method for fitting sizes of a new DCI format and other DCI formats related to D2D communication.

[0016] Technical objects to be achieved by the present invention are not limited to the aforementioned objects, and those skilled in the art to which the present invention pertains may evidently understand other technical objects from the following description.

[0017] In an aspect of the present invention, a method for transmitting and receiving, by a first user equipment, data in a wireless communication system supporting a device-to-device (D2D) communication includes receiving a resource pool for being used for the D2D communication wherein the resource pool comprises at least one selected from the group consisting of a scheduling assignment (SA) resource pool indicating a resource area where the SA is transmitted or a data resource pool indicating a resource area where D2D data is transmitted, transmitting the SA including information related to the D2D data transmission to a second user equipment through the SA resource pool, and transmitting D2D data to the second user equipment, wherein the resource pool is received from a base station through a downlink control information (DCI) format defined for the D2D communication.

[0018] The DCI format may be CRC (cyclic redundancy check)-masked with a separate RNTI (radio network temporary identifier) which is distinguished from C (cell)-RNTI.

[0019] The separate RNTI may be a D2D-RNTI or a sidelink-RNTI.

[0020] When a size of the DCI format is different from a size of DCI format 0, a zero bit may be inserted into the DCI format until the size of the DCI format becomes the same as the size of the DCI format 0.

[0021] The inserting of the zero bit into the DCI format may be performed by only the resource pool.

[0022] The DCI format may be DCI format 5.

[0023] The obtaining of the resource pool may include blind-decoding PDCCH in a search space.

[0024] The blind-decoding may include performing a CRC-check for the PDCCH with the C-RNTI and the D2D-RNTI, respectively.

[0025] In another aspect of the present invention, a first user equipment for transmitting and receiving data in a wireless communication system supporting a device-to-device (D2D) communication includes a radio frequency (RF) unit for transmitting and receiving a wireless signal and a processor functionally connected to the RF unit, wherein the processor is configured to receive a resource pool for being used for the D2D communication, in which the resource pool comprises at least one selected from the group consisting of a scheduling assignment (SA) resource pool indicating a resource area where the SA is transmitted or a data resource pool indicating a resource area where D2D data is transmitted, transmit the SA including information related to the D2D data transmission to a second user equipment through the SA resource pool, and transmit D2D data to the second user equipment, in which the resource pool is received from a base station through a downlink control information (DCI) format defined for the D2D communication.

[0026] The processor may be configured to perform a CRC-check for a PDCCH (physical downlink control channel) with C-RNTI and D2D-RNTI in a search space.

[0027] According to the present specification, direct communication between user equipments is possible by newly defining D2D control information required for demodulating D2D data.

[0028] Further, according to the present specification, the efficiency of the resource use may be enhanced and the transmission delay may be reduced by transmitting and receiving D2D control information and D2D data respectively or together.

[0029] Further, according to the present specification, the power of the D2D communication UE may be efficiently controlled by defining a new field for adjusting SA transmission power and D2D data transmission power.

[0030] Further, according to the present specification, power consumption of the D2D UE may be reduced by operating in D2D RX mode or DTX mode in D2D SF in which SA and/or D2D data is not transmitted.

[0031] Further, according to the present specification, the burden on the monitoring of the D2D UE may be reduced by utilizing indication information indicating the D2D SF where D2D-related information and transmitted and received.

[0032] Further, according to the present specification, transmission power control may be performed easily and quickly in the UE by distinguishing transmission power control information of cellular communication and D2D communication.

[0033] Further, according to the present specification, D2D communication may be more quickly and accurately performed by distinguishing transmission power control information of SA and D2D data in D2D communication.

[0034] Further, according to the present specification, power control related to the transmission of D2D data may be dynamically performed by performing transmission power control of D2D data using DCI format 3/3A.

[0035] Further, according to the present specification, the number of times of blind decoding of an UE may be reduced by performing zero padding in order to fit a new DCI format and other DCI formats related to D2D communication.

[0036] Further, according to the present specification, the number of times or complexity of blind decoding of the UE may be reduced by performing a blind decoding for the PDCCH using C-RNTI and D2D-RNTI.

[0037] Advantages which may be obtained by the present invention are not limited to the aforementioned advantages, and various other advantages may be evidently understood by those skilled in the art to which the present invention pertains from the following description.

[0081] Hereafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. A detailed description to be disclosed hereinbelow together with the accompanying drawing is to describe embodiments of the present invention and not to describe a unique embodiment for carrying out the present invention. The detailed description below includes details in order to provide a complete understanding. However, those skilled in the art know that the present invention can be carried out without the details.

[0082] In some cases, in order to prevent a concept of the present invention from being ambiguous, known structures and devices may be omitted or may be illustrated in a block diagram format based on core function of each structure and device.

[0083] In the specification, a base station means a terminal node of a network directly performing communication with a terminal. In the present document, specific operations described to be performed by the base station may be performed by an upper node of the base station in some cases. That is, it is apparent that in the network constituted by multiple network nodes including the base station, various operations performed for communication with the terminal may be performed by the base station or other network nodes other than the base station. A base station (BS) may be generally substituted with terms such as a fixed station, Node B, evolved-NodeB (eNB), a base transceiver system (BTS), an access point (AP), and the like. Further, a ‘terminal’ may be fixed or movable and be substituted with terms such as user equipment (UE), a mobile station (MS), a user terminal (UT), a mobile subscriber station (MSS), a subscriber station (SS), an advanced mobile station (AMS), a wireless terminal (WT), a Machine-Type Communication (MTC) device, a Machine-to-Machine (M2M) device, a Device-to-Device (D2D) device, and the like.

[0084] Hereinafter, a downlink means communication from the base station to the terminal and an uplink means communication from the terminal to the base station. In the downlink, a transmitter may be a part of the base station and a receiver may be a part of the terminal. In the uplink, the transmitter may be a part of the terminal and the receiver may be a part of the base station.

[0085] Specific terms used in the following description are provided to help appreciating the present invention and the use of the specific terms may be modified into other forms within the scope without departing from the technical spirit of the present invention.

[0086] The following technology may be used in various wireless access systems, such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier-FDMA (SC-FDMA), non-orthogonal multiple access (NOMA), and the like. The CDMA may be implemented by radio technology universal terrestrial radio access (UTRA) or CDMA2000. The TDMA may be implemented by radio technology such as Global System for Mobile communications (GSM)/General Packet Radio Service (GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). The OFDMA may be implemented as radio technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, E-UTRA (Evolved UTRA), and the like. The UTRA is a part of a universal mobile telecommunication system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) as a part of an evolved UMTS (E-UMTS) using evolved-UMTS terrestrial radio access (E-UTRA) adopts the OFDMA in a downlink and the SC-FDMA in an uplink. LTE-advanced (A) is an evolution of the 3GPP LTE.

[0087] The embodiments of the present invention may be based on standard documents disclosed in at least one of IEEE 802, 3GPP, and 3GPP2 which are the wireless access systems. That is, steps or parts which are not described to definitely show the technical spirit of the present invention among the embodiments of the present invention may be based on the documents. Further, all terms disclosed in the document may be described by the standard document.

[0088] 3GPP LTE/LTE-A is primarily described for clear description, but technical features of the present invention are not limited thereto.

[0089] General System

[0090] FIG. 1 illustrates a structure a radio frame in a wireless communication system to which the present invention can be applied.

[0091] In 3GPP LTE/LTE-A, radio frame structure type 1 may be applied to frequency division duplex (FDD) and radio frame structure type 2 may be applied to time division duplex (TDD) are supported.

[0092] FIG. 1(a) exemplifies radio frame structure type 1. The radio frame is constituted by 10 subframes. One subframe is constituted by 2 slots in a time domain. A time required to transmit one subframe is referred to as a transmissions time interval (TTI). For example, the length of one subframe may be 1 ms and the length of one slot may be 0.5 ms.

[0093] One slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the time domain and includes multiple resource blocks (RBs) in a frequency domain. In 3GPP LTE, since OFDMA is used in downlink, the OFDM symbol is used to express one symbol period. The OFDM symbol may be one SC-FDMA symbol or symbol period. The resource block is a resource allocation wise and includes a plurality of consecutive subcarriers in one slot.

[0094] FIG. 1(b) illustrates frame structure type 2. Radio frame type 2 is constituted by 2 half frames, each half frame is constituted by 5 subframes, a downlink pilot time slot (DwPTS), a guard period (GP), and an uplink pilot time slot (UpPTS), and one subframe among them is constituted by 2 slots. The DwPTS is used for initial cell discovery, synchronization, or channel estimation in a terminal. The UpPTS is used for channel estimation in a base station and to match uplink transmission synchronization of the terminal. The guard period is a period for removing interference which occurs in uplink due to multi-path delay of a downlink signal between the uplink and the downlink.

[0095] In frame structure type 2 of a TDD system, an uplink-downlink configuration is a rule indicating whether the uplink and the downlink are allocated (alternatively, reserved) with respect to all subframes. Table 1 shows the uplink-downlink configuration.

[0096]

TABLE 1
	Downlink-
Uplink-	to-Uplink
Downlink	Switch-point	Subframe number
configuration	periodicity	0	1	2	3	4	5	6	7	8	9
0	5	ms	D	S	U	U	U	D	S	U	U	U
1	5	ms	D	S	U	U	D	D	S	U	U	D
2	5	ms	D	S	U	D	D	D	S	U	D	D
3	10	ms	D	S	U	U	U	D	D	D	D	D
4	10	ms	D	S	U	U	D	D	D	D	D	D
5	10	ms	D	S	U	D	D	D	D	D	D	D
6	5	ms	D	S	U	U	U	D	S	U	U	D

[0097] Referring to Table 1, for each sub frame of the radio frame, ‘D’ represents a subframe for downlink transmission, TTI represents a subframe for uplink transmission, and ‘S’ represents a special subframe constituted by three fields such as the DwPTS, the GP, and the UpPTS. The uplink-downlink configuration may be divided into 7 configurations and the positions and/or the numbers of the downlink subframe, the special subframe, and the uplink subframe may vary for each configuration.

[0098] A time when the downlink is switched to the uplink or a time when the uplink is switched to the downlink is referred to as a switching point. Switch-point periodicity means a period in which an aspect of the uplink subframe and the downlink subframe are switched is similarly repeated and both 5 ms or 10 ms are supported. When the period of the downlink-uplink switching point is 5 ms, the special subframe S is present for each half-frame and when the period of the downlink-uplink switching point is 5 ms, the special subframe S is present only in a first half-frame.

[0099] In all configurations, subframes #0 and #5 and the DwPTS are intervals only the downlink transmission. The UpPTS and a subframe just subsequently to the subframe are continuously intervals for the uplink transmission.

[0100] The uplink-downlink configuration may be known by both the base station and the terminal as system information. The base station transmits only an index of configuration information whenever the uplink-downlink configuration information is changed to announce a change of an uplink-downlink allocation state of the radio frame to the terminal. Further, the configuration information as a kind of downlink control information may be transmitted through a physical downlink control channel (PDCCH) similarly to other scheduling information and may be commonly transmitted to all terminals in a cell through a broadcast channel as broadcasting information.

[0101] The structure of the radio frame is just one example and the number subcarriers included in the radio frame or the number of slots included in the subframe and the number of OFDM symbols included in the slot may be variously changed.

[0102] FIG. 2 is a diagram illustrating a resource grid for one downlink slot in the wireless communication system to which the present invention can be applied.

[0103] Referring to FIG. 2, one downlink slot includes the plurality of OFDM symbols in the time domain. Herein, it is exemplarily described that one downlink slot includes 7 OFDM symbols and one resource block includes 12 subcarriers in the frequency domain, but the present invention is not limited thereto.

[0104] Each element on the resource grid is referred to as a resource element and one resource block includes 12×7 resource elements. The number of resource blocks included in the downlink slot, NDL is subordinated to a downlink transmission bandwidth.

[0105] A structure of the uplink slot may be the same as that of the downlink slot.

[0106] FIG. 3 illustrates a structure of a downlink subframe in the wireless communication system to which the present invention can be applied.

[0107] Referring to FIG. 3, a maximum of three fore OFDM symbols in the first slot of the sub frame is a control region to which control channels are allocated and residual OFDM symbols is a data region to which a physical downlink shared channel (PDSCH) is allocated. Examples of the downlink control channel used in the 3GPP LTE include a Physical Control Format Indicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH), a Physical Hybrid-ARQ Indicator Channel (PHICH), and the like.

[0108] The PFCICH is transmitted in the first OFDM symbol of the subframe and transports information on the number (that is, the size of the control region) of OFDM symbols used for transmitting the control channels in the subframe. The PHICH which is a response channel to the uplink transports an Acknowledgement (ACK)/Not-Acknowledgement (NACK) signal for a hybrid automatic repeat request (HARQ). Control information transmitted through a PDCCH is referred to as downlink control information (DCI). The downlink control information includes uplink resource allocation information, downlink resource allocation information, or an uplink transmission (Tx) power control command for a predetermined terminal group.

[0109] The PDCCH may transport A resource allocation and transmission format (also referred to as a downlink grant) of a downlink shared channel (DL-SCH), resource allocation information (also referred to as an uplink grant) of an uplink shared channel (UL-SCH), paging information in a paging channel (PCH), system information in the DL-SCH, resource allocation for an upper-layer control message such as a random access response transmitted in the PDSCH, an aggregate of transmission power control commands for individual terminals in the predetermined terminal group, a voice over IP (VoIP). A plurality of PDCCHs may be transmitted in the control region and the terminal may monitor the plurality of PDCCHs. The PDCCH is constituted by one or an aggregate of a plurality of continuous control channel elements (CCEs). The CCE is a logical allocation wise used to provide a coding rate depending on a state of a radio channel to the PDCCH. The CCEs correspond to a plurality of resource element groups. A format of the PDCCH and a bit number of usable PDCCH are determined according to an association between the number of CCEs and the coding rate provided by the CCEs.

[0110] The base station determines the PDCCH format according to the DCI to be transmitted and attaches the control information to a cyclic redundancy check (CRC) to the control information. The CRC is masked with a unique identifier (referred to as a radio network temporary identifier (RNTI)) according to an owner or a purpose of the PDCCH. In the case of a PDCCH for a specific terminal, the unique identifier of the terminal, for example, a cell-RNTI (C-RNTI) may be masked with the CRC. Alternatively, in the case of a PDCCH for the paging message, a paging indication identifier, for example, the CRC may be masked with a paging-RNTI (P-RNTI). In the case of a PDCCH for the system information, in more detail, a system information block (SIB), the CRC may be masked with a system information identifier, that is, a system information (SI)-RNTI. The CRC may be masked with a random access (RA)-RNTI in order to indicate the random access response which is a response to transmission of a random access preamble.

[0111] FIG. 4 illustrates a structure of an uplink subframe in the wireless communication system to which the present invention can be applied.

[0112] Referring to FIG. 4, the uplink subframe may be divided into the control region and the data region in a frequency domain. A physical uplink control channel (PUCCH) transporting uplink control information is allocated to the control region. A physical uplink shared channel (PUSCH) transporting user data is allocated to the data region. One terminal does not simultaneously transmit the PUCCH and the PUSCH in order to maintain a single carrier characteristic.

[0113] A resource block (RB) pair in the subframe are allocated to the PUCCH for one terminal. RBs included in the RB pair occupy different subcarriers in two slots, respectively. The RB pair allocated to the PUCCH frequency-hops in a slot boundary.

[0114] Physical Downlink Control Channel: PDCCH

[0115] Control information transmitted through the PDCCH is referred to as Downlink Control Information (DCI). In the PDCCH, the size and purpose of control information may depend on the DCI format or the coding rate.

[0116] DCI Format

[0117] DCI formats 0, 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, 3, 3A, and 4 are defined in the current LTE-A (Release 10). The DCI formats 0, 1A, 3, and 3A are defined to have the same message size to reduce the number of times of blind decoding, which will be described later. The DCI formats may be divided into i) the DCI formats 0 and 4 used for uplink grant, ii) the DCI formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B and 2C used for downlink scheduling assignment, and iii) the DCI formats 3 and 3A for power control commands depending on the purpose of use of control information to be transmitted.

[0118] The DCI format 0 used for uplink grant may include a carrier indicator necessary for carrier aggregation, which will be described later, an offset (flag for format 0/format 1A differentiation) used to differentiate between the DCI formats 0 and 1A from each other, a frequency hopping flag that indicates whether frequency hopping is used for uplink PUSCH transmission, information on resource block assignment, which should be used by UE to transmit a PUSCH, a modulation and coding scheme, a new data indicator used to empty a buffer for initial transmission in relation to a HARQ process, a transmit power control (TPC) command for a scheduled PUSCH, information on a cyclic shift for a demodulation reference signal (DMRS) and OCC index, and a UL index and channel quality indicator request (CSI request) necessary for a TDD operation, etc. Meanwhile, the DCI format 0 does not include a redundancy version, unlike DCI formats related to downlink scheduling assignment since the DCI format 0 uses synchronous HARQ. The carrier offset is not included in the DCI formats when cross-carrier scheduling is not used.

[0119] The DCI format 4, which is newly added to DCI formats in the LTE-A Release 10, supports application of spatial multiplexing to uplink transmission in the LTE-A. The DCI format 4 has a larger message size because it further includes information for spatial multiplexing as compared with the DCI format 0. The DCI format 4 includes additional control information in addition to control information included in the DCI format 0. That is, the DCI format 4 further includes information on a modulation and coding scheme for the second transmission block, precoding information for multi-antenna transmission, and sounding reference signal (SRS) request information. Meanwhile, the DCI format 4 does not include an offset for differentiation between the DCI formats 0 and 1A because it has a larger size than that of the DCI format 0.

[0120] The DCI formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, and 2C related to downlink scheduling assignment may be broadly divided into the DCI formats 1, 1A, 1B, 1C, and 1D, which do not support spatial multiplexing, and the DCI formats 2, 2A, 2B, and 2C, which support spatial multiplexing.

[0121] The DCI format 1C only supports consecutive frequency allocation as compact downlink allocation and does not include carrier offset and redundancy version, compared to the other formats.

[0122] The DCI format 1A is for downlink scheduling and random access procedure. The DCI format 1A may include a carrier offset, an indicator that indicates whether downlink distributed transmission is used, PDSCH resource allocation information, a modulation and coding scheme, a redundancy version, a HARQ processor number for indicating a processor used for soft combining, a new data offset used to empty a buffer for initial transmission in relation to a HARQ process, a TPC command for a PUCCH, an uplink index necessary for a TDD operation, etc.

[0123] The DCI format 1 includes control information similar to that of the DCI format 1A. The DCI format 1 supports non-consecutive resource allocation, whereas the DCI format 1A is related to consecutive resource allocation. Accordingly, the DCI format 1 further includes a resource allocation header, and thus slightly increases control signaling overhead as a trade-off for an increase in flexibility of resource allocation.

[0124] Both the DCI formats 1B and 1D further include precoding information, compared to the DCI format 1. The DCI format 1B includes PMI acknowledgement, and the DCI format 1D includes downlink power offset information. Most of the control information included in the DCI formats 1B and 1D corresponds to that of the DCI format 1A.

[0125] The DCI formats 2, 2A, 2B, and 2C basically include most of the control information included in the DCI format 1A, and further include information for spatial multiplexing. The information for spatial multiplexing includes a modulation and coding scheme for the second transmission block, a new data offset, and a redundancy version.

[0126] The DCI format 2 supports closed loop spatial multiplexing, and the DCI format 2A supports open loop spatial multiplexing. Both the DCI formats 2 and 2A include precoding information. The DCI format 2B supports dual layer spatial multiplexing combined with beamforming, and further includes cyclic shift information for a DMRS. The DCI format 2C, which may be understood as an extended version of the DCI format 2B, supports spatial multiplexing for up to 8 layers.

[0127] The DCI formats 3 and 3A may be used to complement transmission power control included in the aforementioned DCI formats for uplink grant and downlink scheduling assignment, namely to support semi-persistent scheduling. A 1-bit command is used per UE in the case of the DCI format 3, whereas a 2-bit command is used per UE in the case of the DCI format 3A.

[0128] One of the DCI formats described above is transmitted through a PDCCH, and a plurality of PDCCHs may be transmitted in a control region. UE may monitor the plurality of PDCCHs.

[0129] DCI Format 0

[0130] Hereinafter, information transmitted via the DCI format 0 will be discussed in more detail.

[0131] Table 2 shows information transmitted in DCI format 0.

[0132]

TABLE 2
Format 0 (Release 8)	Format 0 (Release 10)
	Carrier Indicator (CIF)
Flag for format 0/format 1A	Flag for format 0/format 1A
differentiation	differentiation
Hopping flag (FH)	Hopping flag (FH)
Resource block assignment (RIV)	Resource block assignment (RIV)
MCS and RV	MCS and RV
NDI (New Data Indicator)	NDI (New Data Indicator)
TPC for PUSCH	TPC for PUSCH
Cyclic shift for DM RS	Cyclic shift for DM RS
UL index (TDD only)	UL index (TDD only)
Downlink Assignment Index (DAI)	Downlink Assignment Index (DAI)
CSI request (1 bit)	CSI request (1 or 2 bits: 2 bit
	is for multi carrier)
	SRS request
	Resource allocation type (RAT)

[0133] Referring to the above Table 2, information transmitted through DCI format 0 is as follows.

[0134] 1) Carrier indicator—Includes 0 or 3 bits.

[0135] 2) Flag for DCI format 0/1A differentiation—Includes 1 bit, wherein a value of 0 indicates DCI format 0 and a value of 1 indicates DCI format 1A.

[0136] 3) Frequency hopping flag—Includes 1 bit. In this field, the Most Significant Bit (MSB) of a corresponding resource allocation may be used for multi-cluster allocation if necessary.

[0137] 4) Resource block assignment and hopping resource allocation—Includes ┌log₂(N_RB^DL(N_RB^DL+1)/2)┐ bits.

[0138] Here, in the case of PUSCH hopping in single-cluster allocation, in order to acquire a value of ñ_PRB(i), NUL_hop MSBs are used.

[0139] $\left(\lceil {\log }_2\left(\frac{N_{\mathrm{RB}}^{\mathrm{DL}}\left(N_{\mathrm{RB}}^{\mathrm{DL}}+1\right)}{2}\right)\rceil -N_{{\mathrm{UL}}_{\mathrm{hop}}}\right)$
bits provide resource allocation of a first slot within an uplink subframe. In addition, if PUSCH hopping is not present in single-cluster allocation,

[0140] $\left(\lceil {\log }_2\left(\frac{N_{\mathrm{RB}}^{\mathrm{DL}}\left(N_{\mathrm{RB}}^{\mathrm{DL}}+1\right)}{2}\right)\rceil \right)$
bits provide resource allocation within an uplink subframe. In addition, if PUSCH hopping is not present in multi-cluster allocation, resource allocation information is obtained from concatenation between the frequency hopping flag field and resource block assignment and hopping resource assignment field, and

[0141] $\lceil {\log }_2\left(\left(\frac{\frac{N_{\mathrm{RB}}^{\mathrm{UL}}}{P}+1}{4}\right)\right)\rceil$
bits provide resource allocation within an uplink subframe. At this time, the P value is determined by the number of downlink resource blocks.

[0142] 5) Modulation and coding scheme (MCS)—Includes 5 bits.

[0143] 6) New data indicator—Includes 1 bit.

[0144] 7) Transmit power control (TPC) command for PUSCH—Includes 2 bits.

[0145] 8) Cyclic shift for demodulation reference signal (DMRS) and Index of orthogonal cover/orthogonal cover code (OC/OCC) and—Includes 3 bits.

[0146] 9) Uplink Index—Includes 2 bits. This field is present only in TDD operation according to uplink-downlink configuration 0.

[0147] 10) Downlink assignment index (DAI)—Includes 2 bits. This field is present only in TDD operation according to uplink-downlink configurations 1 to 6.

[0148] 11) Channel state information (CSI) request—Includes 1 or 2 bits. Here, a 2-bit field is only applied when the DCI is mapped to UE for which one or more downlink cells are configured, by a Cell-RNT (C-RNTI) in a UE-specific manner.

[0149] 12) Sounding reference signal (SRS) request—Includes 0 or 1 bit. This field is present only when a scheduled PUSCH is mapped in a UE-specific manner by the C-RNTI.

[0150] 13) Resource allocation type—Includes 1 bit.

[0151] If the number of information bits in DCI format 0 is less than the payload size (including added padding bits) of DCI format 1A, 0 is appended to DCI format 0 such that the number of information bits becomes equal to the payload size of DCI format 1A.

[0152] DCI Format 1A

[0153] Hereinafter, information transmitted via the DCI format 1A will be discussed in more detail.

[0154] The DCI format 1A refers to DCI formats which are used for compact scheduling of one PDSCH codeword in a cell. That is, DCI format 1A may include control information that is used for rank-1 transmission such as single antenna transmission, single stream transmission, or transmission diversity transmission.

[0155] Table 3 shows an example of DCI format 1A defined in 3GPP LTE/LTE-A standards

[0156]

TABLE 3
Carrier Indicator (CIF)	0 or 3	bits
Flag for format 0/format 1A differentiation	1	bit
Localized/Distributed VRB assignment Flag	1	bit
Resource block assignment (RIV)	N	bit
MCS	5	bits
HARQ process number	3 bits (FDD), 4 bits (TDD)
NDI (New Data Indicator)	1	bit
Redundancy Version (RV)	2	bits
TPC for PUCCH	2	bits
Downlink Assignment Index (DAI)	0 bit (FDD), 2 bits (TDD)
SRS (Sounding Reference Signal) request	0 or 1	bit

[0157] DCI format 1A including control information as Table 3 may be provided from the base station to the UE through PDCCH or EPDCCH.

[0158] DCI format 1A includes information for scheduling DL transmission (transmitting one PDSCH codeword as rank 1). Hence, when a complex PDSCH transmission scheme such as rank 2 or greater and/or a plurality of codewords transmission and the like is not appropriately performed, it can be used to support the most basic PDSCH transmission scheme (i.e., the fallback).

[0159] Physical Uplink Control Channel (PUCCH)

[0160] The uplink control information (UCI) transmitted through the PUCCH may include a scheduling request (SR), HARQ ACK/NACK information, and downlink channel measurement information.

[0161] The HARQ ACK/NACK information may be generated according to a downlink data packet on the PDSCH is successfully decoded. In the existing wireless communication system, 1 bit is transmitted as ACK/NACK information with respect to downlink single codeword transmission and 2 bits are transmitted as the ACK/NACK information with respect to downlink 2-codeword transmission.

[0162] The channel measurement information which designates feedback information associated with a multiple input multiple output (MIMO) technique may include a channel quality indicator (CQI), a precoding matrix index (PMI), and a rank indicator (RI). The channel measurement information may also be collectively expressed as the CQI.

[0163] 20 bits may be used per subframe for transmitting the CQI.

[0164] The PUCCH may be modulated by using binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) techniques. Control information of a plurality of terminals may be transmitted through the PUCCH and when code division multiplexing (CDM) is performed to distinguish signals of the respective terminals, a constant amplitude zero autocorrelation (CAZAC) sequence having a length of 12 is primary used. Since the CAZAC sequence has a characteristic to maintain a predetermined amplitude in the time domain and the frequency domain, the CAZAC sequence has a property suitable for increasing coverage by decreasing a peak-to-average power ratio (PAPR) or cubic metric (CM) of the terminal. Further, the ACK/NACK information for downlink data transmission performed through the PUCCH is covered by using an orthogonal sequence or an orthogonal cover (OC).

[0165] Further, the control information transmitted on the PUCCH may be distinguished by using a cyclically shifted sequence having different cyclic shift (CS) values. The cyclically shifted sequence may be generated by cyclically shifting a base sequence by a specific cyclic shift (CS) amount. The specific CS amount is indicated by the cyclic shift (CS) index. The number of usable cyclic shifts may vary depending on delay spread of the channel. Various types of sequences may be used as the base sequence the CAZAC sequence is one example of the corresponding sequence.

[0166] Further, the amount of control information which the terminal may transmit in one subframe may be determined according to the number (that is, SC-FDMA symbols other an SC-FDMA symbol used for transmitting a reference signal (RS) for coherent detection of the PUCCH) of SC-FDMA symbols which are usable for transmitting the control information.

[0167] In the 3GPP LTE system, the PUCCH is defined as a total of 7 different formats according to the transmitted control information, a modulation technique, the amount of control information, and the like and an attribute of the uplink control information (UCI) transmitted according to each PUCCH format may be summarized as shown in Table 4 given below.

[0168]

TABLE 4
PUCCH Format	Uplink Control Information (UCI)
Format 1	Scheduling Request (SR) (unmodulated waveform)
Format 1a	1-bit HARQ ACK/NACK with/without SR
Format 1b	2-bit HARQ ACK/NACK with/without SR
Format 2	CQI (20 coded bits)
Format 2	CQI and 1- or 2-bit HARQ ACK/NACK (20 bits) for
	extended CP only
Format 2a	CQI and 1-bit HARQ ACK/NACK (20 + 1 coded bits)
Format 2b	CQI and 2-bit HARQ ACK/NACK (20 + 2 coded bits)

[0169] PUCCH format 1 is used for transmitting only the SR. A waveform which is not modulated is adopted in the case of transmitting only the SR and this will be described below in detail.

