Signal processing with channel eigenmode decomposition and channel inversion for MIMO systems

• US 20030235255A1
• Filed: 06/24/2002
• Published: 12/25/2003
• Est. Priority Date: 06/24/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ketchum, John W., Walton, Jay R.
• Granted Patent: US 7,613,248 B2
• Time in Patent Office: Days
• US Class Current: 375/285
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0439 utilizing channel inversion
• 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 1/0618 Space-time coding
• CPC Class Codes: H04L 25/0202 Channel estimation
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 25/03834 using pulse shaping

Abstract

Techniques for processing a data transmission at a transmitter and receiver, which use channel eigen-decomposition, channel inversion, and (optionally) “water-pouring”. At the transmitter, (1) channel eigen-decomposition is performed to determine eigenmodes of a MIMO channel and to derive a first set of steering vectors, (2) channel inversion is performed to derive weights (e.g., one set for each eigenmode) used to minimize ISI distortion, and (3) water-pouring may be performed to derive scaling values indicative of the transmit powers allocated to the eigenmodes. The first set of steering vectors, weights, and scaling values are used to derive a pulse-shaping matrix, which is used to precondition modulation symbols prior to transmission. At the receiver, channel eigen-decomposition is performed to derive a second set of steering vectors, which are used to derive a pulse-shaping matrix used to condition received symbols such that orthogonal symbol streams are recovered.

Claims

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

processing data in accordance with a particular processing scheme to provide a plurality of streams of modulation symbols;

deriving a pulse-shaping matrix based on an estimated response of the MIMO channel and in a manner to reduce intersymbol interference at a receiver; and

preconditioning the plurality of modulation symbol streams based on the pulse-shaping matrix to provide a plurality of streams of preconditioned symbols for transmission over the MIMO channel.

2. The method of claim 1, further comprising:

deriving a plurality of weights based on an estimated channel response matrix for the MIMO channel, wherein the weights are used to invert a frequency response of the MIMO channel, and wherein the pulse-shaping matrix is further derived based on the weights.

3. The method of claim 2, further comprising:

decomposing the estimated channel response matrix to obtain a plurality of matrices of eigen-vectors and a plurality of matrices of singular values, and

wherein the weights are derived based on the matrices of singular values and the pulse-shaping matrix is further derived based on the matrices of eigen-vectors.

4. The method of claim 2, wherein the estimated channel response matrix is descriptive of a plurality of eigenmodes of the MIMO channel.

5. The method of claim 4, wherein one set of weights is derived for each eigenmode used for data transmission and wherein the weights in each set are derived to invert the frequency response of the corresponding eigenmode.

6. The method of claim 4, further comprising:

deriving a plurality of scaling values based on the matrices of singular values, wherein the scaling values are used to adjust transmit powers for the eigenmodes of the MIMO channel, and wherein the pulse-shaping matrix is further derived based on the scaling values.

7. The method of claim 6, wherein the scaling values are derived based on water-pouring analysis.

8. The method of claim 3, wherein the estimated channel response matrix is provided in the frequency domain and is decomposed in the frequency domain.

9. The method of claim 3, wherein the estimated channel response matrix is decomposed using channel eigen-decomposition.

10. The method of claim 4, wherein eigenmodes associated with transmission capabilities below a particular threshold are not used for data transmission.

11. The method of claim 3, wherein the singular values in each matrix are sorted based on their magnitude.

12. The method of claim 4, wherein the singular values in each matrix are randomly ordered such that the eigenmodes of the MIMO channel are associated with approximately equal transmission capabilities.

13. The method of claim 1, 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 streams of modulation symbols with the pulse-shaping matrix.

14. The method of claim 1, 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 a plurality of streams of transformed modulation symbols with the pulse-shaping matrix.

15. The method of claim 1, wherein the pulse-shaping matrix is derived to maximize capacity by allocating more transmit power to eigenmodes of the MIMO channel having greater transmission capabilities.

16. The method of claim 1, wherein the pulse-shaping matrix is derived to provide approximately equal received signal-to-noise-and-interference ratios (SNRs) for the plurality of modulation symbol streams at the receiver.

17. The method of claim 1, wherein the particular processing scheme defines a separate coding and modulation scheme for each modulation symbol stream.

18. The method of claim 1, wherein the particular processing scheme defines a common coding and modulation scheme for all modulation symbol streams.

