Beamforming options with partial channel knowledge

1. A method for transmission beamforming, the method comprising:

obtaining one or more channel knowledge metrics for one or more channels;

determining a confidence level of each channel knowledge metric;

selecting beamforming specifications based on the channel knowledge metrics and the confidence levels;

transmitting a signal stream on the one or more channels using the selected beamforming specifications; and

selecting one or more known eigen-directions using the one or more channel knowledge metrics and the confidence levels;

determining parts of the one or more channels not observable or estimable; and

selecting random values for the determined parts, wherein the random values selected are orthogonal to the known eigen-directions.

2. The method of claim 1 , wherein the eigen-directions and the random values are the beamforming specifications.

3. The method of claim 1 , wherein the random values are selected using a conditional probability distribution and a joint probability distribution.

4. The method of claim 1 , wherein transmitting the signal stream comprises transmitting different signal stream layers in directions corresponding to the known eigen-direction and the random values.

5. The method of claim 1 , wherein obtaining the one or more channel knowledge metrics comprises:

receiving feedback from a receiver; and

using the feedback to obtain the one or more channel knowledge metrics.

6. The method of claim 5 , wherein the feedback comprises one or more precoding vectors.

7. The method of claim 5 , wherein the feedback comprises a quantized version of a channel covariance matrix.

8. The method of claim 5 , wherein the feedback comprises a quantized version of an interference covariance matrix.

9. The method of claim 5 , wherein the feedback comprises eigen-directions of a whitened channel, wherein the eigen-direction are computed using interference.

10. The method of claim 5 , wherein the feedback comprises channel quality indicators (CQI) and rank based on a pseudo eigen-beamforming operation synchronized between a base station and a wireless communication device.

11. The method of claim 5 , wherein the feedback comprises channel quality indicators (CQI) and rank based on a pseudo eigen-beamforming operation with random beamforming that is not known by a base station, and wherein the base station transmits along a set of random beams in the orthogonal space of known directions using the CQI and rank recommended.

12. The method of claim 1 , wherein the one or more channel knowledge metrics are obtained using long term static observations.

13. The method of claim 12 , wherein the long term static observations comprise at least one of a number of transmit antennas used, an antenna spacing on a transmitter, a number of receive antennas used, an antenna spacing on a receiver, and a type of antenna used.

14. The method of claim 1 , wherein the one or more channel knowledge metrics are obtained using receiver-to-transmitter traffic.

15. The method of claim 14 , wherein the receiver-to-transmitter traffic comprises sounding reference signal (SRS) transmissions.

16. The method of claim 1 , further comprising selecting the beamforming specifications using a transmitter knowledge of interference structure metric.

17. The method of claim 16 , wherein the transmitter knowledge of interference structure metric comprises a long term covariance matrix of interference.

18. The method of claim 16 , wherein the transmitter knowledge of interference structure metric comprises dominant eigen-directions of interference.

19. The method of claim 1 , wherein obtaining the one or more channel knowledge metrics comprises:

receiving a sounding reference signal (SRS) from a receiver; and

determining one or more channel knowledge metrics using the SRS.

20. The method of claim 1 , wherein the beamforming specifications comprises a group or groups of antennas to use for transmitting the signal stream.

21. The method of claim 1 , wherein the beamforming specifications comprises weights assigned to one or more transmit antennas used for transmitting the signal stream.

22. The method of claim 1 , wherein the beamforming specifications comprises weights assigned to each symbol of the signal stream.

23. The method of claim 1 , wherein the method is performed by a wireless device.

24. The method of claim 23 , wherein the wireless device is a base station.

25. The method of claim 23 , wherein the wireless device is a wireless communication device.

26. The method of claim 23 , wherein the wireless device is configured to operate in a multiple-input and multiple-output (MIMO) wireless communication system.

27. A wireless device configured for transmission beamforming, comprising:

a processor;

memory in electronic communication with the processor;

instructions stored in the memory, the instructions being executable by the processor to:

obtain one or more channel knowledge metrics for one or more channels;

determine a confidence level of each channel knowledge metric;

select beamforming specifications based on the channel knowledge metrics and the confidence levels;

transmit a signal stream on the one or more channels using the selected beamforming specifications;

select one or more known eigen-directions using the one or more channel knowledge metrics and the confidence levels;

determine parts of the one or more channels not observable or estimable; and

select random values for the determined parts, wherein the random values selected are orthogonal to the known eigen-directions.

28. The wireless device of claim 27 , wherein the eigen-directions and the random values are the beamforming specifications.