[0170] PUCCH format 1a or 1b is used for transmitting the HARQ ACK/NACK. PUCCH format 1a or 1b may be used when only the HARQ ACK/NACK is transmitted in a predetermined subframe. Alternatively, the HARQ ACK/NACK and the SR may be transmitted in the same subframe by using PUCCH format 1a or 1b.

[0171] PUCCH format 2 is used for transmitting the CQI and PUCCH format 2a or 2b is used for transmitting the CQI and the HARQ ACK/NACK.

[0172] In the case of an extended CP, PUCCH format 2 may be transmitted for transmitting the CQI and the HARQ ACK/NACK.

[0173] FIG. 5 illustrates one example of a type in which PUCCH formats are mapped to a PUCCH region of an uplink physical resource block in the wireless communication system to which the present invention can be applied.

[0174] In FIG. 5, N_RB^UL represents the number of resource blocks in the uplink and 0, 1, . . . , N_RB^UL−1 mean numbers of physical resource blocks. Basically, the PUCCH is mapped to both edges of an uplink frequency block. As illustrated in FIG. 5, PUCCH format 2/2a/2b is mapped to a PUCCH region expressed as m=0, 1 and this may be expressed in such a manner that PUCCH format 2/2a/2b is mapped to resource blocks positioned at a band edge. Further, both PUCCH format 2/2a/2b and PUCCH format 1/1a/1b may be mixedly mapped to a PUCCH region expressed as m=2. Next, PUCCH format 1/1a/1b may be mapped to a PUCCH region expressed as m=3, 4, and 5. The number (N_RB⁽²⁾) of PUCCH RBs which are usable by PUCCH format 2/2a/2b may be indicated to terminals in the cell by broadcasting signaling.

[0175] PUCCH format 2/2a/2b is described. PUCCH format 2/2a/2b is a control channel for transmitting channel measurement feedback (CQI, PMI, and RI).

[0176] A reporting period of the channel measurement feedbacks (hereinafter, collectively expressed as CQI information) and a frequency wise (alternatively, a frequency resolution) to be measured may be controlled by the base station. In the time domain, periodic and aperiodic CQI reporting may be supported. PUCCH format 2 may be used for only the periodic reporting and the PUSCH may be used for aperiodic reporting. In the case of the aperiodic reporting, the base station may instruct the terminal to transmit a scheduling resource loaded with individual CQI reporting for the uplink data transmission.

[0177] FIG. 6 illustrates a structure of a CQI channel in the case of a general CP in the wireless communication system to which the present invention can be applied.

[0178] In SC-FDMA symbols 0 to 6 of one slot, SC-FDMA symbols 1 and 5 (second and sixth symbols) may be used for transmitting a demodulation reference signal and the CQI information may be transmitted in the residual SC-FDMA symbols. Meanwhile, in the case of the extended CP, one SC-FDMA symbol (SC-FDMA symbol 3) is used for transmitting the DMRS.

[0179] In PUCCH format 2/2a/2b, modulation by the CAZAC sequence is supported and the CAZAC sequence having the length of 12 is multiplied by a QPSK-modulated symbol. The cyclic shift (CS) of the sequence is changed between the symbol and the slot. The orthogonal covering is used with respect to the DMRS.

[0180] The reference signal (DMRS) is loaded on two SC-FDMA symbols separated from each other by 3 SC-FDMA symbols among 7 SC-FDMA symbols included in one slot and the CQI information is loaded on 5 residual SC-FDMA symbols. Two RSs are used in one slot in order to support a high-speed terminal. Further, the respective terminals are distinguished by using the CS sequence. CQI information symbols are modulated and transferred to all SC-FDMA symbols and the SC-FDMA symbol is constituted by one sequence. That is, the terminal modulates and transmits the CQI to each sequence.

[0181] The number of symbols which may be transmitted to one TTI is 10 and modulation of the CQI information is determined up to QPSK. When QPSK mapping is used for the SC-FDMA symbol, since a CQI value of 2 bits may be loaded, a CQI value of 10 bits may be loaded on one slot. Therefore, a CQI value of a maximum of 20 bits may be loaded on one subframe. A frequency domain spread code is used for spreading the CQI information in the frequency domain.

[0182] The CAZAC sequence (for example, ZC sequence) having the length of 12 may be used as the frequency domain spread code. CAZAC sequences having different CS values may be applied to the respective control channels to be distinguished from each other. IFFT is performed with respect to the CQI information in which the frequency domain is spread.

[0183] 12 different terminals may be orthogonally multiplexed on the same PUCCH RB by a cyclic shift having 12 equivalent intervals. In the case of a general CP, a DMRS sequence on SC-FDMA symbol 1 and 5 (on SC-FDMA symbol 3 in the case of the extended CP) is similar to a CQI signal sequence on the frequency domain, but the modulation of the CQI information is not adopted.

[0184] The terminal may be semi-statically configured by upper-layer signaling so as to periodically report different CQI, PMI, and RI types on PUCCH resources indicated as PUCCH resource indexes (n_PUCCH^{(1,{tilde over (p)})}, n_PUCCH^{(2,{tilde over (p)})}, and n_PUCCH^{(3,{tilde over (p)})}). Herein, the PUCCH resource index (n_PUCCH^{(2,{tilde over (p)})}) is information indicating the PUCCH region used for PUCCH format 2/2a/2b and a CS value to be used.

[0185] PUCCH Channel Structure

[0186] PUCCH formats 1a and 1b are described.

[0187] In PUCCH format 1a and 1b, the CAZAC sequence having the length of 12 is multiplied by a symbol modulated by using a BPSK or QPSK modulation scheme. For example, a result acquired by multiplying a modulated symbol d(0) by a CAZAC sequence r(n) (n=0, 1, 2, . . . , N−1) having a length of N becomes y(0), y(1), y(2), . . . , y(N−1). y(0), . . . , y(N−1) symbols may be designated as a block of symbols. The modulated symbol is multiplied by the CAZAC sequence and thereafter, the block-wise spread using the orthogonal sequence is adopted.

[0188] A Hadamard sequence having a length of 4 is used with respect to general ACK/NACK information and a discrete Fourier transform (DFT) sequence having a length of 3 is used with respect to the ACK/NACK information and the reference signal.

[0189] The Hadamard sequence having the length of 2 is used with respect to the reference signal in the case of the extended CP.

[0190] Sounding Reference Signal (SRS)

[0191] The SRS is primarily used for the channel quality measurement in order to perform frequency-selective scheduling and is not associated with transmission of the uplink data and/or control information. However, the SRS is not limited thereto and the SRS may be used for various other purposes for supporting improvement of power control and various start-up functions of terminals which have not been scheduled. One example of the start-up function may include an initial modulation and coding scheme (MCS), initial power control for data transmission, timing advance, and frequency semi-selective scheduling. In this case, the frequency semi-selective scheduling means scheduling that selectively allocates the frequency resource to the first slot of the subframe and allocates the frequency resource by pseudo-randomly hopping to another frequency in the second slot.

[0192] Further, the SRS may be used for measuring the downlink channel quality on the assumption that the radio channels between the uplink and the downlink are reciprocal. The assumption is valid particularly in the time division duplex in which the uplink and the downlink share the same frequency spectrum and are divided in the time domain.

[0193] Subframes of the SRS transmitted by any terminal in the cell may be expressed by a cell-specific broadcasting signal. A 4-bit cell-specific ‘srsSubframeConfiguration’ parameter represents 15 available subframe arrays in which the SRS may be transmitted through each radio frame. By the arrays, flexibility for adjustment of the SRS overhead is provided according to a deployment scenario.

[0194] A 16-th array among them completely turns off a switch of the SRS in the cell and is suitable primarily for a serving cell that serves high-speed terminals.

[0195] FIG. 7 illustrates an uplink subframe including a sounding reference signal symbol in the wireless communication system to which the present invention can be applied.

[0196] Referring to FIG. 7, the SRS is continuously transmitted through a last SC FDMA symbol on the arrayed subframes. Therefore, the SRS and the DMRS are positioned at different SC-FDMA symbols.

[0197] The PUSCH data transmission is not permitted in a specific SC-FDMA symbol for the SRS transmission and consequently, when sounding overhead is highest, that is, even when the SRS symbol is included in all subframes, the sounding overhead does not exceed approximately 7%.

[0198] Each SRS symbol is generated by a base sequence (random sequence or a sequence set based on Zadoff-Ch (ZC)) associated with a given time wise and a given frequency band and all terminals in the same cell use the same base sequence. In this case, SRS transmissions from a plurality of terminals in the same cell in the same frequency band and at the same time are orthogonal to each other by different cyclic shifts of the base sequence to be distinguished from each other.

[0199] SRS sequences from different cells may be distinguished from each other by allocating different base sequences to respective cells, but orthogonality among different base sequences is not assured.

[0200] General Carrier Aggregation

[0201] A communication environment considered in embodiments of the present invention includes multi-carrier supporting environments. That is, a multi-carrier system or a carrier aggregation system used in the present invention means a system that aggregates and uses one or more component carriers (CCs) having a smaller bandwidth smaller than a target band at the time of configuring a target wideband in order to support a wideband.

[0202] In the present invention, multi-carriers mean aggregation of (alternatively, carrier aggregation) of carriers and in this case, the aggregation of the carriers means both aggregation between continuous carriers and aggregation between non-contiguous carriers. Further, the number of component carriers aggregated between the downlink and the uplink may be differently set. A case in which the number of downlink component carriers (hereinafter, referred to as ‘DL CC’) and the number of uplink component carriers (hereinafter, referred to as ‘UL CC’) are the same as each other is referred to as symmetric aggregation and a case in which the number of downlink component carriers and the number of uplink component carriers are different from each other is referred to as asymmetric aggregation. The carrier aggregation may be used mixedly with a term such as the carrier aggregation, the bandwidth aggregation, spectrum aggregation, or the like.

[0203] The carrier aggregation configured by combining two or more component carriers aims at supporting up to a bandwidth of 100 MHz in the LTE-A system. When one or more carriers having the bandwidth than the target band are combined, the bandwidth of the carriers to be combined may be limited to a bandwidth used in the existing system in order to maintain backward compatibility with the existing IMT system. For example, the existing 3GPP LTE system supports bandwidths of 1.4, 3, 5, 10, 15, and 20 MHz and a 3GPP LTE-advanced system (that is, LTE-A) may be configured to support a bandwidth larger than 20 MHz by using on the bandwidth for compatibility with the existing system. Further, the carrier aggregation system used in the preset invention may be configured to support the carrier aggregation by defining a new bandwidth regardless of the bandwidth used in the existing system.

[0204] The LTE-A system uses a concept of the cell in order to manage a radio resource.

[0205] The carrier aggregation environment may be called a multi-cell environment. The cell is defined as a combination of a pair of a downlink resource (DL CC) and an uplink resource (UL CC), but the uplink resource is not required. Therefore, the cell may be constituted by only the downlink resource or both the downlink resource and the uplink resource. When a specific terminal has only one configured serving cell, the cell may have one DL CC and one UL CC, but when the specific terminal has two or more configured serving cells, the cell has DL CCs as many as the cells and the number of UL CCs may be equal to or smaller than the number of DL CCs.

[0206] Alternatively, contrary to this, the DL CC and the UL CC may be configured. That is, when the specific terminal has multiple configured serving cells, a carrier aggregation environment having UL CCs more than DL CCs may also be supported. That is, the carrier aggregation may be appreciated as aggregation of two or more cells having different carrier frequencies (center frequencies). Herein, the described ‘cell’ needs to be distinguished from a cell as an area covered by the base station which is generally used.

[0207] The cell used in the LTE-A system includes a primary cell (PCell) and a secondary cell (SCell. The P cell and the S cell may be used as the serving cell. In a terminal which is in an RRC_CONNECTED state, but does not have the configured carrier aggregation or does not support the carrier aggregation, only one serving constituted by only the P cell is present. On the contrary, in a terminal which is in the RRC_CONNECTED state and has the configured carrier aggregation, one or more serving cells may be present and the P cell and one or more S cells are included in all serving cells.

[0208] The serving cell (P cell and S cell) may be configured through an RRC parameter. PhysCellId as a physical layer identifier of the cell has integer values of 0 to 503. SCellIndex as a short identifier used to identify the S cell has integer values of 1 to 7. ServCellIndex as a short identifier used to identify the serving cell (P cell or S cell) has the integer values of 0 to 7. The value of 0 is applied to the P cell and SCellIndex is previously granted for application to the S cell. That is, a cell having a smallest cell ID (alternatively, cell index) in ServCellIndex becomes the P cell.

[0209] The P cell means a cell that operates on a primary frequency (alternatively, primary CC). The terminal may be used to perform an initial connection establishment process or a connection re-establishment process and may be designated as a cell indicated during a handover process. Further, the P cell means a cell which becomes the center of control associated communication among serving cells configured in the carrier aggregation environment. That is, the terminal may be allocated with and transmit the PUCCH only in the P cell thereof and use only the P cell to acquire the system information or change a monitoring procedure. An evolved universal terrestrial radio access (E-UTRAN) may change only the P cell for the handover procedure to the terminal supporting the carrier aggregation environment by using an RRC connection reconfiguration message (RRCConnectionReconfigutaion) message of an upper layer including mobile control information (mobilityControlInfo).

[0210] The S cell means a cell that operates on a secondary frequency (alternatively, secondary CC). Only one P cell may be allocated to a specific terminal and one or more S cells may be allocated to the specific terminal. The S cell may be configured after RRC connection establishment is achieved and used for providing an additional radio resource. The PUCCH is not present in residual cells other than the P cell, that is, the S cells among the serving cells configured in the carrier aggregation environment. The E-UTRAN may provide all system information associated with a related cell which is in an RRC_CONNECTED state through a dedicated signal at the time of adding the S cells to the terminal that supports the carrier aggregation environment. A change of the system information may be controlled by releasing and adding the related S cell and in this case, the RRC connection reconfiguration (RRCConnectionReconfigutaion) message of the upper layer may be used. The E-UTRAN may perform having different parameters for each terminal rather than broadcasting in the related S cell.

[0211] After an initial security activation process starts, the E-UTRAN adds the S cells to the P cell initially configured during the connection establishment process to configure a network including one or more S cells. In the carrier aggregation environment, the P cell and the S cell may operate as the respective component carriers. In an embodiment described below, the primary component carrier (PCC) may be used as the same meaning as the P cell and the secondary component carrier (SCC) may be used as the same meaning as the S cell.

[0212] FIG. 8 illustrates examples of a component carrier and carrier aggregation in the wireless communication system to which the present invention can be applied.

[0213] FIG. 8a illustrates a single carrier structure used in an LTE system. The component carrier includes the DL CC and the UL CC. One component carrier may have a frequency range of 20 MHz.

[0214] FIG. 8b illustrates a carrier aggregation structure used in the LTE system. In the case of FIG. 8b, a case is illustrated, in which three component carriers having a frequency magnitude of 20 MHz are combined. Each of three DL CCs and three UL CCs is provided, but the number of DL CCs and the number of UL CCs are not limited. In the case of carrier aggregation, the terminal may simultaneously monitor three CCs, and receive downlink signal/data and transmit uplink signal/data.

[0215] When N DL CCs are managed in a specific cell, the network may allocate M (M≤N) DL CCs to the terminal. In this case, the terminal may monitor only M limited DL CCs and receive the DL signal. Further, the network gives L (L≤M≤N) DL CCs to allocate a primary DL CC to the terminal and in this case, UE needs to particularly monitor L DL CCs. Such a scheme may be similarly applied even to uplink transmission.

[0216] A linkage between a carrier frequency (alternatively, DL CC) of the downlink resource and a carrier frequency (alternatively, UL CC) of the uplink resource may be indicated by an upper-layer message such as the RRC message or the system information. For example, a combination of the DL resource and the UL resource may be configured by a linkage defined by system information block type 2 (SIB2). In detail, the linkage may mean a mapping relationship between the DL CC in which the PDCCH transporting a UL grant and a UL CC using the UL grant and mean a mapping relationship between the DL CC (alternatively, UL CC) in which data for the HARQ is transmitted and the UL CC (alternatively, DL CC) in which the HARQ ACK/NACK signal is transmitted.

[0217] Cross Carrier Scheduling

[0218] In the carrier aggregation system, in terms of scheduling for the carrier or the serving cell, two types of a self-scheduling method and a cross carrier scheduling method are provided. The cross carrier scheduling may be called cross component carrier scheduling or cross cell scheduling.

[0219] The cross carrier scheduling means transmitting the PDCCH (DL grant) and the PDSCH to different respective DL CCs or transmitting the PUSCH transmitted according to the PDCCH (UL grant) transmitted in the DL CC through other UL CC other than a UL CC linked with the DL CC receiving the UL grant.

[0220] Whether to perform the cross carrier scheduling may be UE-specifically activated or deactivated and semi-statically known for each terminal through the upper-layer signaling (for example, RRC signaling).

[0221] When the cross carrier scheduling is activated, a carrier indicator field (CIF) indicating through which DL/UL CC the PDSCH/PUSCH the PDSCH/PUSCH indicated by the corresponding PDCCH is transmitted is required. For example, the PDCCH may allocate the PDSCH resource or the PUSCH resource to one of multiple component carriers by using the CIF. That is, the CIF is set when the PDSCH or PUSCH resource is allocated to one of DL/UL CCs in which the PDCCH on the DL CC is multiply aggregated. In this case, a DCI format of LTE-A Release-8 may extend according to the CIF. In this case, the set CIF may be fixed to a 3-bit field and the position of the set CIF may be fixed regardless of the size of the DCI format. Further, a PDCCH structure (the same coding and the same CCE based resource mapping) of the LTE-A Release-8 may be reused.

[0222] On the contrary, when the PDCCH on the DL CC allocates the PDSCH resource on the same DL CC or allocates the PUSCH resource on a UL CC which is singly linked, the CIF is not set. In this case, the same PDCCH structure (the same coding and the same CCE based resource mapping) and DCI format as the LTE-A Release-8 may be used.

[0223] When the cross carrier scheduling is possible, the terminal needs to monitor PDCCHs for a plurality of DCIs in a control region of a monitoring CC according to a transmission mode and/or a bandwidth for each CC. Therefore, a configuration and PDCCH monitoring of a search space which may support monitoring the PDCCHs for the plurality of DCIs are required.

[0224] In the carrier aggregation system, a terminal DL CC aggregate represents an aggregate of DL CCs in which the terminal is scheduled to receive the PDSCH and a terminal UL CC aggregate represents an aggregate of UL CCs in which the terminal is scheduled to transmit the PUSCH. Further, a PDCCH monitoring set represents a set of one or more DL CCs that perform the PDCCH monitoring. The PDCCH monitoring set may be the same as the terminal DL CC set or a subset of the terminal DL CC set. The PDCCH monitoring set may include at least any one of DL CCs in the terminal DL CC set. Alternatively, the PDCCH monitoring set may be defined separately regardless of the terminal DL CC set. The DL CCs included in the PDCCH monitoring set may be configured in such a manner that self-scheduling for the linked UL CC is continuously available. The terminal DL CC set, the terminal UL CC set, and the PDCCH monitoring set may be configured UE-specifically, UE group-specifically, or cell-specifically.

[0225] When the cross carrier scheduling is deactivated, the deactivation of the cross carrier scheduling means that the PDCCH monitoring set continuously means the terminal DL CC set and in this case, an indication such as separate signaling for the PDCCH monitoring set is not required. However, when the cross carrier scheduling is activated, the PDCCH monitoring set is preferably defined in the terminal DL CC set. That is, the base station transmits the PDCCH through only the PDCCH monitoring set in order to schedule the PDSCH or PUSCH for the terminal.

[0226] FIG. 9 illustrates one example of a subframe structure depending on cross carrier scheduling in the wireless communication system to which the present invention can be applied.

[0227] Referring to FIG. 9, a case is illustrated, in which three DL CCs are associated with a DL subframe for an LTE-A terminal and DL CC′A′ is configured as a PDCCH monitoring DL CC. When the CIF is not used, each DL CC may transmit the PDCCH scheduling the PDSCH thereof without the CIF. On the contrary, when the CIF is used through the upper-layer signaling, only one DL CC ‘A’ may transmit the PDCCH scheduling the PDSCH thereof or the PDSCH of another CC by using the CIF. In this case, DL CC ‘B’ and ‘C’ in which the PDCCH monitoring DL CC is not configured does not transmit the PDCCH.

[0228] Multi-Input Multi-Output (MIMO)

[0229] An MIMO technology uses multiple transmitting (Tx) antennas and multiple receiving (Rx) antennas by breaking from generally one transmitting antenna and one receiving antenna up to now. In other words, the MIMO technology is a technology for achieving capacity increment or capability enhancement by using a multiple input multiple output antenna at a transmitter side or a receiver side of the wireless communication system. Hereinafter, “MIMO” will be referred to as “multiple input multiple output antenna”.

[0230] In more detail, the MIMO technology does not depend on one antenna path in order to receive one total message and completes total data by collecting a plurality of data pieces received through multiple antennas. Consequently, the MIMO technology may increase a data transfer rate within in a specific system range and further, increase the system range through a specific data transfer rate.

[0231] In next-generation mobile communication, since a still higher data transfer rate than the existing mobile communication is required, it is anticipated that an efficient multiple input multiple output technology is particularly required. In such a situation, an MIMO communication technology is a next-generation mobile communication technology which may be widely used in a mobile communication terminal and a relay and attracts a concern as a technology to overcome a limit of a transmission amount of another mobile communication according to a limit situation due to data communication extension, and the like.

[0232] Meanwhile, the multiple input multiple output (MIMO) technology among various transmission efficiency improvement technologies which have been researched in recent years as a method that may epochally improve a communication capacity and transmission and reception performance without additional frequency allocation or power increment has the largest attention in recent years.

[0233] FIG. 10 is a configuration diagram of a general multiple input multiple output (MIMO) communication system.

[0234] Referring to FIG. 10, when the number of transmitting antennas increases to NT and the number of receiving antennas increases to NR at the same time, since a theoretical channel transmission capacity increases in proportion to the number of antennas unlike a case using multiple antennas only in a transmitter or a receiver, a transfer rate may be improved and frequency efficiency may be epchally improved. In this case, the transfer rate depending on an increase in channel transmission capacity may theoretically increase to a value acquired by multiplying a maximum transfer rate (Ro) in the case using one antenna by a rate increase rate (Ri) given below.
R_i=min(N_T,N_R)  [Equation 1]

[0235] That is, for example, in an MIMO communication system using four transmitting antennas and four receiving antennas, a transfer rate which is four times higher than a single antenna system may be acquired.

[0236] Such an MIMO antenna technology may be divided into a spatial diversity scheme increasing transmission reliability by using symbols passing through various channel paths and a spatial multiplexing scheme improving the transfer rate by simultaneously transmitting multiple data symbols by using multiple transmitting antennas. Further, a research into a scheme that intends to appropriately acquire respective advantages by appropriately combining two schemes is also a field which has been researched in recent years.

[0237] The respective schemes will be described below in more detail.

[0238] First, the spatial diversity scheme includes a space-time block coding series and a space-time Trelis coding series scheme simultaneously using a diversity gain and a coding gain. In general, the Trelis is excellent in bit error rate enhancement performance and code generation degree of freedom, but the space-time block code is simple in operational complexity. In the case of such a spatial diversity gain, an amount corresponding to a multiple (NT×NR) of the number (NT) of transmitting antennas and the number (NR) of receiving antennas may be acquired.

[0239] Second, the spatial multiplexing technique is a method that transmits different data arrays in the respective transmitting antennas and in this case, mutual interference occurs among data simultaneously transmitted from the transmitter in the receiver. The receiver receives the data after removing the interference by using an appropriate signal processing technique. A noise removing scheme used herein includes a maximum likelihood detection (MLD) receiver, a zero-forcing (ZF) receiver, a minimum mean square error (MMSE) receiver, a diagonal-bell laboratories layered space-time (D-BLAST), a vertical-bell laboratories layered space-time), and the like and in particular, when channel information may be known in the transmitter side, a singular value decomposition (SVD) scheme, and the like may be used.

[0240] Third, a technique combining the space diversity and the spatial multiplexing may be provided. When only the spatial diversity gain is acquired, the performance enhancement gain depending on an increase in diversity degree is gradually saturated and when only the spatial multiplexing gain is acquired, the transmission reliability deteriorates in the radio channel. Schemes that acquire both two gains while solving the problem have been researched and the schemes include a space-time block code (Double-STTD), a space-time BICM (STBICM), and the like.

[0241] In order to describe a communication method in the MIMO antenna system described above by a more detailed method, when the communication method is mathematically modeled, the mathematical modeling may be shown as below.

[0242] First, it is assumed that NT transmitting antennas and NR receiving antennas are present as illustrated in FIG. 13.

[0243] First, in respect to a transmission signal, when NT transmitting antennas are provided, since the maximum number of transmittable information is NT, NT may be expressed as a vector given below.
s=└s₁,s₂, . . . ,s_NT┘^T  [Equation 2]

[0244] Meanwhile, transmission power may be different in the respective transmission information s1, s2, . . . , sNT and in this case, when the respective transmission power is P1, P2, . . . , PNT, the transmission information of which the transmission power is adjusted may be expressed as a vector given below.
ŝ=└ŝ₁,ŝ₂, . . . ,ŝ_NT┘^T=└P₁s₁,P₂s₂, . . . ,P_NTs_NT┘^T  [Equation 3]

[0245] Further, ŝ may be expressed as described below as a diagonal matrix P of the transmission power.

[0246] $\begin{array}{cc}\hat{s}=\left[\begin{array}{cccc}{P}_1& & & 0\\ & P_2& & \\ & & \ddots & \\ 0& & & P_{N_T}\end{array}\right]\left[\begin{array}{c}{s}_1\\ s_2\\ ⋮\\ s_{N_T}\end{array}\right]=\mathrm{Ps}& \left[\mathrm{Equation}4\right]\end{array}$

[0247] Meanwhile, the information vector ŝ of which the transmission power is adjusted is multiplied by a weight matrix W to constitute NT transmission signals x1, x2, . . . , xNT which are actually transmitted. Herein, the weight matrix serves to appropriately distribute the transmission information to the respective antennas according to a transmission channel situation, and the like. The transmission signals x1, x2, . . . , xNT may be expressed as below by using a vector x.

[0248] $\begin{array}{cc}x=\hspace{1em}\left[\begin{array}{c}{x}_1\\ x_2\\ ⋮\\ x_i\\ ⋮\\ x_{N_T}\end{array}\right]=\left[\begin{array}{cccc}{w}_{11}& w_{12}& \dots & w_{1N_T}\\ w_{21}& w_{22}& \dots & w_{2N_T}\\ ⋮& & \ddots & \\ w_{i1}& w_{i2}& \dots & w_{{\mathrm{iN}}_T}\\ ⋮& & \ddots & \\ w_{N_{T}1}& w_{N_{T}2}& \dots & w_{N_T{N}_T}\end{array}\right]\left[\begin{array}{c}{\hat{s}}_1\\ {\hat{s}}_2\\ ⋮\\ {\hat{s}}_j\\ ⋮\\ {\hat{s}}_{N_T}\end{array}\right]=W\hat{s}=\mathrm{WPs}& \left[\mathrm{Equation}5\right]\end{array}$

[0249] Herein, wij represents a weight between the i-th transmitting antenna and j-th transmission information and W represents the weight as the matrix. The matrix W is called a weight matrix or a precoding matrix.

[0250] Meanwhile, the transmission signal x described above may be divided into transmission signals in a case using the spatial diversity and a case using the spatial multiplexing.

[0251] In the case using the spatial multiplexing, since different signals are multiplexed and sent, all elements of an information vector s have different values, while when the spatial diversity is used, since the same signal is sent through multiple channel paths, all of the elements of the information vector s have the same value.

[0252] Of course, a method mixing the spatial multiplexing and the spatial diversity may also be considered. That is, for example, a case may also be considered, which transmits the same signal by using the spatial diversity through three transmitting antennas and different signals are sent by the spatial multiplexing through residual transmitting antennas.

[0253] Next, when NR receiving antennas are provided, received signals y1, y2, . . . , yNR of the respective antennas are expressed as a vector y as described below.
y=[y₁,y₂, . . . ,y_NR]^T  [Equation 6]

[0254] Meanwhile, in the case of modeling the channel in the MIMO antenna communication system, respective channels may be distinguished according to transmitting and receiving antenna indexes and a channel passing through a receiving antenna i from a transmitting antenna j will be represented as hij. Herein, it is noted that in the case of the order of the index of hij, the receiving antenna index is earlier and the transmitting antenna index is later.

