MIMO RECEIVER HAVING IMPROVED SIR ESTIMATION AND CORRESPONDING METHOD

• US 20110305262A1
• Filed: 06/18/2009
• Published: 12/15/2011
• Est. Priority Date: 11/10/2008
• Status: Active Grant

• Current Assignee: Icera Inc. (NVIDIA Corporation)
• Original Assignee: Icera Inc. (NVIDIA Corporation)
• Inventors: Medles, Abdelkader
• Granted Patent: US 9,184,807 B2
• Time in Patent Office: Days
• US Class Current: 375/147
• CPC Class Codes: H04B 17/24 with feedback of measurements to the transmitter
• CPC Class Codes: H04B 17/336 Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0632 Channel quality parameters, e.g. channel quality indicator [CQI]
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication

Abstract

A method and corresponding receiver product, the method comprising: receiving a plurality of data streams over a wireless multiple-input-multiple-output data channel, whereby each data stream is received at all of a plurality of receive antennas from all of a plurality of transmit antennas with a respective weighting having been applied to each stream as transmitted from each different transmit antenna; receiving a common pilot signal over a common pilot channel; receiving an indication of the weightings; extracting the individual data streams from the plurality received at the receive antennas; and using the weightings and the common pilot signal together with information regarding the extracted data streams to calculate, for each of the streams, an estimate of signal power relative to interference from the one or more others of said data streams.

Claims

1. A method of operating a wireless receiver, the method comprising:

receiving a plurality of data streams over a wireless multiple-input-multiple-output data channel, whereby each data stream is received at all of a plurality of receive antennas of the receiver from all of a plurality of transmit antennas of a transmitter with a respective weighting having been applied to each stream as transmitted from each different transmit antenna;

receiving a common pilot signal over a common pilot channel common to said receiver and one or more other receivers;

receiving an indication of said weightings;

extracting the individual data streams from the plurality received at said receive antennas;

using said weightings and the common pilot signal together with information regarding the extracted data streams to calculate, for each of said streams, an estimate of signal power relative to interference from the one or more others of said data streams; and

based on said estimates, performing at least one of the steps of;

decoding said data streams, and feeding back a metric relating to channel quality from the receiver to the transmitter for use in subsequent transmission over said channel.

2. The method of claim 1, wherein the calculation of said estimate comprises calculating both the signal power and the interference power and determining the estimate of the signal power relative to the interference power therefrom.

3. The method of claim 1, wherein said estimate of signal power relative to interference power is an estimate of signal power relative to interference power and noise power.

4. The method of claim 3, wherein the calculation of said estimate comprises calculating each of the signal power, interference power and noise power and determining the estimate of the signal power relative to the interference and noise power therefrom.

5. The method of claim 1, wherein the method comprises measuring an overall power received in each of the individual extracted data streams, and the use of said information in said calculation comprises using said measurements of overall power.

6. The method of claim 5, wherein said calculation comprises:

(i) for each extracted data stream, using a corresponding pilot stream from the common pilot channel to generate a respective estimate of equivalent channel response for each antenna;

(ii) using said estimated channel responses and said weightings to calculate estimates of signal power, noise power and interference power of the pilot streams; and

(iii) using said estimates of signal power, noise power and interference power from the pilot streams together with said measurements of received power in each extracted data stream to calculate said estimates of signal power, noise power and interference power from the other data streams.

7. The method of claim 1, wherein said reception comprises receiving only two data streams over a two-by-two wireless multiple-input-multiple-output data channel, whereby each data stream is received at both of two receive antennas of the receiver from both of two transmit antennas of the transmitter.

8. The method of claim 1, wherein said extraction of the individual data streams comprises processing inputs from the receive antennas through one of an equaliser and rake processor.

9. The method of claim 1, wherein said calculation is performed following de-scrambling and de-spreading of the data streams.

10. The method of claim 1, wherein said calculation is performed prior to log likelihood ratio calculation on said data streams.

11. The method of claim 1, wherein said calculation is performed prior to decoding of said data streams.

12. The method of claim 3, wherein the calculation of said estimate of signal power, noise power and interference power comprises calculating the ratio of signal power to interference plus noise power.

13. The method of claim 1, wherein said calculation is performed without using a dedicated pilot signal for said channel by instead using said weightings, common pilot channel and information of said extracted data streams.

14. The method of claim 7, wherein step (ii) comprises calculating:

for a first pilot stream;

signal power {circumflex over (P)}₁^S,CPICH=|{circumflex over (β

)}_1,1|²,pilot interference power Î

₁^S,CPICH=|{circumflex over (β

)}_1,2|²; and

for a second pilot stream;

signal power {circumflex over (P)}₂^S,CPICH=|{circumflex over (β

)}_2,2|²,and interference power Î

₂^S,CPICH=|{circumflex over (β

)}_2,1|²;

wherein estimates of β

_i,1 and β

_i,2 are generated from Y_i,1 (k) and Y_i,2 (k) respectively;

Y_i,1(k)=w₁Z_i,1(k)+w₂Z_i,2(k);

and which correspond to

Y_i,2(k)=w₃Z_i,1(k)+w₄Z_i,2(k)

Y_i,1(k)=β

_i,1+n_i,1(k)

Y_i,2(k)=β

_i,2+n_i,2(k),

where Z_i,1(k) is the channel response from the first antenna on the i^th pilot stream, Z_i,2(k) is the channel response from the second antenna on the i^th stream pilot, w_{1 . . . 4} are the weightings, and n_i,1 and n_i,2 are noise terms from the two respective antennas on the i^th pilot stream.

