Abstract:
An operational mechanism enables extending the range of cognitive networks through the use of repeater transceivers and selective routing.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 12/172,124, filed Jul. 11, 2008 which is a continuation-in-part of U.S. patent application Ser. No. 10/730,753, filed Dec. 8, 2003 (now U.S. Pat. No. 7,457,295) which claims priority to U.S. Patent Application No. 60/432,223 filed Dec. 10, 2002. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates in general to communication systems and subsystems thereof, and is particularly directed to a ‘repeater’ embodiment that may be employed by the communications controller of a spectral reuse transceiver of a communication system of the type disclosed in the above-identified &#39;124 application, to enable spectral-reuse methods in transceivers having many of the benefits of the communication system disclosed in the &#39;124 application, extending the communications range of the cognitive network. 
       BACKGROUND OF THE INVENTION 
       [0003]    As described in the &#39;124 application (and its incorporated references), in some radio bands, such as the 217 220 MHz VHF band, as a non-limiting example, governmental licensing agencies (e.g., the Federal Communications Commission (FCC)) customarily grant primary licensees non exclusive use of the band for a variety of communication services, such as push to talk voice transmission. Primary users pay for this licensed use with an expectation that they will not encounter interference by other users. The FCC also allows secondary users to access the same band and the same channels within the band on a ‘non-interfering’ or secondary basis, whereby a channel may be used by a secondary, non-licensed, user, so long as the primary user is not using that channel. 
         [0004]    The FCC and similar agencies in foreign countries are continually looking for ways to allow the expanded use of these licensed radio frequency bands without reducing the quality of service available to primary users. For secondary users, these bands provide a cost free opportunity with excellent radio transmission properties for telemetry and other applications. Because secondary users must not interfere with primary users, however, complaints of interference from a primary user to the FCC may result in its issuing an administrative order requiring the secondary user to move to another portion of the band or leave the band entirely. Such a spectral transition is disruptive to the secondary user&#39;s service and can be expensive, especially if site visits, equipment modification, or exchange are required in order to implement the mandated change. It will be appreciated, therefore, that there is a need for a mechanism that allows a secondary user to employ a licensed band on a non interfering basis and that will adapt the radio&#39;s frequency usage should new primary users appear. It should be noted that primary users always have priority over secondary users and there is no first use channel frequency right for secondary users. 
         [0005]    Advantageously, the invention described in the &#39;753 application incorporated into the &#39;124 application successfully addresses this need by means of a monitored spectral activity-based link utilization control mechanism, and the present application extends the range of the transceiver links through ‘repeatering’. Briefly reviewing this link utilization control mechanism, which may be used with a star-configured communication system among other topologies and configurations, such as that depicted in the reduced complexity diagram of  FIG. 1 , a spectral reuse transceiver installed at a master site  10  communicates with respective spectral reuse transceivers installed at a plurality of remote sites  12 . Each spectral reuse transceiver operates with a selectively filtered form of frequency hopping for producing a sub-set of non interfering radio channels or ‘sub-channels’. It should be noted here that other configuration or network topologies may be used consistent with the invention disclosed herein. Thus the invention may be used with radio links between transceivers in other topologies, such as point-to-point, and individual links in mesh networks without limitation, consistent herewith. 
         [0006]    For this purpose, the master site  10  periodically initiates a clear sub-channel assessment routine, in which the master site and each of the remote sites  12  participate, in order to compile or ‘harvest’ a list of non-interfering or ‘clear’ sub-channels (such as 6.25 KHz wide sub-channels), which may be used by participants of the network for conducting communication sessions that do not ostensibly interfere with any licensed user. By transmitting on only clear sub-channels, a respective site&#39;s spectral reuse transceiver is ensured that it will not interfere with any primary user of the band of interest. 
         [0007]    Except when it is transmitting a message to the master site, each remote user site sequentially steps through and monitors a current list of clear sub-channels (that it has previously obtained from the master site), in accordance with a pseudo-random (PN) hopping sequence that is known a priori by all the users of the network, listening for a message that may be transmitted to it by the master site transceiver. During the preamble period of any message transmitted by the master site, each remote site&#39;s transceiver scans all frequency bins within a given spectrum for the presence of radio frequency (RF) energy. Any bin containing energy above a prescribed threshold is marked as a non-clear sub-channel, while the remaining sub-channels are identified as clear (and therefore available for reuse) sub-channels. 