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

processing data in accordance with a particular processing scheme to provide a plurality of streams of modulation symbols;

obtaining an estimated channel response matrix for the MIMO channel;

decomposing the estimated channel response matrix to obtain a plurality of matrices of eigen-vectors and a plurality of matrices of singular values;

deriving a plurality of weights based on the matrices of singular values, wherein the weights are used to invert the frequency response of the MIMO channel;

deriving a pulse-shaping matrix based on the matrices of eigen-vectors and the weights; and

preconditioning the plurality of streams of modulation symbols based on the pulse-shaping matrix to provide a plurality of streams of preconditioned symbols for transmission over the MIMO channel.

20. The method of claim 19, further comprising:

deriving a plurality of scaling values based on the matrices of singular values, wherein the scaling values are used to adjust transmit powers for eigenmodes of the MIMO channel, and wherein the pulse-shaping matrix is further derived based on the scaling values.

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

process data in accordance with a particular processing scheme to provide a plurality of streams of modulation symbols;

derive a pulse-shaping matrix based on an estimated response of the MIMO channel and in a manner to reduce intersymbol interference at a receiver; and

precondition the plurality of streams of modulation symbols based on the pulse-shaping matrix to provide a plurality of streams of preconditioned symbols for transmission over the MIMO channel.

22. In a multiple-input multiple-output (MIMO) communication system, a method for processing a data transmission received via a MIMO channel, comprising:

obtaining an estimated channel response matrix for the MIMO channel;

decomposing the estimated channel response matrix to obtain a plurality of matrices of eigen-vectors;

deriving a pulse-shaping matrix based on the matrices of eigen-vectors; and

conditioning a plurality of streams of received symbols based on the pulse-shaping matrix to provide a plurality of streams of recovered symbols which are estimates of modulation symbols transmitted for the data transmission, wherein the modulation symbols are preconditioned at a transmitter, prior to transmission over the MIMO channel, in a manner to reduce intersymbol interference at a receiver.

23. The method of claim 22, wherein the conditioning is performed in the time domain based on a time-domain pulse-shaping matrix.

24. The method of claim 22, wherein the conditioning is performed in the frequency domain and includes

transforming the plurality of received symbol streams to the frequency domain;

multiplying the transformed received symbol streams with a frequency-domain pulse-shaping matrix to provide a plurality of conditioned symbol streams; and

transforming the plurality of conditioned symbol streams to the time domain to provide the plurality of recovered symbol streams.

25. The method of claim 22, wherein the conditioning orthogonalizes a plurality of streams of modulation symbols transmitted over the MIMO channel.

26. The method of claim 22, further comprising:

demodulating the plurality of recovered symbol streams in accordance with one or more demodulation schemes to provide a plurality of demodulated data streams; and

decoding the plurality of demodulated data streams in accordance with one or more decoding schemes to provide decoded data.

27. The method of claim 22, further comprising:

deriving channel state information (CSI) comprised of the estimated channel response matrix for the MIMO channel; and

sending the CSI back to the transmitter.

28. In a multiple-input multiple-output (MIMO) communication system, a method for processing a data transmission received via a MIMO channel, comprising:

obtaining an estimated channel response matrix for the MIMO channel;

decomposing the estimated channel response matrix to obtain a plurality of matrices of eigen-vectors;

deriving a pulse-shaping matrix based on the matrices of eigen-vectors;

conditioning a plurality of streams of received symbols based on the pulse-shaping matrix to provide a plurality of streams of recovered symbols which are estimates of modulation symbols transmitted for the data transmission, wherein the modulation symbols are preconditioned at a transmitter, prior to transmission over the MIMO channel, in a manner to reduce intersymbol interference at a receiver;

demodulating the plurality of recovered symbol streams in accordance with one or more demodulation schemes to provide a plurality of demodulated data streams; and

decoding the plurality of demodulated data streams in accordance with one or more decoding schemes to provide decoded data.

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

obtain an estimated channel response matrix for a MIMO channel used for a data transmission;

decompose the estimated channel response matrix to obtain a plurality of matrices of eigen-vectors;

derive a pulse-shaping matrix based on the matrices of eigen-vectors; and

condition a plurality of streams of received symbols based on the pulse-shaping matrix to provide a plurality of streams of recovered symbols which are estimates of modulation symbols transmitted for the data transmission, wherein the modulation symbols are preconditioned at a transmitter, prior to transmission over the MIMO channel, in a manner to reduce intersymbol interference at a receiver.

