Phase-noise resilient generation of a channel quality indicator

• US 8,477,888 B2
• Filed: 06/24/2008
• Issued: 07/02/2013
• Est. Priority Date: 06/24/2008
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Lu, Feng, Sripathi, Prashant Udupa, Zhao, Liang, Subrahmanya, Parvathanathan, Rao, Subramanya P.
• Primary Examiner(s): Ahn, Sam K
• Assistant Examiner(s): Garcia, Santiago
• Application Number:
  US12/145,322
• Publication Number:
  US 20090316842A1
• Time in Patent Office: 1,834 Days
• Field of Search: 375/246, 375/346
• US Class Current: 375/346
• CPC Class Codes: H04B 17/345 Interference values signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] H04B17/336
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/20 using signal quality detector
• 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

Abstract

System(s) and method(s) are provided for generating phase-noise resilient channel quality indicator(s). A pilot signal utilized to determine a channel quality indicator is rotated to be aligned to a phase reference signal. Separate noise evaluations in quadrature and in-phase directions are utilized, at least in part, to generate a net noise estimate that is phase-noise compensated or resilient. For example, various combination schemes of quadrature and in-phase noise evaluations can be exploited to generate a net noise estimate, the schemes include weighted average of in-phase and quadrature noise estimates and running averages thereof. Simulation of net noise estimates as a function of geometry conditions reveal that the combination schemes provide substantive mitigation of phase-noise, thus making CQI generation phase-noise resilient.

Claims

1. A method comprising:

evaluating an in-phase noise variance for a pilot signal in the presence of a phase noise by a processor of an electronic device;

evaluating a quadrature noise variance for the pilot signal in the presence of the phase noise by the processor; and

estimating a net noise variance for the pilot signal based at least in part on the evaluated in-phase noise variance or the evaluated quadrature noise variance by the processor, wherein estimating a net noise variance for the pilot signal based at least in part on the evaluated in-phase noise variance or the evaluated quadrature noise variance comprises combining the evaluated in-phase noise variance and the evaluated quadrature noise variance by;

computing a running average (<

N^(I)>

) of a set of in-phase noise variance estimates;

computing a running average (<

N^(Q)>

) of a set of quadrature noise variance estimates;

assigning <

N^(I)>

to the net noise variance estimate when a ratio of <

N^(Q)>

to <

N^(I)>

is greater than a threshold; and

assigning a weighted average of <

N^(Q)> and

<

N^(I)>

to the net noise variance estimate when the ratio of <

N^(Q)>

to <

N^(I)>

is one of lower than or equal to the threshold.

2. The method of claim 1, wherein the weight of <

N^(Q)>

is ½ and

the weight of <

N^(I)>

is ½

.

3. The method of claim 1, wherein weights in the weighted average are optimal weights (w_I,w_Q) each based at least in part on a first variance (σ

_I²) of the set of in-phase noise variance estimates, or a second variance (σ

_Q²) of the set of quadrature noise variance estimates.

4. The method of claim 3, wherein

5. The method of claim 4, further comprising computing σ

_I² and σ

_Q².

6. The method of claim 5, further comprising generating a channel quality indicator based at least in part on the estimated net noise variance.

7. The method of claim 6 further comprising:

computing a desensitization factor Γ

, wherein

8. The method of claim 7, further comprising controlling power allocation based at least in part on the estimated net noise variance and the compensated signal strength.

9. An apparatus comprising:

means for rotating a pilot signal onto a phase reference signal;

means for evaluating an in-phase noise for the rotated pilot signal in the presence of a phase noise;

means for evaluating a quadrature noise for the rotated pilot signal in the presence of a phase noise; and

means for estimating a net noise for the rotated pilot signal based at least in part on the evaluated in-phase noise and the evaluated quadrature noise, wherein the means for estimating a net noise for the rotated pilot signal based at least in part on the evaluated in-phase noise and the evaluated quadrature noise comprises means for combining the evaluated in-phase noise and the evaluated quadrature noise, the means for combining further comprising;

means for computing a running average (<

N^(I)>

)of a set of in-phase noise estimates;

means for computing a running average (<

N^(Q)>

) of a set of quadrature noise estimates;

means for assigning <

N^(I)>

to the net noise estimate when a ratio of <

N^(Q)>

to <

N^(I)>

is greater than a threshold; and

means for assigning a weighted average of <

N^(Q)> and

<

N^(I)>

to the net noise estimate when the ratio of <

N^(Q)>

to <

N^(I)>

is one of lower than or equal to the threshold.