15. The method of claim 7, wherein step (iii) comprises estimating the per stream power by calculating the signal power ratio between the pilot and the data streams:

32. A computer program product comprising code which when executed on a processor will perform a method according to claim 1.

16. A receiver comprising:

a plurality of receive antenna for receiving a plurality of data streams over a wireless multiple-input-multiple-output data channel, whereby each data stream is received at all of said plurality of receive antennas from all of a plurality of transmit antennas of a transmitter with a respective weighting having been applied to each stream as transmitted from each different transmit antenna; and

for receiving a common pilot signal over a common pilot channel common to said receiver and one or more other receivers;

wherein the receiver further comprises a processing means configured to;

receive an indication of said weightings;

extract the individual data streams from the plurality received at said receive antennas;

use said weightings and the common pilot signal together with information regarding the extracted data streams to calculate, for each of said streams, an estimate of signal power relative to interference from the one or more others of said data streams; and

based on said estimates, performing at least one of the steps of;

decoding said data streams, and feeding back a metric relating to channel quality from the receiver to the transmitter for use in subsequent transmission over said channel.

17. The receiver of claim 16, wherein the processing means is configured to calculate said estimate by calculating both the signal power and the interference power and determining the estimate of the signal power relative to the interference power therefrom.

18. The receiver of claim 16, wherein the processing means is configured to calculate said estimate of signal power relative to interference power as an estimate of signal power relative to interference power and noise power.

19. The receiver of claim 18, wherein the processing means is configured to calculate said estimate by calculating each of the signal power, interference power and noise power and determining the estimate of the signal power relative to the interference and noise power therefrom.

20. The receiver of claim 16, wherein the processing means is configured to measure an overall power received in each of the individual extracted data streams, and the use of said information in said calculation comprises using said measurements of overall power.

21. The receiver of claim 20, wherein the processing means is configured to perform said calculation by:

(i) for each extracted data stream, using a corresponding pilot stream from the common pilot channel to generate a respective estimate of equivalent channel response for each antenna;

(ii) using said estimated channel responses and said weightings to calculate estimates of signal power, noise power and interference power of the pilot streams; and

(iii) using said estimates of signal power, noise power and interference power from the pilot streams together with said measurements of received power in each extracted data stream to calculate said estimates of signal power, noise power and interference power from the other data streams.

22. The receiver of claim 16, wherein the receiver comprises only two receive antennas for receiving only two data streams over a two-by-two wireless multiple-input-multiple-output data channel, whereby each data stream is received at both of two receive antennas of the receiver from both of two transmit antennas of the transmitter.

23. The receiver of claim 16, wherein the processing means is configured to extract said individual data streams by performing one of equalisation processing and rake processing on the inputs from the receive antennas.

24. The receiver of claim 16, wherein the processing means is configured to perform said calculation following de-scrambling and de-spreading of the data streams.

25. The receiver of any of claim 16, wherein the processing means is configured to perform said calculation prior to log likelihood ratio calculation on said data streams.

26. The receiver of claim 16, wherein the processing means is configured to perform said calculation is prior to decoding of said data streams.

27. The receiver of claim 18, wherein the processing means is configured to perform said calculation of signal power, noise power and interference power by calculating the ratio of signal power to interference plus noise power.

28. The receiver of claim 16, wherein the processing means is configured to perform said calculation without using a dedicated pilot signal for said channel by instead using said weightings, common pilot channel and information of said extracted data streams.

29. The receiver of claim 22, wherein the processing means is configured to perform step (ii) by calculating:

for a first pilot stream;

signal power {circumflex over (P)}₁^S,CPICH=|{circumflex over (β

)}_1,1|²,pilot interference power Î

₁^S,CPICH=|{circumflex over (β

)}_1,2|²; and

for a second pilot stream;

signal power {circumflex over (P)}₂^S,CPICH=|{circumflex over (β

)}_2,2|²,and interference power Î

₂^S,CPICH=|{circumflex over (β

)}_2,1|²;

wherein estimates of β

_i,1 and β

_i,2 are generated from Y_i,1 (k) and Y_i,2 (k) respectively;

Y_i,1(k)=w₁Z_i,1(k)+w₂Z_i,2(k);

and which correspond to

Y_i,2(k)=w₃Z_i,1(k)+w₄Z_i,2(k)

Y_i,1(k)=β

_i,1+n_i,1(k)

Y_i,2(k)=β

_i,2+n_i,2(k),

where Z_i,1(k) is the channel response from the first antenna on the i^th pilot stream, Z_i,2(k) is the channel response from the second antenna on the i^th stream pilot, w_{1 . . . 4} are the weightings, and n_i,1 and n_i,2 are noise terms from the two respective antennas on the i^th pilot stream.

30. The receiver of claim 22, wherein the processing means is configured to perform step (iii) by estimating the per stream power by calculating the signal power ratio between the pilot and the data streams:

31. A user equipment comprising:

a plurality of receive antenna for receiving a plurality of data streams over a wireless multiple-input-multiple-output data channel, whereby each data stream is received at all of said plurality of receive antennas from all of a plurality of transmit antennas of a transmitter with a respective weighting having been applied to each stream as transmitted from each different transmit antenna; and

for receiving a common pilot signal over a common pilot channel common to said receiver and one or more other receivers;

wherein the receiver further comprises a processing means configured to;

receive an indication of said weightings;

extract the individual data streams from the plurality received at said receive antennas;

use said weightings and the common pilot signal together with information regarding the extracted data streams to calculate, for each of said streams, an estimate of signal power relative to interference from the one or more others of said data streams; and

based on said estimates, performing at least one of the steps of;

decoding said data streams, and feeding back a metric relating to channel quality from the receiver to the transmitter for use in subsequent transmission over said channel.