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

a TX data processor operative to process data in accordance with a particular processing scheme to provide a plurality of streams of modulation symbols; and

a TX MIMO processor operative to derive a pulse-shaping matrix based on an estimated response of a MIMO channel and in a manner to reduce intersymbol interference at a receiver, and to precondition the plurality of modulation symbol streams based on the pulse-shaping matrix to provide a plurality of streams of preconditioned symbols for transmission over the MIMO channel.

31. The transmitter unit of claim 30, wherein the TX MIMO processor is further operative to derive a plurality of weights based on an estimated channel response matrix for the MIMO channel, wherein the weights are used to invert the frequency response of the MIMO channel, and wherein the pulse-shaping matrix is derived based in part on the weights.

32. The transmitter unit of claim 31, wherein the TX MIMO processor is further operative to decompose the estimated channel response matrix to obtain a plurality of matrices of eigen-vectors and a plurality of matrices of singular values, and wherein the weights are derived based on the matrices of singular values and the pulse-shaping matrix is further derived based on the matrices of eigen-vectors.

33. The transmitter unit of claim 31, wherein the TX MIMO processor is further operative to derive a plurality of scaling values used to adjust transmit powers for the eigenmodes of the MIMO channel, and wherein the pulse-shaping matrix is further derived based on the scaling values.

34. The transmitter unit of claim 33, wherein the scaling values are derived based on water-pouring analysis on a plurality of matrices of singular values obtained from the estimated channel response matrix.

35. An apparatus in a multiple-input multiple-output (MIMO) communication system, comprising:

means for processing data in accordance with a particular processing scheme to provide a plurality of streams of modulation symbols;

means for deriving a pulse-shaping matrix based on an estimated response of a MIMO channel and in a manner to reduce intersymbol interference at a receiver; and

means for preconditioning the plurality of modulation symbol streams based on the pulse-shaping matrix to provide a plurality of streams of preconditioned symbols for transmission over the MIMO channel.

36. A digital signal processor comprising:

means for processing data in accordance with a particular processing scheme to provide a plurality of streams of modulation symbols;

means for deriving a pulse-shaping matrix based on an estimated response of a multiple-input multiple-output (MIMO) channel and in a manner to reduce intersymbol interference at a receiver; and

means for preconditioning the plurality of modulation symbol streams based on the pulse-shaping matrix to provide a plurality of streams of preconditioned symbols for transmission over the MIMO channel.

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

an RX MIMO processor operative to obtain an estimated channel response matrix for a MIMO channel used for a data transmission, decompose the estimated channel response matrix to obtain a plurality of matrices of eigen-vectors, derive a pulse-shaping matrix based on the matrices of eigen-vectors, and condition a plurality of streams of received symbols based on the pulse-shaping matrix to obtain a plurality of streams of recovered symbols which are estimates of modulation symbols transmitted over the MIMO channel, wherein the modulation symbols were preconditioned at a transmitter, prior to transmission over the MIMO channel, in a manner to reduce intersymbol interference at the receiver unit; and

an RX data processor operative to process the plurality of recovered symbol streams in accordance with a particular processing scheme to provide decoded data.

38. The receiver unit of claim 37, wherein the RX MIMO processor is operative to condition the plurality of streams of received symbols in the time domain based on a time-domain pulse-shaping matrix.

39. An apparatus in a multiple-input multiple-output (MIMO) communication system, comprising:

means for obtaining an estimated channel response matrix for a MIMO channel used for a data transmission;

means for decomposing the estimated channel response matrix to obtain a plurality of matrices of eigen-vectors; and

means for deriving a pulse-shaping matrix based on the matrices of eigen-vectors; and

means for conditioning a plurality of streams of received symbols based on the pulse-shaping matrix to provide a plurality of streams of recovered symbols which are estimates of modulation symbols transmitted for the data transmission, wherein the modulation symbols are preconditioned at a transmitter, prior to transmission over the MIMO channel, in a manner to reduce intersymbol interference at a receiver.

40. A digital signal processor comprising:

means for obtaining an estimated channel response matrix for a multiple-input multiple-output (MIMO) channel used for a data transmission;

means for decomposing the estimated channel response matrix to obtain a plurality of matrices of eigen-vectors;

means for deriving a pulse-shaping matrix based on the matrices of eigen-vectors; and

means for conditioning a plurality of streams of received symbols based on the pulse-shaping matrix to provide a plurality of streams of recovered symbols which are estimates of modulation symbols transmitted for the data transmission, wherein the modulation symbols are preconditioned at a transmitter, prior to transmission over the MIMO channel, in a manner to reduce intersymbol interference at a receiver.