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

• US 5,634,190 A
• Filed: 06/06/1995
• Issued: 05/27/1997
• 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): Eisenzopf, Reinhard J.
• Assistant Examiner(s): BANKS HAROLD, MARSHA DENISE
• Application Number:
  US08/465,938
• Time in Patent Office: 721 Days
• Field of Search: 455/12.1, 455/13.1, 455/13.2, 455/15, 455/20, 455/33.1, 455/54.1, 455/56.1, 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;

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 first 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, 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;

wherein said at least one terrestrial repeater station is further comprised of a second transceiver for receiving a first communication signal from said second one of said satellites associated with said second satellite coverage area and for transmitting said received first communication signal to said first one of said satellites associated with said first satellite coverage area, whereby a communication return link is established between said first station and said second station.

2. 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;

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 first 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, 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;

wherein said at least one terrestrial repeater station is further comprised of means for demodulating a call request transmission that is received from said first satellite, and means for extracting call destination information from said demodulated call request transmission.

3. A communication system as set forth in claim 2 wherein said at least one terrestrial repeater station is further comprised of means for selecting a satellite to receive said transmission from said terrestrial repeater station.

4. A communication system as set forth in claim 2 wherein said demodulating means includes means for despreading a spread spectrum signal that is received from said first satellite.

5. 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;

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 first 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, 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;

wherein said first and second earth orbiting satellites are a portion of a constellation of low earth orbit (LEO) repeater satellites.

6. A communication system as set forth in claim 5 wherein said constellation is comprised of 48 satellites distributed in eight orbital planes with six equally-spaced satellites per plane, said orbital planes being inclined at 52 degrees with respect to the equator.

7. A method for operating a communication system having a constellation of low earth orbit (LEO) repeater 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 region, comprising the steps of:

initiating a communication with a first ground station by forming a communication request that includes information for specifying a destination for the communication;

transmitting the communication request from the first ground station to a first LEO repeater satellite;

repeating the communication request by receiving and transmitting the communication request with the first LEO repeater satellite;

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

extracting the information that specifies the destination for the communication from the received communication request;

selecting, at least partially in accordance with the extracted information, at least one further LEO repeater satellite;

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

repeating the communication request by receiving and transmitting the communication request with the at least one selected LEO repeater satellite;

receiving the repeated communication request 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 call request.

8. A method as set forth in claim 7 wherein the step of extracting includes a step of despreading and demodulating a spread spectrum communication signal.

9. A method as set forth in claim 7 wherein the constellation is comprised of 48 satellites distributed in eight orbital planes with six equally-spaced satellites per plane, and wherein the orbital planes are inclined at 52 degrees with respect to the equator.

10. A ground-based repeater station for use with a plurality of low earth orbit (LEO) 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 LEO communication satellites associated with a first coverage area and for transmitting said received transmission on an uplink to a second one of said LEO 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 LEO communication satellites associated with said second coverage area and for transmitting said received transmission on an uplink to said first one of said LEO communication satellites associated with said first coverage area;

means for demodulating a call request transmission that is received from said first LEO communication satellite;

means for extracting call destination information from said demodulated call request transmission; and

means for selecting a LEO communication satellite to receive said uplink transmission.

11. A ground-based repeater station as set forth in claim 10 wherein said demodulating means includes means for despreading a spread spectrum signal that is received from said first LEO communication satellite.

12. A method for operating a communication system having a constellation of low earth orbit (LEO) repeater 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 region, comprising the steps of:

initiating a communication by sending a transmission from a user terminal to a first LEO repeater satellite;

repeating the transmission through the first LEO repeater 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 the first LEO repeater satellite;

repeating the communication request by receiving and transmitting the communication request with the first LEO repeater satellite;

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

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

repeating the communication request by receiving and transmitting the communication request with the at least one further LEO repeater satellite;

receiving the repeated communication request 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 call request.

13. A method as set forth in claim 12 wherein the steps of transmitting and receiving each include a step of amplifying a spread spectrum communication signal.

14. A method as set forth in claim 12 wherein the constellation is comprised of 48 satellites distributed in eight orbital planes with six equally-spaced satellites per plane, and wherein the orbital planes are inclined at 52 degrees with respect to the equator.