Universal telephone network-radio frequency enhanced bridge

[0001] The present invention relates to a communication system, and more particularly, to a communication system providing an enhanced bridge between a telephone network and a radio frequency (RF) communications system.

[0002] When locating radio frequency (RF) communications systems within a building, several obstacles are encountered, such as, blindspots that include areas within the building where RF communications signals do not penetrate adequately from a single transmitter location. In addition, mobile transmitters can be moved into these blindspots and be unable to reach a fixed RF receiver point. The installation of multiple fixed RF modems to service and provide communications to multiple mobile RF units is one possible way to overcome problems relating to blindspots and other problems. However, a plurality of fixed RF modems that are dispersed through a building requires a relatively large communications infrastructure to carry messages to and from the fixed RF modems to a centralized communications location. The installation of special wiring may be costly and difficult to install particularly within a building that is serving dynamic and time critical needs such as a hospital. Therefore, a desire exists to develop communications systems that are capable of providing a communications infrastructure to a plurality of fixed RF modems within a building without the aforementioned deficiencies.

[0003] In one embodiment, a dual transceiver enhanced bridge is provided for communicating RF messages from a radio frequency (RF) communication system and telephone subscriber loop (TSL) messages from a telephone network. The radio frequency (RF) communication system includes a plurality of RF transmitting and receiving units. The dual transceiver enhanced bridge comprises a TSL modem connected to the telephone network. The TSL messages are transmitted on and received from the telephone network using the TSL modem. In addition, the TSL modem converts TSL messages received from the telephone network to predetermined format messages. An RF modem is connected to the TSL modem. The RF modem converts RF messages received from the plurality of RF transmitting and receiving units on the RF communication system. Also, the RF modem converts the RF messages to predetermined format messages. Additionally, the TSL modem converts predetermined format messages received from the RF modem to TSL messages before transmission over the telephone network, and the RF modem converts the predetermined format messages received from the TSL modem to RF messages before transmission over the RF communication system. A memory unit is connected between the TSL modem and the RF modem. The memory unit stores predetermined format messages received from the TSL modem and the RF modem. A controller is connected to the TSL modem, the RF modem, and the memory unit. The controller controls the transfer of the predetermined format messages between the memory unit to the RF modem and the TSL modem.

[0004] In another embodiment, a method is provided for communicating RF messages from a radio frequency (RF) communication system and telephone subscriber loop (TSL) of a telephone network. The radio frequency (RF) communication system includes a plurality of RF transmitting and receiving units. The method comprises the steps of connecting a TSL modem connected to the telephone network. The TSL modem receives the TSL messages from the telephone network via the TSL system. The TSL messages received from the telephone network are converted to predetermined format messages using the TSL modem. The predetermined format messages are stored in a memory device. The RF messages are received at the RF modem from the plurality of transmitting and receiving units via the RF communication system. The RF messages received from the plurality of transmitting and receiving units via the RF communication system are converted to predetermined format messages using the RF modem. The predetermined format messages are stored in the memory device. The RF modem is used to convert the predetermined format messages provided by the TSL modem, and the predetermined format messages are converted to RF messages. The converted RF messages are transmitted to at least one of the plurality of RF transmitting and receiving units using the RF modem. The TSL modem is used to convert the predetermined format messages provided from the RF modem, and the predetermined format messages are converted to TSL messages. The converted TSL messages are transmitted over the telephone network.

[0005] FIG. 1 is a block diagram view of one exemplary embodiment of a telephone subscriber loop-radio frequency (TSL-RF) enhanced bridge operating between remote RF transmitting and receiving units and a telephone network.

[0006] FIG. 2 is a block diagram view of one exemplary embodiment of a TSL-RF enhanced bridge.

[0007] FIG. 3 is a data structure view of one exemplary embodiment of a message.

[0008] FIG. 4 is a data structure view of one exemplary embodiment of a data field of a message.

[0009] In one embodiment as shown in FIG. 1, a communication system 100 includes a telephone subscriber loop-radio frequency (TSL-RF) enhanced bridge 110. A connection to a telephone network 160 is provided via a telephone connection 150.