         [0008]    Whenever a remote site notices a change in its clear sub-channel assessment, it reports this to the master site at the first opportunity. As the master site has received clear sub-channel lists from all the remote sites, it logically combines all of the clear sub-channel lists, to produce a composite clear sub-channel list. This composite clear sub-channel list is stored in the master site&#39;s transceiver and is broadcast to all of the remote sites over a prescribed one of the clear sub-channels that is selected in accordance with a PN sequence through which clear sub-channels are selectively used among the users of the network. When the composite clear sub-channel list is received at a respective remote site it is stored in the site&#39;s transceiver. 
         [0009]    To ensure that all communications among the users of the network are properly synchronized (in terms of the composite clear sub-channel list and the order through which the units traverse, or ‘hop’ through, the clear sub-channel entries of the clear sub-channel list), the master site&#39;s transceiver transmits an initialization message on an a priori established clear sub-channel, which each of the remote units monitors. This initialization message contains the clear sub-channel list, an identification of the preamble channel, a PN sequence tap list, and a PN seed that defines the initial sub-channel and hopping sequence for the duration of an upcoming transmit burst. Once a remote site has received an initialization message, that site will transition to normal multiple access mode. 
         [0010]    This procedure is similar to that disclosed in the &#39;124 application which is intended for use with a star-configured communication system such as that depicted in the reduced complexity diagram of  FIG. 1  in which a spectral reuse transceiver installed at a master site  10  communicates with respective spectral reuse transceivers installed at a plurality of remote sites  12 . Each spectral reuse transceiver operates with a selectively filtered form of frequency hopping for producing a sub-set of non interfering radio channels or ‘sub-channels’. 
         [0011]    For further details of the architecture and operation of the spectral reuse link control mechanism disclosed in the above-referenced &#39;753 and &#39;124 applications, attention may be directed to those documents. They will not be detailed here in order to focus the present description on the problem of simplex and duplex ‘repeater’ embodiments, whereby one or more remote site transceivers operate in repeater mode to extend the range of the network. 
       SUMMARY OF THE INVENTION 
       [0012]    In accordance with the present invention, the simplex cognitive ‘repeater’ goal is successfully addressed by designating one or more transceivers in the cognitive network to perform the repeater function, prescribing one or more lists of distant transceivers being served by repeaters in a distant network, prescribing a set of routing rules for the repeaters, including rules for routing messages received from distant transceivers and rules for routing messages received from the base station or other transceivers in the network, and prescribing a set of rules to enable distant transceivers to participate in the cognitive aspects of the network. 
         [0013]    In another embodiment of the present invention, the network and one or more distant networks each operate on independent frequencies (‘duplex mode’), wherein the local network and any far networks are independent cognitive networks. The cognitive ‘duplex repeater’ goal is successfully addressed by designating one or more transceivers in the cognitive network to perform the repeater function, prescribing one or more lists of distant transceivers being served by repeaters in a distant network, interconnecting each repeater transceiver to the distant network&#39;s respective base station transceiver, prescribing a set of routing rules for the repeaters, including rules for routing messages received from distant transceivers and rules for routing messages received from the base station or other transceivers in the network, and prescribing a set of rules to enable distant transceivers to participate in the cognitive aspects of the network. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  diagrammatically illustrates the overall architecture of a communication network, respective terminal unit transceiver sites of which employ the spectral reuse transceiver of the invention disclosed in the above-referenced &#39;753 application. 
           [0015]      FIG. 2   a  graphically illustrates a cognitive network with simplex repeater comprising one network with a simplex repeater transceiver, and two far remote transceivers. 
           [0016]      FIG. 2   b  illustrates the exchange of transmissions of the network of  FIG. 2   a.    
           [0017]      FIG. 3  is a flowchart of a routine for implementing the repeating of packets by a simplex repeater transceiver according to an embodiment of the present invention. 
           [0018]      FIG. 4   a  graphically illustrates a cognitive network with duplex repeater comprising one network with a base station, duplex repeater transceiver, far base station, and a far remote transceiver. 
           [0019]      FIG. 4   b  illustrates the exchange of messages in a duplex transceiver configuration. 
