METHODS FOR DETERMINING RECONSTRUCTION WEIGHTS IN A MIMO SYSTEM WITH SUCCESSIVE INTERFERENCE CANCELLATION

• US 20110051832A1
• Filed: 08/26/2009
• Published: 03/03/2011
• Est. Priority Date: 08/26/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Rao, Subramanya P., Sidi, Jonathan, Mergen, Gokhan
• Granted Patent: US 8,391,429 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
• CPC Class Codes: H04J 11/004 using regenerative subtractive interference cancellation
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0048 in conjunction with detection of multiuser or interfering signals, e.g. iteration between CDMA or MIMO detector and FEC decoder for spatial equalizer H04L25/03286
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 1/1812 Hybrid protocols; Hybrid automatic repeat request [HARQ]

Abstract

Certain aspects provide a method for determining decoding order and reconstruction weights for decoded streams to be cancelled in a MIMO system with successive interference cancellation, based on estimates of the channel characteristics, the received composite signal and parameters of the system.

Claims

1. A method for wireless communications, comprising:

receiving a composite wireless multiple input multiple output (MIMO) signal that comprises a plurality of separately encoded data streams;

decoding one of the plurality of separately encoded data streams to obtain a decoded stream;

reconstructing the decoded stream by re-encoding and re-modulating the decoded stream to obtain a reconstructed stream;

calculating a reconstruction weight vector for the decoded stream; and

cancelling the interference of the decoded stream on the received composite signal by scaling the reconstructed stream with the reconstruction weight vector and subtracting the result from the composite received signal.

2. The method of claim 1, wherein calculating a reconstruction weight vector for the decoded stream comprises:

estimating the channel properties based on the received pilot signal;

calculating a constant related to the traffic to pilot ratio, based on the characteristics of a stream, such as its signal amplitude and modulation type.

multiplying the constant with the estimate of the channel from pilot signal to generate a matrix; and

extracting one of the columns of the matrix to be the reconstruction weight vector of the decoded stream.

3. The method of claim 1, wherein calculating a reconstruction weight vector for the decoded stream comprises:

correlating the reconstructed stream with the received composite signal vector to obtain a reconstruction weight vector.

4. The method of claim 1, wherein calculating reconstruction weight vectors for decoded streams comprises:

calculating the reconstruction weight vectors for a first plurality of streams with a first technique; and

calculating the reconstruction weight vectors for a second plurality of streams with a second technique.

5. The method of claim 4, wherein the first technique calculates the reconstruction weight vector based on correlation of the reconstructed stream with the received composite signal.

6. The method of claim 4, wherein the second technique calculates the reconstruction weight vector based on the statistics of pilot signal, signal amplitude and modulation scheme of the stream.

7. An apparatus for wireless communications, comprising:

means for receiving a composite wireless multiple input multiple output (MIMO) signal that comprises a plurality of separately encoded data streams;

means for decoding one of the plurality of separately encoded data streams to obtain a decoded stream;

means for reconstructing the decoded stream by re-encoding and re-modulating the decoded stream to obtain a reconstructed stream;

means for calculating a reconstruction weight vector for the decoded stream; and

means for cancelling the interference of the decoded stream on the received composite signal by scaling the reconstructed stream with the reconstruction weight vector and subtracting the result from the composite received signal.

8. The apparatus of claim 7, wherein the means for calculating a reconstruction weight vector for the decoded stream comprises:

means for estimating the channel properties based on the received pilot signal;

means for calculating a constant related to the traffic to pilot ratio, based on the characteristics of a stream, such as its signal amplitude and modulation type.

means for multiplying the constant with the estimate of the channel from pilot signal to generate a matrix; and

means for extracting one of the columns of the matrix to be the reconstruction weight vector of the decoded stream.

9. The apparatus of claim 7, wherein the means for calculating a reconstruction weight vector for the decoded stream comprises:

means for correlating the reconstructed stream with the received composite signal vector to obtain a reconstruction weight vector.

10. The apparatus of claim 7, wherein the means for calculating reconstruction weight vectors for decoded streams comprises:

means for calculating the reconstruction weight vectors for a first plurality of streams with a first technique; and

means for calculating the reconstruction weight vectors for a second plurality of streams with a second technique.

