POWER CONTROL FOR WIRELESS LAN STATIONS

• US 20110077044A1
• Filed: 12/09/2010
• Published: 03/31/2011
• Est. Priority Date: 08/20/2008
• Status: Abandoned Application

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Merlin, Simone, Vermani, Sameer, Sampath, Hemanth
• Application Number:
  US12/963,918
• Publication Number:
  US 20110077044A1
• Time in Patent Office: Days
• US Class Current: 455/522
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/146 Uplink power control
• CPC Class Codes: H04W 52/241 taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
• CPC Class Codes: H04W 52/243 taking into account interferences
• CPC Class Codes: H04W 52/245 taking into account received signal strength
• CPC Class Codes: H04W 52/247 where the output power of a terminal is based on a path parameter sent by another terminal
• CPC Class Codes: H04W 52/248 where transmission power control commands are generated based on a path parameter
• CPC Class Codes: H04W 52/367 Power values between minimum and maximum limits, e.g. dynamic range
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment

Abstract

Techniques and apparatus for controlling the transmit power of an uplink (UL) signal from a user terminal in a wireless communications system in an effort to achieve some target characteristic, such as a target carrier-to-interference (C/I) ratio, at an access point (AP) are provided. In this manner, such a user terminal may help avoid or compensate for imbalances in received radio frequency (RF) power between UL signals received from multiple user terminals by the AP. For example, the transmit power at each user terminal may be controlled in an effort to achieve a target post-processing C/I ratio of 28 dB per spatial stream in an effort to reduce large power imbalances and optimize throughput per user terminal The user terminal and the AP may compose part of a multiple-input multiple-output (MIMO) communication system utilizing spatial-division multiple access (SDMA) techniques.

Claims

1. A method for wireless communication, comprising:

receiving a plurality of uplink (UL) signals;

determining power of the received plurality of UL signals;

determining adjustment information for a UL signal in the plurality of UL signals based on at least the power of the received UL signals and a target carrier-to-interference (C/I) ratio; and

transmitting the adjustment information.

2. The method of claim 1, wherein receiving the plurality of UL signals comprises receiving a Request to Transmit (RTX) message or a physical layer convergence protocol (PLCP) protocol data unit (PPDU).

3. The method of claim 1, wherein the adjustment information for the UL signal comprises a back-off value for a station (STA) that transmitted the UL signal.

4. The method of claim 1, wherein determining the adjustment information comprises:

determining a maximum of the power of the received UL signals; and

determining the adjustment information for the UL signal based on the maximum power and the target C/I ratio.

5. The method of claim 4, wherein determining the adjustment information comprises:

determining a thermal noise floor power; and

determining the adjustment information for the UL signal based on the maximum power, the target C/I ratio, and the thermal noise floor power.

6. The method of claim 5, wherein determining the adjustment information comprises:

determining a maximum value between the maximum power of the received UL signals subtracted by a maximum back-off value and a sum of the thermal noise floor power and the target C/I ratio; and

subtracting the maximum value from the received power of the UL signal to calculate the adjustment information for the UL signal.

7. The method of claim 6, wherein the adjustment information is bounded by a lower bound of 0 and an upper bound equal to the maximum back-off value.

8. The method of claim 6, wherein the maximum back-off value is about 40 dB.

9. The method of claim 1, wherein the target C/I ratio is about 30 dB.

10. The method of claim 1, wherein transmitting the adjustment information comprises transmitting a Clear to Transmit (CTX) message with a field indicating the adjustment information for the UL signal.

11. The method of claim 1, wherein the UL signal in the plurality of UL signals comprises a UL multiuser multiple-input multiple-output (UL-MU-MIMO) signal.

12. An apparatus for wireless communications, comprising:

means for receiving a plurality of uplink (UL) signals;

means for determining power of the received plurality of UL signals;

means for determining adjustment information for a UL signal in the plurality of UL signals based on at least the power of the received UL signals and a target carrier-to-interference (C/I) ratio; and

means for transmitting the adjustment information.

13. The apparatus of claim 12, wherein the means for receiving the plurality of UL signals is configured to receive a Request to Transmit (RTX) message or a physical layer convergence protocol (PLCP) protocol data unit (PPDU).

14. The apparatus of claim 12, wherein the adjustment information for the UL signal comprises a back-off value for a station (STA) that transmitted the UL signal.

15. The apparatus of claim 12, wherein the means for determining the adjustment information is configured to:

determine a maximum of the power of the received UL signals; and

determine the adjustment information for the UL signal based on the maximum power and the target C/I ratio.

16. The apparatus of claim 15, wherein the means for determining the adjustment information is configured to:

determine a thermal noise floor power; and

determine the adjustment information for the UL signal based on the maximum power, the target C/I ratio, and the thermal noise floor power.

17. The apparatus of claim 16, wherein the means for determining the adjustment information is configured to:

determine a maximum value between the maximum power of the received UL signals subtracted by a maximum back-off value and a sum of the thermal noise floor power and the target C/I ratio; and

subtract the maximum value from the received power of the UL signal to calculate the adjustment information for the UL signal.

