Demand-based connection management integrated services access terminal (ISAT) for satellite communications system

Abstract

A demand-based connection management satellite communication network includes a plurality of geographically distributed earth stations, each earth station having a frame relay protocol-based switch for interfacing message signals between terminal devices and modem unit. One of the earth stations is a hub station whose modem unit includes plural demodulators tuned to carrier frequencies transmitted from other, remote stations. Each remote station has at least one hub-programmable demodulator and/or a programmable modulator. When an originating station receives a request from a terminal device for connectivity with a terminal device at a destination station, it transmits a connectivity request message to the hub station. In response, the hub station checks a demodulator and/or modulator frequency assignment database for demodulator availability. If each originating and destination station has an available demodulator and modulator pair, the hub transmits tuning messages to the two stations, which tune their programmable modem components to each other's carrier frequency, and thereby provide bidirectional connectivity between the two remote stations.

1. A method of providing satellite communication network connectivity between communication devices coupled to geographically distributed earth stations comprising the steps of:
 (a) at each remote earth station of a plurality of remote earth stations, coupling a modulator, having a transmission carrier frequency associated with said each remote earth station, to an uplink port of a frame relay protocol-based switch with which one or more communication devices served by said each remote earth station are interfaced, and coupling a tunable demodulator to a downlink port of said frame relay protocol-based switch;  
 (b) installing, at a hub earth station of said plurality of earth stations, a plurality of demodulators, which are operative to demodulate messages modulated on respectively different carrier frequencies transmitted from said remote earth stations, and coupling respective ones of said plurality of demodulators to respectively different downlink ports of a frame relay protocol-based switch of said hub station;  
 (c) in response to a request, from a communication device coupled to an originating remote earth station of said plurality of remote earth stations, for communication connectivity with a communication device coupled to a destination remote station of said plurality of remote earth stations, causing the modulator of said originating remote earth station to transmit a communication connectivity request message to said hub earth station; and  
 (d) at said hub earth station, in response to said communication connectivity request message, transmitting to said originating remote earth station an originating remote earth station demodulator tuning message that is effective to tune the tunable demodulator at said originating remote earth station to the transmission carrier frequency associated with said destination remote earth station, and transmitting to said destination remote earth station a destination remote earth station demodulator tuning message that is effective to tune the tunable demodulator at said destination remote earth station to the transmission carrier frequency associated with said originating remote earth station.  
 
     
     
       2. A method according to  claim 1 , where step (a) further comprises installing at each remote earth station a further demodulator, which is tuned to the transmission carrier frequency associated with hub earth station, and is operative to demodulate a demodulator tuning message transmitted thereto from said hub earth station. 
     
     
       3. A method according to  claim 1 , further including step (e): at said destination remote earth station, causing the frame relay protocol-based switch thereof to controllably route a downlink-directed message from said demodulator to a virtual port selected in accordance with the contents of said downlink-directed message. 
     
     
       4. A method according to  claim 1 , wherein
 step (a) further comprises, at each remote earth station, installing a first demodulator tuned to the transmission carrier frequency associated with said hub earth station, and being operative to demodulate a demodulator tuning-message transmitted thereto from said hub earth station, and a second demodulator which is programmably tunable to demodulate messages modulated on a programmable carrier frequency transmitted from another remote earth station, and coupling said second demodulator to a downlink port of the frame relay protocol-based switch of said each remote earth station,  
 and step (d) further comprises, in response to said communication connectivity request message, transmitting to said originating remote earth station an originating remote earth station demodulator tuning message for causing said second demodulator at said originating remote earth station to be tuned to the transmission carrier frequency associated with said destination remote earth station, and transmitting to said destination remote earth station a destination remote earth station demodulator tuning message that is operative to tune the second demodulator at said destination remote earth station to the transmission carrier frequency associated with said originating remote earth station.  
 
