Method for controlling traffic load in mobile communication system

[0002] 1. Field of the Invention

[0003] The present invention relates to a method for controlling a traffic load in a mobile communication system, and more particularly, to a method for controlling a traffic load in a mobile communication system, which can assure a quality of a packet data service required in a CDMA mobile communication system.

[0004] 2.Background of the Related Art

[0005] In general, a plurality of terminals which have a packet data service available may be present in a cell of a base station. Therefore, if the plurality of terminals request the packet data services on the same time, requests over an available cell service capacity are disregarded. In this instance, there may be a case when a particular terminal is always served well while another particular terminal is not served, continuously. And, even under a traffic congestion, it is desirable that a terminal with a preset higher service grade compared to a terminal being served currently is supported for the service. Therefore, it is required that the system distributes the traffic load for assuring a service quality required by all the terminals in the cell. Moreover, there can be a case when a terminal with high predefined priority due to handoff should be served in a cell of a heavy traffic load. That is, a traffic overload congestion may be occurred in the cell. Actually, since a countermeasure for the occurrence of the traffic load congestion or for a situation when assurance of a bandwidth and a duration required in a supplemental channel request message(SCRM) from a terminal is difficult in the occurrence of the traffic load congestion, a next generation system provides a supplemental channel assignment message(SCAM) with the bandwidth and the duration considering a capacity.

[0006] However, current SCAM has no definition on taking the predefined priority into account in consideration of a service quality. The related art method has a problem in that all the services required in a traffic load congestion are refused. In conclusion, no next generation mobile communication system suggested up to now have provided a countermeasure on the traffic load control.

[0007] Accordingly, the present invention is directed to a method for controlling a traffic load in a mobile communication system that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.

[0008] An object of the present invention is to provide a method for controlling a traffic load in a mobile communication system, which can assure a quality of a packet data service.

[0009] Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

[0010] To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, in the method for controlling a traffic load in a mobile communication system, the system prepares dynamic priority numbers of each terminal in a form of a table in advance for providing to each terminal according to a traffic load. And, in a certain traffic load congestion, each terminal calculates a dynamic priority for the terminal. A sequence of a packet data service of each terminal is determined based on the dynamic priority group number and a group parameter the system permits to serve.

[0011] In other aspect of the present invention, there is provided a method for controlling a traffic load in a mobile communication system, in which dynamic priority group numbers (P_DPROTG) which will be made available to each terminal in a cell depending on a traffic load is prepared in the system. Then, a permitted dynamic priority group number(P_DPROTG) is transmitted from the system to each terminal in fixed time intervals depending on the traffic load. In the meantime, each terminal calculates a dynamic priority(DRPOT) of the terminal. Each terminal compares the P_DPROTG from the system and the DPROT calculated by the terminal itself, to determine a dynamic priority group number to which the terminal belongs. According to a result of the determination, each terminal determines, and executes a user data transmission to the system. Thus, a quality of each packet data service is assured to a certain extent in the traffic load congestion.

[0012] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

[0013] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention:

[0014] In the drawings:

[0015] FIG. 1 illustrates a diagram showing a protocol procedure between a mobile subscriber (MS) and a base station(B S) in accordance with a preferred embodiment of the present invention;

[0016] FIG. 2 illustrates a state diagram on a MUX and a QoS sublayer for a dynamic priority group number field(P_DPROTG) in a base station in accordance with a preferred embodiment of the present invention; and,

[0017] FIG. 3 illustrates a table showing a service interface primitive of a MUX and a QoS sublayer at the base station.

[0018] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. FIG. 1 illustrates a diagram showing a protocol procedure between a mobile subscriber (MS) and a base station(BS) in accordance with a preferred embodiment of the present invention, FIG. 2 illustrates a state diagram on a MUX and a QoS sublayer for a dynamic priority group number field(P_DPROTG) in a base station in accordance with a preferred embodiment of the present invention, and FIG. 3 illustrates a table showing a service interface primitive of a MUX and a QoS sublayer at the base station.

[0019] In the present invention, at first, dynamic priorities of mobile subscribers are calculated. The dynamic priority(DPROT) is calculated with an equation (1), below.