11. The apparatus of claim 10, wherein the first technique calculates the reconstruction weight vector based on correlation of the reconstructed stream with the received composite signal.

12. The apparatus of claim 10, wherein the second technique calculates the reconstruction weight vector based on the statistics of pilot signal, signal amplitude and modulation scheme of the stream.

13. An apparatus for wireless communications, comprising:

logic for receiving a composite wireless multiple input multiple output (MIMO) signal that comprises a plurality of separately encoded data streams;

logic for decoding one of the plurality of separately encoded data streams to obtain a decoded stream;

logic for reconstructing the decoded stream by re-encoding and re-modulating the decoded stream to obtain a reconstructed stream;

logic for calculating a reconstruction weight vector for the decoded stream; and

logic for cancelling the interference of the decoded stream on the received composite signal by scaling the reconstructed stream with the reconstruction weight vector and subtracting the result from the composite received signal.

14. The apparatus of claim 13, wherein the logic for calculating a reconstruction weight vector for the decoded stream comprises:

logic for estimating the channel properties based on the received pilot signal;

logic for calculating a constant related to the traffic to pilot ratio, based on the characteristics of a stream, such as its signal amplitude and modulation type.

logic for multiplying the constant with the estimate of the channel from pilot signal to generate a matrix; and

logic for extracting one of the columns of the matrix to be the reconstruction weight vector of the decoded stream.

15. The apparatus of claim 13, wherein the logic for calculating a reconstruction weight vector for the decoded stream comprises:

logic for correlating the reconstructed stream with the received composite signal vector to obtain a reconstruction weight vector.

16. The apparatus of claim 13, wherein the logic for calculating reconstruction weight vectors for decoded streams comprises:

logic for calculating the reconstruction weight vectors for a first plurality of streams with a first technique; and

logic for calculating the reconstruction weight vectors for a second plurality of streams with a second technique.

17. The apparatus of claim 16, wherein the first technique calculates the reconstruction weight vector based on correlation of the reconstructed stream with the received composite signal.

18. The apparatus of claim 16, wherein the second technique calculates the reconstruction weight vector based on the statistics of pilot signal, signal amplitude and modulation scheme of the stream.

19. 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 composite wireless multiple input multiple output (MIMO) signal that comprises a plurality of separately encoded data streams;

instructions for decoding one of the plurality of separately encoded data streams to obtain a decoded stream;

instructions for reconstructing the decoded stream by re-encoding and re-modulating the decoded stream to obtain a reconstructed stream;

instructions for calculating a reconstruction weight vector for the decoded stream; and

instructions for cancelling the interference of the decoded stream on the received composite signal by scaling the reconstructed stream with the reconstruction weight vector and subtracting the result from the composite received signal.

20. The computer-program product of claim 19, wherein the instructions for calculating a reconstruction weight vector for the decoded stream comprise:

instructions for estimating the channel properties based on the received pilot signal;

instructions for calculating a constant related to the traffic to pilot ratio, based on the characteristics of a stream, such as its signal amplitude and modulation type.

instructions for multiplying the constant with the estimate of the channel from pilot signal to generate a matrix; and

instructions for extracting one of the columns of the matrix to be the reconstruction weight vector of the decoded stream.

21. The computer-program product of claim 19, wherein the instructions for calculating a reconstruction weight vector for the decoded stream comprise:

instructions for correlating the reconstructed stream with the received composite signal vector to obtain a reconstruction weight vector.

22. The computer-program product of claim 19, wherein the instructions for calculating reconstruction weight vectors for decoded streams comprise:

instructions for calculating the reconstruction weight vectors for a first plurality of streams with a first technique; and

instructions for calculating the reconstruction weight vectors for a second plurality of streams with a second technique.

23. The computer-program product of claim 22, wherein the first technique calculates the reconstruction weight vector based on correlation of the reconstructed stream with the received composite signal.

24. The computer-program product of claim 22, wherein the second technique calculates the reconstruction weight vector based on the statistics of pilot signal, signal amplitude and modulation scheme of the stream.