[0255] The multiple channels are gathered into one to be expressed even as vector and matrix forms. An example of expression of the vector will be described below.

[0256] FIG. 11 is a diagram illustrating a channel from multiple transmitting antennas to one receiving antenna.

[0257] As illustrated in FIG. 11, a channel which reaches receiving antenna I from a total of NT transmitting antennas may be expressed as below.
h_i^T=[h_i1,h_i2, . . . ,h_iNT]  [Equation 7]

[0258] Further, all of channels passing through NR receiving antennas from NT transmitting antennas may be shown as below through matrix expression shown in Equation given above.

[0259] $\begin{array}{cc}H=\left[\begin{array}{c}{h}_1^T\\ h_2^T\\ ⋮\\ h_i^T\\ ⋮\\ h_{N_R}^T\end{array}\right]=\left[\begin{array}{cccc}{h}_{11}& h_{12}& \dots & h_{1N_T}\\ h_{21}& h_{22}& \dots & h_{2N_T}\\ ⋮& & \ddots & \\ h_{i1}& h_{i2}& \dots & h_{{\mathrm{iN}}_T}\\ ⋮& & \ddots & \\ h_{N_{R}1}& h_{N_{R}2}& \dots & h_{N_R{N}_T}\end{array}\right]& \left[\mathrm{Equation}8\right]\end{array}$

[0260] Meanwhile, since additive white Gaussian noise (AWGN) is added after passing through a channel matrix H given above in an actual channel, white noises n1, n2, . . . , nNR added to NR receiving antennas, respectively are expressed as below.
n=[n₁,n₂, . . . ,n_NR]^T  [Equation 9]

[0261] Each of the transmission signal, the reception signal, the channel, and the white noise in the MIMO antenna communication system may be expressed through a relationship given below by modeling the transmission signal, the reception signal, the channel, and the white noise.

[0262] $\begin{array}{cc}y=\hspace{1em}\left[\begin{array}{c}{y}_1\\ y_2\\ ⋮\\ y_i\\ ⋮\\ y_{N_R}\end{array}\right]=\left[\begin{array}{cccc}{h}_{11}& h_{12}& \dots & h_{1N_T}\\ h_{21}& h_{22}& \dots & h_{2N_T}\\ ⋮& & \ddots & \\ h_{i1}& h_{i2}& \dots & h_{{\mathrm{iN}}_T}\\ ⋮& & \ddots & \\ h_{N_{R}1}& h_{N_{R}2}& \dots & h_{N_R{N}_T}\end{array}\right]\left[\begin{array}{c}{x}_1\\ x_2\\ ⋮\\ x_j\\ ⋮\\ x_{N_T}\end{array}\right]+\left[\begin{array}{c}{n}_1\\ n_2\\ ⋮\\ n_i\\ ⋮\\ n_{N_R}\end{array}\right]=\mathrm{Hx}+n& \left[\mathrm{Equation}10\right]\end{array}$

[0263] The numbers of rows and columns of the channel matrix H representing the state of the channel are determined by the numbers of transmitting and receiving antennas. In the case of the channel matrix H, the number of rows becomes equivalent to NR which is the number of receiving antennas and the number of columns becomes equivalent to NR which is the number of transmitting antennas. That is, the channel matrix H becomes an NR×NR matrix.

[0264] In general, a rank of the matrix is defined as the minimum number among the numbers of independent rows or columns. Therefore, the rank of the matrix may not be larger than the number of rows or columns. As an equation type example, the rank (rank(H)) of the channel matrix H is limited as below.
rank(H)≤min(N_T,N_R)  [Equation 11]

[0265] Further, when the matrix is subjected to Eigen value decomposition, the rank may be defined as not 0 but the number of Eigen values among the Eigen values. By a similar method, when the rank is subjected to singular value decomposition, the rank may be defined as not 0 but the number of singular values. Accordingly, a physical meaning of the rank in the channel matrix may be the maximum number which may send different information in a given channel.

[0266] In the present specification, a ‘rank’ for MIMO transmission represents the number of paths to independently transmit the signal at a specific time and in a specific frequency resource and ‘the number of layers’ represents the number of signal streams transmitted through each path. In general, since the transmitter side transmits layers of the number corresponding to the number of ranks used for transmitting the signal, the rank has the same meaning as the number layers if not particularly mentioned.

[0267] Coordinated Multi-Point Transmission and Reception (COMP)

[0268] According to a demand of LTE-advanced, CoMP transmission is proposed in order to improve the performance of the system. The CoMP is also called co-MIMO, collaborative MIMO, network MIMO, and the like. It is anticipated that the CoMP will improves the performance of the terminal positioned at a cell edge and improve an average throughput of the cell (sector).

[0269] In general, inter-cell interference decreases the performance and the average cell (sector) efficiency of the terminal positioned at the cell edge in a multi-cell environment in which a frequency reuse index is 1. In order to alleviate the inter-cell interference, the LTE system adopts a simple passive method such as fractional frequency reuse (FFR) in the LTE system so that the terminal positioned at the cell edge has appropriate performance efficiency in an interference-limited environment. However, a method that reuses the inter-cell interference or alleviates the inter-cell interference as a signal (desired signal) which the terminal needs to receive is more preferable instead of reduction of the use of the frequency resource for each cell. The CoMP transmission scheme may be adopted in order to achieve the aforementioned object.

[0270] The CoMP scheme which may be applied to the downlink may be classified into a joint processing (JP) scheme and a coordinated scheduling/beamforming (CS/CB) scheme.

[0271] In the JP scheme, the data may be used at each point (base station) in a CoMP wise. The CoMP wise means a set of base stations used in the CoMP scheme. The JP scheme may be again classified into a joint transmission scheme and a dynamic cell selection scheme.

[0272] The joint transmission scheme means a scheme in which the signal is simultaneously transmitted through a plurality of points which are all or fractional points in the CoMP wise. That is, data transmitted to a single terminal may be simultaneously transmitted from a plurality of transmission points. Through the joint transmission scheme, the quality of the signal transmitted to the terminal may be improved regardless of coherently or non-coherently and interference with another terminal may be actively removed.

[0273] The dynamic cell selection scheme means a scheme in which the signal is transmitted from the single point through the PDSCH in the CoMP wise. That is, data transmitted to the single terminal at a specific time is transmitted from the single point and data is not transmitted to the terminal at another point in the CoMP wise. The point that transmits the data to the terminal may be dynamically selected.

[0274] According to the CS/CB scheme, the CoMP wise performs beamforming through coordination for transmitting the data to the single terminal. That is, the data is transmitted to the terminal only in the serving cell, but user scheduling/beamforming may be determined through coordination of a plurality of cells in the CoMP wise.

[0275] In the case of the uplink, CoMP reception means receiving the signal transmitted by the coordination among a plurality of points which are geographically separated. The CoMP scheme which may be applied to the uplink may be classified into a joint reception (JR) scheme and the coordinated scheduling/beamforming (CS/CB) scheme.

[0276] The JR scheme means a scheme in which the plurality of points which are all or fractional points receives the signal transmitted through the PDSCH in the CoMP wise. In the CS/CB scheme, only the single point receives the signal transmitted through the PDSCH, but the user scheduling/beamforming may be determined through the coordination of the plurality of cells in the CoMP wise.

[0277] Relay Node (RN)

[0278] The relay node transfers data transmitted and received between the base station and the terminal through two different links (a backhaul link and an access link). The base station may include a donor cell. The relay node is wirelessly connected to a wireless access network through the donor cell.

[0279] Meanwhile, in respect to the use of a band (spectrum) of the relay node, a case in which the backhaul link operates in the same frequency band as the access link is referred to as ‘in-band’ and a case in which the backhaul link and the access link operate in different frequency bands is referred to as ‘out-band’. In both the cases of the in-band and the out-band, a terminal (hereinafter, referred to as a legacy terminal) that operates according to the existing LTE system (for example, release-8) needs to be able to access the donor cell.

[0280] The relay node may be classified into a transparent relay node or a non-transparent relay node according to whether the terminal recognizing the relay node. Transparent means a case in which it may not be recognized whether the terminal communicates with the network through the relay node and non-transparent means a case in which it is recognized whether the terminal communicates with the network through the relay node.

[0281] In respect to control of the relay node, the relay node may be divided into a relay node which is constituted as a part of the donor cell or a relay node that autonomously controls the cell.

[0282] The relay node which is constituted as a part of the donor cell may have a relay node identity (ID), but does not have a cell identity thereof.

[0283] When at least a part of radio resource management (RRM) is controlled by a base station to which the donor cell belongs, even though residual parts of the RRM are positioned at the relay node, the relay node is referred to as the relay node which is constituted as a part of the donor cell. Preferably, the relay node may support the legacy terminal. For example, various types including smart repeaters, decode-and-forward relay nodes, L2 (second layer) relay nodes, and the like and a type-2 relay node correspond to the relay node.

[0284] In the case of the relay node that autonomously controls the cell, the relay node controls one or a plurality of cells and unique physical layer cell identities are provided to the respective cells controlled by the relay node. Further, the respective cells controlled by the relay node may use the same RRM mechanism. In terms of the terminal, there is no difference between accessing the cell controlled by the relay node and accessing a cell controlled by a general base station. The cell controlled by the relay node may support the legacy terminal. For example, a self-backhauling relay node, an L3 (third layer) relay node, a type-1 relay node, and a type-la relay node correspond to the relay node.

[0285] The type-1 relay node as the in-band relay node controls a plurality of cells and the plurality of respective cells are recognized as separate cells distinguished from the donor cell in terms of the terminal. Further, the plurality of respective cells may have physical cell IDs (they are defined in the LTE release-8) and the relay node may transmit a synchronization channel, the reference signal, and the like thereof. In the case of a single-cell operation, the terminal may receive scheduling information and an HARQ feedback directly from the relay node and transmit control channels (scheduling request (SR), CQI, ACK/NACK, and the like) thereof to the relay node. Further, the type-1 relay node is shown as a legacy base station (a base station that operates according to the LTE release-8 system) to the legacy terminals (terminal that operate according to the LTE release-8 system). That is, the type-1 relay node has the backward compatibility. Meanwhile, the terminals that operate according to the LTE-A system recognize the type-1 relay node as a base station different from the legacy base station to provide performance improvement.

[0286] The type-1a relay node has the same features as the type-1 relay node including operating as the out-band The operation of the type-1a relay node may be configured so that an influence on an L1 (first layer) operation is minimized or is not present.

[0287] The type-2 relay node as the in-band relay node does not have a separate physical cell ID, and as a result, a new cell is not formed. The type-2 relay node is transparent with respect to the legacy terminal and the legacy terminal may not recognize the presence of the type-2 relay node. The type-2 relay node may transmit the PDSCH, but at least does not transmit the CRS and the PDCCH.

[0288] Meanwhile, in order for the relay node to operate as the in-band, some resources in the time-frequency space needs to be reserved for the backhaul link and the resources may be configured not to be used for the access link. This is referred to as resource partitioning.

[0289] A general principle in the resource partitioning in the relay node may be described as below. Backhaul downlink and access downlink may be multiplexed in the time division multiplexing scheme on one carrier frequency (that is, only one of the backhaul downlink and the access downlink is activated at a specific time). Similarly, backhaul uplink and access uplink may be multiplexed in the time division multiplexing scheme on one carrier frequency (that is, only one of the backhaul uplink and the access uplink is activated at a specific time).

[0290] In the backhaul link multiplexing in the FDD, backhaul downlink transmission may be performed in a downlink frequency band and backhaul uplink transmission may be performed in an uplink frequency band. In the backhaul link multiplexing in the TDD, THE backhaul downlink transmission may be performed in the downlink subframe of the base station and the relay node and the backhaul uplink transmission may be performed in the uplink subframe of the base station and the relay node.

[0291] In the case of the in-band relay node, for example, when both backhaul downlink reception from the base station and access downlink transmission to the terminal are performed in the same frequency band, signal interference may occurs at a receiver side of the relay node by a signal transmitted from a transmitter side of the relay node. That is, the signal interference or RF jamming may occur at an RF front-end of the relay node. Similarly, even when both the backhaul uplink transmission to the base station and the access uplink reception from the terminal are performed in the same frequency band, the signal interference may occur.

[0292] Therefore, in order for the relay node to simultaneously transmit and receive the signal in the same frequency band, when sufficient separation (for example, the transmitting antenna and the receiving antenna are installed to be significantly geographically spaced apart from each other like installation on the ground and underground) between a received signal and a transmitted signal is not provided, it is difficult to implement the transmission and reception of the signal.

[0293] As one scheme for solving a problem of the signal interference, the relay node operates not transmit the signal to the terminal while receiving the signal from the donor cell. That is, a gap is generated in transmission from the relay node to the terminal and the terminal may be configured not to expect any transmission from the relay node during the gap. The gap may be configured to constitute a multicast broadcast single frequency network (MBSFN) subframe.

[0294] FIG. 12 illustrates a structure of relay resource partitioning in the wireless communication system to which the present invention can be applied.

[0295] In FIG. 12, in the case of a first subframe as a general subframe, a downlink (that is, access downlink) control signal and downlink data are transmitted from the relay node and in the case of a second subframe as the MBSFN subframe, the control signal is transmitted from the relay node from the terminal in the control region of the downlink subframe, but no transmission is performed from the relay node to the terminal in residual regions. Herein, since the legacy terminal expects transmission of the PDCCH in all downlink subframes (in other words, since the relay node needs to support legacy terminals in a region thereof to perform a measurement function by receiving the PDCCH every subframe), the PDCCH needs to be transmitted in all downlink subframes for a correct operation of the legacy terminal. Therefore, eve on a subframe (second subframe) configured for downlink (that is, backhaul downlink) transmission from the base station to the relay node, the relay does not receive the backhaul downlink but needs to perform the access downlink transmission in first N (N=1, 2, or 3) OFDM symbol intervals of the subframe. In this regard, since the PDCCH is transmitted from the relay node to the terminal in the control region of the second subframe, the backward compatibility to the legacy terminal, which is served by the relay node may be provided. In residual regions of the second subframe, the relay node may receive transmission from the base station while no transmission is performed from the relay node to the terminal. Therefore, through the resource partitioning scheme, the access downlink transmission and the backhaul downlink reception may not be simultaneously performed in the in-band relay node.

[0296] The second subframe using the MBSFN subframe will be described in detail. The control region of the second subframe may be referred to as a relay non-hearing interval. The relay non-hearing interval means an interval in which the relay node does not receive the backhaul downlink signal and transmits the access downlink signal. The interval may be configured by the OFDM length of 1, 2, or 3 as described above. In the relay node non-hearing interval, the relay node may perform the access downlink transmission to the terminal and in the residual regions, the relay node may receive the backhaul downlink from the base station. In this case, since the relay node may not simultaneously perform transmission and reception in the same frequency band, It takes a time for the relay node to switch from a transmission mode to a reception mode. Therefore, in a first partial interval of a backhaul downlink receiving region, a guard time (GT) needs to be set so that the relay node switches to the transmission/reception mode. Similarly, even when the relay node operates to receive the backhaul downlink from the base station and transmit the access downlink to the terminal, the guard time for the reception/transmission mode switching of the relay node may be set. The length of the guard time may be given as a value of the time domain and for example, given as a value of k (k≥1) time samples (Ts) or set to the length of one or more OFDM symbols. Alternatively, when the relay node backhaul downlink subframes are consecutively configured or according to a predetermines subframe timing alignment relationship, a guard time of a last part of the subframe may not be defined or set. The guard time may be defined only in the frequency domain configured for the backhaul downlink subframe transmission in order to maintain the backward compatibility (when the guard time is set in the access downlink interval, the legacy terminal may not be supported). In the backhaul downlink reception interval other than the guard time, the relay node may receive the PDCCH and the PDSCH from the base station. This may be expressed as a relay (R)-PDCCH and a relay-PDSCH (R-PDSCH) in a meaning of a relay node dedicated physical channel.

[0297] Reference Signal (RS)

[0298] Downlink Reference Signal

[0299] In the wireless communication system, since the data is transmitted through the radio channel, the signal may be distorted during transmission. In order for the receiver side to accurately receive the distorted signal, the distortion of the received signal needs to be corrected by using channel information. In order to detect the channel information, a signal transmitting method know by both the transmitter side and the receiver side and a method for detecting the channel information by using an distortion degree when the signal is transmitted through the channel are primarily used. The aforementioned signal is referred to as a pilot signal or a reference signal (RS).

[0300] When the data is transmitted and received by using the MIMO antenna, a channel state between the transmitting antenna and the receiving antenna need to be detected in order to accurately receive the signal. Therefore, the respective transmitting antennas need to have individual reference signals.

[0301] The downlink reference signal includes a common RS (CRS) shared by all terminals in one cell and a dedicated RS (DRS) for a specific terminal. Information for demodulation and channel measurement may be provided by using the reference signals.

[0302] The receiver side (that is, terminal) measures the channel state from the CRS and feeds back the indicators associated with the channel quality, such as the channel quality indicator (CQI), the precoding matrix index (PMI), and/or the rank indicator (RI) to the transmitting side (that is, base station). The CRS is also referred to as a cell-specific RS. On the contrary, a reference signal associated with a feed-back of channel state information (CSI) may be defined as CSI-RS.

[0303] The DRS may be transmitted through resource elements when data demodulation on the PDSCH is required. The terminal may receive whether the DRS is present through the upper layer and is valid only when the corresponding PDSCH is mapped. The DRS may be referred to as the UE-specific RS or the demodulation RS (DMRS).

[0304] FIG. 13 illustrates a reference signal pattern mapped to a downlink resource block pair in the wireless communication system to which the present invention can be applied.

[0305] Referring to FIG. 13, as a wise in which the reference signal is mapped, the downlink resource block pair may be expressed by one subframe in the timedomain×12 subcarriers in the frequency domain. That is, one resource block pair has a length of 14 OFDM symbols in the case of a normal cyclic prefix (CP) (FIG. 13a) and a length of 12 OFDM symbols in the case of an extended cyclic prefix (CP) (FIG. 13b). Resource elements (REs) represented as ‘0’, ‘1’, ‘2’, and ‘3’ in a resource block lattice mean the positions of the CRSs of antenna port indexes ‘0’, ‘1’, ‘2’, and ‘3’, respectively and resource elements represented as ‘D’ means the position of the DRS.

[0306] Hereinafter, when the CRS is described in more detail, the CRS is used to estimate a channel of a physical antenna and distributed in a whole frequency band as the reference signal which may be commonly received by all terminals positioned in the cell. Further, the CRS may be used to demodulate the channel quality information (CSI) and data.

[0307] The CRS is defined as various formats according to an antenna array at the transmitter side (base station). The 3GPP LTE system (for example, release-8) supports various antenna arrays and a downlink signal transmitting side has three types of antenna arrays of three single transmitting antennas, two transmitting antennas, and four transmitting antennas. When the base station uses the single transmitting antenna, a reference signal for a single antenna port is arrayed. When the base station uses two transmitting antennas, reference signals for two transmitting antenna ports are arrayed by using a time division multiplexing (TDM) scheme and/or a frequency division multiplexing (FDM) scheme. That is, different time resources and/or different frequency resources are allocated to the reference signals for two antenna ports which are distinguished from each other.

[0308] Moreover, when the base station uses four transmitting antennas, reference signals for four transmitting antenna ports are arrayed by using the TDM and/or FDM scheme. Channel information measured by a downlink signal receiving side (terminal) may be used to demodulate data transmitted by using a transmission scheme such as single transmitting antenna transmission, transmission diversity, closed-loop spatial multiplexing, open-loop spatial multiplexing, or multi-user MIMO.

[0309] In the case where the MIMO antenna is supported, when the reference signal is transmitted from a specific antenna port, the reference signal is transmitted to the positions of specific resource elements according to a pattern of the reference signal and not transmitted to the positions of the specific resource elements for another antenna port. That is, reference signals among different antennas are not duplicated with each other.

[0310] General D2D Communication

[0311] Generally, D2D communication is limitatively used as the term for communication between objects or object intelligent communication, but the D2D communication in the present invention may include all communication between various types of devices having a communication function such as a smart phone and a personal computer in addition to simple devices with a communication function.

[0312] FIG. 14 is a diagram for schematically describing the D2D communication in a wireless communication system to which the present invention may be applied.

[0313] FIG. 14a illustrates a communication scheme based on an existing base station eNB, and the UE1 may transmit the data to the base station on the uplink and the base station may transmit the data to the UE2 on the downlink. The communication scheme may be referred to as an indirect communication scheme through the base station. In the indirect communication scheme, a Un link (referred to as a backhole link as a link between base stations or a link between the base station and the repeater) and/or a Uu link (referred to as an access link as a link between the base station and the UE or a link between the repeater and the UE) which are defined in the existing wireless communication system may be related.

[0314] FIG. 14b illustrates a UE-to-UE communication scheme as an example of the D2D communication, and the data exchange between the UEs may be performed without passing through the base station. The communication scheme may be referred to as a direct communication scheme between devices. The D2D direct communication scheme has advantages of reducing latency and using smaller wireless resources as compared with the existing indirect communication scheme through the base station.

[0315] FIG. 15 illustrates examples of various scenarios of the D2D communication to which the method proposed in the specification may be applied.

[0316] The D2D communication scenario may be divided into (1) an out-of-coverage network, (2) a partial-coverage network, and (3) in-coverage network according to whether the UE1 and the UE2 are positioned in coverage/out-of-coverage.

[0317] The in-coverage network may be divided into an in-coverage-single-cell and an in-coverage-multi-cell according to the number of cells corresponding to the coverage of the base station.

[0318] FIG. 15a illustrates an example of an out-of-coverage network scenario of the D2D communication.

[0319] The out-of-coverage network scenario means perform the D2D communication between the D2D UEs without control of the base station.

[0320] In FIG. 15a, only the UE1 and the UE2 are present and the UE1 and the UE2 may directly communicate with each other.

[0321] FIG. 15b illustrates an example of a partial-coverage network scenario of the D2D communication.

[0322] The partial-coverage network scenario means performing the D2D communication between the D2D UE positioned in the network coverage and the D2D UE positioned out of the network coverage.

[0323] In FIG. 15b, it may be illustrated that the D2D UE positioned in the network coverage and the D2D UE positioned out of the network coverage communicate with each other.

[0324] FIG. 15c illustrates an example of the in-coverage-single-cell and FIG. 15d illustrates an example of the in-coverage-multi-cell scenario.

[0325] The in-coverage network scenario means that the D2D UEs perform the D2D communication through the control of the base station in the network coverage.

[0326] In FIG. 15c, the UE1 and the UE2 are positioned in the same network coverage (alternatively, cell) under the control of the base station.

[0327] In FIG. 15d, the UE1 and the UE2 are positioned in the network coverage, but positioned in different network coverages. In addition, the UE1 and the UE2 performs the D2D communication under the control of the base station managing the network coverage.

[0328] Here, the D2D communication will be described in more detail.

[0329] The D2D communication may operate in the scenario illustrated in FIG. 15, but generally operate in the network coverage and out of the network coverage. The link used for the D2D communication (direct communication between the UEs) may be referred to as D2D link, directlink, or sidelink, but for the convenience of description, the link is commonly referred to as the sidelink.

[0330] The sidelink transmission may operate in uplink spectrum in the case of the FDD and in the uplink (alternatively, downlink) subframe in the case of the TDD. For multiplexing the sidelink transmission and the uplink transmission, time division multiplexing (TDM) may be used.

[0331] The sidelink transmission and the uplink transmission do not simultaneously occur. In the uplink subframe used for the uplink transmission and the sidelink subframe which partially or entirely overlaps with UpPTS, the sidelink transmission does not occur. Alternatively, the transmission and the reception of the sidelink do not simultaneously occur.

[0332] A structure of a physical resource used in the sidelink transmission may be used equally to the structure of the uplink physical resource. However, the last symbol of the sidelink subframe is constituted by a guard period and not used in the sidelink transmission.

[0333] The sidelink subframe may be constituted by extended CP or normal CP.

[0334] The D2D communication may be largely divided into discovery, direct communication, and synchronization.

[0335] 1) Discovery

[0336] The D2D discovery may be applied in the network coverage. (including inter-cell and intra-cell). Displacement of synchronous or asynchronous cells may be considered in the inter-cell coverage. The D2D discovery may be used for various commercial purposes such as advertisement, coupon issue, and finding friends to the UE in the near area.

[0337] When the UE 1 has a role of the discovery message transmission, the UE 1 transmits the discovery message and the UE 2 receives the discovery message. The transmission and the reception of the UE 1 and the UE 2 may be reversed. The transmission from the UE 1 may be received by one or more UEs such as UE2.

[0338] The discovery message may include a single MAC PDU, and here, the single MAC PDU may include a UE ID and an application ID.

[0339] A physical sidelink discovery channel (PSDCH) may be defined as the channel transmitting the discovery message. The structure of the PSDCH channel may reuse the PUSCH structure.

[0340] A method of allocating resources for the D2D discovery may use two types Type 1 and Type 2.

[0341] In Type 1, eNB may allocate resources for transmitting the discovery message by a non-UE specific method.

[0342] In detail, a wireless resource pool for discovery transmission and reception constituted by the plurality of subframes is allocated at a predetermined period, and the discovery transmission UE transmits the next discovery message which randomly selects the specific resource in the wireless resource pool.

[0343] The periodical discovery resource pool may be allocated for the discovery signal transmission by a semi-static method. Setting information of the discovery resource pool for the discovery transmission includes a discovery period, the number of subframes which may be used for transmission of the discovery signal in the discovery period (that is, the number of subframes constituted by the wireless resource pool).

[0344] In the case of the in-coverage UE, the discovery resource pool for the discovery transmission is set by the eNB and may notified to the UE by using RRC signaling (for example, a system information block (SIB)).

[0345] The discovery resource pool allocated for the discovery in one discovery period may be multiplexed to TDM and/or FDM as a time-frequency resource block with the same size, and the time-frequency resource block with the same size may be referred to as a ‘discovery resource’.

[0346] The discovery resource may be used for transmitting the discovery MAC PDU by one UE. The transmission of the MAC PDU transmitted by one UE may be repeated (for example, repeated four times) contiguously or non-contiguously in the discovery period (that is, the wireless resource pool). The UE randomly selects the first discovery resource in the discovery resource set) which may be used for the repeated transmission of the MAC PDU and other discovery resources may be determined in relation with the first discovery resource. For example, a predetermined pattern is preset and according to a position of the first selected discovery resource, the next discovery resource may be determined according to a predetermined pattern. Further, the UE may randomly select each discovery resource in the discovery resource set which may be used for the repeated transmission of the MAC PDU.

[0347] In Type 2, the resource for the discovery message transmission is UE-specifically allocated. Type 2 is sub-divided into Type-2A and Type-2B again. Type-2A is a type in which the UE allocates the resource every transmission instance of the discovery message in the discovery period, and the type 2B is a type in which the resource is allocated by a semi-persistent method.

[0348] In the case of Type 2B, RRC_CONNECTED UE request allocation of the resource for transmission of the D2D discovery message to the eNB through the RRC signaling. In addition, the eNB may allocate the resource through the RRC signaling. When the UE is transited to a RRC_IDLE state or the eNB withdraws the resource allocation through the RRC signaling, the UE releases the transmission resource allocated last. As such, in the case of the type 2B, the wireless resource is allocated by the RRC signaling and activation/deactivation of the wireless resource allocated by the PDCCH may be determined.

[0349] The wireless resource pool for the discovery message reception is set by the eNB and may notified to the UE by using RRC signaling (for example, a system information block (SIB)).

[0350] The discovery message reception UE monitors all of the discovery resource pools of Type 1 and Type 2 for the discovery message reception.

[0351] 2) Direct Communication

[0352] An application area of the D2D direct communication includes in-coverage and out-of-coverage, and edge-of-coverage. The D2D direct communication may be used on the purpose of public safety (PS) and the like.

[0353] When the UE 1 has a role of the direct communication data transmission, the UE 1 transmits direct communication data and the UE 2 receives direct communication data. The transmission and the reception of the UE 1 and the UE 2 may be reversed. The direct communication transmission from the UE 1 may be received by one or more UEs such as UE2.

[0354] The D2D discovery and the D2D communication are not associated with each other and independently defined. That is, the in groupcast and broadcast direct communication, the D2D discovery is not required. As such, when the D2D discovery and the D2D communication are independently defined, the UEs need to recognize the adjacent UEs. In other words, in the case of the groupcast and broadcast direct communication, it is not required that all of the reception UEs in the group are close to each other.

[0355] A physical sidelink shared channel (PSSCH) may be defined as a channel transmitting D2D direct communication data. Further, a physical sidelink control channel (PSCCH) may be defined as a channel transmitting control information (for example, scheduling assignment (SA) for the direct communication data transmission, a transmission format, and the like) for the D2D direct communication. The PSSCH and the PSCCH may reuse the PUSCH structure.

[0356] A method of allocating the resource for D2D direct communication may use two modes mode 1 and mode 2.

