Method and apparatus for processing data in a multiple-input multiple-output (MIMO) communication system utilizing channel state information

• US 6,785,341 B2
• Filed: 05/11/2001
• Issued: 08/31/2004
• Est. Priority Date: 05/11/2001
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Howard, Steven J., Ketchum, John W., Wallace, Mark, Walton, Jay R.
• Primary Examiner(s): Ghebretinsae, Temesghen
• Application Number:
  US09/854,235
• Publication Number:
  US 20030035491A1
• Time in Patent Office: 1,208 Days
• Field of Search: 375/267, 375/260, 375/144, 375/148, 375/346, 375/347
• US Class Current: 375/267
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/0689 using different transmission schemes, at least one of them being a diversity transmission scheme
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• 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: H04B 7/10 Polarisation diversity; Directional diversity
• CPC Class Codes: H04B 7/12 Frequency diversity
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• 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 1/005 Iterative decoding, including iteration between signal detection and decoding operation
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Techniques to “successively” process received signals at a receiver unit in a MIMO system to recover transmitted data, and to “adaptively” process data at a transmitter unit based on channel state information available for the MIMO channel. A successive cancellation receiver processing technique is used to process the received signals and performs a number of iterations to provide decoded data streams. For each iteration, input (e.g., received) signals for the iteration are processed to provide one or more symbol streams. One of the symbol streams is selected and processed to provide a decoded data stream. The interference due to the decoded data stream is approximately removed (i.e., canceled) from the input signals provided to the next iteration. The channel characteristics are estimated and reported back to the transmitter system and used to adjust (i.e., adapt) the processing (e.g., coding, modulation, and so on) of data prior to transmission.

Claims

1. A method for processing data at a receiver unit in a multiple-input multiple-output (MIMO) communication system, comprising:

processing a plurality of input signals having included therein one or more symbol streams corresponding to one or more data streams to provide a decoded data stream for one of the one or more symbol streams;

deriving a plurality of modified signals based on the input signals and having components due to the decoded data stream approximately removed;

performing the processing and selectively performing the deriving for each of one or more iterations, one iteration for each data stream to be decoded, and wherein the input signals for each iteration subsequent to a first iteration are the modified signals from a preceding iteration; and

determining channel state information (CSI) indicative of characteristics of a MIMO channel used for transmitting the data steams, wherein the data streams are adaptively processed at a transmitter unit based in part on the CSI.

2. The method of claim 1, wherein the deriving is omitted for a last iteration.

3. The method of claim 1, wherein the processing includes

processing the input signals in accordance with a particular receive processing scheme to provide the one or more symbol streams, and

processing a selected one of the one or more symbol streams to provide the decoded data stream.

4. The method of claim 3, further comprising:

for each iteration,

estimating a quality of each of one or more unprocessed symbol streams included in the input signals; and

selecting one unprocessed symbol stream for processing based on estimated qualities for the one or more unprocessed symbol streams.

5. The method of claim 4, wherein the quality of each unprocessed symbol stream is estimated based on a signal-to-noise-plus-interference-ratio (SNR).

6. The method of claim 4, wherein the unprocessed symbol stream having the best estimated quality is selected for processing.

7. The method of claim 3, wherein the receive processing scheme performs linear spatial processing on the input signals.

8. The method of claim 7, wherein the receive processing scheme implements a channel correlation matrix inversion (CCMI) technique.

9. The method of claim 7, wherein the receive processing scheme implements a minimum mean square error (MMSE) technique.

10. The method of claim 7, wherein the receive processing scheme implements a full-CSI processing technique.

11. The method of claim 3, wherein the receive processing scheme performs space-time processing on the input signals.

12. The method of claim 11, wherein the receive processing scheme implements a minimum mean-square error linear space-time equalizer (MMSE-LE).

13. The method of claim 11, wherein the receive processing scheme implements a decision feedback space-time equalizer (DFE).

14. The method of claim 11, wherein the receive processing scheme implements a maximum-likelihood sequence estimator (MLSE).

15. The method of claim 1, wherein the deriving includes

generating a remodulated symbol stream based on the decoded data stream;

forming a plurality of interference signals based on the remodulated symbol stream; and

removing the interference signals from the input signals to derive the modified signals that serve as input signals for a succeeding iteration.

16. The method of claim 15, wherein the interference signals are formed based on a channel coefficient matrix H indicative of characteristics of the MIMO channel.

17. The method of claim 1, further comprising:

transmitting the CSI from the receiver unit to the transmitter unit.

18. The method of claim 1, wherein the CSI comprises signal-to-noise-plus-interference-ratio (SNR) estimates for each of one or more transmission channels that compose the MIMO channel.

19. The method of claim 1, wherein the CSI comprises characterizations for one or more transmission channels that compose the MIMO channel.

20. The method of claim 1, wherein the CSI comprises an indication of a particular data rate supported by each of one or more transmission channels used for data transmission.

21. The method of claim 1, wherein the CSI comprises an indication of a particular processing scheme to be used for each of one or more transmission channels.

22. The method of claim 1, wherein the CSI comprises signal measurements and noise plus interference measurements for one or more transmission channels.