10. The apparatus of claim 9, wherein weights in the weighted average are optimal weights (w_I,w_Q) each based at least in part on a first variance (σ

_I²) of the set of in-phase noise estimates, or a second variance (σ

_Q²) of the set of quadrature noise estimates.

11. The apparatus of claim 10, wherein

12. The apparatus of claim 11, further comprising means for computing σ

_I² and σ

_Q².

13. The apparatus of claim 9, wherein the phase reference signal is at least one of a filtered version of the pilot symbol stream or an averaged version of the pilot stream.

14. The apparatus of claim 9 further comprising:

means for evaluating a desensitization factor Γ

, wherein

15. A non-transitory computer program product comprising a computer-readable medium including:

code for causing a computer to rotate a pilot signal onto a phase reference signal;

code for causing a computer to evaluate an in-phase noise variance for the rotated pilot signal in the presence of a phase noise;

code for causing a computer to evaluate a quadrature noise variance for the rotated pilot signal in the presence of a phase noise;

code for causing a computer to estimate a net noise variance for the rotated pilot signal based at least in part on the evaluated in-phase noise variance or the evaluated quadrature noise variance, comprising;

code for causing the computer to quantify a running average (<

N^(I)>

) of a set of in-phase noise variance estimates;

code for causing the computer to quantify a running average (<

N^(Q)>

) of a set of quadrature noise variance estimates;

code for causing the computer to assign <

N^(I)>

to the net noise variance estimate when a ratio of <

N^(Q)>

to <

N^(I)>

is greater than a threshold; and

code for causing the computer to assign a weighted average of <

N^(Q)> and

<

N^(I)>

to the net noise variance estimate when the ratio of <

N^(Q)>

to <

N^(I)>

is one of lower than or equal to the threshold; and

code for causing a computer to generate a channel quality indicator based at least in part on the estimated net noise variance.

16. The computer program product of claim 15, wherein weights in the weighted average are optimal weights (w_I,w_Q) each based at least in part on a first variance (σ

_I²) of the set of in-phase noise variance estimates, or a second variance (σ

_Q²) of the set of quadrature noise variance estimates.

17. The computer program product of claim 16,

wherein

18. The computer program product of claim 17, the computer-readable medium further comprising code for causing a computer to calculate σ

_I² and σ

_Q².

19. The computer program of claim 15, code for causing a computer to generate a channel quality indicator based at least in part on the estimated net noise variance further comprising:

code for causing the computer to determine a desensitization factor Γ

, wherein

20. An electronic device that operates in a wireless environment, the electronic device comprising:

a processor configured to evaluate an in-phase noise for a pilot signal in the presence of a phase noise;

to evaluate a quadrature noise for the pilot signal in the presence of a phase noise; and

to estimate a net noise for the pilot signal based at least in part on the evaluated in-phase noise or the evaluated quadrature noise by;

quantifying a running average (<

N^(I)>

) of a set of in-phase noise estimates;

quantifying a running average (<

N^(Q)>

) of a set of quadrature noise estimates;

assigning <

N^(I)>

to the net noise estimate when a ratio of <

N^(Q)>

to <

N^(I)>

is greater than a threshold; and

assigning a weighted average of <

N^(Q)> and

<

N^(I)>

to the net noise estimate when the ratio of <

N^(Q)>

to <

N^(I)>

is one of lower than or equal to the threshold; and

a memory coupled to the processor.

21. The electronic device of claim 20, wherein weights in the weighted average are optimal weights (w_I,w_Q) each based at least in part on a first variance (σ

_I²) of the set of in-phase noise estimates, or a second variance (σ

_Q²) of the set of quadrature noise estimates.

22. The electronic device of claim 21, wherein

23. The electronic device of claim 22, the processor further configured to calculate σ

_I² and σ

_Q².

24. The electronic device of claim 20, wherein the pilot signal is a received pilot signal rotated onto a phase reference signal, the phase reference signal is at least one of a filtered version of the received pilot signal or an averaged version of the received pilot signal.

25. The electronic device of claim 20, the processor further configured to generate a channel quality indicator based at least in part on the estimated net noise.