[0357] Mode 1 means a mode of scheduling a resource used for transmitting data or control information for D2D direct communication. Mode 1 is applied to in-coverage.

[0358] The eNB sets a resource pool required for D2D direct communication. Here, the resource pool required for D2D direct communication may be divided into a control information pool and a D2D data pool. When the eNB schedules the control information and the D2D data transmission resource in the pool set to the transmission D2D UE by using the PDCCH or the ePDCCH, the transmission D2D UE transmits the control information and the D2D data by using the allocated resource.

[0359] The transmission UE requests the transmission resource to the eNB, and the eNB schedules the control information and the resource for transmission of the D2D direct communication data. That is, in the case of mode 1, the transmission UE needs to be in an RRC_CONNECTED state in order to perform the D2D direct communication. The transmission UE transmits the scheduling request to the eNB and a buffer status report (BSR) procedure is performed so that the eNB may determine an amount of resource required by the transmission UE.

[0360] The reception UEs monitor the control information pool and may selectively decode the D2D data transmission related with the corresponding control information when decoding the control information related with the reception UEs. The reception UE may not decode the D2D data pool according to the control information decoding result.

[0361] Mode 2 means a mode in which the UE arbitrarily selects the specific resource in the resource pool for transmitting the data or the control information for D2D direct communication. In the out-of-coverage and/or the edge-of-coverage, the mode 2 is applied.

[0362] In mode 2, the resource pool for transmission of the control information and/or the resource pool for transmission of the D2D direct communication data may be pre-configured or semi-statically set. The UE receives the set resource pool (time and frequency) and selects the resource for the D2D direct communication transmission from the resource pool. That is, the UE may select the resource for the control information transmission from the control information resource pool for transmitting the control information. Further, the UE may select the resource from the data resource pool for the D2D direct communication data transmission.

[0363] In D2D broadcast communication, the control information is transmitted by the broadcasting UE. The control information explicitly and/or implicitly indicate the position of the resource for the data reception in associated with the physical channel (that is, the PSSCH) transporting the D2D direct communication data.

[0364] 3) Synchronization

[0365] A D2D synchronization signal (alternatively, a sidelink synchronization signal) may be used so that the UE obtains time-frequency synchronization. Particularly, in the case of the out-of-coverage, since the control of the eNB is impossible, new signal and procedure for synchronization establishment between UEs may be defined.

[0366] The UE which periodically transmits the D2D synchronization signal may be referred to as a D2D synchronization source. When the D2D synchronization source is the eNB, the structure of the transmitted D2D synchronization signal may be the same as that of the PSS/SSS. When the D2D synchronization source is not the eNB (for example, the UE or the global navigation satellite system (GNSS)), a structure of the transmitted D2D synchronization signal may be newly defined.

[0367] The D2D synchronization signal is periodically transmitted for a period of not less than 40 ms. Each UE may have multiple physical-layer sidelink synchronization identities. The D2D synchronization signal includes a primary D2D synchronization signal (alternatively, a primary sidelink synchronization signal) and a secondary D2D synchronization signal (alternatively, a secondary sidelink synchronization signal).

[0368] Before transmitting the D2D synchronization signal, first, the UE may search the D2D synchronization source. In addition, when the D2D synchronization source is searched, the UE may obtain time-frequency synchronization through the D2D synchronization signal received from the searched D2D synchronization source. In addition, the corresponding UE may transmit the D2D synchronization signal.

[0369] Hereinafter, for clarity, direct communication between two devices in the D2D communication is exemplified, but the scope of the present invention is not limited thereto, and the same principle described in the present invention may be applied even to the D2D communication between two or more devices.

[0370] One of D2D discovery methods includes a method for performing, by all of pieces of UE, discovery using a dispersive method (hereinafter referred to as “dispersive discovery”). The method for performing D2D discovery dispersively means a method for autonomously determining and selecting, by all of pieces of UE, discovery resources dispersively and transmitting and receiving discovery messages, unlike a centralized method for determining resource selection at one place (e.g., an eNB, UE, or a D2D scheduling device).

[0371] In the following specification, a signal (or message) periodically transmitted by pieces of UE for D2D discovery may be referred to as a discovery message, a discovery signal, or a beacon. This is collectively referred to as a discovery message, for convenience of description.

[0372] In dispersive discovery, dedicated resources may be periodically allocated as resources for transmitting and receiving, by UE, a discovery message separately from cellular resources. This is described below with reference to FIG. 17.

[0373] FIG. 16 shows an example of a frame structure to which discovery resources are allocated, to which methods proposed according to embodiments of the present invention may be applied.

[0374] Referring to FIG. 16, in the dispersive discovery method, a discovery subframe (i.e., a “discovery resource pool”) 1601 for discovery, of all of cellular uplink frequency-time resources, is allocated fixedly (or dedicatedly), and the remaining region may include an existing LTE uplink Wide Area Network (WAN) subframe region 1603. The discovery resource pool may include one or more subframes.

[0375] The discovery resource pool may be periodically allocated at a specific time interval (i.e., a “discovery period”). Furthermore, the discovery resource pool may be repeatedly configured within one discovery period.

[0376] FIG. 16 shows an example in which a discovery resource pool is allocated in a discovery period of 10 sec and 64 contiguous subframes are allocated to each discovery resource pool. The size of a discovery period and time/frequency resources of a discovery resource pool is not limited thereto.

[0377] UE autonomously selects resources (i.e., “discovery resources”) for transmitting its own discovery message within a discovery pool dedicatedly allocated thereto and transmits the discovery message through the selected resources. This is described below with reference to FIG. 17.

[0378] FIG. 17 is a diagram schematically showing a discovery process to which methods proposed according to embodiments of the present invention may be applied.

[0379] Referring to FIGS. 16 and 17, a discovery method basically includes a three-step procedure: a resource sensing step S1701 for discovery message transmission, a resource selection step S1703 for discovery message transmission, and a discovery message transmission and reception step S1705.

[0380] First, in the resource sensing step S1701 for discovery message transmission, all of pieces of UE performing D2D discovery receive (i.e., sense) all of discovery messages in a dispersive way (i.e., autonomously) during 1 period of D2D discovery resources (i.e., a discovery resource pool). For example, assuming that an uplink bandwidth is 10 MHz in FIG. 16, all of pieces of UE receive (i.e., sense) all of discovery messages transmitted in N=44 RBs (6 RBs of a total of 50 RBs are used for PUCCH transmission because the entire uplink bandwidth is 10 MHz) during K=64 msec (64 subframes).

[0381] Furthermore, in the resource selection step S1703 for discovery message transmission, UE sorts resources having a low energy level from the sensed resources and randomly selects discovery resources within a specific range (e.g., within lower x % (x=a specific integer, 5, 7, 10, . . . )) from the selected resources.

[0382] Discovery resources may include one or more resource blocks having the same size and may be multiplexed within a discovery resource pool in a TDM and/or FDM manner.

[0383] Furthermore, in the discovery message transmission and reception step S1705, the UE transmits and receives discovery messages based on discovery resources selected after one discovery period (after P=10 seconds in the example of FIG. 16) and transmits and receives discovery messages periodically according to a random resource hopping pattern in a subsequent discovery period.

[0384] Such a D2D discovery procedure continues to be performed even in an RRC_IDLE state not having a connection with an eNB in addition to an RRC_CONNECTED state in which the UE has a connection with the eNB.

[0385] If such a discovery method is taken into consideration, all of pieces of UE sense all of resources (i.e., discovery resource pools) transmitted by surrounding pieces of UE and randomly select discovery resources within a specific range (e.g., within low x %) from all the sensed resources.

[0386] Hereinafter, methods for transmitting D2D control information and/or D2D data proposed in the present disclosure will be described in more detail with reference to FIGS. 18 to 29.

[0387] As described above, D2D may be represented as a sidelink.

[0388] Furthermore, D2D control information may be represented as a Sidelink Control Information (SCI), and the D2D control information may be sent and received over a PSCCH (Physical Sidelink Control Channel).

[0389] Furthermore, D2D data may be sent and received over a PSSCH (Physical Sidelink Shared Channel), and the transmission and reception of the D2D data may be represented as PSSCH transmission and reception.

[0390] In performing D2D communication, it is necessary to define D2D control information in order for a D2D UE to demodulate D2D data.

[0391] As described above, the D2D control information may be represented as SCI, both of which may be interchangeably used hereinafter.

[0392] Here, the D2D control information may be transmitted over a different channel (or in a different signal) than a D2D communication channel for delivering the D2D data.

[0393] As described above, the D2D communication channel may be represented as PSSCH, both of which may be interchangeably used hereinafter.

[0394] Furthermore, methods to be described below may apply equally when control information required to deliver a D2D discovery message is transmitted separately.

[0395] The D2D control information may include some of or the entire information, such as a New Data Indicator (NDI), Resource Allocation (RA) (or a resource configuration), a Modulation and Coding Scheme/Set (MCS), a Redundancy Version (RV), and a Tx UE ID.

[0396] The D2D control information may have a different combination of pieces of information depending on a scenario to which the D2D communication of FIG. 15 is applied.

[0397] In general, control information (CI) may be decoded before a data channel is decoded because the data channel is used to demodulate the data channel.

[0398] Accordingly, UEs that receive the control information need to be aware the location of time and frequency resources through which the control information is transmitted and related parameters for the demodulation of the data channel.

[0399] For example, in an LTE (-A) system, in the case of a PDCCH, a UE ID-based hashing function is used by a transmission stage (e.g., an eNB) and a reception stage (e.g., UE) in common so that the UE can be aware that the PDCCH will be transmitted to a specific location among specific symbols of each subframe.

[0400] Furthermore, in an LTE (-A) system, in the case of a BCH, an eNB and UE share information, indicating that system information is delivered in a specific symbol of a specific subframe (SF) with a periodicity of 40 ms, in advance.

[0401] As described above, in order for UE to properly obtain the control information, demodulation-related information (or parameters) of the control information may need to be sufficiently delivered to the UE in advance.

[0402] Likewise, in a system supporting D2D communication, in order for a D2D UE to successfully demodulate D2D control information, parameters related to the transmission of the D2D control information may need to be shared by the D2D UE in advance.

[0403] The parameters related to the transmission of the D2D control information may include, for example, a subframe/slot index, a symbol index, or an RB index.

[0404] Furthermore, the parameters related to the transmission of the D2D control information may be the DCI of a specific format and may be obtained through a PDCCH from an eNB or another D2D UE.

[0405] The DCI of the specific format means a newly defined DCI format and may be, for example, a DCI format 5.

[0406] In an embodiment, the D2D control information may be designated to be transmitted in all of subframes designated as D2D subframes (i.e., subframes designated for D2D transmission), a series of subframes (a set of subframes or a subframe set) that belong to all the subframes and that has a specific index, or a subframe set having a specific period.

[0407] Such potential transmission subframe or subframe set of the D2D control information may be recognized by UE in advance through (higher-layer) signaling or based on UE-specific information (e.g., a UE ID) in such a manner that the UE may autonomously calculate the transmission subframe or subframe set.

[0408] Furthermore, a resource region in which a D2D data channel is delivered and a resource region in which D2D control information is delivered may be differently configured in a time domain.

[0409] That is, the D2D control information may be defined to be transmitted in a designated time unit, that is, periodically (or while hopping in a designated time-frequency domain pattern). The D2D data channel may be defined to be delivered only in a resource region indicated by the D2D control information.

[0410] In this method, unlike a method for transmitting D2D control information and D2D data together, the D2D control information and the D2D data are transmitted separately.

[0411] Specifically, if the D2D control information and the D2D data are separately transmitted, (1) parameters (e.g., scrambling, CRC, CRC masking, or demodulation sequence generation parameters) applied to the D2D control information and the D2D data are independently set, or (2) parameters applied to the D2D data are indicated through the D2D control information.

[0412] In the case of (2), a D2D UE attempts (e.g., explicit or blind decoding) to monitor and decode the D2D control information using a potential parameter in a potential resource (i.e., subframe or subframe set) in which the D2D control information is reserved to be transmitted, and does not perform decoding attempts at the D2D control information in a resource region other than the potential resource.

[0413] In this case, there is an advantage in that power consumption of UE can be reduced.

[0414] Furthermore, if UE demodulates D2D data, the UE only has to demodulate designated information at a designated point using a parameter and D2D data resource region information obtained through the D2D control information. Accordingly, there is an advantage in that power consumption of UE can be reduced.

[0415] In an embodiment for implementing the aforementioned methods, a method for UEs to perform blind search (or decoding) on a specific resource region in order to obtain D2D control information at a specific point of time and decoding D2D control information matched with each UE is described below.

[0416] In this case, it can be found out whether D2D control information is matched with each UE, based on UE-specific information or UE group-specific (UE group-common) information.

[0417] That is, only a corresponding UE may perform (blind) decoding on D2D control information by applying UE-specific scrambling or CRC masking to the D2D control information, or all of a plurality of UEs (or a group or all) may decode the D2D control information by applying UE-group common scrambling or CRC masking to the D2D control information.

[0418] Accordingly, a UE or a UE group may obtain information related to D2D data demodulation from D2D control information that has been successfully decoded.

[0419] The D2D control information (or SCI) includes parameters (in this case, including parameters obtained through blind search from a given D2D control channel set in addition to predetermined parameters) used in a D2D control channel (PSCCH) in addition to explicit information included in D2D control information.

[0420] The parameters used in the D2D control channel may include scrambling, CRC masking, use resource information, and reference signal-related parameters.

[0421] Accordingly, UE may not perform blind decoding on D2D data.

[0422] To sum up, a UE or a UE group performs blind decoding on D2D control information through a specific parameter at a specific point of time using its own unique information or based on previously (higher-layer) signaled information in order to obtain the D2D control information.

[0423] Through such blind decoding, the UE or UE group may obtain both scheduling information related to data demodulation and various parameters used to generate and transmit a D2D control channel (or control information).

[0424] Accordingly, the UE or UE group uses the parameter related to the D2D control channel and the decoded scheduling information to decode and demodulate a D2D data channel.

[0425] In this case, the D2D data channel may be represented as a physical sidelink shared channel (PSSCH).

[0426] The scheduling information may refer to explicit information, such as resource allocation information, an NDI, an MCS, or a Tx UE ID required to demodulate D2 data.

[0427] Furthermore, as described above, the scheduling information may be represented as Sidelink Control Information (SCI).

[0428] UE is not required to perform parameter blind search, such as that performed on a D2D control channel (or a PSCCH) with respect to a D2D data channel (PSSCH), because it uses a parameter through blind search with respect to the D2D control channel without any change or uses a new parameter generated based on the parameter to generate the D2D data channel.

[0429] In another embodiment, a D2D control channel and a D2D data channel may be transmitted in the same subframe (from the standpoint of a UE or a UE group) or may be implemented to have different periodicities in time.

[0430] That is, such a method is a method for UE to perform blind decoding on a D2D control channel in a specific subframe and demodulating the D2D data of the same subframe based on corresponding information.

[0431] In this case, it is assumed that the UE will not perform blind decoding on the D2D data.

[0432] Instead, the UE may perform blind decoding only on the D2D control channel so that blind decoding complexity is dependent only on a D2D control channel in a corresponding subframe.

[0433] That is, the UE performs blind decoding only on D2D control information in the corresponding subframe.

[0434] If the UE has to perform blind decoding on D2D data, when D2D control information and D2D data are transmitted in the same subframe, the UE's trials of blind decoding may increase suddenly.

[0435] In this case, the number of UEs capable of detecting D2D control information through blind decoding in a specific subframe may be limited.

[0436] That is, if the transmission periods of D2D control information and D2D data are fixed, there may be a case where the D2D control information and the D2D data are transmitted in the same subframe in some situations depending on their periodicity.

[0437] In this case, if there is a limit to blind decoding trials in a corresponding subframe, the blind decoding trials of a D2D control information channel and/or a D2D data channel may have to be reduced.

[0438] In order to reduce such a problem, the blind decoding of UE may be introduced only in a D2D control channel so as to prevent a limitation to blind decoding trials caused by a variation of blind decoding complexity.

[0439] Furthermore, there is an advantage that the degree of freedom of scheduling for a D2D data channel may be increased by introducing blind decoding only in a D2D control channel.

[0440] That is, although D2D control information and D2D data are placed in the same subframe, if blind decoding is applied to a D2D control channel only, there is no limitation to blind decoding complexity.

[0441] Accordingly, although a D2D control channel is periodically transmitted in a specific subframe, a subframe for transmitting a D2D data channel may be determined and allocated even without avoiding a subframe in which the D2D control channel is transmitted.

[0442] Assuming that a D2D control channel is detected once and then transmitted in a specific subframe after D2D data associated with the D2D control channel is transmitted, D2D control information does not need to be transmitted again in the transmission opportunity subframe (i.e., a D2D control channel transmission period or PSCCH period) of the D2D control channel during an interval of time until a subframe in which the D2D data will be transmitted.

[0443] Likewise, from the standpoint of UE, blind decoding (or monitoring) may not be performed on a D2D control channel until a D2D data subframe indicated by D2D control information after blind decoding is performed on the D2D control channel.

[0444] In this case, the power consumption of the UE can be reduced. This may be differently configured for each UE.

[0445] If the period in which a D2D control channel is transmitted (or a PSCCH period) and a subframe offset are differently configured in each UE, each UE may be aware of a subframe in which monitoring for D2D control information needs not to be performed.

[0446] That is, when each UE performs blind decoding on D2D control information in a specific subframe, it may be aware how long it may perform discontinuous reception (DRX) or discontinuous transmission (DTX) by taking into consideration the monitoring subframe period and offset of its own D2D control information.

[0447] After receiving and demodulating D2D control information (i.e. scheduling assignment), UE may calculate how long it does not need to monitor D2D control information, that is, how long it may perform DTX, by properly using a specific bit value and D2D control information subframe period (i.e., PSCCH period) information carried on corresponding subframe index, UE ID, or D2D control information.

[0448] FIG. 18 is a diagram showing an example of a method for transmitting and receiving D2D control information and D2D data, which is proposed according to the present disclosure.

[0449] In FIG. 18, C1 represents a resource that belongs to D2D resources allocated to UE 1 (or a UE-group 1) and that is used to transmit D2D control information.

[0450] The C1 1801 may be obtained through an (E-)PDCCH, an SIB, “preconfigured”, or “relaying by UE.”

[0451] For example, UE may obtain the C1 (or the SCI format 0) through the DCI format 5 transmitted through a PDCCH.

[0452] Furthermore, the period of the C1 corresponds to a period #1.

[0453] C2 1802 represents a resource that belongs to D2D resources allocated to UE 2 (or a UE-group 2) and that is used to transmit D2D control information.

[0454] The period of the C2 corresponds to a period #2.

[0455] The periods of the C1 and C2 may be represented as a PSCCH period #1 and a PSCCH period #2, respectively.

[0456] In FIG. 18, first C1 information indicates parameters related to the transmission of D2D data #1 1803 and indicates various types of information (e.g., scheduling information, such as a DM RS sequence, an MCS, and RA) for reception UE in order to demodulate the D2D data #1.

[0457] Furthermore, the first C2 information indicates parameters related to the transmission of D2D data #2 1804 and indicates various types of information (e.g., scheduling information) for reception UE in order to demodulate the D2D data #2.

[0458] In FIG. 18, second C 1 information 1805 and second C2 information 1806 indicate parameters (e.g., scheduling information) following the first D2D data #1 1803 and the first D2D data #2 1804, that is, parameters associated with second Data #1 and Data #2 1807.

[0459] Each UE performs blind decoding on D2D control information, corresponding to each UE, with respect to a corresponding subframe because it is aware in advance of the location of a subframe for D2D control information where the UE may perform monitoring.

[0460] FIG. 19 is a diagram showing another example of a method for transmitting and receiving D2D control information and D2D data, which is proposed according to the present disclosure.

[0461] In FIG. 19, UE may be aware that D2D data (D2D data #1) related to a C1 1901 is delivered in a D2D data #1 subframe 1902 by performing blind decoding on the C1 1901.

[0462] Furthermore, if the UE is aware in advance that there is no C 1 in a subframe 1903 periodically reserved (or allocated) for the purpose of transmitting D2D control information after the C 1, the UE may skip the reserved subframe 1903 without performing monitoring or blind decoding.

[0463] That is, FIG. 19 shows that UE does not perform additional monitoring and blind decoding on D2D control information in a periodically reserved subframe present between the C1 and the data #1.

[0464] In this case, it may be considered that the UE performs a DTX operation in a specific subframe in order to reduce power consumption because it may be aware in advance that it does not need to perform monitoring and blind decoding on D2D control information in the specific subframe.

[0465] FIG. 20 is a diagram showing yet another example of a method for transmitting and receiving D2D control information and D2D data, which is proposed according to the present disclosure.

[0466] In the example of FIG. 19, UE has skipped blind decoding for all of subframes periodically reserved between the C1 and the data #1.

[0467] In contrast, FIG. 20 shows a method for UE to skip a reserved D2D control information subframe from a monitoring subframe only when a previously agreed condition is satisfied, rather than skipping blind decoding for all of reserved D2D control information subframes, if a D2D control information subframe reserved to transmit D2D control information is present between the D2D control information and a D2D data subframe indicated by the D2D control information.

[0468] From FIG. 20, it may be seen that UE performs blind decoding in a C11 2001 and a C13 2003 and skips blind decoding in a C12 2002.

[0469] That is, all of the monitoring subframes C11, C12, and C13 of candidate D2D control information between the C11 2001 and data #11 2004 are not skipped.

[0470] For example, the UE performs monitoring on the last subframe C13 2003 of the candidate subframes present between the C11 2001 and the data #11 2004 for blind decoding.

[0471] In some embodiments, if N D2D control information candidate subframes are present between a D2D control information (or scheduling information) subframe and a D2D data transmission subframe, blind decoding for K candidate subframes placed at the last portion may be skipped.

[0472] In this case, the value k may be configured depending on system operation.

[0473] In some embodiments, if a D2D control information subframe is divided into a subframe used for D2D transmission and a subframe used for D2D reception (i.e., if two types of subframes are present because they cannot be transmitted and received at the same time due to a half-duplex constraint), the blind decoding skip rule may apply only to the subframe used for D2D transmission.

[0474] If there is no distinction between a subframe used for D2D transmission and a subframe used for D2D reception, the blind decoding skip rule may apply by taking into consideration both the two types (D2D transmission and D2D reception) of subframes.

[0475] In some embodiments, if the valid period of D2D control information is present, the UE may assume that additional D2D control information does not arrive during the valid period, and neglect D2D control information that arrives between a D2D control information subframe and a D2D data subframe—that is, the blind decoding skip rule may apply.

[0476] Furthermore, assuming that D2D control information subframes are used by a plurality of UEs, each UE may calculate a subframe that the UE has to monitor, among the D2D control information subframes, by using its own ID or another parameter, such as a D2D subframe index.

[0477] In this case, a method for each UE to calculate its own D2D control information subframe may be performed in a similar way to a method for calculating a paging subframe that the UE has to calculate using a UE ID and another parameter—that is, a method for calculating the index of a subframe that the UE has to receive after waking up from sleep mode.

[0478] FIG. 21 is a diagram showing an example of a method for configuring D2D control information depending on D2D transmission mode, which is proposed according to the present disclosure.

[0479] FIG. 21 shows that some of resources allocated using each of two D2D resource allocation methods, that is, two types of transmission mode (transmission mode 1 and transmission mode 2), are configured as common resources if the two D2D resource allocation methods are used.

[0480] FIG. 21a shows the resource allocation of D2D control information in an in-coverage scenario, that is, transmission mode 1, and FIG. 21b shows the resource allocation of D2D control information in a partial or out-coverage scenario, that is, transmission mode 2.

[0481] The resource of control information in transmission mode 1 is indicated by C1 or C2, and the resource of control information in transmission mode 2 is indicated by P or S.

[0482] From FIG. 21, it may be seen that the resources C1 and P have been configured to be aligned in the same time resource and/or the same frequency resource.

[0483] That is, FIG. 21 shows that the resources C1 and P have been configured as common resources (e.g., cell-specific or UE group-specific).

[0484] In the resource configurations of FIG. 21, if UE changes a resource allocation method, it may use the common resource subframe as a fallback subframe in which a D2D control channel may be monitored.

[0485] That is, common resources configured using different resource allocation methods may mean candidate subframes in which UE is obliged to monitor D2D control information when mode of a resource allocation method switches.

[0486] Accordingly, UEs to which resources have been allocated according to transmission mode 1 or UEs to which resources have been allocated according to transmission mode 2 may need to perform blind decoding on the resource P or C1 corresponding to common resources.

[0487] In this case, UEs within a cell may have different resource allocation methods, that is, different types of transmission mode. Resources may be configured in such a way that a single UE has the two types of transmission mode.

[0488] Transmission mode 1 and transmission mode 2 do not only mean a resource allocation method for D2D communication, but also mean concepts indicative of a resource allocation method for D2D discovery.

[0489] That is, from the standpoint of a single UE, a D2D discovery resource may be set as transmission mode 1 and a D2D communication resource may be set as transmission mode 2, or vice versa.

[0490] From the standpoint of a plurality of UEs, transmission mode 1, transmission mode 2, D2D discovery, and D2D communication combinations may be configured in various ways.

[0491] In this case, pre-designated UE (e.g., a UE group, all UEs within a cell, or all D2D-enabled UEs) may be defined to monitor a common resource set by defining the concept of a default resource set or common resource set in transmission mode 1 or transmission mode 2.

[0492] Timing relations between a Scheduling Grant (SG) (or DCI), Scheduling Assignment (SA), and D2D data transmission in D2D communication, which is proposed according to the present disclosure, are described in detail below.

[0493] A Scheduling Grant (SG) used hereinafter is indicative of Downlink Control Information (DCI) transmitted from an eNB to D2D UE, and may mean a parameter related to D2D communication.

[0494] The scheduling grant may be transmitted in a PDCCH/EPDCCH and may be represented as a DCI format 5.

[0495] Furthermore, the Scheduling Assignment (SA) may be indicative of D2D control information, and may mean control information transmitted and received between D2D UEs, including resource allocation information for the transmission and reception of D2D data.

[0496] The Scheduling Assignment (SA) may be transmitted through a PSCCH and may be represented as an SCI format 0.

[0497] First, details relating to a method for notifying UE of a resource used for D2D data transmission and a resource used for Scheduling Assignment (SA) transmission for transmitting D2D data transmission-related scheduling information are described with reference to Table 3 below.

[0498] Furthermore, a method described with reference to Table 5 is only an example, and D2D data transmission and SA transmission may be performed using other methods than the method of Table 5.

[0499]

TABLE 5
		Signaling methods
		Resource (or Resource Pool) indication methods(to be
		used for the following transmission)
Resource		Being transmitted
Allocation	Scenarios	For Scheduling Assignment	For Data communication
Mode 1	In-coverage	SIB (or (E)PDCCH)	SIB (or (E)PDCCH)
(eNB		(This can be triggered by	(This can be triggered by
schedules)		D2D scheduling request	D2D scheduling request
		(D-SR))	(D-SR))
	Edge-of-coverage	Via other forwarding UE(s)	Via other forwarding UE(s)
		SIB or other sig.	SIB or other sig.
		forwarding	forwarding
	Out-coverage	Pre-configured or other	Pre-configured or other
	Semi-static resource pool restricting the available resources for data and/or
	control may be needed
	D2D communication capable UE shall support at least Mode 1 for in-
	coverage
Mode 2	In-coverage	SIB (or (E)PDCCH)	SIB (or (E)PDCCH)
(UE selects)	Edge-of-coverage	Via other forwarding UE(s)	Via other forwarding UE(s)
		SIB or other sig.	SIB or other sig.
		forwarding	forwarding
	Out-coverage	Pre-configured or other	Pre-configured or other
	The resource pools for data and control may be the same
	Semi-static and/or pre-configured resource pool restricting the available
	resources for data and/or control may be needed
	D2D communication capable UE shall support Mode 2 for at least edge-of-
	coverage and/or out-of-coverage

[0500] In Table 5, Mode 1 and Mode 2 in a D2D resource allocation method may be divided as follows.

[0501] From a transmission UE perspective, UE may operate in the two types of mode for resource allocation:

[0502] Mode 1: eNodeB or rel-10 relay node schedules the exact resources used by UE to transmit direct data and direct control information

[0503] Mode 2: a UE on its own selects resources from resource pools to transmit direct data and direct control information

[0504] Referring to Table 5, resource allocation used for SA transmission and D2D data transmission in Mode 1 and Mode 2 may be implemented through an SIB in the case of the in-coverage scenario. That is, an eNB may notify UE of resource allocation for SA transmission and D2D data transmission through an SIB.

[0505] In some embodiments, scheduling assignment may be performed and data resources may be allocated using the dynamic control signal (e.g., a PDCCH, an EPDCCH, or a MAC CE) of an eNB.

[0506] In some embodiments, resource pools may be allocated in advance through an SIB, and UE may be notified of (time-frequency resources) detailed resource allocation information (SA resources and D2D data resources) through a dynamic control signal within the allocated resource range.