           [0020]      FIG. 5  is a flowchart of a routine for implementing the repeating of packets by a duplex repeater transceiver according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    This invention essentially involves special cases of the sub-channel hopping control mechanism executed by the communications control processor of the spectral reuse transceiver of the type disclosed in the &#39;124 and &#39;753 applications. This involves the execution of one or more prescribed discriminators or sub-channel selection filters, so as to effectively reduce the receiving end of a transceiver link. As will be described, these filter functions are readily implemented by appropriately setting the configuration parameters used by the communications controller of the transceiver disclosed in the &#39;753 application to control the operation of the transceiver. The architecture of the transceiver of the &#39;753 application may remain unchanged, except as noted. As a consequence, the present invention has been illustrated in the drawings by diagrammatic illustrations which include a generalized network architecture diagram and a sub-channel sub-division diagram that show only those details that are pertinent to the invention, so as not to obscure the disclosure with details which will be readily apparent to one skilled in the art having the benefit of the description herein. 
         [0022]    As pointed out above, an objective of the invention is to extend the reach of a network, particularly a cognitive network, as described in the &#39;124 application by interconnecting one or more distant transceivers to the network through one or more intermediate transceivers in the network, each transceiver performing a repeater function for each of one or more respective distant transceivers. The operation and effect of these repeaters, including a simplex repeater and a duplex repeater, will be discussed individually below. 
         [0023]      FIG. 1  graphically illustrates a spectral reuse transceiver of the type described in the &#39;124 application, installed at a master site  10  which communicates with respective spectral reuse transceivers installed at a number of remote sites  12 . Each spectral reuse transceiver operates with a selectively filtered form of ‘slow’ frequency hopping, moving only when a sub-channel with less interference becomes available, so as to avoid interfering with another transceiver. 
         [0024]    For the purposes of extending the range of the network of the present invention, one or more transceivers in the network may be advantageously selected to reach distant transceivers that are out of the range of the network&#39;s base station. 
         [0025]    Referring to  FIGS. 2   a  and  2   b , which graphically illustrate a simplex repeating operation, a network  200  in  FIG. 2   a  comprises a base station (BS- 1 )  206  with the non-limiting example of two remote stations REM- 1   208  and REM- 2   218  within radio coverage area  204  of base station  206 . Remote REM- 1   208  is further functioning as a simplex repeater, according to the present invention, extending network  200  radio coverage area  204  to include radio range  205  of remote REM- 1   208 . Radio coverage area  205  includes two far remotes REM- 3   209  and REM- 4   219 , which are capable of communicating with remote REM- 1   208 . According to the present invention, messages received by simplex repeater REM- 1   208  from base station BS- 1   206  or from a far remote such as REM- 3   209  are repeated on the same frequency, using the repeating rules described below, thereby advantageously extending the coverage area  204  of base station BS- 1   206  to include the coverage area  205  of simplex repeater REM- 1   208 . Any one of remotes  208 ,  218 ,  209   219  may be configured to support simplex repeater functionality described herein. All radios in network  200  cooperate to ensure that only one radio is transmitting at any instant, such cooperation including using radio media access methods such as poll/response, TDMA, and other access methods understood by persons skilled in the radio art. 
         [0026]      FIG. 2   b  further illustrates the exchange of messages using the simplex repeater of the present invention. Base station BS- 1   206  transmits a message  210  and that message is received by REM- 1   208  operating as a simplex repeater according to the present invention. REM- 1   208 , according to simplex repeating rules, rebroadcasts message  210  as message  211 . Message  211  is received by base station BS- 1   206  and far remote REM- 3   209 , thereby extending the coverage area of base station BS- 1  to include far remote REM- 3 . Note that as a result of the repeating of message  210  as message  211 , base station BS- 1  receives its own original message  210  in the form of repeated message  211 . 
         [0027]    According to one embodiment of the present invention, BS- 1  would discard message  211 . In another embodiment of the present invention, BS- 1  will use message  211  as a positive acknowledgment of the receipt of message  210  by remote  208 . In yet another embodiment of the present invention, REM- 1   208  only repeats messages  210  if that message is a broadcast message or is addressed to or received from a far remote whose address or site ID is in a provided “repeat list” of approved far remote sites. In another embodiment of the present invention, the address is an IP address. 
         [0028]    Similarly, a message  212  received from far remote REM- 3   209  is received by REM- 1   208  and is subsequently repeated by REM- 1  in the form of message  213 , message  213  being received by BS- 1   206  and REM- 3   209 . In another embodiment of the present invention, REM- 1  only repeats message  212  if that message is a broadcast message or is addressed to or received from a far remote whose address or site ID is NOT included in the “repeat list” of approved far remote sites. In another embodiment of the present invention, the address may be an IP address. In this instance, message  213  is ‘new’ for base station BS- 1   206 , and is a duplicate of message  212  for far remote REM- 3 . Upon receiving the repeated message  213 , REM- 3  may discard it or use it as a positive acknowledgment of the receipt of message  212  by REM- 1 . 
