Antenna switching and uplink sounding channel measurement

1. A method that facilitates downlink precoding for user equipment antenna configurations with unequal number of transmit and receive chains, comprising:

transmitting a modulated sounding reference signal on each antenna in a plurality of antennas of a user equipment, the modulated sounding reference signal compensates for discrepancies in device transfer functions between downlink and uplink;

transmitting a non-modulated sounding reference signal on each antenna in the plurality of antennas of the user equipment; and

alternately connecting a transmit chain to each antenna in the plurality of antennas to facilitate transmission of sounding reference signals on the plurality of antennas of the user equipment.

2. The method of claim 1 , further comprising reporting downlink channel quality information on a channel quality indicator channel.

3. The method of claim 1 , further comprising employing a modulation symbol based at least in part on a downlink channel estimate to generate the modulated sounding reference signal.

4. The method of claim 3 , wherein the modulation symbol is at least one of an inversion of a downlink channel estimate, a multimedia message system environment type inversion of the downlink channel estimate, a phase of a complex conjugate of a downlink channel or the complex conjugate itself.

5. The method of claim 1 , wherein the modulated and non-modulated sounding reference signals are sequences of ones.

6. The method of claim 1 , wherein the modulated and non-modulated sounding reference signals are known sequences of bits.

7. A wireless communications apparatus, comprising:

a memory that retains instructions related to transmitting a modulated sounding reference signal on each antenna in a plurality of antennas of a user equipment, the modulated sounding reference signal compensates for discrepancies in device transfer functions between downlink and uplink, transmitting a non-modulated sounding reference signal on each antenna in the plurality of antennas of the user equipment, and alternately connecting a transmit chain to each antenna in the plurality of antennas to facilitate transmission of sounding reference signals on the plurality of antennas of the user equipment; and

a processor, coupled to the memory, configured to execute the instructions retained in the memory.

8. The wireless communications apparatus of claim 7 , the memory further retains instructions for reporting downlink channel quality information on a channel quality indicator channel.

9. The wireless communications apparatus of claim 7 , the memory further retains instructions for employing a modulation symbol based at least in part on a downlink channel estimate to generate the modulated sounding reference signal.

10. The wireless communications apparatus of claim 9 , wherein the modulation symbol is at least one of an inversion of a downlink channel estimate, a multimedia message system environment type inversion of the downlink channel estimate, a phase of a complex conjugate of a downlink channel or the complex conjugate itself.

11. A wireless communications apparatus that facilitates downlink precoding for user equipment antenna configurations with unequal number of transmit and receive chains, comprising:

means for transmitting a modulated sounding reference signal on each antenna in a plurality of antennas of a user equipment, the modulated sounding reference signal compensates for discrepancies in device transfer functions between downlink and uplink;

means for transmitting a non-modulated sounding reference signal on each antenna in the plurality of antennas of the user equipment; and

means for alternately connecting a transmit chain to each antenna in the plurality of antennas to facilitate transmission of sounding reference signals on the plurality of antennas of the user equipment.

12. The wireless communications apparatus of claim 11 , further comprising means for reporting downlink channel quality information on a channel quality indicator channel.

13. The wireless communications apparatus of claim 11 , further comprising means for employing a modulation symbol based at least in part on a downlink channel estimate to generate the modulated sounding reference signal.

14. The wireless communications apparatus of claim 13 , wherein the modulation symbol is at least one of an inversion of a downlink channel estimate, a multimedia message system environment type inversion of the downlink channel estimate, a phase of a complex conjugate of a downlink channel or the complex conjugate itself.

15. The wireless communications apparatus of claim 11 , wherein the modulated and non-modulated sounding reference signals are sequences of ones.

16. The wireless communications apparatus of claim 11 , wherein the modulated and non-modulated sounding reference signals are known sequences of bits.

17. A computer program product, comprising:

a computer-readable medium comprising:

code for causing at least one computer to transmit a modulated sounding reference signal on each antenna in a plurality of antennas of a user equipment, the modulated sounding reference signal compensates for discrepancies in device transfer functions between downlink and uplink;

code for causing at least one computer to transmit a non-modulated sounding reference signal on each antenna in the plurality of antennas of the user equipment; and

code for causing at least one computer to alternately connect a transmit chain to each antenna in the plurality of antennas to facilitate transmission of sounding reference signals on the plurality of antennas of the user equipment.

18. The computer program product of claim 17 , the computer-readable medium further comprises code for causing at least one computer to employ a modulation symbol based at least in part on a downlink channel estimate to generate the modulated sounding reference signal.

19. The computer program product of claim 18 , wherein the modulation symbol is at least one of an inversion of a downlink channel estimate, a multimedia message system environment type inversion of the downlink channel estimate, a phase of a complex conjugate of a downlink channel or the complex conjugate itself.

20. In a wireless communications system, an apparatus comprising:

a processor configured to:

transmit a modulated sounding reference signal on each antenna in a plurality of antennas of a user equipment, the modulated sounding reference signal compensates for discrepancies in device transfer functions between downlink and uplink;

transmit a non-modulated sounding reference signal on each antenna in the plurality of antennas of the user equipment; and

alternately connect a transmit chain to each antenna in the plurality of antennas to facilitate transmission of sounding reference signals on the plurality of antennas of the user equipment.