[0507] In this case, the SA for direct communication may deliver the detailed resource allocation information (e.g., using relative location information or offset information) used in direct data communication.

[0508] That is, UE may receive SA and data resource pools through an SIB and may receive detailed SA and data transmission resources through the SA.

[0509] If a plurality of resource pools has been allocated to UE in advance, SA may be used to indicate one or some of the allocated resource pools.

[0510] In Table 3, in the case of the out-coverage scenario, UE may be aware of SA resource pools and data resource pools based on resource configuration information that has been pre-configured or received from coverage UE.

[0511] In this case, if the UE has to determine detailed resources for SA transmission and D2D data transmission, it may autonomously select SA resources.

[0512] Thereafter, the UE may include resources allocated in relation to D2D data transmission in SA contents and transmit the SA contents to D2D reception UE so that the D2D reception UE is aware of a resource region in which D2D data is received.

[0513] In this case, in order to reduce information included in the SA contents, resource region information (e.g., time and frequency indices) in which SA has been detected may be used as part of D2D data resource allocation information.

[0514] That is, the final resource region is calculated using both the SA resource-related information and the SA contents information.

[0515] For example, an SA (transmission) resource-related parameter may be used to obtain only time domain information (e.g., a time domain parameter and a subframe index) of a D2D data resource region, and information delivered in SA may be used to provide notification of frequency domain information (e.g., a frequency domain parameter and an RB index).

[0516] In some embodiments, the SA resource-related parameter may be used to designate the absolute locations (e.g., time and frequency indices) of D2D data resources, and resource allocation information included in SA contents may be used to provide notification of the relative locations of D2D data resources.

[0517] In some embodiments, the SA (transmission) resource-related parameter may be used to provide notification of a random back-off or transmission probability value.

[0518] Furthermore, signaling contents transmitted from an eNB to D2D transmission UE may include a resource configuration, an MCS, etc. for direct scheduling assignment.

[0519] The signaling contents may be represented as Downlink Control Information (DCI) or a Scheduling Grant (SG).

[0520] The timing relation between an eNB-dynamic control signal and an SA transmission time is described in detail below.

[0521] If a D2D resource pool is allocated through a System Information Block (SIB) and UE autonomously determines SA resources and resources for D2D data transmission based on the allocated D2D resource pool, an eNB-dynamic control signal, such as a PDCCH/EPDCCH, may not be required.

[0522] In a situation in which all resources are managed by an eNB as in the in-coverage scenario, however, if an eNB controls D2D SA and resource allocation for direct data in real time, the utilization of the resources may become further efficient. In this case, an eNB-dynamic control signal is necessary.

[0523] Accordingly, a method using an eNB-dynamic control signal (e.g., a scheduling grant or an MAC CE using DCI) and when D2D transmission UE that has received an eNB-dynamic control signal (i.e., an eNB scheduling grant for SA and/or data for D2D) will transmit SA to D2D reception UE need to be clearly defined.

[0524] As described above, an eNB may transmit an SG to D2D UE for (1) scheduling regarding SA transmission and (2) scheduling regarding data transmission.

[0525] In this case, the scheduling may mean scheduling related to D2D transmission, and scheduling information may include resource allocation information, an MCS, an RV, and an NDI.

[0526] In some embodiments, an eNB may transmit a single SG to D2D UE in order to indicate whether it is scheduling regarding SA transmission or scheduling regarding D2D data transmission.

[0527] In this case, an implicit association may be formed between SA and data so that D2D UE is capable of estimating scheduled information for SA and data each.

[0528] For example, D2D UE may receive an SG related to SA transmission from an eNB and check the location or approximate location of D2D data transmission resources having linkage to the SA (or the same is true of scheduling information).

[0529] In some embodiments, D2D UE may receive an SG related to data transmission from an eNB and check a resource location and relation information related to SA transmission having linkage to data.

[0530] Methods 1 through 4 below show timing relations between a dynamic control signal transmitted from an eNB to D2D transmission UE and SA transmitted from D2D transmission UE to D2D reception UE.

[0531] That is, the timing relation between the reception of a Scheduling Grant (DCI) from an eNB and the transmission of Scheduling Assignment (SA) and/or data from D2D transmission UE to D2D reception UE is described in detail below with reference to FIGS. 22 to 25 in connection with the methods 1 through 4.

[0532] Method 1

[0533] FIG. 22 is a diagram showing an example of the timing relation between SG reception and SA transmission in D2D UE, which is proposed according the present disclosure.

[0534] FIG. 22 shows an example in which, if a D2D Scheduling Assignment (SA) subframe (SF) has been periodically configured, when D2D transmission UE receives a Scheduling Grant (SG) from an eNB in a D2D SA SF period (or a PSCCH period) 2201 at step S2210, the D2D transmission UE transmits a scheduling assignment in a D2D SA SF 2202 that first arrives after the received SG SF at step S2220.

[0535] Method 2

[0536] FIG. 23 is a flowchart illustrating an example of the timing relation between SG reception and SA transmission in D2D UE, which is proposed according to the present disclosure.

[0537] FIG. 23 shows a method for transmitting SA from D2D transmission UE to D2D reception UE in consideration of the processing time of UE (or a system) after receiving an SG from an eNB.

[0538] That is, the D2D transmission UE receives SG from the eNB, configures an SA based on the received SG, and transmits the SA to the D2D reception UE in consideration of the time taken to transmit the SA, that is, processing delay.

[0539] In this case, if the processing delay is taken into consideration, the SA transmission of the D2D transmission UE may be performed in a fourth subframe #n+4 after an SG subframe (subframe #n) received from the eNB.

[0540] That is, when D2D transmission UE receives an SG in a subframe #n at step S2301, it may transmit SA to D2D reception UE in a fourth subframe #n+4 2301 at step S2302.

[0541] In this case, if the fourth subframe #n+4 2301 is not a D2D SA subframe, the D2D transmission UE may transmit the SG in a D2D SA subframe 2302 that first arrives after the fourth subframe #n+4.

[0542] In contrast, if the D2D transmission UE receives the SG from the eNB in the subframe #n and a D2D SA SF that first arrives subsequently is present in the fourth subframe #n+4, the D2D transmission UE determines that the D2D SA SF is not valid or available.

[0543] Accordingly, the D2D transmission UE transmits the D2D SA in a subsequent (or next period) available D2D SA SF.

[0544] The n+4 is an example, and may be generalized as “n+k”—that is, D2D SA is transmitted in a k-th SA SF after the SG is received.

[0545] The value k may be configured by taking into consideration the development of the future technology, performance of UE, and so on.

[0546] Furthermore, the value k may be differently configured for each UE depending on the capability of the UE.

[0547] FIG. 23a shows an example of a method for transmitting SA in a subframe #n+k, and FIG. 23b shows an example of a method for transmitting SA in an SA SF that is first reaches after a subframe #n+k.

[0548] Regarding the configuration of the value k, the difference with an LTE (-A) system is that resources are not explicitly allocated, but a D2D resource pool is determined. In this case, resources are selected and transmitted, and different values are configured for each UE if a collision between resources is permitted.

[0549] The method of FIG. 23 may apply equally to D2D data transmission.

[0550] That is, when D2D UE receives control information (or scheduling information) related to D2D data transmission from an eNB in a subframe n, the D2D UE may transmit D2D data in a subframe n+k′ by taking into consideration the processing time of the D2D UE.

[0551] The control information related to the D2D data transmission may be an SG or SA related to the resource allocation of the D2D data transmission.

[0552] The value k′ may be configured differently from the value k at an SA transmission timing.

[0553] In general, the k′> (or =) k relation may be established by taking into consideration a probability that D2D data transmission may occur a bit later.

[0554] Method 3

[0555] Next, an operation in which SA SFs are configured as a group, that is, a plurality of SFs are allocated for SA and operated, is described below.

[0556] FIG. 24 is a diagram showing another example of the timing relation between SG reception and SA transmission in D2D UE, which is proposed according to the present disclosure.

[0557] FIG. 24 shows a method for transmitting SA from D2D transmission UE to D2D reception UE in the first SA SF after a subframe n+4 when the D2D transmission UE receives an SG (or resource allocation DCI) from an eNB in a subframe SF #n.

[0558] In this case, if the first SA SF after the subframe n+4 is a group of M consecutive SA SFs, when the D2D transmission UE receives the SG in the subframe SF #n at step S2410, it transmits the SA in the SA SF group that is first met after the subframe n+4 at step S2430.

[0559] In which of M SFs in the SA SF group the SA will be transmitted may be finally indicated through the SG at step S2420.

[0560] Furthermore, if an SA or data transmission subframe (SF) includes a plurality of subframes, a specific bit (or specific field) of a DCI format may be used to determine the location of the SA or data transmission subframe.

[0561] For example, a bit for differentiating between the DCI formats 0 and 1, a hopping bit, or some or all of RA bits may be used to determine the location of the SA or data transmission subframe.

[0562] Furthermore, the SG may be divided into one for SA and one for data, and may be further divided for special purposes if necessary.

[0563] Accordingly, a bit for differentiating between the DCI formats 0 and 1, a hopping bit, or some or all of RA bits may be used to distinguish the purpose of the SG.

[0564] Method 4

[0565] A method for providing notification of the location of an SA SF through Radio Resource Control (RRC) is described below.

[0566] FIG. 25 is a diagram showing yet another example of the timing relation between SG reception and SA transmission in D2D UE, which is proposed according to the present disclosure.

[0567] FIG. 25 shows a method in which the location of an SA SF is notified through RRC in advance at step S2510 and an SG (e.g., PDCCH DCI) is used merely for an activation purpose to enable the use of the SA SF at step S2520.

[0568] In this case, a special index may be defined to find out an association between RRC signaling and activation DCI.

[0569] That is, a DCI indicative of the activation of an SA SF may be defined to indicate the RRC of a certain index.

[0570] A DCI, that is, an SG, accurately indicates the activation of an SA SF or SF set transmitted through RRC. In this case, an RRC set including a series of indices mapped to the DCI may be designated in advance.

[0571] Furthermore, D2D transmission UE transmits SA to D2D reception UE through the SA SF whose activation has been indicated by the SG at step S2530.

[0572] A method for providing notification of the time location of SA resources and/or D2D data resources through the RRC signaling of FIG. 25 is described in detail later with reference to FIGS. 30 to 33.

[0573] The timing relation between SA transmission and D2D data transmission in D2D UE, which is proposed according to the present disclosure, is described in detail below with reference to FIGS. 26 to 28.

[0574] FIG. 26 is a diagram showing an example of the timing relation between D2D SA transmission and D2D data transmission, which is proposed according to the present disclosure.

[0575] Regarding the timing between a D2D SA SF and a D2D data SF, D2D data may be implicitly transmitted and received according to a predetermined rule.

[0576] FIG. 26 shows a method for transmitting SA from D2D transmission UE to D2D reception UE in a subframe #n at step S2610 and transmitting D2D data to the D2D reception UE in an available D2D data SF 2601 that first arrives after a subframe n+k at step S2620, as in the timing relation between SG transmission and SA transmission shown in FIG. 23.

[0577] Likewise, the value k is configurable, and may be configured to vary for each UE.

[0578] Furthermore, as in the timing relation between SG transmission and SA transmission shown in FIG. 24, UE may be notified of an available D2D data SF group, and a specific SF (e.g., a subframe #m) within the D2D data SF group may be separately indicated.

[0579] In this case, a parameter (k) indicative of the specific SF may be included in SA contents.

[0580] The value of the indication parameter k may be differently interpreted depending on the following conditions.

[0581] That is, the value of the indication parameter k may be differently interpreted depending on each UE, the location of a resource pool, the UE group, or the scenario (i.e., in-coverage, out-coverage, and edge-of-coverage).

[0582] FIG. 27 is a diagram showing another example of the timing relation between D2D SA transmission and D2D data transmission, which is proposed according to the present disclosure.

[0583] Unlike the method of FIG. 26, FIG. 27 shows a method for transmitting a D2D data SF within “n+k” (2701) at step S2720 when a D2D SA SF is determined (a subframe #n) at step S2710.

[0584] In this case, although D2D data is transmitted in a subframe right after the D2D SA SF, there is no problem if UE is notified of this in advance.

[0585] In this case, D2D reception UE may decode the D2D data by preparing to buffer both the SA SF and the data SF, which is received subsequent to the SA SF, by taking into consideration the processing time (or processing delay).

[0586] In this case, the value k is configurable, and may be configured to vary for each UE.

[0587] FIG. 28 is a diagram showing yet another example of the timing relation between D2D SA transmission and D2D data transmission, which is proposed according to the present disclosure.

[0588] That is, FIG. 28 shows a method for directly indicating a D2D data SF explicitly through SA.

[0589] Assuming that D2D reception UE receives SA in a subframe #n at step S2810, D2D transmission UE may calculate a value k based on some of SA contents or an SA transmission resource parameter and explicitly notify the D2D reception UE of the calculated value k in a subframe #n+k in which D2D data is received at step S2820.

[0590] A method for transmitting D2D data related to the valid period of SA contents is described below.

[0591] SA contents may indicate SA information for which an MCS value, whether frequency hopping is used or not, and frequency hopping-related resource allocation are applied or configured in a resource region for SA transmission.

[0592] FIG. 29 is a flowchart illustrating an example of a method for transmitting and receiving D2D data, which is proposed according to the present disclosure.

[0593] In the method of FIG. 29, if a D2D SA SF is periodically configured, it is assumed that D2D data between SA SF transmission periods is transmitted using the same SA value.

[0594] In this case, D2D reception UE that receives D2D data may receive multiple pieces of D2D data through the SA value that has been received once from D2D transmission UE.

[0595] That is, the D2D reception UE may determine that the same one SA value is applied to multiple data subframes.

[0596] Referring to FIG. 29, the D2D reception UE receives SA from the D2D transmission UE through a periodically configured SA subframe at step S2910.

[0597] Afterwards, the D2D reception UE receives at least one D2D data from the D2D transmission UE using the received SA for a specific interval of time at step S2920.

[0598] The specific interval of time may be an SA period or SA contents valid time interval in which the SA has been received.

[0599] The SA contents valid time interval may be determined in advance, may be simply defined as an SF index, or may be defined as a multiple of an SA SF period.

[0600] Furthermore, the SA contents valid time interval may be defined as a combination of an SA SF and a normal SF, or may be defined as a D2D data SF period or a multiple of the D2D data SF period.

[0601] In this case, the SF may mean a normal SF index or a D2D SF index.

[0602] In this case, if there are multiple pieces of D2D data for the specific interval of time, the SA includes resource allocation information related to the multiple pieces of D2D data.

[0603] That is, the D2D reception UE may receive multiple pieces of D2D data based on the SA received at step S2910, without receiving an additional SA for the specific interval of time.

[0604] In another embodiment, D2D control information may be transmitted as control information transmitted through SA and control information embedded (or included) in D2D data, separately.

[0605] That is, (1) control information, such as RA or an MCS, and (2) control information, such as an NDI, may be transmitted separately through direct SA and direct data, respectively, based on the attributes of the control information.

[0606] FIGS. 30 to 33 are diagrams showing examples of methods for providing notification of the locations of SA resources and/or D2D data resources, which is proposed according to the present disclosure.

[0607] FIGS. 30 and 31 show methods for transmitting and receiving SA and/or D2D data using a subframe pattern in which SA resources and/or D2D data resources may be transmitted and received.

[0608] A subframe pattern in which the SA resources and/or the D2D data resources may be transmitted and received may be represented as a Resource Pattern for Transmission (RPT).

[0609] The RPT means time resources and/or frequency resources for guaranteeing a plurality of transmission opportunities for D2D data Transport Blocks (TBs).

[0610] Accordingly, the RPT may be divided into a Time-RPT (T-RPT) and a Frequency RPT (F-RPT).

[0611] Specifically, FIG. 30 shows a method for explicitly notifying D2D UE of a subframe pattern related to SA resources and/or D2D data resources. FIG. 31 shows a method for implicitly transmitting a subframe pattern related to SA resources and/or D2D data resources to D2D UE.

[0612] UE uses some of all UL subframes as D2D subframes.

[0613] That is, the UE performs communication with an eNB in the remaining UL subframes, other than the D2D subframes, among all the UL subframes.

[0614] Accordingly, eNB-to-UE transmission and D2D Tx UE-D2D Rx UE transmission do not occur at the same time.

[0615] If UE transmits a D2D signal to another UE in a D2D subframe, it may not receive a D2D signal from the another UE in the same band of the D2D subframe. The reason for this is that the D2D signal transmitted by the UE interferes strongly with the reception of a D2D signal from the another UE.

[0616] In order to solve such a problem, a subframe pattern (or configuration) between a D2D transmission subframe in which a D2D signal is transmitted and a D2D reception subframe in which a D2D signal is received may be differently configured.

[0617] Furthermore, in order to solve the problem of interference caused by the transmission and reception of D2D signals by a single UE and to reduce interference between two adjacent UEs by decreasing the probability of use of redundant time resources by the two UEs, the patterns of subframes in which the two UEs transmit D2D signals may be differently configured.

[0618] Specifically, an eNB can solve the interference problem which may occur between UEs by configuring a subframe pattern used for D2D transmission by each UE by taking into consideration the distance between the UEs (by checking the degree of mutual interference).

[0619] In this case, the eNB explicitly notifies D2D UE of D2D transmission subframe patterns 3010 through high layer signaling, such as RRC signaling.

[0620] In this case, the eNB may dynamically configure the D2D transmission subframe pattern in the D2D UE through an EPDCCH or a PDCCH. That is, if a D2D transmission subframe pattern is transmitted to D2D UE through an EPDCCH or PDCCH, there is an advantage in that the D2D transmission subframe pattern can be configured by rapidly handling a change of the location of UE.

[0621] According to another method, in order to reduce a signaling burden of an eNB, the eNB may not determine a D2D (transmission) subframe pattern and notify UE of the D2D (transmission) subframe, but instead the UE may autonomously select a required D2D (transmission) subframe pattern.

[0622] That is, such a method is a method for D2D UE to implicitly obtain a D2D subframe pattern.

[0623] In this case, the D2D UE may select the D2D subframe pattern using a similar random method based on its own UE ID (or a UE-specific parameter having a similar characteristic).

[0624] In some embodiments, D2D UE may receive minimum signaling information from an eNB and select a subframe pattern using a similar random method using the minimum signaling information as a factor for determining a similar random value.

[0625] If such an implicit subframe pattern selection method is used, the aforementioned interference between UEs can be reduced because proper subframe patterns (or subframe sets) are given and a subframe pattern is randomly selected from the proper subframe patterns (or subframe sets).

[0626] As shown in FIG. 30, an eNB may deliver the candidate group 3010 of subframe patterns related to D2D transmission, which may be potentially used by specific UE, through high layer signaling, such as RRC signaling, and transmit (or designate) one or more subframe patterns 3020 to be actually used for D2D transmission at a specific point of time through an EPDCCH or a PDCCH.

[0627] Specifically, the eNB transmits predefined N subframe patterns, that is, a candidate group of N subframe patterns (e.g., a subframe pattern #0, a subframe pattern #1, a subframe pattern #2, . . . , ), to D2D UE through high layer signaling, such as RRC signaling.

[0628] Thereafter, the eNB specifies one or more of the N subframe patterns 3010 as a D2D transmission subframe pattern 3020 and transmits the D2D transmission subframe pattern 3020 to the D2D UE through a PDCCH or an EPDCCH.

[0629] In this case, in the process for transmitting the predefined N subframe patterns to the D2D UE, the eNB may render the actual subframe pattern #k (k=0, 1, 2, . . . , ) in a bitmap of subframes (SF pattern #0 (10001010), SF pattern #1 (00111001), . . . ) repeating with a given periodicity.

[0630] Furthermore, as shown in FIG. 31, the eNB may transmit the candidate group 3010 of subframe patterns related to D2D transmission, which may be potentially used, to specific UE through high layer signaling, such as RRC signaling. D2D UE that has received the candidate group 3010 may select the subframe pattern 3120 used for actual transmission at a specific point of time using a UE identification parameter (e.g., a UE ID 3110).

[0631] In this case, the UE identification parameter (or seed) 3110 may be allocated in advance by the eNB.

[0632] Thereafter, the D2D UE may perform D2D transmission and reception through the selected subframe pattern.

[0633] FIGS. 32 and 33 are diagrams showing examples of methods for changing a subframe pattern related to SA resources and/or D2D data resources, which is proposed according the present disclosure.

[0634] FIG. 32 shows a method for explicitly providing notification of a changed subframe pattern, and FIG. 33 shows a method for implicitly providing notification of a changed subframe pattern.

[0635] FIGS. 32 and 33 show operations for D2D UE to change a subframe pattern allocated thereto using the methods of FIGS. 30 and 31.

[0636] FIGS. 32 and 33 show a subframe pattern repeating with a periodicity of 8 ms (i.e., 8 subframes). An eNB may transmit a subframe pattern #0{10001010} 3210 and a subframe pattern #1{00111001} 3210 in advance to D2D UE through high layer signaling.

[0637] In this case, the value “1” is a subframe related to D2D transmission, and it means that a signal related to D2D transmission may be transmitted and received in a corresponding subframe.

[0638] Furthermore, the value “0” is a subframe not related to D2D transmission, and this means that a signal related to D2D transmission may not be transmitted and received in a corresponding subframe.

[0639] The meanings of the value “0” and the value “1” may be reversed.

[0640] Thereafter, the eNB designates a D2D subframe pattern (e.g., an SF pattern #0 3220) that will be actually used by D2D UE through a PDCCH. The D2D UE operates based on the designated D2D subframe pattern.

[0641] Thereafter, the eNB transmits D2D subframe pattern change information 3230, providing notification of a changed D2D subframe pattern, to the D2D UE through a PDCCH (or through different control information or different message or through RRC signaling) if the D2D subframe pattern has been changed.

[0642] The D2D subframe pattern change information may designate a changed subframe pattern using some fields within a PDCCH or EPDCCH.

[0643] If existing DCI for an UL grant is reused for DCI for D2D, it may be used as subframe pattern change information to designate a changed subframe pattern using one of the DCI fields that is not used.

[0644] Some DCI fields that are not used may include an indicator to determine the DCI formats 0/1A, a CQI request field, and an NDI field.

[0645] Part of a DM RS cyclic shift field or MCS/RV field using a plurality of bits may be used.

[0646] If resources for scheduling assignment transmission and resources for D2D data transmission are designated to UE through a single PDCCH or EPDCCH at the same time, a subframe pattern for scheduling assignment and a subframe pattern for D2D data may be allocated to respective states designated by the fields within the DCI.

[0647] In the method of FIG. 33, UE may randomly select a D2D subframe pattern (e.g., an SF pattern #0 3320) that belongs to the candidate group of D2D subframe patterns and that will be actually used by using a UE ID, and the UE operate based on the selected D2D subframe pattern.

[0648] In this case, an eNB may transmit a D2D subframe pattern (change) indicator, indicating that a D2D subframe pattern has been changed, to the D2D UE through a PDCCH (or different control information or different message or through RRC signaling).

[0649] In this case, the D2D UE may randomly reselect a D2D subframe pattern (e.g., an SF pattern #1 3330) using a pseudo-random selection parameter (seed, a D2D UE identification parameter) using a UE ID.

[0650] In this case, the eNB may notify the D2D UE of the UE ID in advance through RRC signaling.

[0651] That is, if the D2D UE selects or reselects a subframe pattern using a similar random method, the eNB may previously deliver a parameter or seed value for determining a similar random value to the D2D UE.

[0652] Furthermore, the D2D UE may determine the index of a D2D transmission subframe using a similar random value without a pattern.

[0653] In this case, the eNB may deliver a parameter or seed value to determine the similar random value to the D2D UE.

[0654] Furthermore, the D2D UE may determine a subframe pattern or the index of a subframe based only on signaling information for determining such a similar random value. A unique value of the D2D UE may be included in the signaling information, based on which the subframe pattern or the index of the subframe may be determined.

[0655] In another example, a method for D2D reception UE to obtain the transmission bandwidth of SA in order to detect the SA transmitted by D2D transmission UE is described below.

[0656] In this case, the transmission bandwidth of the SA may be pre-fixed so that the D2D reception UE is aware of the transmission bandwidth of the SA.

[0657] In this case, a portion that belongs to a resource allocation field included in an SG and that corresponds to the number of allocated RBs may be fixed as a predetermined value, such as “0”, or may be defined as the pre-fixed transmission bandwidth of SA.

[0658] A field (or bits) included in the SG related to the transmission bandwidth of the SA may be used for other purposes (e.g., for the purpose of designating the actual location of an SA SF within an SA SF group) in addition to the transmission bandwidth of the SA.

[0659] The UE scheduling of eNB-to-D2D transmission (Tx) (and/or D2D reception (Rx)) for D2D transmission is described below with reference to FIGS. 34 to 37.

[0660] FIG. 34 is a flowchart illustrating an example of a UE scheduling method for D2D transmission to which a method proposed in the present disclosure may be applied.

[0661] First, the eNB performs a Scheduling Grant (SG) procedure along with D2D transmission (Tx) UE or D2D reception (Rx) UE (Step#1, S3410).

[0662] That is, the eNB transmits an SG related to D2D transmission to the D2D Tx UE or the D2D Rx UE.

[0663] The SG procedure (Step#1) may be divided into the following two methods.

[0664] (1) The first method Method#1 is a method for allocating D2D transmission-related resources through RRC signaling and then dynamically controlling detailed operations, such as the activation/release of the allocated resource, through a physical/MAC control channel (e.g., a PDCCH).

[0665] (2) The second method Method#2 is a method for controlling a D2D operation by transmitting resource allocation and/or scheduling information related to D2D transmission through a physical/MAC control channel.

[0666] In the methods (1) and (2), the D2D UE may receive scheduling information (e.g., an MCS, an RV, or a DM RS parameter) related to D2D communication from the eNB and determine D2D transmission-related resources based on the scheduling information, or the D2D UE may autonomously determine D2D transmission-related resources.

[0667] Resource allocation information may be included in the scheduling information, and the scheduling information and the resource allocation information may be separately interpreted.

[0668] If the D2D UE receives scheduling information related to D2D transmission from the eNB according to the method (1), it may receive the scheduling information through an RRC signal and/or a control channel, such as a PDCCH.

[0669] In this case, if the D2D UE receives the scheduling information from the eNB through RRC signaling, the DCI format of the PDCCH may not include fields, such as an MCS, RV, and DM RS parameter related to D2D transmission.

[0670] Accordingly, if fields related to D2D transmission are defined to be included in the DCI format of a PDCCH, the total length of the DCI format may be reduced by eliminating the unnecessary fields, or the DCI format may be made to be the same length and transmitted by zero padding or the like.

[0671] Likewise, if the D2D UE itself determines scheduling information, such as an MCS or an RV, contents fields related to scheduling information, such as an MCS and an RV, are not required in a PDCCH transmitted in the method (1) or (2).

[0672] Accordingly, the unnecessary fields may be eliminated, or zero-padding may be applied.

[0673] The method (1) is described in more detail later with reference to FIG. 35, and the method (2) is described in more detail later with reference to FIG. 36.

[0674] Thereafter, the D2D transmission UE performs a scheduling procedure related to D2D data transmission for the transmission and reception of D2D data to and from the D2D reception UE (Step#2, S3420). That is, the D2D transmission UE performs an SA transmission procedure.

[0675] Step#2 may be used along with the methods used in Step#1.

[0676] In this case, information which may be included in SA may be as follows. In particular, information related to resources for D2D data reception may be included in the SA.

[0677] Scheduling information (including resource allocation information) related to SA transmission may be construed as being transmitted from the eNB to the D2D transmission UE (through an SG). The SA transmission may be construed as being transmitted from the D2D transmission UE to the D2D reception UE.

• • [0678] Information related to resources for data reception: information related to resources for D2D data reception
  • [0679] RB assignment: RB assignment information
  • [0680] Number and pattern of retransmissions: information about the number and pattern of retransmissions
  • [0681] Frequency hopping pattern: information about a frequency hopping pattern
  • [0682] SPS (incl. periodicity) of data: information about data periodicity
  • [0683] Target ID: ID information of D2D reception UE
  • [0684] MCS/RV of data
  • [0685] Timing advance of data

[0686] Next, a method for D2D transmission UE to receive an SG from an eNB and determine a point of time at which the D2D transmission (Tx) UE transmits SA to D2D reception (Rx) UE is described below.

[0687] The received SG may include scheduling information (including resource allocation information) related to the SA.

[0688] First, it is assumed that the eNB is aware of a D2D transmission subframe in which the D2D transmission UE may transmit the SA.

[0689] The eNB transmits the SG to the D2D transmission UE in an n−k1 (k1 is an integer) subframe of an SA transmission subframe(n), so the D2D transmission UE may transmit the SA to the D2D reception UE.

[0690] The value “k1” may be about 4 when the receive processing capability of UE is taken into consideration in an LTE (-A) system.