[0010] The telephone connection 150 connects the telephone network 160 to the TSL-RF enhanced bridge 110. When the telephone network 160 is connected to the TSL-RF enhanced bridge 110, the telephone network 160 is available to the TSL-RF enhanced bridge 110 as a communications medium. Additionally, as shown in FIG. 1, the TSL-RF enhanced bridge 110 is connected to an RF antenna 120 that can communicate using RF communications with one or more remote RF transmitting and receiving units 130.

[0011] As shown in FIG. 2, the TSL-RF enhanced bridge 110 includes a telephone subscriber loop (TSL) modem 112 that is connected to a power supply unit 111 and the telephone connection 150. The TSL modem 112 is also connected to a controller 118 and a memory unit 114. In one embodiment, the memory unit 114 comprises a buffer and/or memory storage, such as, for example, random access memory. In another embodiment, the controller 118 can comprise a computing device, such as, for example, a microprocessor. It should be appreciated that, in other embodiments, the controller 118 can include a memory unit/device (not shown). A radio frequency (RF) modem 116 is connected to the RF antenna 120 and the memory unit 114. The controller 118 is also connected to the memory unit 114 and the RF modem 116. When the TSL-RF modem 112 is connected to the telephone network 160 via the telephone connection 150, the telephone network 160 has been made accessible as a communication medium with the TSL-RF enhanced bridge 110. In one embodiment, the TSL modem 112 uses signaling on the telephone network 160 that operates above human voice frequencies, and thus, a telephone network 160 can be used as a communication medium sending messages without impacting voice communications on the telephone network 160. In one embodiment, a signaling frequency over the telephone network 160 is chosen so as to not impair voice communication over the telephone network 160. As the signaling frequency is increased, the lower the chances that the signaling will interfere with voice communications. Further, in one embodiment, the frequency response to telephone voice handsets (not shown) connected to the telephone network 160 can be determined, and a signaling frequency can be selected that is outside the frequency response of the telephone voice handsets (not shown). In one embodiment, the selected signaling frequency is greater than or equal to about four (4) KHz. In another embodiment, the signaling frequency is greater than or equal to about twenty-five (25) kHz. Therefore, the TSL modem 112 can be used on a telephone network 160 that is preexisting in a building. In one embodiment, the telephone network 160 includes a network of connective lines comprising, for example, telephone cables and/or fiber optic cable. Further, in even another embodiment, the TSL modem 112 can be constantly connected to the telephone network 160 via the telephone connection 150 without having to wait for a voice call connection to be made before receiving or transmitting messages via the telephone network 160. In addition, it should be appreciated that, in another embodiment, the telephone network 160 can comprise, for example, a private telephone network located in a specific structure, a public switched telephone network (PSTN) or a combination thereof. In yet another embodiment, as shown in FIG. 2, the power supply unit 111 includes a power converter 121 for converting a voltage from the telephone connection 150 to voltages used to operate the TLS-RF enhanced bridge 110. Also shown in FIG. 2 in another embodiment, the power supply unit 111 includes a battery 122 that is used to provide power to the TSL-RF enhanced bridge 110 as a power source, or the battery 122 can provide power to the TSL-RF enhanced bridge 110 during power interruptions. It should be appreciated that, in another embodiment, the power supply 111 can be individually connected to all the components of the TSL-RF enhanced bridge 110. In even another embodiment, the power converter 121 of the power supply 111 can include a connector (not shown) that connects the power supply 111 to power line wiring (not shown) of a building or structure housing the TSL-RF enhanced bridge 110.

