Satellite diversity system, apparatus and method

• US 20050207375A1
• Filed: 06/30/2004
• Published: 09/22/2005
• Est. Priority Date: 03/17/2004
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Schiff, Leonard N.
• Granted Patent: US 7,639,646 B2
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04B 7/18534 for enhancing link reliablility, e.g. satellites diversity

Abstract

Communication diversity using a plurality of satellites is disclosed. The satellites can support multiple regions corresponding to multiple satellite beams. Each satellite can support all regions in the reverse direction and each satellite can be designated as a primary satellite for one of the multiple regions corresponding to one of the multiple satellite beams. Each satellite can receive from any of the regions reverse link signals broadcast by, for example, a mobile station. Each satellite can communicate the received reverse link signals to, for example, a base station or gateway where the signals can be combined to increase signal quality. A mobile station receives forward link signals from the primary satellite and monitors a signal quality from the primary satellite and from a secondary satellite. If the signal quality from the primary satellite drops below a threshold value, the communication signal is transferred to the secondary satellite.

Claims

1. A satellite diversity system comprising:

a first satellite configured to provide a first beam as a primary beam supporting a first region;

a second satellite configured to provide a second beam as a secondary beam supporting a region substantially overlapping the first region; and

a ground station configured to transmit a signal to the first region via the first satellite during a period of time when a communication path through the first satellite is not degraded, and configured to transmit the signal to the first region via the second satellite during the period of time that the communication path through the first satellite is degraded.

2. The system of claim 1, wherein the first satellite is further configure to transmit a first overhead signal at a signal power that is at least a predetermined link margin above a minimum power level required to establish a link with a receiver in the first region;

and

wherein the second satellite is further configured to transmit a second overhead signal that is at a signal power at least greater than the minimum power level required to establish the link with the receiver in the first region.

3. The system of claim 2, wherein the predetermined link margin is greater than or equal to 5 dB.

4. The system of claim 2, wherein the second satellite is configured to transmit the second overhead signal at a signal power that is at least 1 dB greater than the minimum power level.

5. The system of claim 2, wherein the first overhead signal comprises a first pilot signal.

6. The system of claim 2, wherein the second overhead signal comprises a second pilot signal.

7. The system of claim 1, wherein the first satellite is further configured to provide a third satellite beam as a secondary beam supporting a second region;

the second satellite is further configured to provide a fourth satellite beam as a primary beam for a region substantially overlapping the second region; and

wherein the ground station is further configured to transmit an additional signal to the second region via the second satellite during a period of time when a communication path through the second satellite is not degraded, and configured to transmit the signal to the second region via the first satellite during the period of time that the communication path through the second satellite is degraded.

8. The system of claim 1, wherein the ground station is further configured to receive signal metrics and determine, based at least in part on the signal metrics, whether the communication path through the first satellite is degraded.

9. The system of claim 8, wherein the signal metrics comprise Received Signal Strength Indication (RSSI) values determined by a receiver in the first region of a first overhead signal transmitted by the first satellite and a second overhead signal transmitted by the second satellite.

10. The system of claim 9, wherein the first and second overhead signals comprise, respectively, first and second pilot signals.

11. The system of claim 1, wherein the signal comprises a forward link traffic signal.

12. A satellite diversity system comprising:

a forward link transceiver within a satellite, and configured to receive a first forward link signal from a ground station and transmit the first forward link signal in a first satellite beam corresponding to a first region for which the satellite is designated as a primary satellite, and further configured to receive a second forward link signal from the ground station and transmit the second forward link signal in a second satellite beam corresponding to a second region for which the satellite is designated as a secondary satellite; and

a reverse link transceiver within the satellite configured to receive reverse link signals associated with the first and second forward link signals from at least the first and second regions, and configured to transmit the reverse link signals to the ground station.

13. The system of claim 12, wherein the forward link transceiver is further configured to transmit in the first satellite beam a first overhead signal at a signal power that is at least a predetermined link margin above a minimum power level, and wherein the forward link transceiver is further configured to transmit a second overhead signal in the second satellite beam at a signal power less than the signal power of the first overhead signal.