         [0029]    Message  214  illustrates receipt of a message by REM- 1 , sent by BS- 1  and addressed to a far remote that is not in remote REM- 1 &#39;s “repeat list” and is not a broadcast message. In this instance, REM- 1  does not repeat message  214 . Similarly, message  215  illustrates the example of a message received by REM- 1  from a far remote (REM- 3 ) that IS in REM- 1 &#39;s “repeat list” and is not a broadcast message. In this instance, however, REM- 1  does not repeat message  215 . The repeating rules for simplex operation allow the configuration of repeaters and remotes in IP networks to be changed by software without requiring changes to IP addresses, subnets, or masks. Also, the repeating rules permit the exchange of cognitive information, such as interference information, between base stations and all radios (including far remotes through their repeaters), thus extending the range of cognitive radio networks. This will enable, for example, the entire cognitive network, including far remotes, to move to a new frequency channel on command from the base station, including cognitively moving to a new frequency channel to mitigate against radio interference. 
         [0030]    Referring now to  FIG. 3 , flowchart  30  further depicts the repeating rules described above. After an initialization period, a remote transceiver of the present invention waits at block  31  to receive a message from the base station or a far remote. When a message is received, decision block  32  determines whether the message was received from a base station or from a remote. If the message was received from a base station, program flow follows the “Yes” path whereby decision block  33  checks the received message&#39;s destination address. If the destination address is a broadcast message or, is in the remote transceiver&#39;s “repeat list” of transceivers, the “Yes” path is taken whereby the message is repeated at Repeat block  35 ; otherwise, decision block  33  returns to Await Message block  31  via return path  39 . 
         [0031]    Returning to decision block  32 , if the message received is from a far remote (rather than from a base station), the “No” path is taken, whereby decision block  36  checks the receive message&#39;s destination address. If the destination address is not in the “repeat list” of far transceivers, the “Yes” path is taken whereby the message is repeated at Repeat block  38 . This would be the case, for example, if the message is intended for base station BS- 1 , which is not located in a remote coverage area and therefore whose address would not appear in REM- 1 &#39;s repeat list. If the destination address is found in REM- 1 &#39;s repeat list, the message is not intended for BS- 1 , and decision block  33  returns program flow to Await Message block  31  via return path  39  without first repeating the message. 
         [0032]      FIG. 4   a  graphically illustrates a duplex repeating operation. A network  400  comprises the network of base station BS- 1   406  with its associated remote stations REM- 1   408  and REM- 2   418 , with REM- 1  operating as a duplex repeater. The network also includes base station BS- 2   407  with its associated remote stations REM- 3   409  and REM- 4   419 , and an Ethernet cable  402  connecting REM- 1  to BS- 2 . According to the present invention, messages received by duplex repeater REM- 1  from base station BS- 1  are sent over Ethernet connection  402  to base station BS- 2  where the messages may be rebroadcast to remote stations REM- 3   409  and REM- 4   419 . In this embodiment, the coverage area  404  of base station BS- 1  has been extended to include the coverage area  405  of BS- 2 . Similarly, messages received by BS- 2  from a remote  409  or  419  are sent over Ethernet connection  402  to base station duplex repeater REM- 1   408 , from which the messages may be retransmitted to base station BS- 1 . Any of remotes  408  or  418  of BS- 1  may be configured to support the duplex repeater functionality described herein. The remote radios  408 ,  418  of the BS- 1  network  404  may transmit independently of the remote radios  409 ,  419  of the BS- 2  network  405 . 
         [0033]      FIG. 4   b  further illustrates the exchange of messages using the duplex repeater of the present invention. Periodically, far base station BS- 2   407  will send its routing table (for network  405  in  FIG. 4   a ) over Ethernet cable  402  to remote REM- 1   408 . The routing table informs REM- 1 , which is acting as a duplex receiver and as the default gateway of far base station BS- 2 , of the presence of far remote transceivers REM- 3   409  and any others (not shown) on the network  405  of BS- 2 . This routing technique allows fairly large networks to be aggregated without the need for large routing tables. 