     
     
       5. A method according to  claim 4 , wherein each earth station includes a communication control processor, associated with said each remote station's frame relay switch, which stores table entries indicating whether there currently exists an active communication link to said destination remote earth station, and wherein step (c) comprises, in response to a call being placed from a communication device, causing said communication control processor to examine said table entries and, in response to said table entries indicating no existing active communication link, generating a link request message for transmission to said hub earth station, said link request message designating which remote earth station is the destination remote earth station. 
     
     
       6. A method according to  claim 5 , wherein step (c) further comprises, in response to said table entries indicating the existence of an active communication link between said originating and destination remote earth stations, causing said originating remote earth station's control processor to forward a call routing message to an idle voice circuit in said destination remote earth station, so that said idle voice circuit may seize a line to a called communication device and thereby complete a communication path between a calling communication device at the originating remote earth station and said called communication at the destination remote earth station. 
     
     
       7. A method according to  claim 4 , wherein said hub earth station includes a network management facility computer and an associated network configuration database, and wherein, in step (d), said network management facility computer examines said network configuration database, to determine availability of a tunable demodulator in each of the originating and destination remote earth stations. 
     
     
       8. A method according to  claim 7 , wherein step (d) further comprises, in response to either or both of said originating and destination remote earth stations containing no available tunable demodulator, returning a busy signal to the communication device of said originating remote earth station. 
     
     
       9. A method according to  claim 7 , wherein step (d) further comprises, in response to termination of call traffic between said originating and destination remote earth stations, causing said originating remote earth station to forward a message to said hub earth station, indicating that traffic between linked remote earth stations has been completed, and causing said hub earth station's network management facility computer to update its network configuration database, so as to allow said tunable demodulators in said originating and destination remote earth stations to be tuned to frequencies associated with other remote earth stations. 
     
     
       10. A method according to  claim 4 , wherein step (d) further comprises causing tunable demodulators in each of said originating and destination remote earth stations to be maintained tuned to their assigned frequencies as long as a voice call is present. 
     
     
       11. A satellite communication system comprising:
 a plurality of geographically distributed remote earth stations; and  
 a hub earth station; and wherein  
 each remote earth station includes a modulator having a transmission carrier frequency associated with said each remote earth station and being coupled to an uplink port of a frame relay protocol-based switch, and a tunable demodulator, which is operative to demodulate messages modulated on a carrier frequency transmitted from another remote earth station, and being coupled to a downlink port of said frame relay protocol-based switch;  
 said hub earth station includes a plurality of demodulators, each of which is operative to demodulate messages modulated on carrier frequencies transmitted from said remote earth stations, and is coupled to respectively different downlink ports of a frame relay protocol-based switch of said hub earth station;  
 in response to a request from a communication device coupled to an originating remote earth station for communication connectivity with a communication device coupled to a destination remote earth station, the modulator of said originating remote earth station is operative to transmit a communication connectivity request message to said hub earth station; and  
 in response to said communication connectivity request message, said hub earth station is operative to transmit, to said originating remote earth station, an originating remote earth station demodulator tuning message that is effective to tune the demodulator at said originating remote earth station to the transmission carrier frequency associated with said destination remote earth station, and to transmit, to said destination remote earth station, a destination remote earth station demodulator tuning message that is effective to tune the demodulator at said destination remote earth station to the transmission carrier frequency associated with said originating remote earth station.  
 
     
     
       12. A satellite communication system according to  claim 11 , wherein each remote earth station includes a further demodulator which is operative to demodulate a demodulator tuning message transmitted thereto on the transmission carrier frequency associated with said hub earth station. 
     
     
       13. A satellite communication system according to  claim 11 , wherein the frame relay protocol-based switch of said destination remote earth station is operative to cause the frame relay protocol-based switch thereof to controllably route a downlink-directed message from said demodulator to a virtual port selected in accordance with contents of said downlink-directed message. 
     
     
       14. A satellite communication system according to  claim 11 , wherein said hub earth station includes a control processor which is operative to store information representative of whether the tunable demodulator of said originating remote earth station and the tunable demodulator of said destination remote earth station are available for establishing communication connectivity between said originating and destination remote earth stations. 
     
