Forward and reverse calibration for ground-based beamforming
Methods and systems for calibrating the return and forward links of a satellite communication system are provided according to embodiments of the invention. The phase and/or amplitude variations caused by the return and forward links are calculated and/or estimated to aid in beamforming, such as ground-based beamforming. Calibration earth stations, distributed within one or more beam patterns, may be used to transmit calibration codes to the gateway to calibrate the return link. Return links variations may be estimated using a weighted minimum mean square algorithm at the gateway. Forward links may be calibrated with calibration codes transmitted from the gateway through a hybrid matrix to at least one calibration station. Forward calibration links may also calibrate for temperature-dependent signal variations such as diplexer variations at the satellite.
1. A method for wireless communication over a satellite return link, the method comprising:
receiving a signal comprising a linear combination of a plurality of orthogonal codes, the plurality of orthogonal codes transmitted by a plurality of calibration stations and received at a satellite by a plurality of satellite feeds, the satellite retransmitting the linear combination of the plurality of orthogonal codes, wherein at least two of the plurality of calibration stations are located within distinct satellite beam coverage areas;
performing a correlation on the received plurality of orthogonal codes to obtain at least one of amplitude or phase information of signal paths originating from the plurality of calibration stations and passing through the satellite;
estimating at least one of amplitude or phase effects of the satellite return link by applying an estimating function to the at least one of amplitude or phase information; and
communicating on the satellite return link based at least in part on the at least one of amplitude or phase effects of the satellite return link.
2. The method of claim 1 , wherein the plurality of orthogonal codes are transmitted by the plurality of calibration stations at times when data is not being transmitted.
3. The method of claim 1 , further comprising:
determining beamforming parameters for processing return link transmissions based at least in part on the at least one of amplitude or phase effects, the return link transmissions transmitted from user terminals in a plurality of satellite beam coverage areas and received at the satellite by a plurality of satellite feeds.
4. The method of claim 3 , further comprising:
transmitting the beamforming parameters to the satellite.
5. The method of claim 1 , wherein either or both of the at least one of amplitude or phase effects are determined based on applying a weighted minimum mean square algorithm to either or both of the at least one of amplitude or phase information obtained from the received plurality of orthogonal codes.
6. The method of claim 5 , wherein weights for the weighted minimum mean square algorithm are determined based on a matrix of feed excitation levels.
7. The method of claim 1 , wherein the plurality of orthogonal codes comprise a plurality of pseudo-noise sequences.
8. The method of claim 1 , wherein each of the plurality of orthogonal codes are transmitted for a period of time less than 100 ms.
9. An apparatus for wireless communication over a satellite return link, comprising:
an antenna to receive a signal comprising a linear combination of a plurality of orthogonal codes, the plurality of orthogonal codes transmitted by a plurality of calibration stations and received at a satellite by a plurality of satellite feeds, wherein the satellite retransmits the linear combination of the plurality of orthogonal codes, and wherein at least two of the plurality of calibration stations are located within distinct satellite beam coverage areas;
a correlator to correlate the received plurality of orthogonal codes to obtain at least one of amplitude or phase information of signal paths originating from the plurality of calibration stations and passing through the satellite;
a channel estimator to estimate at least one of amplitude or phase effects of the satellite return link by applying an estimating function to the at least one of amplitude or phase information; and
a receiver to communicate on the satellite return link based at least in part on the at least one of amplitude or phase effects of the satellite return link.
10. The apparatus of claim 9 , wherein the plurality of orthogonal codes are transmitted by the plurality of calibration stations at times when data is not being transmitted.
11. The apparatus of claim 9 , wherein the channel estimator determines beamforming parameters for processing return link transmissions based at least in part on the at least one of amplitude or phase effects, the return link transmissions transmitted from user terminals in a plurality of satellite beam coverage areas and received at the satellite by a plurality of satellite feeds.
12. The apparatus of claim 11 , further comprising:
a transmitter to transmit the beamforming parameters to the satellite.
13. The apparatus of claim 11 , wherein either or both of the at least one of amplitude or phase effects are determined based on applying a weighted minimum mean square algorithm to either or both of the at least one of amplitude or phase information obtained from the received plurality of orthogonal codes.
14. The apparatus of claim 13 , wherein weights for the weighted minimum mean square algorithm are determined based on a matrix of feed excitation levels.
15. The apparatus of claim 9 , wherein the plurality of orthogonal codes comprise a plurality of pseudo-noise sequences.
16. The apparatus of claim 9 , wherein each of the plurality of orthogonal codes are transmitted for a period of time less than 100 ms.