         [0034]    The two radio networks manage their physical layer transmit and receive operations independently, and can use their cognitive capabilities (described in the &#39;124 application) to avoid interfering with each other. Base station BS- 1   406  broadcasts message  410  which is received by REM- 1   408  operating as a duplex repeater according to the present invention. REM- 1  looks up the address of message  410  in the routing table and, if it finds a match, will send the message over Ethernet cable  402  as message  411  to far base station BS- 2   407 . BS- 2  then broadcasts the message to all far radios  409 ,  419  on BS- 2 &#39;s network  405  as message  412 . 
         [0035]    Similarly, when a message  422  from far remote REM- 3   409  is received by BS- 2 , BS- 2  sends message  422  as message  421  over Ethernet connection  402  to REM- 1   408 , which is acting as a default gateway and duplex repeater for BS- 2 . REM- 1  compares the address of message  421  to addresses in its routing table, and if it does NOT find a match, REM- 1  sends message  421  over the air as message  420  to base station BS- 1   406 . 
         [0036]    In another scenario, BS- 1   406  broadcasts message  430  over the air where it is received by REM- 1  acting as a duplex repeater for BS- 2   407 . In this example, the address of message  430  is NOT found in the routing table of REM- 1 , so REM- 1  will not send message  430  to BS- 2  via Ethernet cable  402 . In yet another scenario, BS- 2  receives message  440  from far remote REM- 3   409 . BS- 2  subsequently sends message  440  as message  441  to REM- 1  over Ethernet cable  402 , REM- 1  acting as the default gateway and duplex repeater for BS- 2 . In the present example, the address of message  441  (and message  440 ) IS found in the routing table of REM- 1 . Because addresses in REM- 1 &#39;s routing table pertain only to transceivers in BS- 2 &#39;s network  405 , the message is not intended for BS- 1 , and REM- 1  will not repeat message  441  for receipt by BS- 1 . 
         [0037]    In another embodiment of the present invention, the address is an IP address. In the preferred embodiment, the testing of IP addresses in the routing table is done by the subnet and mask technique, which is well known to one skilled in the art. The described repeating (routing) technique allows the creation of fairly large networks of IP addresses without large routing tables. The two radio networks  404  and  405  manage their physical layer transmit and receive operations independently, and can use their cognitive capabilities to avoid interfering with each other. 
         [0038]    Referring next to  FIG. 5 , flowchart  50  further describes the repeating rules of the duplex repeater described above in the descriptions of  FIGS. 4   a  and  4   b . In  FIG. 5 , after an initialization period, a remote transceiver acting as a duplex repeater of the present invention waits at block  51  to receive a message from the base station (over the air) or from the far base station (over the Ethernet cable). When a message is received, decision block  52  tests the message source. If the message was received from the base station, the “Yes” path  510  is taken to decision block  53 , where the message address is tested. If the message received has a broadcast address or is in the remote&#39;s routing table, the “Yes” path  54  is taken whereby the message is repeated by Repeat block  55  over an Ethernet cable to the far base station. Otherwise, decision block  53  returns to Await Message block  51 . Returning now to decision block  52 , if the message received is from BS- 2  over the Ethernet cable, the “No” path is taken to block  56 , whereby decision block  56  tests the receive message&#39;s destination address. If the destination address is found in the route list of far transceivers or is a broadcast message, the message is not intended for network  404 , and the “No” path is taken whereby program flow returns to decision block  56  via return path  59  to Await Message block  51 . Otherwise, the message is intended for network  404  and is repeated by Repeat block  58  by transmitting the message over the air to BS- 1   
         [0039]    The example of the Ethernet cable of  FIGS. 4   a  and  4   b , and the descriptions of  FIGS. 4   a ,  4   b  and  5  are not limiting. Asynchronous communications over serial ports and other serial communications methods known to one skilled in the art are anticipated by the present invention. Similarly, the addressing of  FIGS. 2   a ,  2   b ,  3 ,  4   a ,  4   b , and  5  are not limited to IP address. Various routing address schemes known to one skilled in the art, such as IPX, and the various SCADA protocols, are able to be used by the present invention. 
         [0040]    While we have shown and described several embodiments in accordance with the present invention, it is to be understood that the same is not limited thereto but is susceptible to numerous changes and modifications as would be known to persons skilled in the art, and there is no intention that this application be so limited, but it is intended to cover all such changes and modifications as are obvious to one of ordinary skill in the art. For example, the transceivers described in the above-identified &#39;753 application may, without limitation, operate in a star network. Radio links between transceivers in other topologies, such as point-to-point, and individual links in mesh networks, as examples, can employ the cost-reduction and other improvements of the present invention.