     
       15. A satellite communication system according to  claim 11 , wherein a respective remote earth station includes a control processor which is operative to store information representative of whether communication connectivity exists between said respective remote earth station and another remote earth station. 
     
     
       16. A satellite communication system according to  claim 11 , wherein said originating and destination remote earth stations are operative to maintain their tunable demodulators tuned to their assigned frequencies as long as a voice call is present. 
     
     
       17. A earth communication system according to  claim 11 , wherein each remote earth station includes a first demodulator tuned to the transmission carrier frequency associated with said hub earth station, and operative to demodulate a demodulator programming-message transmitted thereto from said hub earth station, and a second demodulator which is operative to demodulate messages modulated on a programmable carrier frequency transmitted from another remote earth station, said second demodulator being coupled to a downlink port of the frame relay protocol-based switch of said respective remote station, and wherein
 said hub earth station is operative, in response to said communication connectivity request message, to transmit, to said originating remote earth station, an originating remote earth station demodulator programming message for causing the second demodulator at said originating remote station to be tuned to the transmission carrier frequency associated with said destination remote earth station, and to transmit, to said destination remote earth station, a destination remote earth station demodulator programming message for causing the second demodulator at said destination remote earth station to be tuned to the transmission carrier frequency associated with said originating remote earth station.  
 
     
     
       18. A satellite communication system according to  claim 17 , wherein each remote earth station includes a communication control processor, associated with said each remote earth station's frame relay switch, which stores table entries indicating whether there currently exists an active communication link to said destination remote earth station, and which is operative, in response to a call being placed from a communication device, for causing said communication control processor to examine said table entries and, in response to said table entries indicating no existing active communication link, for generating a link request message for transmission to said hub earth station, said link request message designating which remote earth station is the destination remote earth station. 
     
     
       19. A satellite communication system according to claim,  18 , wherein said hub earth station includes a network management facility computer and an associated network configuration database, and wherein said network management facility computer is operative to examine a network configuration database, to determine availability of a tunable demodulator in each of said originating and destination remote earth stations. 
     
     
       20. A satellite communication system according to  claim 19 , wherein said originating remote earth station is operative, in response to termination of call traffic therebetween, to forward a message to said hub earth station, indicating that all traffic between the linked stations has been completed, and wherein said hub earth station's network management facility computer is operative to update its network configuration database, so as to allow said tunable demodulators in said originating and destination remote earth stations to be tuned to frequencies associated with other remote earth stations. 
     
     
       21. A method of providing satellite communication network connectivity between communication devices coupled to geographically distributed earth stations comprising the steps of:
 ( a )  at each remote earth station of a plurality of remote earth stations, coupling a modulator, having a transmission carrier frequency associated with said each remote earth station, to an uplink port of a packet switch with which one or more communication devices served by said each remote earth station are interfaced, and coupling a demodulator to a downlink port of said packet switch;      ( b )  installing, at a hub earth station of said plurality of earth stations, a plurality of demodulators, which are operative to demodulate messages modulated on respectively different carrier frequencies transmitted from said remote earth stations, and coupling respective ones of said plurality of demodulators to respectively different downlink ports of the packet switch of said hub station;      ( c )  in response to a request, from a communication device coupled to an originating remote earth station of said plurality of remote earth stations, for communication connectivity with a communication device coupled to a destination remote station of said plurality of remote earth stations, causing the modulator of said originating remote earth station to transmit a communication connectivity request message to said hub earth station; and      ( d )  at said hub earth station, in response to said communication connectivity request message, transmitting to said originating remote earth station an originating remote earth station demodulator tuning message that is effective to tune the demodulator at said originating remote earth station to the transmission carrier frequency associated with said destination remote earth station, and transmitting to said destination remote earth station a destination remote earth station demodulator tuning message that is effective to tune the demodulator at said destination remote earth station to the transmission carrier frequency associated with said originating remote earth station.     
     
