Phase-noise resilient generation of a channel quality indicator
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.
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 I 2 ) of the set of in-phase noise variance estimates, or a second variance (σ Q 2 ) of the set of quadrature noise variance estimates.
4. The method of claim 3 , wherein
w
I
=
(
σ
I
2
)
-
1
(
σ
I
2
)
-
1
+
(
σ
Q
2
)
-
1
and
w
Q
=
(
σ
Q
2
)
-
1
(
σ
I
2
)
-
1
+
(
σ
Q
2
)
-
1
.
5. The method of claim 4 , further comprising computing σ I 2 and σ Q 2 .
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
Γ
=
-
1
2
∑
n
=
0
k
i
-
1
ϕ
2
(
n
)
with k l a code
spreading factor, φ(n) a phase noise sequence, and n an integer; and
compensating a signal strength estimate with the desensitization factor.
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 I 2 ) of the set of in-phase noise estimates, or a second variance (σ Q 2 ) of the set of quadrature noise estimates.
11. The apparatus of claim 10 , wherein
w
I
=
(
σ
I
2
)
-
1
(
σ
I
2
)
-
1
+
(
σ
Q
2
)
-
1
and
w
Q
=
(
σ
Q
2
)
-
1
(
σ
I
2
)
-
1
+
(
σ
Q
2
)
-
1
.
12. The apparatus of claim 11 , further comprising means for computing σ I 2 and σ Q 2 .
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
Γ
=
-
1
2
∑
n
=
0
k
i
-
1
ϕ
2
(
n
)
with k l a code spreading factor, φ(n) a phase noise sequence, and n an integer;
means for compensating a signal strength estimate with the desensitization factor; and
means for generating a channel quality indicator based at least in part on the estimated net noise and the compensated signal strength estimate.
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 I 2 ) of the set of in-phase noise variance estimates, or a second variance (σ Q 2 ) of the set of quadrature noise variance estimates.
17. The computer program product of claim 16 ,
wherein
w
I
=
(
σ
I
2
)
-
1
(
σ
I
2
)
-
1
+
(
σ
Q
2
)
-
1
and
w
Q
=
(
σ
Q
2
)
-
1
(
σ
I
2
)
-
1
+
(
σ
Q
2
)
-
1
.
18. The computer program product of claim 17 , the computer-readable medium further comprising code for causing a computer to calculate σ I 2 and σ Q 2 .
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
Γ
=
-
1
2
∑
n
=
0
k
i
-
1
ϕ
2
(
n
)
with k l a code spreading factor, φ(n) a phase noise sequence, and n an integer; and
code for causing the computer to compensate a signal strength estimate with the desensitization factor.
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 I 2 ) of the set of in-phase noise estimates, or a second variance (σ Q 2 ) of the set of quadrature noise estimates.
22. The electronic device of claim 21 , wherein
w
I
=
(
σ
I
2
)
-
1
(
σ
I
2
)
-
1
+
(
σ
Q
2
)
-
1
and
w
Q
=
(
σ
Q
2
)
-
1
(
σ
I
2
)
-
1
+
(
σ
Q
2
)
-
1
.
23. The electronic device of claim 22 , the processor further configured to calculate σ I 2 and σ Q 2 .
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
Γ
=
-
1
2
∑
n
=
0
k
i
-
1
ϕ
2
(
n
)
with k l a code spreading factor, φ(n) a phase noise sequence, and n an integer; and
to compensate a signal strength estimate with the desensitization factor.
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.