Low earth orbit communication satellite gateway-to-gateway relay system

• US 5,758,261 A
• Filed: 03/03/1997
• Issued: 05/26/1998
• Est. Priority Date: 06/06/1995
• Status: Expired due to Term

• Current Assignee: Globalstar Incorporated
• Original Assignee: Globalstar Incorporated
• Inventors: Wiedeman, Robert A.
• Primary Examiner(s): Vo, Nguyen
• Assistant Examiner(s): BANKS HAROLD, MARSHA DENISE
• Application Number:
  US08/810,189
• Time in Patent Office: 449 Days
• Field of Search: 455/12.1, 455/13.1, 455/13.2, 455/15, 455/20, 455/422, 455/427, 455/428, 375/200
• US Class Current: 455/13.1
• CPC Class Codes: H04B 7/1856 for call routing
• CPC Class Codes: H04B 7/195 Non-synchronous stations

Abstract

This invention teaches the use of overlapping footprints in a LEO satellite communications system to increase the overall connectivity of the system, thus providing a wide service availability. In particular, this invention teaches the use of at least one terrestrial LEOS relay station (70) that is positioned within an overlap of at least two satellite coverage areas for relaying a communication from a gateway (18A) associated with a first coverage area to a gateway (18B) associated with a second coverage area. A plurality of LEOS relay stations can be so provided to enable a communication, such as a voice communication, to be routed through a plurality of coverage areas and gateways, thereby bypassing a substantial portion of an underlying terrestrial communication system.

Claims

1. A communication system, comprising:

at least first and second earth orbiting satellites individual ones of which comprise means for transceiving first communication signals with terrestrially located user terminals and for transceiving second communication signals with terrestrially located stations, said first communication signals being within a first band of frequencies and said second communication signals being within a second band of frequencies, said at least two earth orbiting satellites having first and second terrestrial coverage areas, respectively; and

at least one terrestrial repeater station that is located within an overlapped region between said first and second terrestrial coverage areas, said at least one terrestrial repeater station being comprised of a transceiver for receiving a first communication signal in said first band of frequencies from a first one of said satellites associated with said first satellite coverage area and for transmitting in said first band of frequencies said received first communication signal to a second one of said satellites associated with said second satellite coverage area, whereby a communication forward link is established between a first station located within said first satellite coverage area and a second station located within said second satellite coverage area.

2. A communications system, comprising:

a plurality of terrestrial transceivers comprised of gateways and user terminals;

a constellation of non-geosynchronous orbit satellites each having an associated ground coverage region for bidirectionally communicating with said terrestrial transceivers that are located within the associated ground coverage regions;

a first gateway including a first controller for initiating a communication, said first controller forming a communication request that includes information for specifying a destination for the communication;

a transmitter for transmitting the communication request from the first gateway to a first satellite;

a transponder on said first satellite for repeating the communication request by receiving and transmitting the communication request;

a terrestrial repeater station for receiving the repeated communication request, said terrestrial repeater station being located within the ground coverage region of the first satellite;

said terrestrial repeater station comprising circuitry for extracting the destination information from the received communication request and for selecting, at least partially in accordance with the extracted destination information, at least one further satellite, said terrestrial repeater station further comprising a transmitter for transmitting the communication request from the terrestrial repeater station to the at least one selected satellite, the at least one selected satellite having a ground coverage region that overlaps the ground coverage region of the first satellite;

a transponder on said at least one selected satellite for repeating the communication request by receiving and transmitting the communication request; and

a second gateway comprised of a receiver for receiving the repeated communication request from the at least one selected satellite and a second controller for establishing a communication link to a terrestrial communication network in accordance with the destination specified by the call request.

3. A system as set forth in claim 2, wherein said extracting circuitry is comprised of means for despreading and demodulating a spread spectrum communication signal.

4. A system as set forth in claim 2, wherein the satellite constellation is comprised of low earth orbit satellites.

5. A system as set forth in claim 2, wherein the satellite constellation is comprised of medium earth orbit satellites.

6. A ground-based repeater station for use with a plurality of non-geosynchronous communication satellites individual ones of which have an associated ground coverage area, comprising:

a first transceiver for receiving a downlink transmission from a first one of said communication satellites associated with a first coverage area and for transmitting said received transmission on an uplink to a second one of said communication satellites associated with a second coverage area that overlaps the first coverage area;

a second transceiver for receiving a downlink transmission from said second one of said communication satellites associated with said second coverage area and for transmitting said received transmission on an uplink to said first one of said communication satellites associated with said first coverage area;

circuitry for demodulating a call request transmission that is received from said first communication satellite; and

a controller for extracting call destination information from said demodulated call request transmission and for selecting at least one communication satellite to receive said uplink transmission.

7. A ground-based repeater station as set forth in claim 6, wherein said circuitry includes means for despreading a spread spectrum signal that is received from said first communication satellite.

8. A ground-based repeater station as set forth in claim 6, wherein the plurality of satellites are in low earth orbit.

9. A ground-based repeater station as set forth in claim 6, wherein the plurality of satellites are in medium earth orbit.