     
       22. A satellite communication system comprising:
   a plurality of geographically distributed remote earth stations; and        a hub earth station; and        wherein each remote earth station includes a modulator having a transmission carrier frequency associated with said each remote earth station and being coupled to an uplink port of a packet switch, and a demodulator, which is operative to demodulate messages modulated on a carrier frequency transmitted from another remote earth station, and being coupled to downlink port of said packet switch;        said hub earth station includes a plurality of demodulators, each of which is operative to demodulate messages modulated on carrier frequencies transmitted from said remote earth stations, and is coupled to respectively different downlink ports of a packet switch of said hub earth station;        in response to a request from a communication device coupled to an originating remote earth station for communication connectivity with a communication device coupled to a destination remote earth station, the modulator of said originating remote earth station is operative to transmit a communication connectivity request message to said hub earth station; and        in response to said communication connectivity request message, said hub earth station operative to transmit, to said originating remote earth station, an originating remote earth station demodulator tuning message that is effective to tune the demodulator at said originating remote earth station to the transmission carrier frequency associated with said destination remote earth station, and to transmit, to said destination remote earth station, a destination remote earth station demodulator tuning message that is effective to tune the demodulator at said destination remote earth station to the transmission carrier frequency associated with said originating remote earth station.     
     
     
       23. A earth communication system comprising:
   a plurality of geographically distributed remote earth stations, wherein each remote earth station is coupled to a communication device and includes a modulator and demodulator;        wherein the communication device is capable of generating a request for communication connectivity with a second communication device coupled to a second remote earth station;        wherein the modulator has a transmission carrier frequency associated with each remote earth station and is coupled to an uplink port of a packet switch and is capable of transmitting a communication connectivity request message,        wherein the demodulator demodulates messages transmitted from another remote earth station and is coupled to a downlink port of the packet switch; and        a hub earth station, wherein the hub earth station includes a plurality of demodulators, wherein each demodulator is tuned to carrier frequencies transmitted from the remote earth stations, is coupled to respectively different downlink ports of the packet switch and is capable of transmitting tuning messages to each remote earth station effective to tune the demodulator of an originating remote earth station to the frequency associated with a destination remote earth station and to tune the demodulator of the destination remote earth station to the frequency associated with the originating remote earth station.     
     
     
       24. A hub earth station, comprising:
   a plurality of demodulators, each of which is coupled to respectively different downlink ports of a frame relay protocol - based switch of said hub earth station and is operative to demodulate messages modulated on carrier frequencies transmitted from a plurality of remote earth stations;        a receiver that accepts a communication connectivity request message from an originating remote earth station, wherein the communication connectivity request message is generated by a modulator in the originating remote earth station in response to a request from a communication device coupled to the originating remote earth station for communication connectivity with a communication device coupled to a destination remote earth station; and        a transmitter that sends, to the originating remote earth station, an originating remote earth station demodulator tuning message that is effective to tune a demodulator at the originating remote earth station to the transmission carrier frequency associated with the destination remote earth station, and for transmitting, to the destination remote earth station, a destination remote earth station demodulator tuning message that is effective to tune a demodulator at the destination remote earth station to the transmission carrier frequency associated with the originating remote earth station.     
     
     
       25. A method for use with a hub earth station comprising a plurality of demodulators, each of which is coupled to respectively different downlink ports of a frame relay protocol- based switch of said hub earth station and is operative to demodulate messages modulated on carrier frequencies transmitted from a plurality of remote earth stations, said method comprising the steps of:      receiving a communication connectivity request message from an originating remote earth station, wherein the communication connectivity request message is generated by a modulator in the originating remote earth station in response to a request from a communication device coupled to the originating remote earth station for communication connectivity with a communication device coupled to a destination remote earth station; and        transmitting, to the originating remote earth station, an originating remote earth station demodulator tuning message that is effective to tune the demodulator at the originating remote earth station to the transmission carrier frequency associated with the destination remote earth station, and for transmitting, to the destination remote earth station, a destination remote earth station demodulator tuning message that is effective to tune a demodulator at the destination remote earth station to the transmission carrier frequency associated with the originating remote earth station.