[0691] The value “k1” may be 2 or 3 according to the evolution of the technology.

[0692] The D2D transmission UE that has received the SG may also check the location of a D2D data transmission subframe through the received SG.

[0693] That is, the SG may be used for D2D data transmission timing (subframe) and frequency resource allocation, in relation to D2D data transmission, as well as for SA scheduling.

[0694] Next, a method for D2D transmission UE to receive an SG from an eNB and transmitting SA to D2D reception UE in a SA transmission-valid resource after a certain time is described below.

[0695] The received SG may include scheduling information related to SA transmission

[0696] The eNB transmits the SG to the D2D transmission UE based on a point of time at which D2D transmission resources were requested from the D2D transmission UE without checking an SA transmission valid subframe in detail.

[0697] That is, when the D2D transmission UE receives the SG from the eNB, it generates SA based on the received SG.

[0698] Thereafter, the D2D transmission UE checks an SA-available subframe in which the generated SA may be transmitted and transmits the generated SA to the D2D reception UE in an available or valid D2D subframe (i.e., a valid subframe in terms of SA transmission).

[0699] In this case, the D2D transmission UE receives the SG from the eNB, but may not immediately transmit the SA to the D2D reception UE even though the next subframe is available.

[0700] The reason for this is that time corresponding to “n+k2” is required in order for the D2D transmission UE to receive the SG, perform reception processing, generate SA using the SG, that is, information related to the received SA, and prepare for D2D data transmission.

[0701] In this case, k2 has an integer value. The value “k2” may be 2 or 3 according to the evolution of the technology. That is, the value “k2” may have various values, such as 1, 2, 3, or 4 depending on the reception capability of the UE.

[0702] If k2=4, the D2D transmission UE receives an SG from the eNB and transmits SA to the D2D reception UE after 4 subframes.

[0703] If there is no available subframe for the SA transmission immediately after the 4 subframes, the D2D transmission UE transmits the SA to the D2D reception UE in the next subframe.

[0704] If the next available subframe is not present, the D2D transmission UE may transmit the SA to the D2D reception UE in the next subframe.

[0705] That is, it may be interpreted that the SA is transmitted in the earliest SA-available subframe after the subframe n+4.

[0706] In this case, all subframes not designated as D2D transmission may correspond to subframes in which SA transmission is impossible.

[0707] In some embodiments, subframes in which a synchronization signal is transmitted, such as subframes 0 and 5, may be excluded from the SA-available subframes.

[0708] In some embodiments, subframes in which a paging subframe is transmitted, such as subframes 0, 4, 5, and 9, may also be excluded from the SA-available subframes.

[0709] In this case, if a channel for delivering D2D-essential information is determined in a specific D2D subframe, the specific D2D subframe may be excluded from the SA-available subframe even if the specific D2D subframe (e.g., a WAN synchronization signal and a channel similar to a BCH) is designated as a D2D subframe.

[0710] In some embodiments, a dedicated subframe for SA transmission may be configured, and SA may be transmitted only in the SA-dedicated subframe.

[0711] That is, the D2D transmission UE receives the SG from the eNB (in a subframe n) and may transmit the SA to the D2D reception UE in an SA (transmission)-available subframe after the subframe n+k3.

[0712] In this case, the D2D UE which has received the SG may also check the location of a data transmission subframe. That is, the SG may also be used for data transmission timing and frequency resource allocation, in relation to data transmission, as well as for SA scheduling.

[0713] Thereafter, the D2D transmission UE transmits D2D data to the D2D reception UE based on the SA (Step#3, S3430).

[0714] In this case, the D2D transmission UE may transmit required control information along with the D2D data.

[0715] The control information may be transmitted in a piggyback fashion along with the D2D data.

[0716] Next, the validity of SG is described below.

[0717] If D2D UE receives an SG1 from an eNB and then receives an SG2 from the eNB, the D2D UE may determine that the received SG1 is no longer valid.

[0718] A point of time at which the validity of SG is determined may apply after the n+k4 subframe after a subsequent transmitted SG, that is, a SG2, is received (in a subframe n).

[0719] In this case, the value “k4” is an integer, and the value “k4” may have a value of 2, 3, or 4 by taking into consideration the point of time at which the SG2 may be actually applied,

[0720] Furthermore, the eNB may transmit the SG1 and the SG2 to the D2D UE at the same time.

[0721] In this case, the SG1 and the SG2 may be merged into a single DCI format and transmitted.

[0722] If separate channel coding is performed on each SG, the probability that the D2D UE may successfully receive each SG may be increased.

[0723] As described above, the D2D UE may provide feedback on the results of the reception of each SG to the eNB and use a PUCCH as a channel for providing feedback on the results of the reception of each SG.

[0724] Furthermore, the transmission power control for the D2D UE may be implemented through the SG.

[0725] In this case, the eNB may control the transmission power of the D2D UE by transmitting a TPC command to the D2D UE using a TPC field or the DCI formats 3/3A.

[0726] If the DCI formats 3/3A are used, the eNB may reserve and use a specific field of the corresponding format for D2D power control.

[0727] This field may be partitioned in advance to indicate whether it is for D2D power control or for LTE (-A) power control through RRC signaling.

[0728] Furthermore, a valid time when the SG is available may be determined.

[0729] That is, after a lapse of a specific time (or a specific number of subframes) or a specific number of D2D subframes since the D2D UE receives the SG from the eNB, the D2D UE may automatically discard the received SG.

[0730] In some embodiments, an SG timer may be newly defined so that the sG may be considered invalid when the SG timer is expired.

[0731] In some embodiments, the preceding SG may be defined as valid until the D2D UE receives the next SG.

[0732] In some embodiments, after receiving an SG, the D2D UE discards the received SG after a specific time or a specific number of subframes. If another SG has been previously received from the eNB, the D2D UE may discard the previously received SG without the lapse of the specific time.

[0733] FIG. 35 is a diagram showing an example of a UE scheduling method for D2D transmission using RRC signaling, to which a method proposed in the present disclosure may be applied.

[0734] That is, FIG. 35 shows a method by which the step S3410 of FIG. 34 is embodied.

[0735] The steps S3520 and S3530 of FIG. 35 are the same as the steps S3420 and S3430 of FIG. 34, and thus only differences between them are described below.

[0736] First, an eNB performs a Scheduling Grant (SG) procedure along with D2D Tx UE or D2D Rx UE (Step#1, S3510).

[0737] As described above with reference to FIG. 34, the step S3510 may be implemented through two methods.

[0738] (1) The first method Method#1 is a method for allocating D2D transmission-related resources through RRC signaling and additionally controlling detailed dynamic operations for the allocated resources, such as activation/release, through a physical/MAC control channel (e.g., a PDCCH).

[0739] (2) The second method Method#2 is a method for controlling a D2D operation by transmitting resource allocation and/or scheduling information related to D2D transmission through a physical/MAC control channel.

[0740] The method Method#1 of (1), that is, RRC signal and dynamic control signal (e.g. (E)PDCCH, PHICH) based scheduling (e.g. semi-static scheduling) for SA (and data, is described in more detail below.

[0741] The method (1) may be divided into 1) RRC signaling transmission for overall resource configuration/allocation for SA (and/or data) transmission S3511 and 2) a dynamic control information transmission (S3512) method for the activation/release of SA (and data) resources allocated through 1).

[0742] First, RRC signaling transmission is described.

[0743] RRC Signaling: Overall Resource Configuration/Allocation for SA (and Data)

[0744] As in an LTE Semi-Persistent Scheduling (SPS) scheduling method, an eNB allocates a specific resource pool (or a specific resource set/group) related to D2D transmission to D2D UE through RRC signaling.

[0745] Similarly, the eNB may allocate a monitoring resource for D2D reception to the D2D UE.

[0746] The specific resource region may be a subframe(s) or a set of resource blocks.

[0747] Accordingly, the D2D UE may perform blind demodulation (or blind decoding) on D2D data or SA by monitoring the specific resource region.

[0748] The monitoring resource may mean a resource that provides notification of monitoring so that the D2D UE performs blind decoding on SA and/or D2D data (Tx-to-Rx for D2D).

[0749] The phrase “A and/or B”, as used herein, may be construed as having the same meaning as at least either A or B (A, B, and A&B).

[0750] The method (1) may be used to provide notification of a data resource region, that is, for D2D data scheduling, as well as for SA scheduling.

[0751] That is, the method (1) means an operation for allocating resources related to D2D transmission through RRC and dynamically activating or releasing the resources using a physical layer and an MAC layer control channel, similarly to Semi-Persistent Scheduling (SPS).

[0752] For more details of the operation, reference may be made to FIGS. 30 to 33.

[0753] Thereafter, the steps S3520 and S3530 are performed.

[0754] FIG. 36 is a diagram showing an example of a UE scheduling method for D2D transmission using a physical layer channel, to which a method proposed in the present disclosure may be applied.

[0755] That is, FIG. 36 shows a method by which the step S3410 of FIG. 34 is embodied.

[0756] The steps S3620 and S3630 of FIG. 36 are the same as steps S3420 and S3430 of FIG. 34, and thus only differences between them are described below.

[0757] First, an eNB performs a scheduling grant procedure along with D2D Tx UE or D2D Rx UE (Step#1, S3610).

[0758] As described above, Step#1 may be implemented through two methods.

[0759] (1) The first method Method#1 is a method for allocating D2D transmission-related resources through RRC signaling and additionally controlling a detailed dynamic operation for the allocated resources, such as activation/release, through a physical/MAC control channel (e.g., a PDCCH).

[0760] (2) The second method Method#2 is a method for controlling a D2D operation by transmitting resource allocation and/or scheduling information related to D2D transmission through a physical/MAC control channel.

[0761] The phrase “A and/or B”, as used herein, may be construed as having the same meaning as at least either A or B.

[0762] The method (2), that is, an (Enhanced) PDCCH transmission method based on dynamic scheduling, is described below with reference to FIG. 36.

[0763] The method (2) refers to a method for notifying the D2D Tx UE (and/or the D2D Rx UE) of an MCS, an RV, an NDI, power control, a PMI, etc. for D2D data demodulation, in addition to resource allocation using a channel (e.g., an EPDCCH, PDCCH, PHICH, or new channel) for delivering control information in a physical layer (or including an MAC layer), instead of transmitting scheduling information (including resource allocation) related to D2D transmission through RRC (S3611).

[0764] The resource allocation, MCS, RV, NDI, power control, PMI, etc. may be called scheduling information related to D2D transmission.

[0765] The purpose of use of SG may be variously defined, apart from the aforementioned purposes of use.

[0766] For example, the SG may be used to notify of the fact that the contents of scheduling information related to D2D transmission have been changed.

[0767] The meaning of the change includes a modification, deletion, and addition.

[0768] In this case, the same signaling format as the SG may be used, or a different signaling format from that of the SG may be used.

[0769] The scheduling information included in the SG may mean a change of D2D transmission-related resource regions in which RC signaling has been designated, a change of resources that need to be used by the D2D Tx UE (and/or the D2D Rx UE) in a corresponding resource region, a change of resource regions substantially allocated by the SG, a change of resource region groups, or a change of some or all of SA contents.

[0770] The SA contents include a variety of types of scheduling information, in addition to RA. The D2D Tx UE (and/or the D2D Rx UE) is notified of a change of the contents of one or more of the variety of types of scheduling information, including the RA, through the SG.

[0771] The eNB may generate a new, compact SG by reducing the bit field of the SG and use the new SG.

[0772] Furthermore, when implementing SG/SA update, like resource re-allocation related to D2D transmission, a PHICH, as well as a PDCCH and an EPDCCH, may be used.

[0773] That is, the eNB may use PHICH resources to notify the D2D UE whether there is a change of SG/SA.

[0774] The D2D UE may monitor a PHICH including information indicative of a change of SG/SA and receive the changed SG/SA.

[0775] The D2D UE receives a modified SG/SA after a time previously designated by the eNB or in a previously designated interval of time through an SG/SA modification notification.

[0776] In this case, the modification notification may have two meanings.

[0777] The first meaning is that the D2D UE is notified that SA will be changed and the D2D UE needs to receive the changed SA through SG monitoring in order to be aware of the changed SA.

[0778] The second meaning is that the D2D UE is notified that SG has been changed or will be changed at a specified point of time and thus the D2D UE needs to receive the SG that has been changed or will be changed.

[0779] As described above, the SG may be used for data scheduling, as well as for SA scheduling.

[0780] Thereafter, the steps S3620 and S3630 are performed.

[0781] FIG. 37 is a flowchart illustrating an example of a method for performing an HARQ procedure for an SG, to which the present disclosure may be applied.

[0782] The steps S3710, S3730, and S3740 of FIG. 37 are the same as the steps S3410 to S3430 of FIG. 34, and thus only differences between them are described below.

[0783] After the step S3710, D2D UE and an eNB perform an SG Hybrid Automatic Retransmission reQuest (HARQ) procedure at the step S3720.

[0784] That is, the D2D UE may transmit a response to a received SG to the eNB between a point of time at which the D2D UE receives the SG from the eNB and a point of time at which the D2D UE transmits SA to another D2D UE. The response may be ACK or NACK.

[0785] As described above, the SG may be control information or resource allocation information related to the SA and/or the D2D data transmission, as in the activation/deactivation of allocated resources in SPS.

[0786] The control information or resource allocation information related to the SA and/or the D2D data transmission may be represented as scheduling information related to D2D transmission.

[0787] The SG HARQ procedure in the step S3720 can prevent performance deterioration or any situation in which communication is impossible, which may occur when the D2D UE does not receive the SG from the eNB and therefore continues to transmit the same SA since the D2D UE cannot transmit SA to another D2D UE or apply any change in the SA contents that have already been transmitted.

[0788] Accordingly, there is a need for confirmation regarding whether an SG has been received. In this case, an UL ACK/NACK mechanism may be used.

[0789] That is, the D2D UE may transmit a response (i.e., ACK or NACK) to the SG to the eNB using an existing PUCCH structure or in an existing embedded PUCCH to PUSCH form (i.e., in an UCI piggyback form).

[0790] In this case, if the SG complies with a mechanism, such as a PDCCH or EPDCCH format, a response to the SG may be easily used using a PUCCH resource connected to each DCI index of the PDCCH or EPDCCH.

[0791] In this case, if information included in the SG is separated into information for SA scheduling and information for D2D data scheduling and received by the D2D UE, the D2D UE may provide a feedback response about whether each SG has been received.

[0792] Furthermore, since there are up to four types of response to the SG, the size of the response may be represented as 1 bit to 2 bits.

[0793] In this case, the response to the SG may be fed back through a PUCCH.

[0794] Hereinafter, methods for sending and receiving SA and/or D2D data will be discussed in detail with reference to FIGS. 38 to 42.

[0795] FIG. 38 is a diagram showing an example of a D2D operation procedure and its associated signaling transmission and reception method, to which a method proposed in the present disclosure may be applied.

[0796] FIG. 38 shows a D2D operation procedure in D2D communication Mode 1 by control from an eNB and a method of performing D2D communication by sending and receiving information associated with this procedure.

[0797] As illustrated in FIG. 38, an SA (Scheduling Assignment) resource pool 3810 and/or data resource pool 3820 related to D2D communication may be pre-configured, and the pre-configured resource pool may be transmitted from an eNB to D2D UEs through high layer signaling.

[0798] The high layer signaling may be RRC signaling.

[0799] The phrase “A and/or B”, as used herein, may be construed as having the same meaning as at least either A or B (A, B, and A&B).

[0800] The SA resource pool and/or data resource pool refers to resources reserved for a UE-to-UE (D2D) link or D2D communication.

[0801] The UE-to-UE link may be represented as a sidelink.

[0802] Specifically, the SA resource pool refers to a resource region for transmitting an SA, and the data resource pool refers to a resource region for transmitting D2D data.

[0803] The SA may be transmitted in an SA period 3830, and the D2D data may be transmitted in a data transmission period 3840.

[0804] The SA period and/or the data transmission period may be transmitted from an eNB to D2D UE through a D2D grant.

[0805] Alternatively, the SA period may be transmitted through a D2D grant, and the data transmission period may be transmitted through an SA.

[0806] The D2D grant represents control information for transmitting an SA (Scheduling Assignment) required for D2D communication from an eNB to D2D UE.

[0807] The D2D grant may be represented as a DCI format 5 and transmitted over a physical layer channel, such as PDCCH or EPDCCH, or a MAC layer channel.

[0808] The D2D grant may include information related to data transmission as well as information related to SA transmission.

[0809] In an example, the SA may include RA (Resource Allocation), MCS, NDI (New Data Indicator), Redundancy Version (RV), etc.

[0810] As discussed previously, an SA resource pool for the SA transmission may be transmitted through RRC signaling.

[0811] The SA may be transmitted over a PSCCH (Physical Sidelink Control Channel), and the D2D data may be transmitted over a PSSCH (Physical Sidelink Shared Channel).

[0812] D2D transmission UE may receive SA information, especially resource allocation (RA) information (hereinafter, “SA RA”) for transmitting an SA, from an eNB through a D2D grant.

[0813] In this case, the D2D transmission UE may transmit the SA RA information received from the eNB directly to D2D reception UE, or may generate new SA RA information based on the received SA RA information and then transmit the newly generated SA RA information to the D2D reception UE.

[0814] Here, if the D2D transmission UE generates a new SA RA, the D2D transmission UE has to perform a SA resource allocation only within a resource region (resource pool) indicated by the D2D grant RA.

[0815] That is, this indicates that only some resource region SA RA among the resource regions D2D grant RAs permitted for use by the eNB may be selected for SA transmission.

[0816] On the contrary, the D2D transmission UE may use the D2D grant RA allocated by the eNB as it is.

[0817] In this case, however, the D2D transmission UE transmits dummy data even if there is no D2D data to transmit or only occupies a D2D SF subframe without D2D data transmission, which may lead to a waste of D2D SF.

[0818] The following relation may be established among resource pools related to D2D communication.

[0819] 1. RRC configured D2D resource pool (A)

[0820] 2. D2D grant RA indicating resource pool (B)

[0821] 3. SA RA indicating resource pool (C)

[0822] If the resource pools satisfy the relation A>=B>=C, this prevents random occupation of D2D SF for D2D transmission and results in protecting resources for WAN data transmission.

[0823] FIG. 39 shows an example of a flowchart related to the method of FIG. 38.

[0824] First of all, an SA resource pool and/or D2D data resource pool related to D2D communication is configured by a high layer (S3910).

[0825] Afterwards, an eNB transmits the SA resource pool and/or D2D data resource pool to D2D UE through high layer signaling (S3920).

[0826] Afterwards, the eNB transmits SA-related control information and/or D2D data-related control information either individually or collectively to D2D transmission UE through a D2D grant (S3930).

[0827] The control information may include RA, MCS, NDI, RV, etc.

[0828] Afterwards, the D2D transmission UE transmits an SA and/or D2D data to D2D reception UE based on the information received in the step S3930 (S3940).

[0829] The SA transmission and the D2D transmission may performed simultaneously, or the D2D data transmission may be performed after the SA transmission.

[0830] Next, allocation of D2D-related resources by semi-persistent scheduling (SPS) will be discussed.

[0831] In this case, D2D UE may have D2D communication-related resources (SA resource pool and/or data resource pool) reserved and allocated in advance through RRC signaling, as shown in FIGS. 38 and 39.

[0832] Afterwards, the D2D UE may receive information on the availability of the reserved and allocated D2D communication-related resources from the eNB through a D2D grant.

[0833] That is, the eNB may instruct the D2D UE to activate the use of the reserve and allocated resources or to stop or release the use of the resources through an (E)PDCCH or the like.

[0834] Here, the eNB may indicate the release of use of D2D communication-related resources allocated to the D2D UE by setting all SA RAs to 0 and transmitting them to the D2D UE.

[0835] In another method, the eNB may set TPC and MCS fields to a specific value (e.g., “0”) and, if a specific condition is met by a combination of various fields, may indicate the release of use of D2D communication-related resources.

[0836] In yet another method, MCS may be “1000 . . . 0000”, with the MSB (Most Significant Bit) set to 1 and the remaining bits set to 0, so as to indicate the release of use of D2D communication-related resources.

[0837] Next, a method of activating/release the use of each resource when transmitting SA resource information and D2D data resource information separately will be discussed.

[0838] In an example, if an s resource-related portion and a data resource-related portion are separated within a specific field, the eNB may instruct the D2D UE to activate and release the use of each resource.

[0839] The specific field may be a TPC field, and the TPC filed may be described by way of example.

[0840] Moreover, the eNB may indicate the release of resource use at different locations by taking an SA transmission period and a data transmission period into consideration.

[0841] The above method may be implemented by transmitting different information (SA resource information and data resource information) to different TPCs, or by allocating different bit sequences to two TPCs, respectively.

[0842] Alternatively, the release of resource use may be indicated by notifying of from which numbered data resource will be released since the point of time of SA resource release.

[0843] Next, a method of updating an SA RA will be discussed.

[0844] In a case where D2D UE receives SA RA information from an eNB through a D2D grant, the actual point of time at which the D2D UE delivers an SA is consistent with an SA periodicty for SA transmission.

[0845] Here, the eNB transmits SA RA information to the D2D UE through a D2D grant at the point of time of SA transmission, so the update time of the SA RA information is consistent with an SA transmission period.

[0846] Specifically, a minimum period for the update of SA RA information may be the same as the SA period.

[0847] That is, if an SA is transmitted even when there is no update of SA RA information, the SA RA information update periodicity and the SA periodicity may be construed as the same.

[0848] On the contrary, the update of TPC information corresponding to transmission power control information may be designed differently from the SA RA information.

[0849] If the eNB transmits TPC information to the D2D transmission UE through a D2D grant with each SA periodicity, the TPC information may be updated with each SA periodicity.

[0850] However, if the D2D UE is considered capable of transmitting multiple SAs or data between SA periods, the TPC information update periodicity may be set shorter than the SA periodicity in order to perform the power control for the SA or data transmission more optimally or efficiently.

[0851] To this end, a DCI format for separately transmitting TPC information only may be newly defined, and the newly defined DCI format may be transmitted between SA periods.

[0852] The newly defined DCI format includes TPC information.

[0853] For example, for an SA (transmission) periodicity of 100 ms, the TPC information periodicity may be set to 10 ms so that the TPC information is updated in accordance with the channel status.

[0854] In this method, however, the efficient use of resources may not be possible if only TPC information is transmitted, so the eNB may also transmit control information (e.g., HARQ information) reflecting the channel status, such as TPC information, to the D2D UE.

[0855] That is, the TPC, HARQ, MCS, RV, and PMI, which reflect the channel status, may be set to a periodicity shorter than the SA periodicity and transmitted more often to properly reflect the channel status and update the corresponding information.

[0856] Here, the above-described methods may be interpreted differently.

[0857] For example, while the SA periodicity is 10 ms, the actual transmission (or update) periodicity of SA RA information may be 100 ms and control information (TPC, HARQ information, etc.) reflecting the channel status may be generated with a periodicity (unit) of 10 ms.

[0858] That is, when the SA periodicity is set, the SA RA update periodicity, the TPC update periodicity, and the HARQ update periodicity may be set to integral multiples of the SA periodicity, individually.

[0859] Here, the SA RA update periodicity occurs more often than the TPC and HARQ update periodicities.

[0860] Accordingly, the SA RA update periodicity, the TPC update periodicity, and the HARQ update periodicity may be predetermined, and transmitted to the D2D UE through RRC signaling.

[0861] Alternatively, information related to SA RA update periodicity, the TPC update periodicity, and the HARQ update periodicity may be transmitted explicitly or implicitly transmitted to the D2D UE.

[0862] Here, the SA periodicity may be configured by RRC signaling, and the TPC periodicity and/or HARQ periodicity may be configured by a D2D grant.

[0863] Alternatively, the SA periodicity, TPC periodicity, and HARQ periodicity may be set to default values. That is, all these periodicities may have the same default value.

[0864] As discussed above, TPC information refers to information for controlling the transmission power of D2D transmission UE.

[0865] Here, the D2D transmission UE may control the transmission power for SA and data based on one piece of TPC information.

[0866] Alternatively, the D2D transmission UE may control transmission power depending on the characteristics of each signal by taking the characteristics of SA and data into consideration.

[0867] In this case, the eNB may include TPC information for SA and TPC information for data separately in a D2D grant and transmit them, or may transmit D2D grants for the respective types of TPC to the D2D UE.

[0868] That is, the D2D grant may allocate the TPC information for SA and the TPC information for data to separate regions.

[0869] The TPC information for SA may be used to indicate the transmission power control for SA, and the TPC information for data may be used to indicate the transmission power control for data.

[0870] Here, each type of TPC information may indicate the absolute Tx power or the delta Tx power compared to the previous transmission power.

[0871] In another method, when two TPC fields (an SA TPC field and a data TPC field) are used to control SA transmission power and data transmission power separately, an offset value to the value of one TPC field may be used to indicate the value of the other TPC field.

[0872] For example, if the first TPC field indicates the (absolute) transmission power for SA and the second TPC field indicates the (absolute) transmission power for data, the value of the second TPC field is not transmitted separately, but may be obtained using an offset value to the absolute transmission power of the first TPC field.

[0873] That is, the first TPC field may represent the absolute value of transmission power for SA or data, and the second TPC field may be represented as an offset value to the value of the first TPC field.

[0874] That is, this method corresponds to a method of indicating a relative difference in power between SA and data.

[0875] In this method, it is highly likely that the transmission power for SA and data may change in almost the same direction. Thus, when the power is set using an offset, the transmission power for SA and data may be controlled by using a small number of bits.

[0876] In general, an SA power control parameter set and a data power control parameter set may be set independently.

[0877] That is, transmission power information of SA and D2D data is set with different parameters, and therefore may be transmitted with different power values.

[0878] In particular, since SA is more important information that D2D data, the SA transmission power may be set higher than the data transmission power or may use more resources.

[0879] Also, D2D data needs to be transmitted in consideration of HARQ operation as well as channel coding, so it may be desirable that D2D data is controlled at a different transmission power than SA.

[0880] However, even if the calculated SA and D2D data transmission power values (initial value, etc.) are different, one TPC value transmitted through a D2D grant may be used to control the transmission power for SA and data.

[0881] In this case, even if D2D UE receives the same TPC information from the eNB, the D2D UE may interpret it differently according to a set criterion so that the actual calculated transmission power is different for SA and data.

[0882] In this case, the criterion for the D2D UE to interpret the transmission power for SA and data with respect to one TPC may be set in advance.

[0883] For example, if the SA transmission power may be adjusted in a range from X_SA (dB) to Y_SA (dB) in a 2-bit TPC table, the D2D data transmission power may be interpreted as being adjusted in a range from X_data to Y_data.

[0884] While only the power transmit adjustment range indicated by a TPC bit field value has been described by way of example, the final transmission power for different power control parameters may be calculated by using different definitions, different initial values, and different default values.

[0885] Next, the configuration of D2D grant RA information and SA RA information may be described in more detail.

[0886] Here, the D2D grant RA may refer to information, especially resource allocation information, related to an SA to be used for D2D communication, and may be represented as an SG (Scheduling Grant) or a DCI format 5.

[0887] Also, the SA RA information may refer to resource allocation information related to actual SA transmission, and may be represented as a PSCCH.

[0888] Specifically, the configuration of SA RA information represents a method in which D2D transmission UE configures RA information transmitted through a D2D grant (related to D2D) and transmits an SA based on the D2D grant RA.

[0889] As described above, when it is assumed that there is an RRC configured resource pool, the eNB selects a restricted set from the original RRC configured resource pool and transmits an RA to the D2D UE through a D2D grant.

[0890] The D2D transmission UE may receive the selected D2D grant RA set from the eNB, transmit it to D2D reception UE as it is or re-select (or create) a resource of the selected D2D grant RA set, and transmit information about this resource to the D2D reception UE.

[0891] Hereinafter, a method in which D2D transmission UE selects a resource from an RA set received from an eNB through a D2D grant and transmits an SA to D2D reception UE through the selected resource will be described in detail with reference to FIG. 40.

[0892] FIG. 40 is a flowchart illustrating an example of an SA transmission method, to which a method proposed in the present disclosure may be applied.

[0893] That is, FIG. 40 illustrates a method in which D2D transmission UE transmits a D2D-related packet to D2D reception UE in a resource selected by itself and likewise receives a D2D-related packet from the D2D reception UE in the resource selected by itself.

[0894] First of all, D2D transmission UE receives reserved and allocated resources related to D2D communication from an eNB (S4010).

[0895] The reserved and allocated resources related to D2D communication may be an SA resource pool and/or data resource pool, and transmitted through RRC signaling.

[0896] Afterwards, the D2D transmission UE selects or determines a resource to use for actual transmission among the received, reserved and allocated resources related to D2D communication (S4020).

[0897] Since D2D UE usually transmits and receives a small amount of D2D packets, it uses less than the resources (or D2D grant RA) reserved and allocated to it and received from the eNB.