[0012] As discussed hereinabove, when the telephone network 160 is connected to the TSL modem 112 via the telephone connection 150, the telephone network 160 is electrically connected to the TSL modem 112 and, the telephone network 160 is made accessible as a communications medium. The TSL modem 112 demodulates telephone subscriber loop (TSL) messages that are transported over the telephone network 160. In one embodiment, the TSL messages comprise messages that have been transmitted over the telephone network 160. In one embodiment, the demodulated messages are demodulated to a predetermined format message. In another embodiment, the predetermined format messages are at baseband. The TSL modem 112 provides the predetermined format messages to the controller 118. From the controller 118, the baseband messages are sent to the memory unit 114. In one embodiment, the memory unit 114 comprises a buffer and message memory comprising, for example, random access memory (RAM). In another embodiment, the TSL modem 112 provides the predetermined format messages directly to the memory unit 114, and the controller 118 controls the transfer of the predetermined format messages between the TSL modem 112 and the memory unit. In even another embodiment, the TSL modem includes a memory 131, and the predetermined format messages are provided to the memory 131 that stores the predetermined format messages before they are transferred to various other components. In one embodiment, the memory 131 comprises, for example, random access memory (RAM). The controller 118 controls the flow of the predetermined format messages that are provided to the RF modem 116 from the memory unit 114. The RF modem 116 also modulates the baseband messages for radio frequency (RF) transmission. The radio frequency (RF) messages are broadcasted by the RF modem from the antenna 120. The RF messages are transmitted to one or more remote RF transmitting and receiving units 130.

[0013] In another direction of data flow (radio frequency (RF) to telephone subscriber loop (TSL)), RF messages transmitted by one or more of the remote RF transmitting and receiving units 130 are received by the antenna 120 of the TSL-RF enhanced bridge 110. In one embodiment, the RF modem 116 demodulates the RF messages to a predetermined format message. In another embodiment, the predetermined format messages are at baseband. Under control of the controller 118, the predetermined format messages are provided to the memory unit 114. The predetermined format messages are read from the memory unit 114 into a TSL modem 112, and the transfer of the predetermined format messages between the memory unit 114 and the TSL modem 112 is also controlled by the controller 118. The TSL modem 112 modulates the baseband messages to a transmission format suitable for transportation on the telephone network 160. In another embodiment, the predetermined format messages are provided to the controller 118 and then are sent to the memory unit 114 from the controller 118. In even another embodiment, the RF modem 116 includes a memory 141 where the predetermined format messages are stored before being transferred to various other components. In one embodiment, the memory 141 comprises, for example, random access memory (RAM).

[0014] In one embodiment, the TSL-RF enhanced bridge 110 links two communication modalities, for example, a telephone network 160 with radio frequency (RF) wireless communication system 140. The messages transmitted on one communications modality are received at the TSL-RF enhanced bridge 110 and retransmitted to the other modality. In one embodiment, the TSL modem 112 can transmit messages over the telephone network 160 using signaling techniques, such as, for example, frequency shift keying (FSK), phase shift keying (PSK), m-ary signaling, orthogonal frequency division multiplexing (OFDM) and harmonic modulation (HM). In another embodiment, the RF modem 116 of the RF communications system can use ultra wideband (UWB) signaling. In another embodiment, the RF modem 116 of the RF communication system can use a wireless point to multipoint application, such as, for example, Bluetooth. It should be appreciated that, in this embodiment, the telephone network 160 including the TSL modem 112 can be adapted to carry Bluetooth protocols to extend the effective range of the Bluetooth application. The messages are transmitted according to a communications protocol that is segmented into layers. In one embodiment, the lowest layer, layer 1, is referred to as the physical layer. Layer 1 is concerned with communications signaling including, for example, the electrical specifics, timing, etc. In addition, the data link layer is referred to as layer 2 and is used to establish error-free transmission of the messages. Additionally in other embodiments, higher layers of the communication protocol relate to responsibilities, such as, message routing, and message sequencing.