29. The wireless device of claim 27 , wherein the random values are selected using a conditional probability distribution and a joint probability distribution.

30. The wireless device of claim 27 , wherein transmitting the signal stream comprises transmitting different signal stream layers in directions corresponding to the known eigen-direction and the random values.

31. The wireless device of claim 27 , wherein obtaining the one or more channel knowledge metrics comprises:

receiving feedback from a receiver; and

using the feedback to obtain the one or more channel knowledge metrics.

32. The wireless device of claim 31 , wherein the feedback comprises one or more precoding vectors.

33. The wireless device of claim 31 , wherein the feedback comprises a quantized version of a channel covariance matrix.

34. The wireless device of claim 31 , wherein the feedback comprises a quantized version of an interference covariance matrix.

35. The wireless device of claim 31 , wherein the feedback comprises eigen-directions of a whitened channel, wherein the eigen-direction are computed using interference.

36. The wireless device of claim 31 , wherein the feedback comprises channel quality indicators (CQI) and rank based on a pseudo eigen-beamforming operation synchronized between a base station and a wireless communication device.

37. The wireless device of claim 31 , wherein the feedback comprises channel quality indicators (CQI) and rank based on a pseudo eigen-beamforming operation with random beamforming that is not known by a base station, and wherein the base station transmits along a set of random beams in the orthogonal space of known directions using the CQI and rank recommended.

38. The wireless device of claim 27 , wherein the one or more channel knowledge metrics are obtained using long term static observations.

39. The wireless device of claim 38 , wherein the long term static observations comprise at least one of a number of transmit antennas used, an antenna spacing on a transmitter, a number of receive antennas used, an antenna spacing on a receiver, and a type of antenna used.

40. The wireless device of claim 27 , wherein the one or more channel knowledge metrics are obtained using receiver-to-transmitter traffic.

41. The wireless device of claim 40 , wherein the receiver-to-transmitter traffic comprises sounding reference signal (SRS) transmissions.

42. The wireless device of claim 27 , wherein the instructions are further executable to select beamforming specifications using a transmitter knowledge of interference structure metric.

43. The wireless device of claim 42 , wherein the transmitter knowledge of interference structure metric comprises a long term covariance matrix of interference.

44. The wireless device of claim 42 , wherein the transmitter knowledge of interference structure metric comprises dominant eigen-directions of interference.

45. The wireless device of claim 27 , wherein obtaining one or more channel knowledge metrics comprises:

receiving a sounding reference signal (SRS) from a receiver; and

determining one or more channel knowledge metrics using the SRS.

46. The wireless device of claim 27 , wherein the beamforming specifications comprises a group or groups of antennas to use for transmitting the signal stream.

47. The wireless device of claim 27 , wherein the beamforming specifications comprises weights assigned to one or more transmit antennas used for transmitting the signal stream.

48. The wireless device of claim 27 , wherein the beamforming specifications comprises weights assigned to each symbol of the signal stream.

49. The wireless device of claim 27 , wherein the wireless device is a base station.

50. The wireless device of claim 27 , wherein the wireless device is a wireless communication device.

51. The wireless device of claim 27 , wherein the wireless device is configured to operate in a multiple-input and multiple-output (MIMO) wireless communication system.

52. A wireless device configured for transmission beamforming, comprising:

means for obtaining one or more channel knowledge metrics for one or more channels;

means for determining a confidence level of each channel knowledge metric;

means for selecting beamforming specifications based on the channel knowledge metrics and the confidence levels;

means for transmitting a signal stream on the one or more channels using the selected beamforming specifications;

means for selecting one or more known eigen-directions using the one or more channel knowledge metrics and the confidence levels;

means for determining parts of the one or more channels not observable or estimable; and

means for selecting random values for the determined parts, wherein the random values selected are orthogonal to the known eigen-directions.

53. A computer-program product for a wireless device configured for transmission beamforming, the computer-program product comprising a computer-readable medium having instructions thereon, the instructions comprising:

code for obtaining one or more channel knowledge metrics for one or more channels;

code for determining a confidence level of each channel knowledge metric;

code for selecting beamforming specifications based on the channel knowledge metrics and the confidence levels;

code for transmitting a signal stream on the one or more channels using the selected beamforming specifications;

code for selecting one or more known eigen-directions using the one or more channel knowledge metrics and the confidence levels;

code for determining parts of the one or more channels not observable or estimable; and

code selecting random values for the determined parts, wherein the random values selected are orthogonal to the known eigen-directions.