[0898] Thereafter, the D2D transmission UE transmits an SA and/or D2D data to the D2D reception UE through the determined resource (S4030).

[0899] As described above, the SA and the D2D may be transmitted simultaneously, or the D2D data may be transmitted after the SA transmission.

[0900] Here, the D2D UE may operate in Rx mode (listening to other signals) in the remaining resource blocks not used for D2D communication or enter into DTX (Discontinuous Transmission) state to perform energy saving or power saving operation.

[0901] Through this operation, the D2D transmission UE operating in half-duplex may expand the resource region for reception, thereby receiving resources from more D2D UEs.

[0902] Moreover, the D2D reception UE may receive resources by monitoring D2D-related resources (D2D SFs) only in a specific (or restricted) SF (subframe).

[0903] In addition, the D2D reception UE may likewise perform energy saving by performing DRX (Discontinuous Reception) without monitoring.

[0904] Similarly, the D2D reception UE may acquire more resources that can be transmitted to other D2D UEs, and this increases the opportunities for D2D transmission and enables transmission of more D2D-related packets.

[0905] As shown in FIG. 40, in the method of using as many resources as needed for D2D-related packets D2D UE will actually transmit, D2D transmission UE and D2D reception UE may adjust the size of transmission resources and the size of reception resources as required through a negotiation process of transmitting and receiving signals to each other.

[0906] By this, the efficiency of D2D packet transmission in a full-mesh D2D network may be increased.

[0907] Here, in the process for adjusting the sizes of transmission resources and reception resources, the signals transmitted and received between D2D UEs may be implemented using high layer signals as well as physical layer signals.

[0908] Next, a method for D2D transmission UE to transmit an SA to D2D reception UE through an SA RA will be described in detail with reference to FIG. 41.

[0909] FIG. 41 is a flowchart illustrating an example of another SA transmission method, to which a method proposed in the present disclosure may be applied

[0910] FIG. 41 shows a method in which, when there are multiple D2D data transmission resources (or opportunities) between SA periods, D2D transmission UE notifies D2D reception UE of how many D2D data transmission resources can be used between the SA periods.

[0911] As described above, D2D transmission UE receives resource allocation information related to SA and/or data transmission from an eNB through a D2D grant RA (S4110).

[0912] Afterwards, the D2D transmission UE configuration information related to D2D data transmission resources to D2D reception UE through an SA (S4120).

[0913] Hereinafter, the configuration information related to D2D data transmission resources will be described in more detail.

[0914] The configuration information related to D2D data transmission resources includes indication information for indicating a D2D SF (or D2D data SF) in which D2D data can be transmitted.

[0915] The indication information may indicate the number of consecutive D2D SFs in which D2D data is transmitted or integral multiples of the number of D2D SFs.

[0916] If the indication information indicates continuous D2D SFs, the D2D transmission UE transmits D2D data to the D2D reception UE in the next K consecutive SFs immediately after an SA period (S4130).

[0917] Afterwards, the D2D transmission UE stops the transmission of D2D in SFs subsequent to the K consecutive SFs (S4140).

[0918] In another method of transmitting D2D data, offset information may be used.

[0919] That is, the D2D transmission UE may transmit D2D data to the D2D reception UE in the K consecutive D2D SFs starting from an SF spaced apart by the offset from an SA period, rather than starting from an SF immediately after the SA period, based on offset information related to D2D data transmission, and then stop the transmission of D2D data in the subsequent SFs.

[0920] If the consecutive D2D SFs cannot be occupied within the SA period because the offset value is too large, the D2D data transmission in the unoccupied SFs may be ignored or invalidated.

[0921] Alternatively, regarding D2D data transmission in unoccupied SFs, as many SFs as the unoccupied SFs may be designated as SFs for D2D data transmission, starting from the first SF in the next SA period.

[0922] Here, it is desirable that indication information (or indication bits) for indicating D2D SFs for D2D data transmission may be set in consideration of SA and data allocation periods.

[0923] For example, for a maximum SA period of 100 ms and a data transmission period of 10 ms, there are 10 data transmission opportunities between SA periods.

[0924] The number of cases (combinations) of consecutive SFs among 10 SFs needs to be taken into consideration, and the indication information requires a field with as many bits as needed to support all the combinations.

[0925] In an example, when an indication is required for 8 cases, the size of the indication information may be 3 bits, and when an indication is required for 10 cases, the size of the indication information may be 4 bits.

[0926] In another method of indicating D2D data SFs, the starting position and length of SFs related to D2D data transmission may be indicated. This method may be implemented by an LTE (-A) UL RA method.

[0927] As seen above, the method of indicating the starting position and length of D2D data SFs may increase the efficiency of resource use in terms of reduction of the number of bits of indication information.

[0928] Next, the use of indication information for indicating the position of a D2D data SF in the case of an increase in the SA period will be described.

[0929] Specifically, an increase in the SA period may be solved by repeatedly transmitting indication information for indicating the position of a D2D data SF.

[0930] For example, if the SA period increases to 400 ms, the indication information of 4 bits, which is used for an SA period of 100 ms and a data transmission period of 10 ms, may be repeatedly re-used four times.

[0931] Here, an eNB may notify D2D UE of the position of the D2D data SF by adjusting the number of repetitions of the indication information.

[0932] Signals used for adjusting the number of repetitions and the number of repetitions of the indication information for indicating the position of a D2D data SF may be predetermined.

[0933] In this case, the predetermined value may be transmitted through RRC signaling.

[0934] A bitmap pattern may be used as indication information for indicating the position of a D2D data SF.

[0935] If the indication information has a bitmap pattern, the D2D data SF may be designated very flexibly.

[0936] For example, assuming that the SA period is 100 ms and the data transmission period is 10 ms, 10-bit indication information is required as described above, in order to indicate all combinations for 10 data transmission opportunities.

[0937] For an SA period of 400 ms and a data transmission period of 40 ms, bitmap-type indication information of 10 bits is required, and for a data transmission period of 10 ms, bitmap-type indication information of 40 bits is required.

[0938] However, it is difficult to vary the length of indication information depending on the SA and/or data transmission period in terms of control information design.

[0939] Accordingly, it is desirable that the size of indication information, that is, the length of a bitmap, is fixed.

[0940] To this end, a reference SA period and a reference data transmission period are selected, and the size of indication information, that is, the bitmap length, is determined depending on the selected SA period and data transmission period.

[0941] Here, if the number of cases for indicating the position of a D2D data SF increases due to a change in the SA period and data transmission period, reference bitmap-type indication information (reference bitmap) may be repeatedly used.

[0942] On the contrary, if the number of cases for indicating the position of a D2D data SF decreases, some combinations may be truncated.

[0943] For example, for an SA period of 400 ms and a data transmission period of 10 ms, the position of a D2D data SF may be indicated in accordance with the SA period of 400 ms by repeatedly using bitmap-type indication information used for the SA period of 400 ms and the data transmission period of 10 ms four times.

[0944] The bitmap-type indication information used for the SA period of 400 ms and the data transmission period of 10 ms may be called reference indication information or a reference bitmap.

[0945] For an SA period of 400 ms and a data transmission period of 20 ms, there are 20 data transmission opportunities for 400 ms, and therefore the position of a D2D data SF may be indicated by repeatedly using 10 bits of the reference bitmap two times.

[0946] In contrast, if the SA period decreases to 50 ms and the data transmission period is 10 ms, the most significant 5 bits of a 10-bit D2D data SF indicating bitmap are used as valid information, and the least significant 5 bits may be ignored or invalidated.

[0947] Reversely, the least significant 5 bits of a 10-bit D2D data SF indicating bitmap may be used as valid information, and the most significant 5 bits may be ignored or invalidated.

[0948] Next, a method of reducing the number of bits of indication information (or D2D data SF indicating bitmap) indicating the position of a D2D data SF will be described in detail with reference to FIG. 42.

[0949] FIG. 42 is a flowchart illustrating an example of a D2D data transmission method, to which a method according to the present disclosure may be applied.

[0950] An eNB transmits a predefined (D2D) subframe pattern set to D2D transmission UE through a D2D grant RA (S4210).

[0951] Afterwards, the D2D transmission UE selects one or more subframe patterns from the received subframe pattern set (S4220).

[0952] Specifically, if an eNB transmits 8 resource patterns (or subframe patterns) from an RRC configured D2D resource pool to D2D transmission UE through a D2D grant RA, the D2D transmission UE selects one or more from the received 8 resource patterns and transmits an SA and/or data through the selected resources.

[0953] Here, a 3-bit field or indication information is defined in order to represent the 8 resource patterns.

[0954] That is, the eNB may notify the D2D transmission UE of information about resource patterns by transmitting 3-bit indication information.

[0955] Here, the number of SFS in which data is transmitted between SA periods may be variously selected and used by configuring the subframe pattern in various ways (e.g. initial K consecutive subframes, an offset, an interlaced SF pattern, etc.).

[0956] Afterwards, the D2D transmission UE transmits an SA and/or data to D2D reception UE through the selected subframe pattern (S4230).

[0957] In another embodiment, D2D-related resource pattern (or subframe pattern) may be configured hierarchically and transmitted to D2D UE.

[0958] For example, resource patterns may be configured hierarchically such that an RRC configured resource pool exists at the top layer, a plurality of resource patterns exist in a tree structure at the next layer under the top layer, and more resource patterns exist in a tree structure at the next layer.

[0959] In this case, the eNB selects one or more from 2nd layer resource patterns by using RRC configured 1st layer information and transmits the selected resource pattern to D2D transmission UE through a D2D grant.

[0960] Afterwards, the D2D transmission UE selects one or more from 3rd layer resource patterns under the received 2nd layer resource pattern and transmits an SA and/or data to D2D reception UE through the selected resource pattern.

[0961] Such a hierarchical tree structure for D2D resources and a method of interpreting the same may need to be shared in advance among the eNB and D2D UEs.

[0962] Next, the update time of SA may be discussed.

[0963] As described above, upon receiving a D2D grant from an eNB, D2D transmission UE transmits an SA to D2D reception UE in accordance with an SA period with reference to the received D2D grant.

[0964] If the D2D reception UE receives new SA-related information from the eNB between SA periods, the existing SA information is valid until the next SA period arrives.

[0965] That is, the D2D transmission UE updates the SA in the next SA transmission period. Then, the D2D transmission UE transmits the updated SA to the D2D reception UE in the corresponding SA transmission period.

[0966] Such a method of updating new control information in the next period may apply equally to TPC information, etc.

[0967] The above-mentioned update method is related to the activation of D2D resources.

[0968] However, the release of D2D resources may be set different from the above-described D2D resource activation.

[0969] That is, the D2D transmission UE releases D2D resources immediate after receiving release-related information from the eNB.

[0970] Accordingly, the D2D transmission UE stops the transmission of SA and/or data in the resources for which release is indicated.

[0971] Specifically, if the D2D transmission UE receives information indicating the release of D2D resources between SA periods from the eNB, the D2D transmission UE releases the D2D resources immediately without waiting until the next SA period.

[0972] Alternatively, if the SA period is set and the SA update periodicity is configured longer than the set SA period, the following D2D operation may apply.

[0973] That is, if the SA update periodicity and the SA periodicity are set differently and the SA update periodicity is longer, the activation of D2D resources may be set for each SA update periodicity and the release of D2D resources may be set for each SA transmission time, i.e., each SA period.

[0974] Uplink Power Control

[0975] The purpose of power control in a wireless communication system is to compensate for channel path loss and fading to guarantee Signal-to-Noise Ratio (SNR) required for the system and to provide higher system performance through appropriate rank adaptation. Inter-cell interference may also be adjusted by power control.

[0976] Uplink power control in the conventional system is based on closed-loop correction and/or open-loop power control. Open-loop power control is performed by calculation of User Equipment (UE) and closed-loop correction is performed by a power control command from an evolved Node B (eNB). A Transmit Power Control (TPC) command from the eNB may be defined in a DCI format of a PDCCH.

[0977] A power control procedure is described below with reference to the case of single transmit antenna transmission as an example.

[0978] FIG. 43 illustrates a basic concept of uplink power control.

[0979] Referring to 43, UE generally measures uplink power using a closed-loop scheme and an eNB may adjust uplink power by a closed-loop correction factor A. Power control of an uplink shared channel (PUSCH) may be performed according to the following Equation 12.
P_PUSCH(i)=min{P_CMAX,10 log₁₀(M_PUSCH(i)+P_OPUSCH(j)+α(j)·PL+Δ_TF(i)+f(i)}  [Equation 12]

[0980] In Equation 12, PPUSCH(i) represents transmission power of an ith subframe of a PUSCH and is in units of dBm. PCMAX represents maximum allowable power which is set by a higher layer and is determined according to the class of the UE.

[0981] MPUSCH(i) represents the amount of allocated resources and may be expressed in units of allocated resource blocks (each being a group of subcarriers, for example, 12 subcarriers). MPUSCH(i) has a value between 1 and 110 and is updated every subframe. In Equation 12, PO_PUSCH(j) includes 2 parts: PO_NOMINAL_PUSCH(j) and PO_UE_PUSCH(j), as shown in the following Equation 13.
P_{O_PUSCH}(j)=P_{O_NOMINAL_PUSCH}(j)+P_{O_UE_PUSCH}(j)  [Equation 13]

[0982] In Equation 13, PO_NOMINAL_PUSCH(j) is a value which is given cell-specifically by the higher layer and PO_UE_PUSCH(j) is a value which is given UE-specifically by the higher layer.

[0983] In Equation 12, argument j may have a value of 0, 1, or 2. When j=0, the argument j corresponds to PUSCH transmission which is scheduled dynamically in a PDCCH. When j=1, the argument j corresponds to semi-persistent PUSCH transmission. When j=2, the argument j corresponds to PUSCH transmission based on a random access grant.

[0984] In Equation 12, α(j)·PL is a formula for path loss compensation. Here, PL represents downlink path loss measured by the UE and is defined as “reference signal power-higher layer filtered Reference Signal Received Power (RSRP)”.

[0985] α(j) is a scaling value representing a path loss correction ratio, has one of the values of {0, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1}, and is expressed by a 3-bit value. When a is 1, this indicates that the path loss has been fully compensated for and, when a is less than 1, this indicates that the path loss has been partially compensated for.

[0986] ΔTF(i) in Equation 12 may be given by the following Equation 14.

[0987] $\begin{array}{cc}{\Delta }_{\mathrm{TF}}\left(i\right)=\{\begin{array}{c}\begin{array}{c}10{\log }_{10}\left(2^{\mathrm{MPR}·K_S}-1\right),K_S=1.25,\\ \mathrm{deltaMCS}-\mathrm{Enabled}=1\end{array}\\ 0,K_S=0,\mathrm{deltaMCS}-\mathrm{Enabled}=0\end{array}& \left[\mathrm{Equation}14\right]\end{array}$

[0988] As shown in Equation 14, use of ΔTF(i) may be set by a flag “deltaMCS-Enabled”. When the flag deltaMCS-Enabled has a value of 1, ΔTF(i) is set to be used. When the flag deltaMCS-Enabled has a value of 0, ΔTF(i) is not used since ΔTF(i) has a value of 0. MPR in Equation 14 may be given by the following Equation 15.

[0989] $\begin{array}{cc}\mathrm{MPR}=\frac{\mathrm{TBS}}{N_{\mathrm{RE}}},N_{\mathrm{RE}}=M_{\mathrm{PUSCH}}·N_{\mathrm{SC}}^{\mathrm{RB}}·N_{\mathrm{symb}}^{\mathrm{PUSCH}}& \left[\mathrm{Equation}15\right]\end{array}$

[0990] In Equation 15, TBS stands for a transport block size and NRE is the number of Resource Elements (REs) which is expressed as the number of subcarriers. When data is retransmitted, the value of NRE may be acquired from a value indicated by a first PDCCH for the same transport block.

[0991] f(i) in Equation 12 represents a parameter for adjusting transmission power according to a closed-loop scheme. A PDCCH of DCI format 0, 3, or 3A may be used to provide f(i). That is, f(i) is a parameter that is given UE-specifically.

[0992] In association with f(i), a flag “Accumulation_Enabled” may indicate whether a transmission power value is given through accumulation of the previous transmission power or is given without accumulation of the previous transmission power.

[0993] When the flag “Accumulation_Enabled” is set to enable the accumulation mode, f(i) may be given as shown in the following Equation 16.
f(i)=f(i−1)+δ_PUSCH(i−K_PUSCH)  [Equation 16]

[0994] In Equation 16, δPUSCH is a UE-specific correction value and may be referred to as a Transmit Power Control (TPC) command. δPUSCH may be included in a PDCCH of DCI format 0 to be signaled to the UE or may be joint-coded together with other TPC commands into a PDCCH of DCI format 3/3A to be signaled to the UE. An accumulated value of δPUSCH dB which is signaled in a PDCCH of DCI format 0 or 3 may have a size of 2 bits as shown in the following Table 6.

[0995]

TABLE 6
	TPC Command Field in DCI format 0/3	Accumulated δPUSCH
	0	−1
	1	0
	2	1
	3	3

[0996] When the UE detects PDCCH DCI format 3A, the accumulated value of δPUSCH dB is represented by 1 bit and may have one of the values of {-1, 1}.

[0997] In Equation 16, KPUSCH=4 in the case of FDD.

[0998] When both DCI format 0 and DCI format 3/3A are detected in the same subframe, the UE uses δPUSCH that is provided by DCI format 0. When a TPC command is absent or in the case of a discontinuous reception (DRX) mode, δPUSCH=0 dB. When the transmission power of the UE reaches the maximum transmission power, a TPC command having a positive value is not accumulated (i.e., the maximum transmission power is maintained). When the transmission power of the UE reaches the minimum transmission power, a TPC command having a negative value is not accumulated (i.e., the minimum transmission power is maintained).

[0999] On the other hand, when the flag “Accumulation_Enabled” is set to disable the accumulation mode, f(i) may be given as shown in the following Equation 17. The disabled accumulation mode means that the uplink power control value is given as an absolute value.
f(i)=δ_PUSCH(i−K_PUSCH)  [Equation 17]

[1000] In Equation 17, the value of δ_PUSCH is signaled only when the PDCCH DCI format is 0. At this time, the value of the δ_PUSCH is given as shown in Table 7 below.

[1001]

TABLE 7
		Absolute δPUSCH (dB)
	TPC Command Field in DCI format 0	only DCI format 0
	0	−4
	1	−1
	2	1
	3	4

[1002] In Equation 17, KPUSCH=4 in the case of FDD.

[1003] f(i)=f(i−1) when a PDCCH is detected, when the current mode is a DRX mode, or when the current subframe is not an uplink subframe in TDD.

[1004] Power control for an uplink control channel (PUCCH) may be defined as shown in the following Equation 18.
P_PUCCH(i)=Min{P_CMAX,P_{O_PUCCH}+PL+h(n_CQI,n_HARQ)+Δ_{F_PUCCH}(F)+g(i)}  [Equation 18]

[1005] In Equation 18, PPUCCH(i) is expressed in units of dBm. In Equation 18, ΔF_PUCCH(F) is provided by the higher layer and each ΔF_PUCCH(F) corresponds to a) PUCCH format (F) associated with PUCCH format 1a.

[1006] The value h(nCQI, nHARQ) depends on the PUCCH format, nCQI corresponds to a number information bit for Channel Quality Information (CQI), and nHARQ corresponds to the number of Hybrid Automatic Repeat request (HARQ) bits.

[1007] Hereinafter, a D2D transmission power control method proposed in the present disclosure will be described in more detail with reference to the above description of D2D transmission power control using a TPC command.

[1008] First of all, D2D transmission power control may be implemented through a SG (Scheduling Grant).

[1009] The SG may be represented as a D2D grant.

[1010] Here, the D2D grant may be transmitted through a PDCCH of DCI format 5.

[1011] Particularly, in the D2D transmission power control, a TPC command may be delivered using a TPC (Transmission Power Control) field or DCI format 3/3A.

[1012] When using DCI format 3/3A for the D2D transmission power control, a specific field among the fields of the DCI format 3/3A may be defined and used as a field for D2D power control.

[1013] In order to find out whether the specific field is defined as a field for D2D power control, the specific field needs to be partitioned to indicate whether it is for cellular use or for D2D through RRC signaling.

[1014] When using an existing TPC for D2D transmission power control, power control for both SA (Scheduling Assignment) and data may be supported by sharing TPC bits (2 bits).

[1015] That is, a state (or value) corresponding to 1 bit of the TPC field is allocated for power control for SA and a state corresponding to the other 1 bit is allocated for power control for data, thereby performing dynamic (closed) power control.

[1016] Also, the TPC may be divided into 1-bit units or a 2-bit state.

[1017] Here, splitting a 2-bit state may mean that part of the values ‘00’, ‘01’, ‘10’, and ‘11’ that can be expressed in 2 bits is used for SA power control and the other part may be used for data power control.

[1018] In another embodiment, power control for SA and/or data may be performed by using the existing DCI format 3/3A for D2D transmission power control.

[1019] Here, DCI format 3 may be used for 2-bit power control, and DCI format 3A may be used for 1-bit power control.

[1020] That is, the TPC of DCI format 3 has 12 bit, and the TPC of DCI format 3A has 2 bits.

[1021] First of all, the use of DCI format 3 for D2D transmission power control will be discussed.

[1022] In DCI format 3, a method of configuring a DCI format for SA and data separately may include: (1) a method in which a TPC unit (TPC command) of a length of 2 bits is divided into 1 bit for power control for SA and 1 bit for power control for data; and (2) a method in which 2 bits of a basic TPC unit (TPC command) are allocated for SA and data, respectively.

[1023] Additionally, referring to FIG. 44, the use of two TPC units (2 bits×2=4 bits) for SA and data power control by a single D2D UE will be described.

[1024] In order to perform power control for SA and data using two TPC units, D2D UE needs to be notified in advance through RRC signaling.

[1025] FIG. 44 is a diagram illustrating a method for performing power control for SA and data using DCI format 3, which is proposed according to the present disclosure.

[1026] (a) of FIG. 44 shows a TPC command (2 bits) of the existing DCI format 3.

[1027] (b) of FIG. 44 shows an example of sharing a TPC command of 2 bits of (a) of FIG. 44 for power control for SA and data.

[1028] In this case, as described above, a TPC command of 2 bits may be split into bits for power control for SA and data, respectively, or a state (‘00’, ‘01’, ‘10’, and ‘11’) of the TPC command 2 bits may be split and used for power control for SA and data.

[1029] (c) of FIG. 44 illustrates a method of combining 4 bits into one TPC command and sharing it for power control for SA and data.

[1030] Similarly to the above, in (c) of FIG. 44, as described above, specific bits may be split, or a state that can be expressed in 4 bits may be split into power control for SA and data.

[1031] (d) and (e) of FIG. 44 illustrate a method of transmitting only one TPC for SA or data in a 2-bit TPC command.

[1032] Here, it is desirable that the order of placement of a TPC for SA and a TPC for data is predetermined.

[1033] (f) and (g) of FIG. 44 illustrate a method of consecutively allocating either data or SAs first and then either SAs or data in TPC commands.

[1034] That is, data is consecutively allocated in TPC commands, and then SAs are consecutively allocated in TPC commands.

[1035] Here, the number of consecutively allocated SAs or data pieces may be predetermined or set through RRC signaling.

[1036] Next, a method of performing zero-padding on the DCI format 3 in which TPCs of data and SAs are allocated by the method of FIG. 44 will be described.

[1037] That is, if the total number of bits of the DCI format 3 in which TPCs of data and SAs are allocated is not equal to the length of the DCI format 0, zero bits may be inserted into the DCI format 3 in order to keep the length of the DCI format 3 equal to the length of the DCI format 0.

[1038] As shown in (b) of FIG. 44, in the method of sharing 2-bit TPC commands for use as TPC commands for SAs and data, there may be a difference of 1 bit in length between the DCI format 3 and the DCI format 0.

[1039] Accordingly, 1-bit zero padding is performed on the DCI format 3.

[1040] However, as in the case of (c) of FIG. 44 where 4 bits form a single TPC command with TPC (2 bit) pairs, there may be a length difference of up to 3 bits between the DCI format 0 and the DCI format 3.

[1041] That is, if there is a length difference of 3 bits, 3-bit zero padding is performed on the DCI format 3.

[1042] As a result, the number of bits for zero padding to be inserted into the DCI format 3 is determined depending on the pairing bits of SA and data.

[1043] That is, the number of bits for zero padding to be inserted, which is determined depending on the pairing bits of SA and data, is a maximum of (paired bits−1) bits.

[1044] Here, in the method of pairing SA and data, TPCs of SAs and data may be mapped on a 1-to-1 basis as shown in FIG. 44, or may be paired in an M-to-N fashion.

[1045] Here, M denotes the number of TPCs for SA, and N denotes the number of TPCs for data.

[1046] FIG. 45 is a diagram illustrating a method of performing power control for SA and data using DCI format 3A, which is proposed according to the present disclosure.

[1047] (a) of FIG. 45 shows a TPC command (1 bit) of the existing DCI format 3A.

[1048] (b) and (c) of FIG. 45 illustrate examples of a method for allocating a 1-bit TPC command for power control of SA and data.

[1049] (b) of FIG. 45 shows the allocation of 1-bit TPC commands in the order of an SA TPC command and then a data TPC command, and (c) of FIG. 45 shows the allocation of 1-bit TPC commands in the order of a data TPC command and then an SA TPC command.

[1050] (d) and (e) of FIG. 45 illustrate a method of consecutively allocating either data or SAs first and then either SAs or data in 1-bit TPC commands.

[1051] That is, TPCs of data are consecutively allocated in 1-bit TPC commands, and then TPCs of SAs are consecutively allocated in 1-bit TPC commands.

[1052] The number of consecutively allocated SAs or data pieces may be predetermined or set through RRC signaling.

[1053] Next, a method of performing zero-padding on the DCI format 3A in which TPCs of data and SAs are allocated by the method of FIG. 45 will be described.

[1054] As described above, (b) of FIG. 45 shows a case in which an SA TPC 1 bit and a data TPC 1 bit are paired to form a D2D TPC command of 2 bits.

[1055] In this case, the maximum size difference between the DCI format 3A and the DCI format 0 is 1 bit, so 1-bit zero padding is performed on the DCI format 3A.

[1056] Similarly, in another method ((c) to (e) of FIG. 45) in which the DCI format 3A is modified, the DCI format 3 may have the same size as the DCI format 0 by performing a maximum of 1-bit zero padding on the DCI format 3A.

[1057] The methods of FIGS. 44 and 45 are performed on the assumption that zero padding of a specific number of bits in order to make the length of a DCI format (e.g., DCI format 3/3A) for transmitting TPCS of SAs and data equal to the length of the DCI format 0.

[1058] In the above-described methods proposed in the present disclosure, TPCs may be distinguished in a D2D grant having a D2D RNTI as a method for distinguishing SA TPCs and data TPCs.

[1059] Here, the D2D grant having a D2D RNTI may mean DCI format 5, and the D2D RNTI may be expressed as SL (SideLink)-RNTI.

[1060] Alternatively, in a case where DCI format 3/3A is used, different TPC RNTIs may be used for SA TPCs and data TPCs, separately, as a method for distinguishing SA TPCs and data TPCs.

[1061] Alternatively, SA TPCs and data TPCs may be distinguished by using different fields within DCI format 3/3A as a method for distinguishing SA TPCs and data TPCs.

[1062] Another method of distinguishing SA TPCs and data TPCs is to use the relationship between SA and data transmission timings and TPC transmission timings.

[1063] For example, assuming that a TPC is transmitted in a Subframe #n (eNB-to-UE), when an SA is transmitted (UE-to-UE) in a subframe #n+4 or the first subframe (which may be construed as an available subframe or a subframe in which a D2D grant for D2D can be transmitted or a D2D available subframe, depending on the design method) after the subframe #n+4, the TPC transmitted in the subframe #n is considered a TPC for SA, and when data is transmitted in the subframe #n+4 or the first subframe after the subframe #n+4, the TPC transmitted in the subframe #n is considered a data TPC.

[1064] By applying the method of distinguishing the purpose of TPC (for SA or for data) using such a relationship between transmission timings, the TPC transmitted in the subframe #n (using an EPDCCH, PDCCH, etc.) may be transmitted in such a TPC format in which it is included in a D2D grant (or SG or DCI format 5), or even if the TPC is delivered in a DCI format 3/3A masked with the same or different RNTI or a modification thereof, the purpose of TPC may be easily distinguished.

[1065] Here, when a TDD system is taken into account, the definition of the subframe #n+4 or an available subframe that arrives after the subframe #n+4 needs to be changed into a subframe #n+k.

[1066] Here, k is a value corresponding to “the difference (subframe) between UL grant transmission timing and PUSCH transmission timing” which is defined in TDD UL/DL configuration.

[1067] Alternatively, the k may be defined as “a point of time (subframe) at which DCI format 3/#A is transmitted and this value is applied to D2D transmission”.

