ADAPTIVE BEAM FORMING WITH MULTI-USER DETECTION AND INTERFERENCE REDUCTION IN SATELLITE COMMUNICATION SYSTEMS AND METHODS

• US 20100184370A1
• Filed: 01/19/2010
• Published: 07/22/2010
• Est. Priority Date: 01/05/2005
• Status: Active Grant

• Current Assignee: ATC Technology Corporation (FedEx Corporation)
• Original Assignee: ATC Technology Corporation (FedEx Corporation)
• Inventors: Karabinis, Peter D., Zheng, Dunmin
• Granted Patent: US 8,744,360 B2
• Time in Patent Office: Days
• US Class Current: 455/12.100
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04B 7/18563 Arrangements for interconnecting multiple systems data switching networks H04L12/00

Abstract

Satellite communications methods include receiving communications signals including co-channel interference at a space-based component from a plurality of wireless terminals in a satellite footprint over a satellite frequency band and reducing interference in the communication signals by (a) performing co-channel interference reduction on the communications signals to generate a plurality of interference reduced signals and (b) performing multiple access interference cancellation on the interference reduced signals. An interference reducing detector for a satellite communications system includes an interference reducer configured to perform co-channel interference reduction on communications signals to generate a plurality of interference reduced signals, and a detector configured to perform multiple access interference cancellation on the interference reduced signals. Satellite communications systems and satellite gateways including interference reducing detectors are also disclosed.

Claims

1. A communications method comprising:

receiving at a space-based component over a space-based component frequency band a plurality of signals including interference that is dependent on transmissions of a plurality of terminals communicating with the space-based component over a geographic area and interference that is independent of the transmissions of the plurality of terminals communicating with the space-based component over the geographic area; and

reducing interference of the plurality of signals sequentially by first reducing the interference that is independent of the transmissions of the plurality of terminals communicating with the space-based component over the geographic area and then reducing the interference that is dependent on the transmissions of the plurality of terminals communicating with the space-based component over the geographic area.

2. The method of claim 1 wherein the interference that is independent of the transmissions of the plurality of terminals communicating with the space-based component over the geographic area comprises interference that is dependent on transmissions by an ancillary terrestrial network and/or by one or more terminals communicating with the ancillary terrestrial network, and wherein the ancillary terrestrial network and/or the one or more terminals communicating therewith use at least some frequencies of the space-based component.

3. The method of claim 1, wherein receiving at the space-based component comprises receiving using a plurality of antenna feed elements.

4. The method of claim 3, wherein reducing interference of the plurality of signals sequentially comprises processing pilot signals and determining weights for the plurality of antenna feed elements based on the processing of the pilot signals.

5. The method of claim 4, further comprising generating at least one pilot signal error based on the processing.

6. The method of claim 5, wherein the weights for the antenna feed elements are selected to reduce a mean squared measure of the at least one pilot signal error.

7. The method of claim 4, further comprising applying the weights to signals received by the antenna feed elements to obtain interference reduced signals.

8. The method of claim 7, wherein reducing the interference that is dependent on the transmissions of the plurality of terminals communicating with the space-based component over the geographic area comprises determining a set of channel estimates based on the interference reduced signals, generating a set of bit estimates from the interference reduced signals, and performing interference reduction on the interference reduced signals using the set of channel estimates and the bit estimates.

9. The method of claim 8, wherein performing interference reduction on the interference reduced signals using the channel estimates and the bit estimates comprises generating second interference reduced signals, and wherein the method further comprises determining a set of second channel estimates based on the second interference reduced signals, generating a set of second bit estimates from the second interference reduced signals, and performing interference reduction on the second interference reduced signals using the second channel estimates and the second bit estimates.

10. The method of claim 1, wherein receiving at the space-based component comprises receiving at the space-based component using at least two antenna patterns that differ in at least a polarization orientation.

11. The method of claim 8, wherein generating a set of bit estimates from the interference reduced signals comprises correlating an interference reduced signal with a spreading code.

12. The method of claim 1, wherein reducing the interference that is dependent on transmissions of a plurality of terminals communicating with the space-based component over a geographic area comprises generating bit estimates, and the method further comprises performing interference reduction using the generated bit estimates.