18. The apparatus of claim 17, wherein the adjustment information is bounded by a lower bound of 0 and an upper bound equal to the maximum back-off value.

19. The apparatus of claim 17, wherein the maximum back-off value is about 40 dB.

20. The apparatus of claim 12, wherein the target C/I ratio is about 30 dB.

21. The apparatus of claim 12, wherein the means for transmitting the adjustment information is configured to transmit a Clear to Transmit (CTX) message with a field indicating the adjustment information for the UL signal.

22. The apparatus of claim 12, wherein the UL signal in the plurality of UL signals comprises a UL multiuser multiple-input multiple-output (UL-MU-MIMO) signal.

23. An access point (AP), comprising:

a receiver configured to receive a plurality of uplink (UL) signals;

logic for determining power of the received plurality of UL signals;

logic for determining adjustment information for a UL signal in the plurality of UL signals based on at least the power of the received UL signals and a target carrier-to-interference (C/I) ratio; and

a transmitter configured to transmit the adjustment information.

24. The access point of claim 23, wherein the receiver is configured to receive the plurality of UL signals by receiving a Request to Transmit (RTX) message or a physical layer convergence protocol (PLCP) protocol data unit (PPDU).

25. The access point of claim 23, wherein the adjustment information for the UL signal comprises a back-off value for a station (STA) that transmitted the UL signal.

26. The access point of claim 23, wherein the logic for determining the adjustment information is configured to:

determine a maximum of the power of the received UL signals; and

determine the adjustment information for the UL signal based on the maximum power and the target C/I ratio.

27. The access point of claim 26, wherein the logic for determining the adjustment information is configured to:

determine a thermal noise floor power; and

determine the adjustment information for the UL signal based on the maximum power, the target C/I ratio, and the thermal noise floor power.

28. The access point of claim 27, wherein the logic for determining the adjustment information is configured to:

determine a maximum value between the maximum power of the received UL signals subtracted by a maximum back-off value and a sum of the thermal noise floor power and the target C/I ratio; and

subtract the maximum value from the received power of the UL signal to calculate the adjustment information for the UL signal.

29. The access point of claim 28, wherein the adjustment information is bounded by a lower bound of 0 and an upper bound equal to the maximum back-off value.

30. The access point of claim 28, wherein the maximum back-off value is about 40 dB.

31. The access point of claim 23, wherein the target C/I ratio is about 30 dB.

32. The access point of claim 23, wherein the transmitter is configured to transmit the adjustment information by transmitting a Clear to Transmit (CTX) message with a field indicating the adjustment information for the UL signal.

33. The access point of claim 23, wherein the UL signal in the plurality of UL signals comprises a UL multiuser multiple-input multiple-output (UL-MU-MIMO) signal.

34. A computer-program product for wireless communications, comprising a computer-readable medium having instructions stored thereon, the instructions being executable by one or more processors and the instructions comprising:

instructions for receiving a plurality of uplink (UL) signals;

instructions for determining power of the received plurality of UL signals;

instructions for determining adjustment information for a UL signal in the plurality of UL signals based on at least the power of the received UL signals and a target carrier-to-interference (C/I) ratio; and

instructions for transmitting the adjustment information.

35. The computer-program product of claim 34, wherein the instructions for receiving the plurality of UL signals comprises instructions for receiving a Request to Transmit (RTX) message or a physical layer convergence protocol (PLCP) protocol data unit (PPDU).

36. The computer-program product of claim 34, wherein the adjustment information for the UL signal comprises a back-off value for a station (STA) that transmitted the UL signal.

37. The computer-program product of claim 34, wherein the instructions for determining the adjustment information comprises:

instructions for determining a maximum of the power of the received UL signals; and

instructions for determining the adjustment information for the UL signal based on the maximum power and the target C/I ratio.

38. The computer-program product of claim 37, wherein the instructions for determining the adjustment information comprises:

instructions for determining a thermal noise floor power; and

instructions for determining the adjustment information for the UL signal based on the maximum power, the target C/I ratio, and the thermal noise floor power.

39. The computer-program product of claim 38, wherein the instructions for determining the adjustment information comprises:

instructions for determining a maximum value between the maximum power of the received UL signals subtracted by a maximum back-off value and a sum of the thermal noise floor power and the target C/I ratio; and

instructions for subtracting the maximum value from the received power of the UL signal to calculate the adjustment information for the UL signal.

40. The computer-program product of claim 39, wherein the adjustment information is bounded by a lower bound of 0 and an upper bound equal to the maximum back-off value.

41. The computer-program product of claim 39, wherein the maximum back-off value is about 40 dB.

42. The computer-program product of claim 34, wherein the target C/I ratio is about 30 dB.

43. The computer-program product of claim 34, wherein the instructions for transmitting the adjustment information comprises instructions for transmitting a Clear to Transmit (CTX) message with a field indicating the adjustment information for the UL signal.

44. The computer-program product of claim 34, wherein the UL signal in the plurality of UL signals comprises a UL multiuser multiple-input multiple-output (UL-MU-MIMO) signal.