Precoding for a multipath channel in a MIMO system

• US 7,197,084 B2
• Filed: 03/27/2002
• Issued: 03/27/2007
• Est. Priority Date: 03/27/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ketchum, John W., Bjerke, Bjorn A.
• Primary Examiner(s): Fan; Chieh M.
• Assistant Examiner(s): Lu; Jia
• Application Number:
  US10/108,616
• Publication Number:
  US 20030185310A1
• Time in Patent Office: 1,826 Days
• Field of Search: 375/259, 375/296, 375/316
• US Class Current: 375/296
• CPC Class Codes: H04B 7/005 Control of transmission; Equalising
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/043 using best eigenmode, e.g. beam forming or beam steering
• CPC Class Codes: H04B 7/0443 utilizing "waterfilling" technique
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04L 25/03057 with a recursive structure H04L25/03031 takes precedence
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end

Abstract

Techniques for preceding data for a multipath channel in a MIMO system. In one method, data is coded in accordance with one or more coding schemes to provide coded data, which is further modulated (i.e., symbol mapped) in accordance with one or more modulation schemes to provide modulation symbols. An estimated response of the MIMO channel is obtained (e.g., provided by a receiver), and an equivalent channel response is derived based on the estimated MIMO channel response and a response of a feed-forward filter of a decision feedback equalizer. The modulation symbols are then precoded based on the equivalent channel response to provide precoded symbols, which are further preconditioned based on the estimated MIMO channel response (e.g., using spatio-temporal pulse-shaping) to provide preconditioned symbols for transmission over the MIMO channel. The feed-forward filter may be adapted based on a minimum mean square error (MMSE) criterion.

Claims

1. In a multiple-input multiple-output (MIMO) communication system, a method for processing data for transmission over a multipath MIMO channel, comprising:

coding data in accordance with one or more coding schemes to provide coded data;

modulating the coded data in accordance with one or more modulation schemes to provide modulation symbols;

precoding the modulation symbols based on an equivalent channel response derived based on the estimated response of the MIMO channel and a response of a feed-forward filter of a decision feedback equalizer to provide precoded symbols; and

preconditioning the precoded symbols based on an estimated response of the MIMO channel to provide preconditioned symbols for transmission over the MIMO channel.

2. The method of claim 1, wherein the precoded symbols for each symbol period comprise an estimate of inter-symbol interference caused by precoded symbols in prior symbol periods due to the multipath MIMO channel.

3. The method of claim 1, wherein the preceding is performed as:

$\underset{\_}{c}<br><br>\left(n\right)=v<br><br><br><br>{\mathrm{mod}}_{2<br><br>M}<br><br>\left[\underset{\_}{s}<br><br>\left(n\right)-\underset{l\ne <br><br>0}{\sum <br><br>}<br><br>\underset{\_}{F}<br><br>\left(l\right)<br><br>\underset{\_}{c}<br><br>\left(n-l\right)\right],$

where

c(n) is a vector of precoded symbols for symbol period n;

s(n) is a vector of modulation symbols for symbol period n;

F(l) is a sequence of matrices for the equivalent channel response; and

vmod_2M is a vector modulo-2M arithmetic operation.

4. The method of claim 1, wherein the response of the feed-forward filter is adapted based on a minimum mean square error (MMSE) criterion.

5. The method of claim 1, wherein the response of the feed-forward filter is obtained based on a zero-forcing technique.

6. The method of claim 1, wherein the preconditioning is performed in the time domain using spatio-temporal pulse-shaping.

7. The method of claim 1, further comprising:

decomposing a first sequence of matrices for the estimated response of the MIMO channel to obtain a second sequence of matrices of eigen-vectors and a third sequence of matrices of singular values; and

deriving a pulse-shaping matrix based on the second and third sequences of matrices, wherein the preconditioning is performed based on the pulse-shaping matrix.

8. The method of claim 7, wherein the first sequence of matrices for the estimated response of the MIMO channel is decomposed based on singular value decomposition.

9. The method of claim 7, wherein the pulse-shaping matrix comprises a plurality of sequences of time-domain values, and wherein the preconditioning is performed in the time domain by convolving the precoded symbols with the pulse-shaping matrix.

10. The method of claim 7, wherein the pulse-shaping matrix comprises a plurality of sequences of frequency-domain values, and wherein the preconditioning is performed in the frequency domain by multiplying transformed precoded symbols with the pulse-shaping matrix.

11. The method of claim 1, wherein a separate coding and modulation scheme is used for each data stream transmitted over the MIMO channel.