26. The electronic device of claim 25, wherein to generate a channel quality indicator based at least in part on the estimated net noise includes:

to determine a desensitization factor Γ

, wherein

27. The electronic device of claim 20, wherein the memory stores at least one of a set of in-phase noise estimates, a set of quadrature noise estimates, or a set of desensitization factors.

28. A method comprising:

evaluating an in-phase noise variance for a pilot signal in the presence of a phase noise by a processor of an electronic device;

evaluating a quadrature noise variance for the pilot signal in the presence of the phase noise by the processor; and

estimating a net noise variance for the pilot signal based at least in part on the evaluated in-phase noise variance or the evaluated quadrature noise variance by the processor, wherein estimating a net noise variance for the pilot signal based at least in part on the evaluated in-phase noise variance or the evaluated quadrature noise variance comprises combining the evaluated in-phase noise variance and the evaluated quadrature noise variance by;

computing a running average (<

N^(I)>

) of a set of in-phase noise estimates;

computing a running average (<

N^(Q)>

) of a set of quadrature noise estimates;

computing an offset Δ

=<

N^(I)>

−

<

N^(Q)> and

subtracting the offset from the evaluated quadrature noise; and

generating the net noise variance estimate as a weighted average of the evaluated in-phase noise variance and the evaluated quadrature noise variance adjusted by Δ

.

29. An apparatus comprising:

means for rotating a pilot signal onto a phase reference signal;

means for evaluating an in-phase noise for the rotated pilot signal in the presence of a phase noise;

means for evaluating a quadrature noise for the rotated pilot signal in the presence of a phase noise; and

means for estimating a net noise for the rotated pilot signal based at least in part on the evaluated in-phase noise and the evaluated quadrature noise, wherein the means for estimating a net noise for the rotated pilot signal based at least in part on the evaluated in-phase noise and the evaluated quadrature noise comprises means for combining the evaluated in-phase noise and the evaluated quadrature noise, the means for combining further comprising;

means for computing a running average (<

N^(I)>

) of a set of in-phase noise estimates;

means for computing a running average (<

N^(Q)>

) of a set of quadrature noise estimates;

means for compensating the evaluated quadrature noise; and

means for evaluating a weighted average of the evaluated in-phase noise and the compensated evaluated quadrature noise.

30. An electronic device that operates in a wireless environment, the electronic device comprising:

a processor configured to evaluate an in-phase noise for a pilot signal in the presence of a phase noise;

to evaluate a quadrature noise for the pilot signal in the presence of a phase noise; and

to estimate a net noise for the pilot signal based at least in part on the evaluated in-phase noise or the evaluated quadrature noise by;

quantifying a running average (<

N^(I)>

) of a set of in-phase noise estimates;

quantifying a running average (<

N^(Q)>

) of a set of quadrature noise estimates;

quantifying an offset Δ

=<

N^(I)>

−

<

N^(Q)> and

subtracting the offset from the evaluated quadrature noise; and

generating the net noise estimate as weighted average of the evaluated in-phase noise and the evaluated quadrature noise adjusted by Δ

; and

a memory coupled to the processor.

31. A non-transitory computer program product comprising a computer-readable medium including:

code for causing a computer to rotate a pilot signal onto a phase reference signal;

code for causing a computer to evaluate an in-phase noise variance for the rotated pilot signal in the presence of a phase noise;

code for causing a computer to evaluate a quadrature noise variance for the rotated pilot signal in the presence of a phase noise;

code for causing a computer to estimate a net noise variance for the pilot signal based at least in part on the evaluated in-phase noise variance or the evaluated quadrature noise variance, comprising;

code for causing the computer to quantify a running average (<

N^(I)>

)of a set of in-phase noise variance estimates;

code for causing the computer to quantify a running average (<

N^(Q)>

) of a set of quadrature noise variance estimates;

code for causing the computer to quantify an offset Δ

=<

N^(I)>

−

<

N^(Q)> and

subtracting the offset from the evaluated quadrature noise variance; and

code for causing the computer to generate the net noise variance estimate as a weighted average of the evaluated in-phase noise variance and the evaluated quadrature noise variance adjusted by Δ

; and

code for causing a computer to generate a channel quality indicator based at least in part on the estimated net noise variance.