Satellite telephone interference avoidance system

• US 5,875,180 A
• Filed: 02/06/1997
• Issued: 02/23/1999
• Est. Priority Date: 02/06/1997
• Status: Expired due to Term

• Current Assignee: Globalstar Incorporated
• Original Assignee: Globalstar Incorporated
• Inventors: Wiedeman, Robert A., Monte, Paul A, Gallagher, Vijaya K
• Primary Examiner(s): VU, HUY DUY
• Application Number:
  US08/796,226
• Time in Patent Office: 747 Days
• Field of Search: 370/241, 370/242, 370/252, 370/310, 370/316, 370/317, 370/318, 370/319, 370/321, 370/322, 370/326, 370/327, 370/328, 370/329, 370/330, 370/331, 370/332, 370/333, 370/334 , 370/336, 370/337, 370/341, 370/343, 370/344, 370/431, 370/436, 370/480, 370/496, 370/465, 370/468, 370/522, 455/63, 455/67.3, 455/428, 455/429, 455/430, 455/443, 455/12.1, 455/13.1, 455/13.4
• US Class Current: 370/320
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system

Abstract

A method is disclosed for operating a first satellite communications system of a type that operates co-frequency with at least one second transmission system, such as a second satellite communications system. The method includes steps, executed during the operation of the first satellite communications system, of measuring at a plurality of locations within a coverage area of the first system an amount of interference resulting at least in part from the at least one second transmission system, the amount of interference being measured over a band of frequencies allocated to the first system; (b) transmitting an indication of the measured interference from each location to a central site; and (c) in accordance with the transmitted indications, assigning at least one user terminal to a sub-band of frequencies within the band of frequencies so as to reduce an amount of interference experienced by the user terminal.

Claims

1. A method for operating a first satellite communications system, comprising the steps of:

during the operation of the first satellite communications system, measuring at a plurality of locations within a coverage area of the first system an amount of interference resulting at least in part from at least one second satellite communications system, the amount of interference being measured over a band of frequencies allocated to the first system;

transmitting an indication of the measured interference from each location to a central site; and

in accordance with the transmitted indications, removing an effect of self-interference from the measured interference and, based at least in part on a result of removing the effect of self-interference, assigning at least one user terminal to a sub-band of frequencies within the band of frequencies so as to reduce an amount of interference experienced by the user terminal.

2. A method as set forth in claim 1, wherein the step of transmitting includes a step of transmitting the indication through at least one satellite of the first satellite communications system.

3. A method as set forth in claim 1, wherein the step of transmitting includes a step of transmitting the indication through at least one satellite of a third satellite communications system.

4. A method as set forth in claim 3, wherein the third satellite communications system is a VSAT system.

5. A method as set forth in claim 1, wherein the step of transmitting includes a step of transmitting the indication through a terrestrial data network.

6. A method as set forth in claim 1, wherein the central site is a gateway that services the coverage area.

7. A method as set forth in claim 1, wherein the central site is a control center that is bidirectionally coupled to one or more gateways that service the coverage area.

8. A method as set forth in claim 1, wherein the step of measuring is executed with a plurality of measurement terminals that are spatially distributed within the coverage area, and further comprising a step of transmitting a command to at least one of the measurement terminals, the command specifying at least one measurement parameter.

9. A method as set forth in claim 1, wherein the band of frequencies is channelized into a plurality of frequency channels, wherein the second satellite communications system transmits within a band of frequencies that overlaps the first band of frequencies, and wherein the step of assigning assigns the user terminal from a first frequency channel to a second frequency channel.

10. A method as set forth in claim 1, wherein the step of transmitting includes the steps of:

receiving the transmitted indications at the central site;

wherein the step of removing comprises subtracting an amount of self-interference from the transmitted indications to determine an amount of externally generated interference; and

further comprising a step of

forming a historical database of the externally generated interference within the coverage area.

11. A method as set forth in claim 1, wherein the first and second satellite communications system both transmit a beam having a terrestrial footprint, and wherein the at least one user terminal is located in an overlap zone between the terrestrial footprints of the beams.

12. A method as set forth in claim 1, wherein the band of frequencies is channelized into a plurality of frequency channels, and wherein a plurality of user terminals are assigned to a same frequency channel and share the frequency channel using assigned spreading codes.

13. A method as set forth in claim 1, wherein the steps of measuring and transmitting are executed a plurality of times, and further comprising a step of storing the transmitted indications in a database representing a historical interference distribution within the coverage area, and wherein the step of assigning is performed at least in part based on a predicted interference obtained from indications stored in the database.

14. A method as set forth in claim 1, wherein the step of measuring includes a step of scanning a receiver over at least a portion of the band of frequencies, and measuring an amount of interference within a plurality of the sub-bands of frequencies.