17. An apparatus for wireless communication over a satellite return link, comprising:
means for receiving a signal comprising a linear combination of a plurality of orthogonal codes, the plurality of orthogonal codes transmitted by a plurality of calibration stations and received at a satellite by a plurality of satellite feeds, the satellite retransmitting the linear combination of the plurality of orthogonal codes, wherein at least two of the plurality of calibration stations are located within distinct satellite beam coverage areas;
means for performing a correlation on the received plurality of orthogonal codes to obtain at least one of amplitude or phase information of signal paths originating from the plurality of calibration stations and passing through the satellite;
means for estimating at least one of amplitude or phase effects of the satellite return link by applying an estimating function to the at least one of amplitude or phase information; and
means for communicating on the satellite return link based at least in part on the at least one of amplitude or phase effects of the satellite return link.
18. The apparatus of claim 17 , wherein the plurality of orthogonal codes are transmitted by the plurality of calibration stations at times when data is not being transmitted.
19. The apparatus of claim 17 , wherein the means for estimating determines beamforming parameters for processing return link transmissions based at least in part on the at least one of amplitude or phase effects, the return link transmissions transmitted from user terminals in a plurality of satellite beam coverage areas and received at the satellite by a plurality of satellite feeds.
20. The apparatus of claim 19 , further comprising:
means for transmitting the beamforming parameters to the satellite.
21. The apparatus of claim 17 , wherein either or both of the at least one of amplitude or phase effects are determined based on applying a weighted minimum mean square algorithm to either or both of the at least one of amplitude or phase information obtained from the received plurality of orthogonal codes.
22. The apparatus of claim 21 , wherein weights for the weighted minimum mean square algorithm are determined based on a matrix of feed excitation levels.
23. The apparatus of claim 17 , wherein the plurality of orthogonal codes comprise a plurality of pseudo-noise sequences.
24. The apparatus of claim 17 , wherein each of the plurality of orthogonal codes are transmitted for a period of time less than 100 ms.
25. A method for wireless communication over a forward satellite link, the method comprising:
receiving signals comprising linear combinations of a plurality of orthogonal codes, the plurality of orthogonal codes transmitted by a plurality of gateways and received at a satellite by a plurality of satellite feeds, the satellite retransmitting the linear combinations of the plurality of orthogonal codes, the retransmitted linear combinations of the plurality of orthogonal codes being received by a plurality of calibration stations, wherein at least two of the plurality of calibration stations are located within distinct satellite beam coverage areas;
performing a correlation on the received plurality of orthogonal codes to obtain at least one of amplitude or phase information of signal paths originating from the plurality of gateways and passing through the plurality of satellite feeds of the satellite;
estimating at least one of amplitude or phase effects of the forward satellite link by applying an estimation function to the at least one of amplitude or phase information; and
communicating on the forward satellite link based at least in part on the at least one of amplitude or phase effects of the forward satellite link.
26. The method of claim 25 , wherein the plurality of orthogonal codes are transmitted by the plurality of gateways at times when data is not being transmitted.
27. The method of claim 25 , further comprising:
determining beamforming parameters for forward link transmissions based at least in part on the at least one of amplitude or phase effects, the forward link transmissions transmitted from the plurality of gateways to user terminals in a plurality of satellite beam coverage areas via the plurality of satellite feeds of the satellite.
28. The method of claim 27 , wherein the plurality of orthogonal codes are transmitted from the plurality of gateways without the beamforming parameters applied to the plurality of orthogonal codes.
29. The method of claim 27 , further comprising:
transmitting the beamforming parameters to the satellite.
30. The method of claim 25 , further comprising:
receiving, from the plurality of calibration stations, either or both of phase or amplitude shifts determined from correlations of the plurality of orthogonal codes received at the plurality of calibration stations in the linear combinations with the originally transmitted plurality of orthogonal codes.
31. The method of claim 25 , wherein either or both of the at least one of amplitude or phase effects are determined based on applying a weighted minimum mean square algorithm to either or both of the at least one of amplitude or phase information obtained from the received plurality of orthogonal codes.
32. The method of claim 31 , wherein weights for the weighted minimum mean square algorithm are determined based on a matrix of feed excitation levels.
33. The method of claim 25 , wherein the linear combinations of the plurality of orthogonal codes are generated at the satellite using a hybrid matrix.
34. The method of claim 25 , further comprising:
sending the originally transmitted plurality of orthogonal codes to the plurality of calibration stations for use in the correlating to the plurality of orthogonal codes received in the linear combinations.