12. The method of claim 1, wherein a common coding and modulation scheme is used for all data streams transmitted over the MIMO channel.

13. In a multiple-input multiple-output (MIMO) communication system, a method for processing data for transmission over a multipath MIMO channel, comprising:

coding data in accordance with one or more coding schemes to provide coded data;

modulating the coded data in accordance with one or more modulation schemes to provide modulation symbols;

determining an estimated response of the MIMO channel;

deriving an equivalent channel response based on the estimated response of the MIMO channel and a response of a feed-forward filter of a decision feedback equalizer;

precoding the modulation symbols based on the equivalent channel response to provide precoded symbols; and

preconditioning the precoded symbols based on the estimated response of the MIMO channel and using spatio-temporal pulse-shaping to provide preconditioned symbols for transmission over the MIMO channel.

14. A memory communicatively coupled to a digital signal processing device (DSPD) capable of interpreting digital information to:

code data in accordance with one or more coding schemes to provide coded data;

modulate the coded data in accordance with one or more modulation schemes to provide modulation symbols;

precode the modulation symbols based on an equivalent channel response derived based on the estimated response of a MIMO channel and a response of a feed-forward filter of a decision feedback equalizer to provide precoded symbols; and

precondition the precoded symbols based on an estimated response of a multipath MIMO channel to provide preconditioned symbols for transmission over the multipath MIMO channel.

15. A transmitter unit in a multiple-input multiple-output (MIMO) communication system, comprising:

a TX (Transmit) data processor operative to code data in accordance with one or more coding schemes to provide coded data for a plurality of transmission channels in a multipath MIMO channel, modulate the coded data in accordance with one or more modulation schemes to provide modulation symbols, and precode the modulation symbols based on an equivalent channel response derived based on the estimated response of the MIMO channel and a response of a feed-forward filter of a decision feedback equalizer to provide precoded symbols; and

a TX MIMO processor operative to precondition the precoded symbols based on an estimated response of the MIMO channel to provide preconditioned symbols for transmission over the MIMO channel.

16. The transmitter unit of claim 15, wherein the TX data processor is further operative to precode the modulation symbols based on:

$\underset{\_}{c}<br><br>\left(n\right)=v<br><br><br><br>{\mathrm{mod}}_{2<br><br>M}<br><br>\left[\underset{\_}{s}<br><br>\left(n\right)-\underset{l\ne <br><br>0}{\sum <br><br>}<br><br>\underset{\_}{F}<br><br>\left(l\right)<br><br>\underset{\_}{c}<br><br>\left(n-l\right)\right],$

where

c(n) is a vector of precoded symbols for symbol period n;

s(n) is a vector of modulation symbols for symbol period n;

F(l) is a sequence of matrices for the equivalent channel response; and

vmod_2M is a vector modulo-2M arithmetic operation.

17. The transmitter unit of claim 15, wherein the TX data processor is further operative to adapt the response of the feed-forward filter based on a minimum mean square error (MMSE) criterion.

18. The transmitter unit of claim 15, wherein the TX MIMO processor is further operative to decompose a first sequence of matrices for the estimated response of the MIMO channel to obtain a second sequence of matrices of eigen-vectors and a third sequence of matrices of singular values, derive a pulse-shaping matrix based on the second and third sequences of matrices, and precondition the precoded symbols based on the pulse-shaping matrix.

19. A transmitter apparatus in a multiple-input multiple-output (MIMO) communication system, comprising:

means for coding data in accordance with one or more coding schemes to provide coded data;

means for modulating the coded data in accordance with one or more modulation schemes to provide modulation symbols;

means for precoding the modulation symbols based on an equivalent channel response based on the estimated response of the MIMO channel and a response of a feed-forward filter of a decision feedback equalizer to provide precoded symbols;

means for preconditioning the precoded symbols based on an estimated response of a MIMO channel to provide preconditioned symbols;

means for conditioning and transmitting the preconditioned symbols over the MIMO channel.

20. A digital signal processor for use in a multiple-input multiple-output (MIMO) communication system, comprising:

means for coding data in accordance with one or more coding schemes to provide coded data;

means for modulating the coded data in accordance with one or more modulation schemes to provide modulation symbols;

means for precoding the modulation symbols based on an equivalent channel response derived based on the estimated response of a MIMO channel and a response of a feed-forward filter of a decision feedback equalizer to provide precoded symbols; and

means for preconditioning the precoded symbols based on an estimated response of a MIMO channel to provide preconditioned symbols for transmission over the MIMO channel.