13. The method of claim 1, further comprising transmitting at least some of the plurality of signals to at least one satellite gateway, wherein reducing interference of the plurality of signals is performed at the at least one satellite gateway.

14. The method of claim 13, wherein the at least one satellite gateway is terrestrially based.

15. The method of claim 1, wherein reducing interference of the plurality of signals is performed at least partially at the space-based component and at least partially at a satellite gateway that is terrestrially based.

30. The method of claim 1, further comprising repeatedly reducing the interference that is dependent on the transmissions of the plurality of terminals communicating with the space-based component over the geographic area until a predetermined criterion is met.

31. The method of claim 30, wherein the predetermined criterion comprises a bit error rate.

16. A system comprising:

a plurality of terminals that are configured to transmit a plurality of multiple access signals over a space-based component frequency band in a space-based component footprint;

a space-based component that is configured to receive the plurality of multiple access signals over the space-based component frequency band, the space-based component also receiving interference along with the plurality of multiple access signals in the space-based component frequency band, the interference comprising a component that is dependent on the plurality of multiple access signals and a component that is independent of the plurality of multiple access signals; and

an interference reducing element that is responsive to the space-based component, and that is configured to sequentially perform interference reduction of the interference that is independent of the plurality of multiple access signals and the interference that is dependent on the plurality of multiple access signals.

17. The system of claim 16, further comprising:

an ancillary terrestrial network including a plurality of transmitters configured to transmit a plurality of waveforms over at least some of the space-based component frequency band, and wherein the interference that is independent of the plurality of multiple access signals comprises a component that is dependent on the plurality of waveforms.

18. The system of claim 16, wherein the space-based component includes an antenna having a plurality of antenna feed elements, and the space-based component is configured to receive the plurality of multiple access signals using the antenna having the plurality of antenna feed elements.

19. The system of claim 18, wherein the interference reducing element is further configured to perform interference reduction on a plurality of multiple access signals by processing pilot signals transmitted by a plurality of terminals and determining a set of weights for the antenna feed elements based on the processing of the pilot signals.

20. The system of claim 19, wherein the processing generates at least one pilot signal error.

21. The system of claim 20, wherein the interference reducing element is further configured to select a set of weights for the antenna feed elements to reduce a mean squared measure of the at least one pilot signal error.

22. The system of claim 21, wherein the interference reducing element is further configured to apply the set of weights to signals received by the plurality of antenna feed elements to obtain interference reduced signals.

23. The system of claim 22, wherein the interference reducing element is further configured to determine a set of channel estimates based on the interference reduced signals, generate a set of bit estimates from the interference reduced signals, and perform interference reduction on the interference reduced signals using the set of channel estimates and the set of bit estimates to thereby generate second interference reduced signals.

24. The system of claim 23, wherein the interference reducing element is further configured to determine a set of second channel estimates based on the second interference reduced signals, to generate a set of second bit estimates from the second interference reduced signals, and to perform interference reduction on the second interference reduced signals using the set of second channel estimates and the set of second bit estimates.

25. The system of claim 16, wherein the space-based component receives the plurality of multiple access signals using at least two antenna patterns that differ in at least a polarization orientation.

26. The system of claim 22, wherein the interference reducing element is further configured to generate a plurality of interference reduced bit estimates from the interference reduced signals, and to perform interference reduction using the plurality of interference reduced bit estimates.

27. The system of claim 16, wherein the space-based component is further configured to re-transmit the multiple access signals to a satellite gateway, and wherein the interference reducing element is located at the satellite gateway.

28. The system of claim 27, wherein the satellite gateway is terrestrially-based.

29. An interference reducer for a space-based component that is configured to receive waveforms from radioterminals including interference that is dependent on the waveforms from the radioterminals and interference that is independent of the waveforms from the radioterminals, wherein the interference reducer is configured to reduce the interference that is independent of the waveforms from the radioterminals and to reduce the interference that is dependent on the waveforms from the radioterminals;

and wherein the interference reducer is configured to reduce the interference that is dependent on the waveforms from the radioterminals repeatedly until a predetermined criterion is met.