35. An apparatus for wireless communication over a forward satellite link, comprising:
an antenna to receive signals comprising linear combinations of a plurality of orthogonal codes, the plurality of orthogonal codes transmitted by a plurality of gateways and received at a satellite by a plurality of satellite feeds, the satellite retransmitting the linear combinations of the plurality of orthogonal codes, the retransmitted linear combinations of the plurality of orthogonal codes being received by a plurality of calibration stations, wherein at least two of the plurality of calibration stations are located within distinct satellite beam coverage areas;
a correlator to correlate the received plurality of orthogonal codes to obtain at least one of amplitude or phase information of signal paths originating from the plurality of gateways and passing through the plurality of satellite feeds of the satellite;
a channel estimator to estimate at least one of amplitude or phase effects of the forward satellite link by applying an estimation function to the at least one of amplitude or phase information; and
a transmitter to communicate on the forward satellite link based at least in part on the at least one of amplitude or phase effects of the forward satellite link.
36. The apparatus of claim 35 , wherein the plurality of orthogonal codes are transmitted by the plurality of gateways at times when data is not being transmitted.
37. The apparatus of claim 35 , further comprising:
determining beamforming parameters for forward link transmissions based at least in part on the at least one of amplitude or phase effects, the forward link transmissions transmitted from the plurality of gateways to user terminals in a plurality of satellite beam coverage areas via the plurality of satellite feeds of the satellite.
38. The apparatus of claim 37 , wherein the plurality of orthogonal codes are transmitted from the plurality of gateways without the beamforming parameters applied to the plurality of orthogonal codes.
39. The apparatus of claim 37 , wherein the transmitter transmits the beamforming parameters to the satellite.
40. The apparatus of claim 35 , wherein either or both of the at least one of amplitude or phase effects are determined based on applying a weighted minimum mean square algorithm to either or both of the at least one of amplitude or phase information obtained from the received plurality of orthogonal codes.
41. The apparatus of claim 40 , wherein weights for the weighted minimum mean square algorithm are determined based on a matrix of feed excitation levels.
42. The apparatus of claim 35 , wherein the linear combinations of the plurality of orthogonal codes are generated at the satellite using a hybrid matrix.
43. A apparatus for wireless communication over a forward satellite link, comprising:
means for receiving signals comprising linear combinations of a plurality of orthogonal codes, the plurality of orthogonal codes transmitted by a plurality of gateways and received at a satellite by a plurality of satellite feeds, the satellite retransmitting the linear combinations of the plurality of orthogonal codes, the retransmitted linear combinations of the plurality of orthogonal codes being received by a plurality of calibration stations, wherein at least two of the plurality of calibration stations are located within distinct satellite beam coverage areas;
means for performing a correlation on the received plurality of orthogonal codes to obtain at least one of amplitude or phase information of signal paths originating from the plurality of gateways and passing through the plurality of satellite feeds of the satellite;
means for estimating at least one of amplitude or phase effects of the forward satellite link by applying an estimation function to the at least one of amplitude or phase information; and
means for communicating on the forward satellite link based at least in part on the at least one of amplitude or phase effects of the forward satellite link.
44. The apparatus of claim 43 , wherein the plurality of orthogonal codes are transmitted by the plurality of gateways at times when data is not being transmitted.
45. The apparatus of claim 43 , further comprising:
determining beamforming parameters for forward link transmissions based at least in part on the at least one of amplitude or phase effects, the forward link transmissions transmitted from the plurality of gateways to user terminals in a plurality of satellite beam coverage areas via the plurality of satellite feeds of the satellite.
46. The apparatus of claim 45 , wherein the plurality of orthogonal codes are transmitted from the plurality of gateways without the beamforming parameters applied to the plurality of orthogonal codes.
47. The apparatus of claim 46 , wherein the means for receiving receives, from the plurality of calibration stations, either or both of phase or amplitude shifts determined from correlations of the plurality of orthogonal codes received at the plurality of calibration stations in the linear combinations with the originally transmitted plurality of orthogonal codes.
48. The apparatus of claim 46 , further comprising:
transmitting the beamforming parameters to the satellite.
49. The apparatus of claim 43 , wherein either or both of the at least one of amplitude or phase effects are determined based on applying a weighted minimum mean square algorithm to either or both of the at least one of amplitude or phase information obtained from the received plurality of orthogonal codes.
50. The apparatus of claim 49 , wherein weights for the weighted minimum mean square algorithm are determined based on a matrix of feed excitation levels.
51. The apparatus of claim 43 , wherein the linear combinations of the plurality of orthogonal codes are generated at the satellite using a hybrid matrix.