[0015] The flow of data through the TSL-RF enhanced bridge 110 is governed by a protocol suite. In one embodiment both the TSL modem 112 and the RF modem 116 perform the physical layer of the protocol stack function (level 1) that encompasses various responsibilities, such as, specifics of bit signaling, sensing clear-to-send states etc. In one embodiment, the protocol stack functions are typically divided into seven layers or levels. The levels are intended to represent divisions between naturally grouped functions. Such groupings of the functions promote standardization and an efficient framework for network architecture. Level 1 of the protocol stack functions is termed the physical layer. In one embodiment, the physical layer is concerned with details that include, such as, for example, the representation of the signaling waveforms of the data element (e.g., bits that are used in the channel between a transmitter and a receiver), link flow characteristics (e.g., whether simultaneous bidirectionality is allowed), establishment and tear-down of initial connection, wiring conventions and timing.

[0016] When receiving and demodulating a message 380 (FIG. 3) to a baseband bit stream, the TSL modem 112 and the RF modem 116 send demodulated bits to the memory unit 114 that buffers the bit stream. The controller 118 examines the received, demodulated bit stream and performs higher level protocol functions on the bit steam. In one embodiment, the higher level protocol functions comprise a data link layer protocol that checks to ensure that the received message 380 (FIG. 3) is without error and that appropriate acknowledgments and non-acknowledgments are sent.

[0017] Once a complete and certified correct message 380 (FIG. 3) has been received from one of the RF modem 116 or the TSL modem 112, the controller 118 passes the message 380 (FIG. 3) to the other of the RF modem 116 or the TSL modem 112 for modulation and transmission.

[0018] In one embodiment, the higher level protocol functions of the controller 118 can be locally reprogrammed by a special message inserted in an electrical port (not shown) in the TSL-RF enhanced bridge 110. In another embodiment, the higher level protocol functions of the controller 118 can be remotely reprogrammed by sending a special message to the TSL-RF enhanced bridge 110. It should be appreciated that, in one embodiment, the special message can be sent as a message on the telephone network 160 or an RF message on the RF wireless communications network 140. The higher level protocol stack functions can include levels 2 through 7 of the protocol stack. In one embodiment, level 2 is termed the data link layer and includes, such as, for example, error control procedures to render the physical layer (layer 1) an error free circuit. In another embodiment, the protocol stack functions included in level 2 comprise, for example, acknowledgment/non-acknowledgment (ACK/NAK) agreements where the data packets are requested to be retransmitted if an error is detected in the received packets.

[0019] In one embodiment, the TSL modem 112 comprises a microprocessor operating according to a stored program code to perform the level 1 protocol functions. In another embodiment, the stored program code can be replaced or modified locally by a special message inserted in an electrical port (not shown) in the TSL modem 112. In even another embodiment, the stored program code can be replaced or modified remotely by sending a special message to the TSL-RF enhanced bridge 110. It should be appreciated that, in one embodiment, the special message can be sent as a message on the telephone network 160 or an RF message on the RF wireless communications network 140.

[0020] In another embodiment, the RF modem 116 can comprise a microprocessor operating according to a stored program code that performs the level 1 protocol stack functions. In even another embodiment, the stored program code can be replaced or modified locally by a special message inserted in an electrical port (not shown) in the RF modem 116. In yet another embodiment, the stored program code can be replaced or modified remotely by sending a special message to the TSL-RF enhanced bridge 110. It should be appreciated that, in one embodiment, the special message can be sent as a message on the telephone network 160 or an RF message on the RF wireless communications network 140.

[0021] As shown in FIG. 3, a message format 300 of a message 380 is provided, and time moves in the direction of arrow A. The message format 300 starts with a synchronization preamble 310 that alerts a receiver that a message 380 is being transmitted and also aids in receiver clock recovery. In one embodiment, the synchronization preamble 310 is a sequence of alternating logical zeros and ones. In addition, the synchronization preamble 310 can have a different length depending upon different applications. However in one embodiment, the length of the synchronization preamble 310 can depend upon the characteristics of the communications modality/channel and a false alarm/missed alarm probability specifications.

[0022] As further shown in FIG. 3, the synchronization preamble 310 is followed by a unique word (UW) 320. In one embodiment, the unique word (UW) 320 is a binary word that exhibits low magnitude sidelobes in a non-cyclical autocorrelation and also has a low magnitude cross-correlation to the synchronization preamble 310. In another embodiment, the unique word (UW) 320 comprises a Barker sequence.