[1068] For reference, the subframe is a legacy subframe, or may be a D2D subframe for D2D. In this case, the subframe #n+4 may be defined otherwise.

[1069] In the method of transmitting TPC commands for SA and data and in a shared manner or separately using a specific DCI format, the TPC commands may be delivered along with a TPC transmitted in a D2D grant or independently.

[1070] Here, the TPC transmitted in a D2D grant may represent TPC mode information indicating (or representing) whether the power for SA or data transmission is set to maximum or such power control as using the exiting DCI format 3/3A is performed.

[1071] As described above, different power control schemes may be applied to SA and D2D data.

[1072] Such information may be delivered through a TPC field. However, a D2D data grant may have only one TPC as shown in the following Table 8.

[1073]

TABLE 8
Field Name	Length	Use in D2D grant
Hopping flag	1	Use as is
Resource block	6 (1.4 MHz)	Use as is for resource of data.
assignment	8 (3 MHz)	Resource of SA is derived from
(including N_Ulhop)	8 (5 MHz)	this field.
	13 (10 MHz)
	14 (15 MHz)
	15 (20 MHz)
MCS and RV	5	Use as is for data
TPC	2	Use as is (data)
Number of subframes	2 (for example)	Indicates the number of
used for transmissions		subframes used for data
(as a part of RPT)		transmissions
Subframe pattern	4 (for example)	Indicates the set of subframes
(as a part of RPT)		used for data transmissions

[1074] Here, the TPC value is shared by SA and data, but other power control parameters than the TPC parameter may be configured individually for SA and data.

[1075] In particular, parameters related to open loop power control (OLPC) may be configured separately.

[1076] As seen above, other power control parameters than the TPC parameter may be pre-configured through RRC signaling. Thus, they may be indicated separately without affecting the design of the D2D grant.

[1077] Hereinafter, a method for performing transmission power control for D2D communication proposed in the present disclosure will be briefly described.

[1078] First of all, first UE acquires a resource pool for use in D2D communication.

[1079] Here, the first UE may refer to D2D transmission UE, and the D2D communication may be represented as a sidelink.

[1080] Also, the first UE may acquire the resource pool from an eNB or receive the corresponding resource pool from a user.

[1081] Here, the resource pool may include at least either an SA (scheduling assignment) resource pool indicating an SA transmission resource region or a data resource pool indicating a D2D data transmission resource region.

[1082] Afterwards, the first UE transmits an SA (scheduling assignment) containing information related to D2D data transmission to second UE through the SA resource pool.

[1083] Here, the second UE may be D2D reception UE.

[1084] Afterwards, the first UE transmits D2D data to the second UE based on the SA.

[1085] In the above-described processes, transmission power control for D2D communication may be performed based on control information related to transmission power control for at least either the SA or the D2D data.

[1086] The control information may be represented as a TPC command, transmission power control information, or a transmission power control field.

[1087] Also, the control information may be received from an eNB through a D2D grant, and the D2D grant may be represented as DCI format 5.

[1088] Also, the control information may represent (mode) information indicating whether to use the transmission power for at least either the SA or the D2D data at maximum transmission power.

[1089] If the control information is included in the D2D grant (or DCI format 5), the control information may indicate using the transmission power for the SA or D2D data at maximum transmission power or indicate performing the existing absolute/relative transmission power control.

[1090] Here, if the total number of bits of a D2D grant containing TPC information of the SA and/or the data is less than the length of the DCI format 0, zero bits are inserted into the D2D grant until it becomes equal to the length of the DCI format 0.

[1091] Also, the control information is divided into first control information and second control information. The first control information is transmission power control information for the SA, and the second control information is transmission power control information for the D2D data.

[1092] Also, the control information represents transmission power information for the SA or transmission power control information for the D2D data, and the control information is allocated consecutively or at certain intervals. A detailed structure related to this will be described with reference to FIGS. 44 and 45.

[1093] Also, the control information may be transmitted through a DCI format 3 or DCI format 3A, in which case the control information may be transmitted in the resource pool for use in D2D communication.

[1094] That is, in a case where a DCI format 3 or 3A is transmitted or received in a D2D subframe, it can be determined that the DCI format 3/3A is for performing transmission power control for d2D communication.

[1095] Also, if the total number of bits of the DCI format 3 or 3A containing the control information is less than the length of the DCI format 0, zero bits may be inserted.

[1096] Also, the transmission power control information for the SA and the transmission power control information for the D2D data may be distinguished by using different RNTIs (Radio Network Temporary Identifiers) or different fields.

[1097] Also, the control information may be related to the subframes subsequent to the subframe in which the control information is transmitted.

[1098] Specifically, if the control information is transmitted in a subframe #n and an SA is transmitted in a subframe #n+k or in the first D2D subframe after the subframe #n+k, the control information is transmission power control information for the SA. If D2D data is transmitted in the subframe #n+k or in the first D2D subframe after the subframe #n+k, the control information is transmission power control information for the D2D data.

[1099] The k may have a value of 4, and this value may change depending on the TDD UL/DL configuration.

[1100] Hereinafter, D2D transmission power control, or more specifically a power control method for SA and D2D data, proposed in the present disclosure will be described in detail based on the foregoing.

[1101] That is, the present disclosure provides a method for performing power control for a D2D link (sidelink) by using a TPC (Transmission Power Control) field defined in a D2D grant and a DCI format 3/3A.

[1102] Here, the D2D grant may be transmitted in a newly defined DCI format, as discussed above, and an example of the new DCI format may be a DCI format 5.

[1103] Specifically, the TPC field included in a D2D grant to perform power control for a D2D link may be used for instantaneous power control for SA, and the TPC field included in the DCI format 3/3A may be used for power control for D2D data transmission.

[1104] Here, the TPC field included in the D2D grant may be represented as an SA TPC field.

[1105] Here, the SA represents scheduling information for D2D data transmission, and the SA contains resource allocation (RA) information.

[1106] The resource allocation information included in the SA is provided in the form of an SA resource pool.

[1107] Here, it is highly likely that the resource allocation information in the SA may not change often because of the characteristics of D2D communication.

[1108] In an example, for data transmission and reception such as VoIP, an eNB designates an arbitrary resource for UE in advance, and performs data transmission and reception using the designated resource for a long time.

[1109] Accordingly, the RA information in the SA does not change often, so the eNB does not need to transmit SA to the UE often.

[1110] However, even if the same resource is used for D2D data without change for a certain period of time, the degree of interference with WAN (Wireless Area Network) UE (cellular UE) may change often.

[1111] In order to adaptively cope with frequent changes in interference, it is desirable that power control for D2D data transmission is performed more often than the transmission power control for SA.

[1112] Also, it is desirable that the power control for SA transmission is performed in accordance with an SA period since multiple D2D data transmissions are performed for a single SA transmission, and that power control is performed in accordance with the frequency of occurrence of D2D data transmission.

[1113] For example, assuming that the SA is transmitted in a P_sa period, and D2D data is transmitted at P_data intervals which are shorter than the P_sa period, the TPC field included in a D2D grant transmitted in every P_sa period is defined to be used for power control for SA transmission and the TPC field of the DCI format 3/3A transmitted in a P_data period is defined to be used for power control for D2d data transmission.

[1114] As discussed above, SA and D2D data may be controlled more efficiently and autonomously by using the TPC field of the D2D grant for SA power control and the TPC field of the DCI format 3/3A for D2D data power control.

[1115] Especially, in the case of D2D data transmission, D2D data transmission may end in a specific subframe between SA periods, or there may be strong interference with WAN data transmission or the WAN data transmission may cause strong interference.

[1116] If power control is performed for both SA and D2D data through a D2D grant in such a situation, the problem of latency may make it difficult to quickly cope with this situation.

[1117] That is, in a method (of performing power control for SA and D2D data separately) proposed in the present disclosure, HARQ-related parameters, as well as power control for D2D data transmission, may be changed for each subframe by using a DCI format 3/3A using different RNTIs or the same RNTI.

[1118] The same is true of non-periodical D2D data transmission.

[1119] What matters is that the DCI format 3/3A is non-periodically transmitted in necessary situations, even for each subframe.

[1120] That is, in the case of power control for D2D data transmission using the DCI format 3/3A, when power control for D2D data transmission is required regardless of whether SA or D2D data transmission is periodical or non-periodical (when it is necessary to change other transmission parameters), the power control for D2D data transmission may be immediately performed using the DCI format 3/3A at any random time, which gives flexibility to power control.

[1121] Since SA and D2D data are transmitted and received between UEs over a D2D link, power control information (TPC field) related to SA and D2D data transmission may be received from the eNB through a D2D grant and/or DCI format 3/3A so as to transmit SA and D2D data with proper power control parameters at SA and D2D data transmission timings, rather than maintaining precise synchronization between SA and D2D data transmissions.

[1122] That is, what only matters is satisfying the requirement that power control information related to D2D data transmission should be received until some time after the D2D transmission timing, rather than a strict timing association with the data transmission timing.

[1123] FIG. 46 is a flowchart illustrating an example of a power control method for D2D communication, which is proposed according to the present disclosure.

[1124] A method for transmitting and receiving D2D data in a wireless communication system supporting D2D communication is as follows.

[1125] First of all, an eNB transmits a D2D grant including an SA resource pool and/or a D2D data resource pool to D2D transmission UE. The D2D grant may be a DCI format 5.

[1126] Afterwards, the D2D transmission UE determines an SA resource in the received SA resource pool, or if an SA transmission resource is predetermined by the eNB, transmits an SA to D2D reception UE by using the corresponding resource.

[1127] Afterwards, the D2D transmission UE transmits D2D data to the D2D reception UE by using a D2D data resource in the D2D resource pool.

[1128] The D2D data resource may be indicated by the SA.

[1129] Here, the SA and D2D data may be transmitted and received via a D2D link (or sidelink).

[1130] Here, power control for the SA transmission is performed through the TPC field in the D2D grant.

[1131] That is, the eNB includes the TPC field containing information related to the power control for the SA transmission in the D2D grant and transmits it to the D2D transmission UE.

[1132] Since the D2D transmission UE receives the TPC field related to the power control for the SA transmission in every SA transmission period, the power control for the SA transmission may be performed in every SA period.

[1133] Moreover, power control for the D2D data is performed through the TPC field in the DCI format 3/3A.

[1134] Here, the DCI format 3/3A is transmitted to the D2D transmission UE from the eNB.

[1135] If there is a need to dynamically control D2D data transmission power, the eNB dynamically transmits a PDCCH of the DCI format 3/3A to the D2D transmission UE.

[1136] That is, the D2D transmission UE checks whether power control for D2D transmission is performed by monitoring the PDCCH (DCI format 3/3A) in each subframe or in a given subframe.

[1137] To sum up, information related to transmission power control for SA is transmitted through a D2D grant (S4610 and S4620), and information related to transmission power control for D2D data is transmitted through a DCI format 3/3A (S4630 and S4640).

[1138] In another embodiment of the power control method for D2D communication, the TPC field included in a D2D grant is used for power control for SA and D2D data transmission, and the DCI format 3/3A is used to perform additional power control for D2D data transmission.

[1139] That is, power control for D2D communication, i.e., for SA and D2D data transmission, is performed basically by using the TPC field in the D2D grant, and if there is a need to urgently change power control-related parameters for D2D data transmission due to the characteristics of SA and D2D data transmission, the DCI format 3/3A is transmitted at any time so as to perform power control for D2D data transmission.

[1140] In the above-described methods, it is desirable that, if power control for D2D communication is performed using the DCI format 3/3A, the index for the TPC information of the corresponding UE is pre-configured through RRC.

[1141] Hereinafter, the method of performing a zero (inserting a zero bit) in the DCI format related to the scheduling of SA and/or D2D data proposed in the present specification will be described.

[1142] Further, DCI format 0 and DCI format 1A were already described above in detail, and thus the details thereabout are not omitted here.

[1143] As mentioned above, DCI format 9 and DCI format 1A perform a zero padding process (zero bit insertion process) in DCI format 0 or DCI format 1A through the DCI format size comparison in order to maintain the same payload size (the number of information bits within DCI format 9 which is mapped in the given search space).

[1144] Namely, the zero padding process is configured is a manner that the sizes of the two DCI formats become the same by inserting “0” bit to the DCI format having a small size in order to fit the size of a large DCI format to a DCI format of which the payload size is relatively small.

[1145] The purpose of such a zero padding process is not to increase the number of times of blind decoding in the UE.

[1146] Further, the zero padding process for DCI format size is performed when the zero padding condition is satisfied in DCI format 1A and DCI format 0 section (or field).

[1147] In LTE/LTE-A system, when D2D communication (or sidelink) is introduced, the base station may introduce a new DCI format having the same size as (E-)PDCCH DCI format 0 in order to transmit SA to UE (eNB-to-UE) (in order to perform a scheduling grant).

[1148] In this case, the blind decoding complexity of the UE may be reduced by using the above-described zero padding process.

[1149] Here, DCI format, which is newly introduced in connection with the SA transmission in D2D communication, may be defined as DCI format 5.

[1150] Hereinafter, the newly defined DCI format will be called “DCI format 5” for the convenience of description.

[1151] Hence, the new DCI format (DCI format 5) related to D2D SA transmission has the same size as the above-described DCI format 0, and thus the above-mentioned zero padding process may also be applied to DCI format 5.

[1152] Namely, the size of DCI format 5 is compared with the size of DCI format 0, and the zero bit is inserted until the length of the DCI format of a small size becomes the same as the length of the DCI format of a large size.

[1153] For example, when the size of DCI format 5 is smaller than the size of DCI format 9, the zero bit is added or inserted to the DCI format 5 until the size of the DCI format 5 becomes the same as the size of the DCI format 0.

[1154] Here, when the size of the new DCI format (DCI format 6) is defined as the same as the size of the DCI format 0, a separate D2D-RNTI (radio network temporary identifier), which is distinguished from DCI format 0, may be used for the DCI format 5 in order to distinguish these two DCI formats.

[1155] Namely, a DCI format other than DCI format 5 may be distinguished by masking a separate D2D-RNTI to the DCI format 5.

[1156] D2D-RNTI, which is used for the DCI format 5, is an identifier used to distinguish DCI format 5 from other DCI formats and may also be expressed as sidelink-RNTI or SL-RNTI.

[1157] Hereinafter, the method of fitting the size of the new DCI format (DCI format 5) related to D2D SA transmission and the size of DCI format 0 (or DCI format 1A) to be the same will be described in detail with reference to some embodiments.

[1158] In order to maintain the size of DCI format 5 and the size of DCI format 0 to be the same, the payload size of each DCI format should be the same.

[1159] If considered on the basis of DCI format 0 of Rel-8, the sizes of the frequency hopping field (1 bit), MCS/RV field (5 bits), and TPC field (2 bits) may be reused as themselves in DCI format 5, but other fields such as a resource allocation (RA) field may be preferably configured according to the usage of the D2D scheduling grant.

[1160] Here, DCI format 5 transmitting the D2D grant should simultaneously schedule SA and data transmitted to D2D link (sidelink), and thus a situation that the RA size of DCI format 5 becomes greater than the RA size of DCI format 0 may occur.

[1161] Namely, the RA size of DCI format 5 (particularly, requiring a lot of bits) may become greater than the RA size of DCI format 0 by twice.

[1162] According to the first embodiment, a method of maintaining the sizes of DCI format 0 and DCI format 5 not to be changed using UL RA type 1.

[1163] Namely, the first embodiment is a method of using RL RA type 1 in order to enable SA RA and D2D data RA to be included in one DCI format 5 while maintaining the size of RA payload of DCI format 0.

[1164] Namely, according to the first embodiment, since UL RA type 1 is used for resource allocation of SA and D2D data, the resource allocation granularity may be reduced and the increase of RA bit of DCI format 5 may be prevented.

[1165] Hereinafter, the UL resource allocation method will be briefly described.

[1166] Two UL resource allocation schemes are supported for PDCCH/EPDCCH transmitting UL DCI format (e.g., DCI format 0).

[1167] The UL DCI format supports a method of indicating one resource composed of continuous resource blocks as DL resource allocation (type 0) and indicating two resources composed of continuous resource blocks as DL resource allocation.

[1168] When there is no resource allocation type bit in the UL DCI format, only the resource allocation type 0 is supported.

[1169] On the other hand, if there is a resource allocation type bit in the UL DCI format, if the resource allocation type bit has the value “0”, the resource allocation type 0 is indicated, and otherwise, the resource allocation type 1 is indicated. The UE analyzes the resource allocation field according to the resource allocation type bit within PDCCH/EPDCCH transmitting the detected UL DCI format.

[1170] The resource allocation information according to UL resource allocation type 0 indicates the virtual resource block (VRB) index (n_VRB) which is consecutively allocated to the scheduled UE. The resource allocation field within the scheduling grant includes a start resource block (RB_START) and a resource indication value (RIV) corresponding to the length (L_CRBs) of the resource block which is continually allocated.

[1171] (L_CRBs−1)≤└N_RB^UL/2┘ is satisfied, RIV is defined as Equation 19 below, and otherwise, RIV is defined as Equation 20 below.

[1172] Here, N_RB^UL indicates the number of total resource blocks (RB) in the UL bandwidth.
RIV=N_RB^DL(L_CRBs−1)+RB_start  [Equation 19]
RIV=N_RB^DL(N_RB^DL−L_CRBs+1)+(N_RB^DL−1−RB_start)  [Equation 20]

[1173] Meanwhile, resource allocation information for UL resource allocation type 1 indicates two resource block sets to the scheduled UE. Here, each set includes one or more continuous resource block groups (RBG).

[1174] The size of the RBG is shown as Table 9 below.

[1175]

TABLE 9
	System Bandwidth	RBG Size
	NRBUL	(P)
	≤10	1
	11-26	2
	27-63	3
	64-110	4

[1176] In order to indicate the resource allocation, the combination index (r) corresponding to the start RBG index (S₀) and the last RBG index (S₁−1) of the resource block set 1 and the start RBG index (S₂) and the last RBG index (S₃−1) of the resource block set 2 is defined as Equation 21 below.

[1177] $\begin{array}{cc}r=\sum _{i=0}^{M-1}\langle \begin{array}{c}N-s_i\\ M-i\end{array}\rangle & \left[\mathrm{Equation}21\right]\end{array}$

[1178] In Equation 21, M=4 and N=┌N_RB^UL/P┐+1.

[1179] A second embodiment is a method of drawing SA RA from D2D data RA or D2D data RA from SA RA in order to enable SA RA and D2D data RA to be included in one DCI format 5 while maintaining the RA payload size of DCI format 0.

[1180] The payload bit size of each DCI format may be reduced to an almost same level through the above first embodiment and second embodiment.

[1181] According to the third embodiment, the method of increasing the size of DCI format 0 according to the size of DCI format 5 in order to enable SA RA and D2D data RA to be included in one DCI format 5 while maintaining the size of RA payload of DCI format 0 is provided.

[1182] Namely, the third embodiment is a method of increasing the size of DCI format 0 as N_d2d bit according to the size of DCI format 5 (D2D grant) instead of the method of fitting the size of DCI format 5 to the size of DCI format 0 (method of reducing the bit size of DCI format 5 as the size of DCI format 0 for reference cellular UE, i.e., N_legacy bit).

[1183] The N_legacy bit indicates the size of DCI format 0 for cellular UE, and the N_d2d bit indicates the size of DCI format 5 related to D2D communication.

[1184] Specifically, if the size of the DCI format 5 (DCI format transmitting D2D grant) is determined as N_d2d bit (>N_legacy bit), the sizes of DCI format 5 and DCI format 0 are fitted by performing a zero padding to DCI format 0 in order to fit the size of the corresponding DCI format 5.

[1185] Likewise, the size may be fitted with DCI format 5 using the above-described third embodiment in DCI format 1A.

[1186] Namely, when the size of the DCI format 5 is greater than the size of DCI format 1A, the size of each DCI format becomes the same by performing a zero padding to the DCI format 1A on the basis of DCI format 5.

[1187] Namely, the third embodiment first determines the size of DCI format, in which D2D grant is transmitted, unlike the method of performing a zero padding in the DCI format of a relatively small size in order to fit a relatively large DCI format size among the existing DCI format 0 and DCI format 1A.

[1188] Thereafter, when the size of DCI format 0 or DCI format 1A is smaller than the size of the determined D2D grant DCI format, the padding of zero bit 0 is performed to the DCI format 0 or DCI format 1A until the size becomes the same as the size of the D2D grant DCI format.

[1189] Likewise, the size (or length) of each DCI format should be maintained same in order for the UE to detect DCI format 0/1A and D2D grant DCI format (DCI format 5) by only one time blind decoding.

[1190] As another embodiment, when the UE performs a blind decoding for the PDCCH, if it is assumed that the location of the subframe where (E-)PDCCH for transmitting D2D grant (DCI format 5) is transmitted can be accurately known, D2D grant (DCI format 5) and DCI format 1A may be distinguished using 0/1A field.

[1191] The 0/1A field is a field for distinguishing DCI format 0 and DCI format 1A within DCI format 1A.

[1192] Namely, the fourth embodiment is a method of distinguishing the DCI format 5 and DCI format 1A by using the state or value (e.g., “0”) having indicated the existing DCI format 0 in the 0/1A field as the usage of indicating D2D grant (DCI format 5).

[1193] Yet, since D2D grant (DCI format 5) and UL grant (DCI format 0) may be designed (or implemented) in a manner that may be detected in the same subframe (SF), in this case, an additional method for distinguishing the DCI format 5 and the DCI format 0 is needed.

[1194] Below, the method for distinguishing the DCI format 5 and the DCI format 0 will be described in detail.

[1195] Namely, it is proposed that in order to distinguish the DCI format 5 and the DCI format 0, 0/1A division field included in DCI format 0 and DCI format 1A is used to distinguish DCI format 0 and DCI format 1A like before, and in D2D grant (DCI format 5), it is distinguished from other DCI formats (0/1A) through a separate CRC masking such as D2D-RNTI (or sidelink-RNTI).

[1196] Namely, the UE checks PDCCH with C-RNTI and D2D-RNTI respectively for one PDCCH search space candidate, and as a result of the checking, if the CRC is normal (after decoding), it is understood as the field configuration of the DCI format suitable to the corresponding to RNTI.

[1197] Further, when the D2D operation is enabled, the UE with the D2D capability may have a change in the decoding of (configured) DCI format 0/1A.

[1198] Namely, when there is no D2D grant from the base station (when there is no transmission in the DCI format 5), whether the zero padding is to be inserted may be known by estimating the lengths of DCI format 0 and DCI format 1A, respectively.

[1199] However, when it is known that the UE comes to know that D2D grant (DCI format 5) is transmitted from the base station, the level of zero padding for DCI format 0 or DCI format 1A should be estimated and detected by having the size of the D2D grant DCI format fitted.

[1200] Consequently, the operation of the UE related to the zero padding performance for DCI format 0 or DCI format 1A is closely related to whether D2D grant is transmitted from the base station to the UE.

[1201] The operation related to the performance of the zero padding may be configured to perform the corresponding operation from the moment that the D2D is configured, but it may also be configured to be performed only when the D2D communication is actually performed.

[1202] The operation related to the zero padding performance means an operation of performing a zero padding for DCI format 0/1A according to the above-described D2D grant size.

[1203] As a specific method for performing the operation related to the zero padding only when the D2D is actually performed, the base station may configure the corresponding operation or operation mode in advance through the RRC signaling in a UE-specific manner and may selectively perform the corresponding operation by transmitting the signal for activating or deactivating the corresponding operation or the corresponding operation mode at a certain moment.

[1204] As another embodiment of an operation related to the zero padding, the above zero padding operation may be limited to be operated only at the subframe corresponding to the D2D resource pool in consideration of the fact that the D2D resource is configured in advance.

[1205] Namely, in the subframe which does not correspond to the D2D resource pool, the length between DCI format 0 and DCI format 1A is fitted through the zero padding like before, and in the subframe corresponding to the D2D resource pool, the zero padding procedure for DCI format 0 or DCI format 1A, which fits the size of the DCI format 5, is performed.

[1206] When the zero padding procedure of the DCI format basis is applied in all frames without including the D2D subframe, an unnecessary zero bit is inserted into DCI format 0 and DCI format 1A, whereby a result negative to the communication performance is caused by increasing the coding rate.

[1207] FIG. 47 is a flowchart illustrating an example of a D2D communication procedure proposed in the proposed specification.

[1208] First, the D2D transmission UE obtains a resource pool for being used for D2D communication (S4710).

[1209] The resource pool includes at least one of a scheduling assignment (SA) resource pool indicating a resource area where SA is transmitted or a data resource pool indicating a resource area where D2D data is transmitted.

[1210] Further, the resource pool may have been received by the UE from the base station or may have been configured in advance.

[1211] The resource pool is received from the base station through the DL downlink control information (DCI) defined for D2D communication.

[1212] Further, the DCI format is CRC (cyclic redundancy check)-masked with a separate RNTI which is distinguished from C (cell)-RNTI.

[1213] The separate RNTI may be a D2D-RNTI (radio network temporary identifier) or sidelink-RNTI.

[1214] Further, when the size of the DCI format is different from the size of DCI format 0, the zero bit may be inserted into the DCI format until the size of the DCI format becomes the same as the size of DCI format 0.

[1215] Here, the insertion of the zero bit into the DCI format may be performed only in the resource pool.

[1216] The DCI format may be DCI format 5.

[1217] Specifically, the D2D transmission terminal blind-decodes PDCCH in the search space in order to obtain the resource pool.

[1218] Here, the blind decoding of the D2D transmission UE may mean performing the CRC check for the PDCCH with C-RNTI and D2D-RNTI, respectively.

[1219] Thereafter, the D2D transmission UE transmits SA (scheduling assignment) including information related to the D2D data transmission to the D2D receiving UE through the SA resource pool (S4720).

[1220] Thereafter, the D2D transmission UE transmits D2D data to the D2D receiving UE (S4730).

[1221] <General Points about an Apparatus to which the Present Invention is Applicable>

[1222] FIG. 48 illustrates an example of an internal block diagram of a wireless communication apparatus to which the methods proposed in the present specification are applicable.

[1223] Referring to FIG. 48, a wireless communication system includes a base station 4810 and a plurality of UEs 4820 located in the area of the base station 4810.

[1224] The base station 4810 includes a processor 4811, a memory 4812, and a radio frequency (RF) unit 4813. The processor 4811 implements a function, process and/or method proposed in FIGS. 1 to 47. The layers of the wireless interface protocol may be implemented by the processor 4811. The memory 4812 is connected to the processor 4811 and stores various information for operating the processor 4811. The RF unit 4813 is connected to the processor 4811 and transmits and/or receives a wireless signal.

[1225] The UE 4820 includes a processor 4821, a memory 4822, and an RF unit 4823.

[1226] The processor 4821 implements the function, process and/or method proposed in FIGS. 1 to 47. The layers of the wireless interface protocol may be implemented by the processor 4821. The memory is connected to the processor 4821 and stores various information for operating the processor 4821. The RF unit 4823 is connected to the processor 4821 and transmits and/or receives a wireless signal.

[1227] The memories 4812 and 4822 may be inside or outside the processors 4811 and 4821 and may be connected to the processors 4811 and 4821. Further, the base station 4810 and/or UE 4820 may have a single antenna or multiple antennas.

[1228] In the aforementioned embodiments, the elements and characteristics of the present invention have been combined in specific forms. Each of the elements or characteristics may be considered to be optional unless otherwise described explicitly. Each of the elements or characteristics may be implemented in such a way as to be not combined with other elements or characteristics. Furthermore, some of the elements and/or the characteristics may be combined to form an embodiment of the present invention. The order of the operations described in connection with the embodiments of the present invention may be changed. Some of the elements or characteristics of an embodiment may be included in another embodiment or may be replaced with corresponding elements or characteristics of another embodiment. It is evident that an embodiment may be constructed by combining claims not having an explicit citation relation in the claims or may be included as a new claim by amendments after filing an application.

[1229] An embodiment of the present invention may be implemented by various means, for example, hardware, firmware, software or a combination of them. In the case of implementations by hardware, an embodiment of the present invention may be implemented using one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers and/or microprocessors.

[1230] In the case of an implementation by firmware or software, an embodiment of the present invention may be implemented in the form of a module, procedure, or function for performing the aforementioned functions or operations. Software code may be stored in memory and driven by a processor. The memory may be located inside or outside the processor, and may exchange data with the processor through a variety of known means.

[1231] It is evident to those skilled in the art that the present invention may be materialized in other specific forms without departing from the essential characteristics of the present invention. Accordingly, the detailed description should not be construed as being limitative from all aspects, but should be construed as being illustrative. The scope of the present invention should be determined by reasonable analysis of the attached claims, and all changes within the equivalent range of the present invention are included in the scope of the present invention.

[1232] In a wireless communication system of the present specification, a method of transmitting and receiving data is described centering on the example of application to 3GPP LTE/LTE-A system, but the present invention may be applied to various wireless communication systems.