21. A method for downlink precoding based on sounding channel measurement, comprising:

receiving modulated sounding reference signals, the received modulated sounding reference signals are received from each antenna among a plurality of antennas of a mobile device, the modulated sounding reference signals including calibration factors that compensate for discrepancies in device transfer functions between downlink and uplink;

receiving non-modulated sounding reference signals-from each antenna among the plurality of antennas of the mobile device;

restoring downlink channel information utilizing the modulated sounding reference signals and the non-modulate sounding reference signals; and

performing downlink precoding, at a base station, based at least in part on the restored downlink channel information.

22. The method of claim 21 , further comprising generating calibration factors based upon the received modulate sounding reference signals, the calibration factors compensate for discrepancies between downlink and uplink device transfer functions.

23. The method of claim 22 , wherein restoring downlink channel information comprises employing the calibration factors on the received non-modulated sounding reference signals.

24. The method of claim 23 , further comprising dividing the non-modulated sounding reference signals by the calibration factors.

25. The method of claim 21 , further comprising deriving optimal precoding vectors based upon the downlink channel information.

26. The method of claim 21 , further comprising utilizing downlink channel noise information to maximize precoding gain.

27. A wireless communications apparatus, comprising:

a memory that retains instructions related to receiving modulated sounding reference signals, the received modulated sounding reference signals are received from each antenna among a plurality of antennas of a mobile device, the modulated sounding reference signals including calibration factors that compensate for discrepancies in device transfer functions between downlink and uplink, receiving non-modulated sounding reference signals from each antenna among the plurality of antennas of the-mobile device, restoring downlink channel information utilizing the modulated sounding reference signals and the non-modulate sounding reference signals and performing downlink precoding, at a base station, based at least in part on the restored downlink channel information; and

a processor, coupled to the memory, configured to execute the instructions retained in the memory.

28. The wireless communications apparatus of claim 27 , the memory further retains instructions for generating calibration factors based upon the received modulated sounding reference signals, the calibration factors compensate for discrepancies between downlink and uplink device transfer functions.

29. The wireless communications apparatus of claim 27 , the memory further retains instructions for deriving optimal precoding vectors based upon the downlink channel information.

30. The wireless communications apparatus of claim 27 , the memory further retains instructions for utilizing downlink channel noise information to maximize precoding gain.

31. A wireless communications apparatus for downlink precoding based on sounding channel measurement, comprising:

means for receiving modulated sounding reference signals, the received modulated sounding reference signals are received from each antenna among a plurality of antennas of a mobile device, the modulated sounding reference signals including calibration factors that compensate for discrepancies in device transfer functions between downlink and uplink;

means for receiving non-modulated sounding reference signals from each antenna among the plurality of antennas of the mobile device;

means for restoring downlink channel information utilizing the modulated sounding reference signals and the non-modulate sounding reference signals; and

means for performing downlink precoding, at a base station, based at least in part on the restored downlink channel information.

32. The wireless communications apparatus of claim 31 , further comprising means for generating calibration factors based upon the received modulate sounding reference signals, the calibration factors compensate for discrepancies between downlink and uplink device transfer functions.

33. The wireless communications apparatus of claim 31 , means for restoring downlink channel information comprises means for employing the calibration factors on the received non-modulated sounding reference signals.

34. The wireless communications apparatus of claim 33 , further comprising means for dividing the non-modulated sounding reference signals by the calibration factors.

35. The wireless communications apparatus of claim 31 , further comprising means for deriving optimal precoding vectors based upon the downlink channel information.

36. The wireless communications apparatus of claim 31 , further comprising means for utilizing downlink channel noise information to maximize precoding gain.

37. A computer program product, comprising:

a computer-readable medium comprising:

code for causing at least one computer to receive modulated sounding reference signals, the received modulated sounding reference signals are received from each antenna among a plurality of antennas of a mobile device, the modulated sounding reference signals including calibration factors that compensate for discrepancies in device transfer functions between downlink and uplink;

code for causing at least one computer to receive non-modulated sounding reference signals from each antenna among the plurality of antennas of the mobile device;

code for causing at least one computer to restore downlink channel information utilizing the modulated sounding reference signals and the non-modulate sounding reference signals; and

code for causing at least one computer to perform downlink precoding, as a base station, based at least in part on the restored downlink channel information.

38. The computer program product of claim 37 , the computer-readable medium further comprises code for causing at least one computer to generate calibration factors based upon the received modulate sounding reference signals, the calibration factors compensate for discrepancies between downlink and uplink device transfer functions.

39. The computer program product of claim 37 , the computer-readable medium further comprises code for causing at least one computer to utilize downlink channel noise information to maximize precoding gain.

40. In a wireless communications system, an apparatus comprising:

a processor configured to:

receive modulated sounding reference signals, the received modulated sounding reference signals are received from each antenna among a plurality of antennas of a mobile device, the modulated sounding reference signals including calibration factors that compensate for discrepancies in device transfer functions between downlink and uplink;

receive non-modulated sounding reference signals from each antenna among the plurality of antennas of the mobile device;

restore downlink channel information utilizing the modulated sounding reference signals and the non-modulate sounding reference signals; and

perform downlink precoding, at a base station, based at least in part on the restored downlink channel information.