14. The system of claim 13, wherein the predetermined link margin is greater than or equal to 5 dB.

15. A satellite diversity system comprising:

a gateway transceiver configured to selectively transmit a forward link signal to one or both of a first satellite and a second satellite;

a quality of service module coupled to the gateway transceiver and configured to determine if a communication path through the first satellite is degraded; and

a link control module coupled to the quality of service module and configured to control the gateway transceiver to transmit the forward link signal to the first satellite to be relayed to a mobile station if the communication path through the first satellite is not degraded, and configured to control the gateway transceiver to transmit the forward link signal to the second satellite to be relayed to the mobile station if the communication path through the first satellite is degraded.

16. The system of claim 15, wherein the gateway transceiver is further configured to receive a first reverse link signal from the first satellite and a second reverse link signal from the second satellite, and configured to combine the first and second reverse link signals.

17. The system of claim 16, wherein the gateway transceiver is configured to perform coherent combining of the first and second reverse link signals.

18. The system of claim 15, wherein the quality of service module is configured to determine if the communication path through the first satellite is degraded based at least in part on signal metrics received by the gateway transceiver in reverse link signals.

19. The system of claim 18, wherein the signal metrics comprise a pilot signal strength value from the first satellite and a pilot signal strength value from the second satellite determined by a receiver configured to receive the signals from the first and second satellites.

20. The system of claim 18, wherein the gateway transceiver is configured to receive the signal metrics on a reverse link paging channel

21. A satellite diversity system comprising:

a first satellite having a first beam providing coverage for a first region and a second beam providing coverage for a second region, the first satellite configured as a primary satellite for the first region and a secondary satellite for the second region;

a second satellite having a first beam providing coverage for a third region that substantially overlaps the first region and a second beam providing coverage for a fourth region that substantially overlaps the second region, the second satellite configured as a primary satellite for the fourth region and a secondary satellite for the third region; and

a ground station configured to transmit a first signal to a first mobile station in an overlapping portion of the first and third regions via the first satellite when a signal metric reported by the first mobile station is greater than a predetermined threshold, and configured to transmit the first signal to the first mobile station via the second satellite when the signal metric is not greater than the predetermined threshold.

22. A method of providing satellite diversity, the method comprising:

transmitting a signal to a receiver positioned in a first geographic region using a first satellite;

determining if a communication link from the first satellite to the receiver is degraded; and

transmitting the signal to the receiver using a second satellite if the communication link from the first satellite is degraded.

23. The method of claim 22, wherein the first satellite includes a first plurality of beams, a first beam of the first plurality of beams illuminating the first geographic region, and wherein the second satellite includes a second plurality of beams, a first beam of the second plurality of beams substantially illuminating the first geographic region, and wherein transmitting the signal to the receiver comprises transmitting the signal using the first beam of the corresponding first or second satellite.

24. The method of claim 23, wherein the first satellite comprises a primary satellite for the first beam of the first plurality of beams and the second satellite comprises a secondary satellite for the first beam of the second plurality of beams.

25. The method of claim 22, wherein determining if the communication link is degraded comprises determining if the signal from the first satellite is faded.

26. The method of claim 22, wherein determining if the communication link is degraded comprises:

receiving signal metrics from the receiver;

comparing at least one of the signal metrics to a predetermined threshold; and

determining the communication link is degraded if the at least one of the signal metrics does not exceed the predetermined threshold.

27. The method of claim 26, wherein receiving signal metrics comprises:

receiving a first satellite pilot signal strength value from the receiver; and

receiving a second satellite pilot strength value from the receiver.

28. The method of claim 26, wherein comparing the at least one of the signal metrics to the predetermined threshold comprises comparing a received first satellite pilot strength value to the predetermined threshold.

29. The method of claim 26, wherein receiving signal metrics comprises receiving signal metrics from a mobile station over a reverse link paging channel.

30. The method of claim 26, wherein receiving signal metrics comprises:

receiving a first reverse link signal from the first satellite;

receiving a second reverse link signal from the second satellite;

combining the first reverse link signal with the second reverse link signal to produce a combined reverse link signal; and

determining the signal metrics from the combined reverse link signal.

31. A satellite diversity system comprising:

means for transmitting a signal to a receiver positioned in a first geographic region using a first satellite;

means for receiving signal metrics from the receiver;

means for comparing at least one of the signal metrics to a predetermined threshold;

means for selecting an alternative signal path if the at least one signal metric is not greater than the predetermined threshold; and

means for transmitting the signal to the receiver using a second satellite if the alternative signal path is selected.