[0020] DPROT=K(WQ+SQ)/SQ  (1)

[0021] Where, DPROT denotes a dynamic priority, WQ denotes a waited quantity, SQ denotes a served quantity, WQ+SQ denotes data quantity required through a supplemental channel request message(SCRM), and K is a proportional constant based on a predefined priority. K is fixed according to a priority of a service itself, and a factor is a transit delay(TD) and a permitted peak rate(PPR). Therefore, the coefficient can be expressed as equation (2), below.

[0022] K=F(TD, PR)  (2)

[0023] An available traffic capacity in a cell can be determined by a bandwidth, data rate, Eb/No, and the like, and may be different depending on system managers. Therefore, a determination on a traffic overload in the cell is dependent on an embodiment of the cell. In general, each terminal has its own dynamic priority. Therefore, since management of the dynamic priority for the system or the terminal itself is complicated, it is favorable to manage the dynamic priorities in a number of groups. In detail, it is assumed that the dynamic priorities are divided into, for example, four groups. In this instance, there are a group 1, a group 2, a group 3, and a group 4. The number of groups may be varied depending on a cell size and environment of actual system. The traffic load may be considered in a forward direction side and reverse direction side. In this embodiment, a traffic load is taken into consideration, which is occurred when a data which burst in a reverse direction side, i.e., from a mobile subscriber side, i.e., MS side, to a base station side is send.

[0024] A protocol procedure between the base station and the mobile subscriber will be explained in detail with reference to FIGS. 1˜3.

[0025] First, the base station informs a total number of groups set in the current base station and dynamic priority boundaries to all terminals 10 in a cell the terminals 10 in through a paging channel or common channel in an overhead message at an idle state. A maximum value is provided as the dynamic priority boundary of each group, so that a dynamic priority boundary of one group is to be from a maximum value of a group one stage lower than the group in question+1 to a maximum value of the group in question. Forward and reverse traffic dedicated channels(or fundamental channels) are set up between the system 20 and the terminal 10 according to a preset protocol. The reverse traffic channel is a channel from the terminal 10 to the base station 20, and the forward traffic channel is a channel from the base station 20 to the terminal 10. Under this situation, when the terminal 10 provides a supplemental channel request message(SCRM) to the base station 20 through the set up reverse traffic channel(S20), the base station 20 provides a supplemental channel assignment message(SCAM) which is taken into consideration of its own capacity to the terminal 10 through the set up forward traffic channel in response to the SCRM.(S30).

[0026] In the while, the system(or the base station) monitors a traffic load congestion. Herein, the system may be the foregoing base station itself or a base station controller in the base station. For reference, a base station is provided with the base station controller(BSC) and a base transceiver subsystem(BTS). The system will be called as a base station, hereafter. Then, the base station 20 provides available group number field(P_DPROTG) to each terminal 10 of which packet data service is in an active state through the forward traffic channel. The multiplexer and the QoS sublayer is service provider as well as a service user of the group number field (P_DPROTG). A resource control, receiving the group number field(P_DPROTG) from the signaling control, provides the same to the Mux and QoS control using indication primitive. That is, the group number field(P_DPROTG) is provided added to a physical channel(i.e., the forward channel) indicated by the Mux QoS control. The group number field(P_DPROTG) is provided from the base station 20 to the terminal 10 through the fundamental channel or dedicated control. (S40). In other words, the group number field(P_DPROTG) is not provided through the supplemental channel. And, since the group number field(P_DPROTG) informs an available dynamic priority group to the terminal, the base station has a dynamic priority group table to be made available differently depending on a traffic load. The group number field(P_DPROTG) to be made available differently depending on a traffic load is transmitted by the base station in 20 ms units. Therefore, the base station in a traffic load congestion varies the available group number field(P DPROTG) in conducting a service the most suitable to a quality the service users require.