15. A satellite communications system that operates co-frequency with at least one second satellite communications system within a band of frequencies that is channelized into a plurality of frequency channels, said satellite communications system having a terrestrial coverage area and comprising:

at least one satellite having a beam with an associated terrestrial coverage area;

at least one user terminal located within the beam;

a ground station for communicating with said at least one user terminal via said at least one satellite; and

a plurality of measurement terminals located within said terrestrial coverage area, each of said measurement terminals being bidirectionally coupled to said ground station and comprising a receiver and a measurement unit for measuring an amount of interference due to self-interference and interference from said second satellite communications system, each of said measurement terminals further comprising a transmitter for transmitting an indication of the measured interference to said ground station;

wherein

said ground station is responsive to a measured amount of interference due at least to said interference from said second satellite communications system for assigning or reassigning said at least one user terminal to a frequency channel selected for reducing an amount of power required to provide a desired quality of service to said at least one user terminal.

16. A satellite communications system as set forth in claim 15, wherein said transmitter transmits the indication through at least one satellite of the satellite communications system.

17. A satellite communications system as set forth in claim 15, wherein said transmitter transmits the indication through at least one satellite of a third satellite communications system.

18. A satellite communications system as set forth in claim 17, wherein the third satellite communications system is a VSAT system.

19. A satellite communications system as set forth in claim 15, wherein said transmitter transmits the indication through a terrestrial data network.

20. A satellite communications system as set forth in claim 15, wherein said ground station is comprised of a gateway that services the terrestrial coverage area.

21. A satellite communications system as set forth in claim 15, wherein said ground station is a control center that is bidirectionally coupled to a gateway that services the terrestrial coverage area.

22. A satellite communications system as set forth in claim 15, wherein said ground station is further comprised of a controller for transmitting a command to at least one of the measurement terminals, the command specifying at least one measurement parameter.

23. A satellite communications system as set forth in claim 15, wherein said ground station is further comprised of:

a receiver for receiving the transmitted indications;

a data processor for subtracting the self-interference to determine an amount of externally generated interference; and

a data storage unit for storing a historical database of the externally generated interference within the terrestrial coverage area for use in predictively assigning or reassigning said at least one user terminal to a frequency channel.

24. A satellite communications system as set forth in claim 15, wherein said satellite communications systems each employ a beam having a terrestrial footprint, and wherein said user terminal is located in an overlap zone between the beam footprints.

25. A satellite communications system as set forth in claim 15, wherein said receiver includes a scanner for scanning said receiver over at least a portion of the band of frequencies.

26. A satellite communications system as set forth in claim 15, wherein at least one of said plurality of measurement terminals is comprised of an omni-directional antenna that is coupled to an input of said receiver.

27. A satellite communications system as set forth in claim 15, wherein at least one of said plurality of measurement terminals is comprised of a directional antenna that is coupled to an input of said receiver.

28. A method for operating a satellite communications system, comprising the steps of:

generating a database that is indicative of a variation in interference in both time and frequency within a coverage area of the satellite communications system, the step of generating using measurements made by a plurality of measurement terminals that are spatially distributed within the coverage area; and

assigning or reassigning a user terminal that is located within the coverage area to a frequency channel in accordance with the generated database.

29. A method for operating a satellite communications system, comprising the steps of:

measuring interference in both time and frequency within a coverage area of the satellite communications system, the measured interference being due at least in part to user terminal frequency channel assignments made by a second satellite communications system that operates co-frequency with the satellite communications system, the step of measuring using measurements made by a plurality of measurement terminals that are spatially distributed within the coverage area; and

assigning or reassigning a user terminal of the first system that is located within the coverage area to a frequency channel so as to reduce an amount of satellite power required to provide a desired level of service quality to the user terminal.

30. A method for operating a satellite communications system, comprising the steps of:

measuring interference in both time and frequency within a coverage area of the satellite communications system, the measured interference being due at least in part to frequency channel assignments made by a second satellite communications system that operates co-frequency with the satellite communications system, the step of measuring using measurements made by a plurality of measurement terminals that are spatially distributed within the coverage area;

storing the measured interference; and

predictively allocating frequency channels to at least one gateway that serves the coverage area in accordance with the stored measured interference so as to reduce an amount of satellite power required to provide a desired level of service quality to user terminals serviced by the at least one gateway.

31. A method for operating a satellite communications system, comprising the steps of:

monitoring, at a gateway, return links from a plurality of user terminals to determine an amount of interference experienced by the user terminals, the user terminals being assigned to different frequency channels and communicating with the gateway via at least one satellite; and

in accordance with the determined amount of interference, assigning or reassigning at least one of the user terminals to a different frequency channel so as to reduce an amount of satellite power required to provide a desired level of service quality to the user terminal.

32. A method for operating a communications system, comprising the steps of:

during the operation of the communications system, measuring at a plurality of locations within a coverage area of the communications system an amount of interference resulting from a terrestrially-based or a space-based interference source, the amount of interference being measured over a band of frequencies allocated to the communications system;

transmitting an indication of the measured interference from each location to a central site; and

in accordance with the transmitted indications, removing an effect of self-interference from the measured interference and, based at least in part on a result of removing the effect of self-interference, assigning at least one user terminal of the communications system to a sub-band of frequencies within the band of frequencies so as to reduce an amount of interference experienced by the user terminal.