Apparatus and method for channel quality feedback with a K-best detector in a wireless network
A receiver in a multiple input, multiple output (MIMO) system is configured to perform a method for generating channel quality feedback information. The method includes receiving, from a MIMO transmitter, pilot signals in each MIMO layer. The method also includes estimating the MIMO channel using the received pilot signals and performing a QR decomposition of the estimated MIMO channel. The method further includes predicting a probability of error for each MIMO layer after the QR decomposition of the estimated MIMO channel. The method still further includes determining a corresponding signal-to-noise ratio (SNR) for each MIMO layer based on the probability of error for the each MIMO layer.
1. A method for use in a receiver in a multiple input, multiple output (MIMO) system, the method comprising:
receiving, from a MIMO transmitter, pilot signals in each MIMO layer;
estimating the MIMO channel using the received pilot signals and performing a QR decomposition of the estimated MIMO channel;
predicting a probability of error for each MIMO layer after the QR decomposition of the estimated MIMO channel; and
determining a corresponding signal-to-noise ratio (SNR) for each MIMO layer based on the probability of error for the each MIMO layer.
2. The method of claim 1 , further comprising:
determining channel quality feedback information based on the determined SNR for each MIMO layer.
3. The method of claim 1 , wherein the MIMO system comprises L layers and the SNR for an ith layer among the L layers in the MIMO system is determined based on the probability of error for each layer between the ith layer and the Lth layer, inclusive, wherein L is an integer number.
4. The method of claim 3 , wherein the SNR for the ith layer is determined according to the equation:
SNR
i
≈
min
(
r
ii
2
σ
2
,
max
(
r
i
+
1
,
i
+
1
2
σ
2
,
r
ii
2
r
i
,
i
+
1
2
+
σ
2
)
,
…
,
max
(
r
LL
2
σ
2
,
r
ii
2
r
iL
2
+
σ
2
)
)
.
wherein r ii , r i+1,i+1 , r i,i+1 , r LL , and r iL are values in the QR decomposition of the MIMO channel matrix and σ 2 is a variance of noise.
5. The method of claim 1 , wherein the receiver is a mobile station and the transmitter is a base station in the MIMO system.
6. The method of claim 1 , wherein the receiver comprises a K-Best detector.
7. The method of claim 2 , wherein the channel quality feedback information comprises at least one of a channel quality index, a precoder matrix index, and a rank index.
8. An apparatus for use in a receiver in a multiple input, multiple output (MIMO) system, the apparatus comprising:
a processor configured to:
receive, from a MIMO transmitter, pilot signals in each MIMO layer;
estimate the MIMO channel using the received pilot signals and perform a QR decomposition of the estimated MIMO channel;
predict a probability of error for each MIMO layer after the QR decomposition of the estimated MIMO channel; and
determine a corresponding signal-to-noise ratio (SNR) for each MIMO layer based on the probability of error for the each MIMO layer.
9. The apparatus of claim 8 , the processor further configured to:
determine channel quality feedback information based on the determined SNR for each MIMO layer.
10. The apparatus of claim 8 , wherein the MIMO system comprises L layers and the SNR for an ith layer among the L layers in the MIMO system is determined based on the probability of error for each layer between the ith layer and the Lth layer, inclusive, wherein L is an integer number.
11. The apparatus of claim 10 , wherein the SNR for the ith layer is determined according to the equation:
SNR
i
≈
min
(
r
ii
2
σ
2
,
max
(
r
i
+
1
,
i
+
1
2
σ
2
,
r
ii
2
r
i
,
i
+
1
2
+
σ
2
)
,
…
,
max
(
r
LL
2
σ
2
,
r
ii
2
r
iL
2
+
σ
2
)
)
wherein r ii , r i+1,i+1 , r i,i+1 , r LL , and r iL are values in the QR decomposition of the MIMO channel matrix and σ 2 is a variance of noise.
12. The apparatus of claim 8 , wherein the receiver is a mobile station and the transmitter is a base station in the MIMO system.
13. The apparatus of claim 8 , wherein the receiver comprises a K-Best detector.
14. The apparatus of claim 13 , wherein the channel quality feedback information comprises at least one of a channel quality index, a precoder matrix index, and a rank index.
15. A receiver for use in a multiple input, multiple output (MIMO) system, the receiver comprising:
a plurality of antenna elements; and
a processor coupled to the plurality of antenna elements, the processor configured to:
receive, from a MIMO transmitter, pilot signals in each MIMO layer;
estimate the MIMO channel using the received pilot signals and perform a QR decomposition of the estimated MIMO channel;
predict a probability of error for each MIMO layer after the QR decomposition of the estimated MIMO channel; and
determine a corresponding signal-to-noise ratio (SNR) for each MIMO layer based on the probability of error for the each MIMO layer.
16. The receiver of claim 15 , the processor further configured to:
determine channel quality feedback information based on the determined SNR for each MIMO layer.
17. The receiver of claim 15 , wherein the MIMO system comprises L layers and the SNR for an ith layer among the L layers in the MIMO system is determined based on the probability of error for each layer between the ith layer and the Lth layer, inclusive, wherein L is an integer number.
18. The receiver of claim 17 , wherein the SNR for the ith layer is determined according to the equation:
SNR
i
≈
min
(
r
ii
2
σ
2
,
max
(
r
i
+
1
,
i
+
1
2
σ
2
,
r
ii
2
r
i
,
i
+
1
2
+
σ
2
)
,
…
,
max
(
r
LL
2
σ
2
,
r
ii
2
r
iL
2
+
σ
2
)
)
wherein r ii , r i+1,i+1 , r i,i+1 , r LL , and r iL are values in the QR decomposition of the MIMO channel matrix and σ 2 is a variance of noise.
19. The receiver of claim 15 , wherein the receiver is a mobile station and the transmitter is a base station in the MIMO system.
20. The receiver of claim 15 , wherein the receiver comprises a K-Best detector.