[0027] And, if the dynamic priority group(DPROTG) in the group number field(P_DPROTG) is set to ‘0’, each terminal which is served of a packet data service regularly provides a user data frame to the base station 20 through the reverse traffic channel(R-SCH and R-FCH).(S50). If the dynamic priority group(DPROTG) is set to a value other than ‘0’, each of the terminals being served of a packet data service calculates a dynamic priority for itself, to determine to which i-d group the terminal belongs. For example, if the dynamic priority group(DPROTG) the system(or the base station) permits is 2, the terminal 10 can be served in the same service in a bandwidth the same with the above continuously, if the group the terminal 10 belongs is any one of G1 or G2(DPROT>P-DPROTG). That is, the terminal 10 may execute a burst-transmission. However, if the group the terminal belongs is any one of G3 or G4(DPROT<P-DPROTG), the RLP user frame through the reverse supplemental channel(R-SCH) is aborted. Then, the terminal 10 should wait for a data transmission. As an actual waiting time period is short, it is not a withdrawal of the physical code channel(in this instance, R-SCH), but a blocking of a burst transmission for a time period. For the while, the reverse direction transmission through the channel(the reverse supplemental channel:R-SCH or reverse dedicated control channel:R-DCCH) is made, continuously. And, since this process is done in realtime, it is desirable that the group number field(P-DPROTG) is added to the multiplex sublayer matched to a frame boundary of the traffic channel rather than providing it through a message. The terminal, which should calculate a group to which it belongs and wait for a data transmission, informs a transmission “OK” state, or a transmission “NOT OK” state to the base station 20 through a reverse channel(R-SCH or R-DCCH), for which at least 1 bit of field(TX-STOP) should be present. That is, by adding 1 bit of transmission stop field(TX-STOP) to all frame transmitting and receiving through the reverse channel, a transmission state is informed to the base station 20.(S60). Then, when a traffic overload on the cell is reduced, a value of the dynamic priority group(DPROTG) transmitted to the terminal 10 is lowered. Accordingly, the waiting terminal 10 compares the value of the dynamic priority(DPROT) given from the base station and the value of dynamic priority (DPROT) calculated by itself. As a result of the comparison, if a level of it own is higher, the waiting terminal 10 can only make a burst transmission of the RLP user frame through the reverse fundamental channel(or the dedicated control channel).(S70). In other words, a transition from the burst transmission suspension state to a resumption state should be made, and a number of preamble should be transmitted according to a parameter(RESUME_PREAMBLE) specified in the SCAM. In turn, the base station 20 can match a synchronization of the frame according to the parameter(RESUM_PREAMBLE). Then, the base station 20 keeps transmission of the dynamic priority group number field(P-DPROTG) to the terminal 20 through the dedicated control channel in 20 ms units.(S80).

[0028] In the meantime, even in cases of terminals 10 falling on G1 or G2, each terminal may reduce its own rate(i.e., a bandwidth), to transmit the frames continuously with the reduced bandwidth. For example, if the terminal 10 has a plurality of supplemental channels, a rate adaptation can be made by reducing a number of the supplemental channels. Otherwise, the terminal 10 may keep transmission of the frames in the wide bandwidth the same as before and, if the group level from the base station 20 is lowered, the terminal 10 may transmit the frames only through the fundamental channel without the supplemental channel. The above two operations can be available when the dynamic priority group(DPROTG) is higher than the group number field(P_DPROTG) permitted by the base station 20, which depends on an implementation of the terminal 10.

[0029] A terminal 10, either requesting a supplemental channel after the terminal 10 transmits all the user data frame to the base station 20, transits out of an active state, and transits into the active state again, or intending to make a burst transmission in an active state for making a call, can transmit the supplemental channel request message(SCRM) to the base station 20 only when a value of a permitted dynamic priority group field(P_DPROTG) received from the base station 20 through the fundamental channel is set to ‘0’. However, a terminal 10 with a priority higher than the default predefined priority can request the SCRM.

[0030] In the meantime, in making a call, a call with a high predefined priority should be assured of a QoS(FER, delay, throughput) of a quality better than a call with a low predefined priority. Accordingly, the coefficient K is applied to the equation (1) when the terminal 10 calculates the dynamic priority for the graded service.

[0031] The method for controlling a traffic load in a mobile communication system of the present invention has the following advantages.

[0032] First, the distribution of a traffic load in a traffic load congestion situation assures a service quality a terminal requires.

[0033] Second, a terminal with a high predefined priority can be served, correspondingly. And, the introduction of a dynamic priority assures the same service quality between terminals of identical level.

[0034] Third, the management of the dynamic priorities in groups allows the system for a flexible application of an appropriate rate adaptation to the terminals. That is, by decreasing the dynamic priority group number(P-DPROTG) by 20 ms frame boundary units, the most appropriate service quality can be provided according to a load.

[0035] Fourth, the overhead can be distributed by making the terminal to manage a dynamic priority for a reverse traffic congestion, and making the system to manage a dynamic priority for a forward traffic congestion.

[0036] It will be apparent to those skilled in the art that various modifications and variations can be made in the method for controlling a traffic load in a mobile communication system of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.