Abstract:
A dual transceiver enhanced bridge is provided for wirelessly radio frequency (RF) broadcasting messages received on a power line communication system. The dual transceiver enhanced bridge includes a power line carrier (PLC) modem connected to the power line by a connecting plug. The PLC modem is connected to a memory unit. The dual transceiver enhanced bridge also comprises an RF modem connected to the memory unit. A controller is connected to the PLC modem, the RF modem, and the memory unit to control transmission of messages from the connected devices.

Description:
BACKGROUND OF INVENTION  
         [0001]    The present invention relates to a communication system, and more particularly, to a communication system providing an enhanced bridge between a power line communications (PLC) system 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.  
         SUMMARY OF INVENTION  
         [0003]    In one embodiment, a dual transceiver enhanced bridge is provided for communicating RF messages from a radio frequency (RF) communication system and power line communication (PLC) messages from a power line communication (PLC) system. The radio frequency (RF) communication system includes a plurality of RF transmitting and receiving units. The dual transceiver enhanced bridge comprises a PLC modem connected to a power line. The PLC messages are transmitted on and received from the power line using the PLC modem on the PLC communication system. In addition, the PLC modem converts PLC messages received from the power line to predetermined format messages. An RF modem is connected to the PLC 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 PLC modem converts predetermined format messages received from the RF modem to PLC messages before transmission over the power line, and the RF modem converts the predetermined format messages received from the PLC modem to RF messages before transmission over the RF communication system. A memory unit is connected between the PLC modem and the RF modem. The memory unit stores predetermined format messages received from the PLC modem and the RF modem. A controller is connected to the PLC modem, the RF modem, and the memory unit. The controller controls the transfer the predetermined format messages between the memory unit to the RF modem and the PLC modem.  
           [0004]    In another embodiment, a method for communicating RF messages from a radio frequency (RF) communication system and power line communication (PLC) messages from a power line communication (PLC) system. The radio frequency (RF) communication system includes including a plurality of RF transmitting and receiving units. The method comprises the steps of connecting a PLC modem connected to a power line. The PLC modem receives the PLC messages from the power line via the PLC system. The PLC messages received from the PLC communication system are converted to predetermined format messages using the PLC 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 PLC 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 PLC modem is used to convert the predetermined format messages provided from the RF modem, and the predetermined format messages are converted to PLC messages. The converted PLC messages are transmitted over the power line using the PLC modem. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0005]    [0005]FIG. 1 is a block diagram view of one exemplary embodiment of a power line communications-radio frequency (PLC-RF) enhanced bridge operating between remote RF transmitting and receiving units and a power line.  
         [0006]    [0006]FIG. 2 is a block diagram view of one exemplary embodiment of a PLC-RF enhanced bridge.  
         [0007]    [0007]FIG. 3 is a data structure view of one exemplary embodiment of a message.  
         [0008]    [0008]FIG. 4 is a data structure view of one exemplary embodiment of a data field of a message. 
     
    
     DETAILED DESCRIPTION  
       [0009]    In one embodiment as shown in FIG. 1, a communication system  100  includes a power line communication-radio frequency (PLC-RF) enhanced bridge  110 . A connection to a power line  160  is provided from a power receptacle  150 . The PLC-RF enhanced bridge  110  comprises a power plug  140  that is inserted into the power receptacle  150 , and when an electrical contact is formed, the power line  160  is available to the PLC-RF enhanced bridge  110  as a communications medium. Additionally, as shown in FIG. 1, the PLC-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 .  
         [0010]    As shown in FIG. 2, the PLC-RF enhanced bridge  110  includes a PLC modem  112  that is connected to a power supply unit  111  and the power plug  140 . The PLC modem 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 electrical contact is established between the power line  160  and the power plug  140 , the power line  160  has been made accessible as a communication medium with the PLC-RF enhanced bridge  110 . In one embodiment, as shown in FIG. 2, the power supply unit  111  includes a power converter  121  for converting the power line voltage to voltages used to operate the PLC-RF enhanced bridge  110 . Also shown in FIG. 2, the power supply unit  111  includes a battery  122  that is used to provide power to the PLC-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 PLC-RF enhanced bridge  110 .  
         [0011]    As discussed hereinabove, when the power line  160  is electrically connected to the power plug  140 , the power line  160  is made accessible as a communications medium. The power plug  140  is also connected to the PLC modem  112  that demodulates PLC messages that are transported via the power line  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 PLC 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 PLC 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 PLC modem  112  and the memory unit  114 . In even another embodiment, the PLC 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 .  
         [0012]    In another direction of data flow (radio frequency (RF) to power line communications (PLC)), RF messages transmitted by one or more of the remote RF transmitting and receiving units  130  are received by the antenna  120  of the PLC-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 PLC modem  112 , and the transfer of the predetermined format messages between the memory unit  114  and the PLC modem  112  is also controlled by the controller  118 . The PLC modem  112  modulates the baseband messages to a transmission format suitable for transportation on the power line  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  131  comprises, for example, random access memory (RAM).  
         [0013]    In one embodiment, the PLC-RF enhanced bridge  110  links two communication modalities, for example, a power line communications (PLC) system with radio frequency (RF) wireless communication system. The messages transmitted on one communications modality are received at the PLC-RF enhanced bridge  110  and retransmitted to the other modality. In one embodiment, the PLC modem  112  of the PLC communications system can use 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 PLC communication system including the PLC 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.  
         [0014]    The flow of data through the PLC-RF enhanced bridge  110  is governed by a protocol suite. In one embodiment both the PLC 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.  
         [0015]    When receiving and demodulating a message  380  (FIG. 3) to a baseband bit stream, the PLC 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 a higher level protocol functions on the bit steam. In one embodiment, the higher level protocol comprises 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. Once a complete and certified correct message  380  (FIG. 3) has been received from one of the RF modem  116  or the PLC modem  112 , the controller  118  passes the message  380  (FIG. 3) to the other of the RF modem  116  or the PLC modem  112  for modulation and transmission.  
         [0016]    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 PLC-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 PLC-RF enhanced bridge  110 . It should be appreciated that, in one embodiment, the special message can be sent as a PLC message or an RF message. 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.  
         [0017]    In one embodiment, the PLC 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 PLC modem  112 . In even another embodiment, the stored program code can be replaced or modified remotely by sending a special message to the PLC-RF enhanced bridge  110 . It should be appreciated that, in one embodiment, the special message can be sent as a PLC message or an RF message.  
         [0018]    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 PLC-RF enhanced bridge  110 . It should be appreciate that, in one embodiment, the special message can be sent as a PLC message or an RF message.  
         [0019]    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 about to be 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.  
         [0020]    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. 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.  
         [0021]    In another embodiment, the PLC-RF enhanced bridge  110  performs additional higher layer protocol functions often performed by a router (not shown). In this embodiment, the PLC-RF enhanced bridge  110  performs protocol conversions between the RF communication system and the PLC communication system. These functions may include decryption of received encrypted messages followed by reencryption 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 .  
         [0022]    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  18  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.  
         [0023]    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 PLC communication system. Some RF transmitting and receiving units  130  can send data  360  in segments in parts that need reassembly at the controller  18 . 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.  
         [0024]    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.