10. A communications system, comprising:

a plurality of terrestrial transceivers comprised of gateways and satellite user terminals;

a constellation of non-geosynchronous orbit satellites each having an associated ground coverage region for bidirectionally communicating with said terrestrial transceivers that are located within the associated ground coverage regions;

a first gateway including a first controller for initiating a call from a satellite user terminal to a terrestrial cellular user transceiver, said first controller forming a communication request that includes call routing information;

a transmitter for transmitting the communication request from the first gateway to a first satellite;

a transponder on said first satellite for repeating the communication request by receiving and transmitting the communication request;

a terrestrial repeater station for receiving the repeated communication request, said terrestrial repeater station being located within the ground coverage region of the first satellite;

said terrestrial repeater station comprising circuitry for extracting the call routing information from the received communication request and for selecting, at least partially in accordance with the extracted call routing information, at least one further satellite, said terrestrial repeater station further comprising a transmitter for transmitting the communication request from the terrestrial repeater station to the

at least one selected satellite, the at least one selected satellite having a ground coverage region that overlaps the ground coverage region of the first satellite;

a transponder on said at least one selected satellite for repeating the communication request by receiving and transmitting the communication request; and

a second gateway comprised of a receiver for receiving the repeated communication request from the at least one selected satellite and a second controller for establishing a communication link to the terrestrial cellular user transceiver in accordance with the call routing information.

11. A system as set forth in claim 10, wherein said extracting circuitry is comprised of means for despreading and demodulating a spread spectrum communication signal.

12. A system as set forth in claim 10, wherein the satellite constellation is comprised of low earth orbit satellites.

13. A system as set forth in claim 10, wherein the satellite constellation is comprised of medium earth orbit satellites.

14. A communications system, comprising:

a plurality of terrestrial transceivers comprised of gateways and satellite user terminals;

a constellation of non-geosynchronous orbit satellites each having an associated ground coverage region for bidirectionally communicating with said terrestrial transceivers that are located within the associated ground coverage regions;

a first gateway including a first controller for establishing a call connection, said first gateway including a transmitter for transmitting a communication request from the first gateway to at least one first satellite;

a repeater on said at least one first satellite for repeating the communication request by receiving and transmitting the communication request;

a terrestrial repeater station for receiving the repeated communication request, said terrestrial repeater station being located within the ground coverage region of the at least one first satellite;

said terrestrial repeater station comprising a transmitter for broadcasting the communication request from the terrestrial repeater station to any other satellites of the constellation that have a ground coverage region that overlaps the ground coverage region of the first satellite; and

a second gateway comprised of a receiver for receiving repeated communication requests from one or more of the other satellites and a second controller for forwarding the communication request to a terrestrial telecommunications network for completing the call connection.

15. A system as set forth in claim 14, wherein the satellite constellation is comprised of low earth orbit satellites.

16. A system as set forth in claim 14, wherein the satellite constellation is comprised of medium earth orbit satellites.

17. A communication system, comprising:

at least first and second earth orbiting satellites individual ones of which comprise means for transceiving first communication signals with terrestrially located user terminals and for transceiving second communication signals with terrestrially located stations, said first communication signals being within a first band of frequencies and said second communication signals being within a second band of frequencies, said at least two earth orbiting satellites having first and second terrestrial coverage areas, respectively; and

at least one terrestrial repeater station that is located within an overlapped region between said first and second terrestrial coverage areas, said at least one terrestrial repeater station being comprised of a transceiver for receiving a first communication signal from a first one of said satellites associated with said first satellite coverage area and for transmitting said received first communication signal to a second one of said satellites associated with said second satellite coverage area such that a communication link is established between a first station located within said first satellite coverage area and a second station located within said second satellite coverage area;

wherein

said transceiver of said terrestrial repeater station transmits and receives RF signals in said first band of frequencies that are transceived by said terrestrial user terminals.

18. A method for operating a communication system having a constellation of non-geosynchronous satellites, each having an associated ground coverage region, for bidirectionally communicating with terrestrial transceivers, including ground stations and user terminals that are located within the associated ground coverage regions, comprising the steps of:

initiating a communication by uplinking a transmission to a first satellite;

receiving and retransmitting the transmission, with the first satellite, to a first ground station;

forming a communication request with the first ground station, the communication request including information for specifying a destination for the communication;

transmitting the communication request from the first ground station to a first relay satellite, the first relay satellite being one of the first satellite or another satellite;

receiving and retransmitting the communication request with the first relay satellite;

receiving the retransmitted communication request with a repeater station that is located within the ground coverage region of the first relay satellite;

transmitting the communication request from the repeater station to at least one second relay satellite, the at least one second relay satellite having a ground coverage region that overlaps the ground coverage region of the first relay satellite;

receiving and retransmitting the communication request with the at least one second relay satellite;

receiving the retransmitted communication request from the at least one second relay satellite with at least one further ground station; and

establishing a communication link to a terrestrial communication network in accordance with the destination specified by the communication request.

19. A method as set forth in claim 18, wherein the step of initiating uplinks a spread spectrum communication signal.

20. A method as set forth in claim 18, wherein the step of initiating uplinks a time division, multiple access communication signal.

21. A method as set forth in claim 18, wherein the constellation is comprised of one of low earth orbit satellites or medium earth orbit satellites.