[0023] Additionally, the unique word (UW) 320 can have a different length depending upon different applications. However in one embodiment, the length of the unique word (UW) 320 can depend upon the characteristics of the communications modality/channel and the false alarm/missed alarm probability specifications. The message format 300 further includes a message sequence number field (N) 330 that contains a sequence number allowing a higher level of the protocol to detect a break in the message stream such as might happen if, for example, a message were lost. In this embodiment, the next field is the TAG identification field (TID) 340 that identifies the particular TAG associated with the packet, such as, where the message 380 is received from or where the message 380 is to be transmitted. After the TAG identification field (TID) 340, a message length field (L) 350 is provided and includes a number specifying the number of bits within the message. After the message length field (L) 350, a data field (DATA) 360 is provided. An error detection field 370 follows the data field (DATA) 360. In one embodiment, the error detection field 370 comprises a cyclic redundancy code (CRC) word, and the CRC is computed over the message sequence number field (N) 330, the TAG identification field (TID) 340, the message length field (L) 350, and the data field (DATA) 360. In another embodiment, the type of CRC that is used depends upon the characteristics of the communication modality/channel and the false alarm/missed alarm probability specifications.

[0024] In another embodiment, the TSL-RF enhanced bridge 110 performs additional higher layer protocol functions often performed by a router (not shown). In this embodiment, the TSL-RF enhanced bridge 110 performs protocol conversions between the RF wireless communication system 140 and the telephone network 160. These functions may include decryption of received encrypted messages followed by re-encryption under a different keying variable. As shown in FIG. 4 in one embodiment, the DATA field 360 of a message 380 can consist of three parts. The first part is an encryption bit (EB) 362. The second part is an initialization vector (IV) 364. The third part is the encrypted data 366. The initialization vector (IV) 364 governs the initialization of the cryptographic engine that produces the encrypted data 366. When performing a high level protocol function, the controller 118, after successfully receiving a message 380, examines the encryption bit (EB) 362 of the data field (DATA) 360. If the encryption bit (EB) 362 is a zero, the controller 118 considers the remaining bits in the data field (DATA) 360 to be unencrypted data of the message 380. If the encryption bit (EB) 362 is a one, the controller 118 consults a table (not shown) stored in memory (not shown) and retrieves a cryptographic key for the communication modality/channel where the message 380 was transmitted, and the controller 118 uses the cryptographic key and the initialization vector (IV) 364 to decrypt the encrypted message 380.

[0025] In another embodiment, the controller 118 buffers the received data 366, and the buffered contents can be rewrapped in new data packets according to priorities programmed into the controller 118 and a state of the individual RF communication links. The state information includes, for example, reliability of delivery, link availability, and link existence. In one embodiment, the controller 118 can be provided with a list of known or vetted RF communication link addresses, and if the controller 118 is requested to forward a message 380 to a non-existent address, the controller 118 is programmed to discard the message rather than transmit the message 380. It should be appreciated that, in one embodiment, the controller 118 selects a signaling rate that is best suited to the state of the individual RF communication link where the message 380 is to be sent.

[0026] In another embodiment, the controller 118 can order the messages 380 from a particular RF transmitting and receiving unit 130 before the messages 380 are relayed on the telephone network 160. Some RF transmitting-and receiving units 130 can send data 360 in segments in parts that need reassembly at the controller 118. In the process of managing the reliable accumulation and assembly of these segments of data 360, the controller 118 can be programmed to refrain from transmitting the messages 380 that carry the different segments of data 360 until the segments can be re-assembled in order.

[0027] The foregoing discussion of the invention has been presented for purposes of illustration and description. Further, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings and with the skill and knowledge of the relevant art are within the scope of the present invention. The embodiment described herein above is further intended to explain the best mode presently known of practicing the invention and to enable others skilled in the art to utilize the invention as such, or in other embodiments, and with the various modifications required by their particular application or uses of the invention. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.