Adaptive beam forming with multi-user detection and interference reduction in satellite communication systems and methods
View Patent ↗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.
1. A communications method comprising:
receiving at a transceiver of a given terminal over a frequency band a plurality of signals including multiple access interference that is dependent on transmissions of a plurality of terminals other than the given terminal, the plurality of terminals communicating with the transceiver over a geographic area, and receiving at the transceiver co-channel interference that is independent of the transmissions of the plurality of terminals other than the given terminal; and
reducing interference of the plurality of signals sequentially by first reducing the co-channel interference that is independent of the transmissions of the plurality of terminals other than the given terminal to generate a plurality of interference reduced signals, and then reducing the multiple access interference in the plurality of interference reduced signals that is dependent on the transmissions of the plurality of terminals other than the given terminal, after the first reducing the co-channel interference;
wherein reducing the multiple access interference that is dependent on the transmissions of the plurality of terminals other than the given terminal after the first reducing the co-channel interference comprises generating a set of channel estimates based on the co-channel interference reduced signals, generating a set of bit estimates from the co-channel interference reduced signals, and performing multiple access interference reduction on the co-channel interference reduced signals using the set of channel estimates and the bit estimates.
2. The method of claim 1 wherein the interference that is independent of the transmissions of the plurality of terminals other than the given terminal communicating with the transceiver 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 transceiver.
3. The method of claim 1 , wherein receiving at the transceiver 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 the interference reduced signals.
8. The method of claim 1 , 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.
9. The method of claim 1 , wherein receiving at the transceiver comprises receiving at the transceiver using at least two antenna patterns that differ in at least a polarization orientation.
10. The method of claim 1 , wherein generating a set of bit estimates from the interference reduced signals comprises correlating an interference reduced signal with a spreading code.
11. 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.
12. The method of claim 11 , wherein the at least one satellite gateway is terrestrially based,
13. The method of claim 1 , wherein reducing interference of the plurality of signals is performed at least partially at the transceiver and at least partially at a satellite gateway that is terrestrially based.
14. A system comprising:
a transceiver;
a plurality of terminals that are configured to transmit a plurality of multiple access signals over a frequency band in a footprint of the transceiver;
the transceiver being configured to receive the plurality of multiple access signals over the frequency band, the transceiver also receiving interference along with the plurality of multiple access signals in the frequency band, the interference comprising a multiple access component that is dependent on the plurality of multiple access signals and a co-channel component that is independent of the plurality of multiple access signals; and
an interference reducing element that is responsive to the transceiver, and that is configured to sequentially perform interference reduction of the co-channel interference that is independent of the plurality of multiple access signals to generate a plurality of interference reduced signals and then to perform multiple access interference reduction on the plurality of interference reduced signals to reduce the multiple access interference that is dependent on the plurality of multiple access signals after performing the interference reduction of the co-channel interference,
wherein the interference reducing element is configured to generate a set of channel estimates based on the co-channel interference reduced signals, generate a set of bit estimates from the co-channel interference reduced signals, and perform multiple access interference reduction on the co-channel interference reduced signals using the set of channel estimates and the bit estimates.
15. The system of claim 14 , further comprising:
an ancillary terrestrial network including a plurality of transmitters configured to transmit a plurality of waveforms over at least some of the 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.
16. The system of claim 14 , wherein the transceiver includes an antenna having a plurality of antenna feed elements, and the transceiver is configured to receive the plurality of multiple access signals using the antenna having the plurality of antenna feed elements.
17. The system of claim 16 , 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.
18. The system of claim 17 , wherein the processing generates at least one pilot signal error.
19. The system of claim 18 , 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.
20. The system of claim 19 , 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 the interference reduced signals.
21. The system of claim 14 , 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.
22. The system of claim 14 , wherein the transceiver receives the plurality of multiple access signals using at least two antenna patterns that differ in at least a polarization orientation.
23. The system of claim 20 , 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.
24. The system of claim 14 , wherein the transceiver 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.
25. The system of claim 24 , wherein the satellite gateway is terrestrially-based.