23. The method of claim 1, wherein the CSI comprises signal measurements, noise measurements, and interference measurements for one or more transmission channels.

24. The method of claim 1, wherein the CSI comprises signal to noise ratio and interference measurements for one or more transmission channels.

25. The method of claim 1, wherein the CSI comprises signal components and noise plus interference components for one or more transmission channels.

26. The method of claim 1, wherein the CSI comprises indications of changes in the characteristics of one or more transmission channels.

27. The method of claim 1, wherein the CSI is determined at the receiver unit and reported to the transmitter unit.

28. The method of claim 1, wherein the CSI is determined at the transmitter unit based on one or more signals transmitted by the receiver unit.

29. The method of claim 1, wherein each data stream is coded at the transmitter unit in accordance with a coding scheme selected based on the CSI for the transmission channel used to transmit the data stream.

30. The method of claim 29, wherein each data stream is independently coded in accordance with a coding scheme selected based on the CSI for the transmission channel used to transmit the data stream.

31. The method of claim 29, wherein each data stream is further modulated in accordance with a modulation scheme selected based on the CSI for the transmission channel used to transmit the data stream.

32. The method of claim 31, wherein the coding and modulation schemes are selected at the transmitter unit based on the CSI.

33. The method of claim 32, wherein the coding and modulation schemes are indicated by the CSI.

34. The method of claim 3, wherein the processing of the selected symbol stream includes

demodulating the symbol stream to provide demodulated symbols, and

decoding the demodulated symbols to provide the decoded data stream.

35. The method of claim 34, wherein the processing of the selected symbol stream further includes

deinterleaving the demodulated symbols, wherein the decoding is performed on the deinterleaved symbols to provide the decoded data stream.

36. The method of claim 1, wherein the MIMO system implements orthogonal frequency division modulation (OFDM).

37. The method of claim 36, wherein the processing at the receiver unit is independently performed for each of a plurality of frequency subchannels.

38. A method for processing data at a receiver unit in a multiple-input multiple-output (MIMO) communication system, comprising:

receiving a plurality of signals via a plurality of received antennas;

processing the received signals in accordance with a particular receive processing scheme to provide a plurality of symbol streams corresponding to a plurality of transmitted data streams;

processing a selected one of the symbol streams to provide a decoded data stream;

forming a plurality of interference signals based on the decoded data stream;

deriving a plurality of modified signals based on the received signals and the interference signals;

performing the processing of the received signals and the selected symbol stream and selectively performing the forming and deriving for one or more iterations, one iteration each transmitted data stream to be decoded, wherein a first iteration is performed on the received signals and each subsequent iteration is performed on the modified signals from a preceding iteration; and

determining channel state information (CSI) indicative of characteristics of a MIMO channel used for transmitting the data steams, wherein the data streams are adaptively processed at a transmitter unit based in part on the CSI.

39. A method for communicating data from a transmitter unit to a receiver unit in a multiple-input multiple-output (MIMO) communication system, comprising:

at the receiver unit,

receiving a plurality of signals via a plurality of receive antennas, wherein each received signal comprises a combination of one or more signals transmitted from the transmitter unit,

processing the received signals in accordance with a successive cancellation receiver processing technique to provide a plurality of decoded data streams transmitted from the transmitter unit,

determining channel state information (CSI) indicative of characteristics of a MIMO channel used to transmit the data steams, and

transmitting the CSI back to the transmitter unit; and

at the transmitter unit,

adaptively processing each data stream prior to transmission over the MIMO channel in accordance with the received CSI.

40. The method of claim 39, wherein the successive cancellation receiver processing scheme performs a plurality of iterations to provide the decoded data streams, one iteration for each decoded data stream.

41. The method of claim 40, wherein each iteration includes

processing a plurality of input signals in accordance with a particular linear or non-linear processing scheme to provide one or more symbol streams,

processing a selected one of the one or more symbol streams to provide a decoded data stream, and

deriving a plurality of modified signals based on the input signals and having components due to the decoded data stream approximately removed, wherein the input signals for a first iteration are the received signals and the input signals for each subsequent iteration are the modified signals from a preceding iteration.

42. The method of claim 39, wherein the CSI comprises a signal-to-noise-plus-interference-ratio (SNR) for each of one or more transmission channels that compose the MIMO channel.

43. The method of claim 39, wherein the CSI comprises an indication of a particular data rate supported by each of one or more transmission channels that compose the MIMO channel.

44. The method of claim 39, wherein the CSI comprises an indication of a particular processing scheme to be used for each of one or more transmission channels that compose the MIMO channel.

45. The method of claim 39, wherein the adaptive processing at the transmitter unit includes

encoding a data stream in accordance with a particular coding scheme selected based on the CSI associated with the data stream.

46. The method of claim 45, wherein the adaptive processing at the transmitter unit further includes

modulating the encoded data stream in accordance with a particular modulation scheme selected based on the CSI associated with the data stream.

47. A multiple-input multiple-output (MIMO) communication system, comprising:

a receiver unit comprising

a plurality of front-end processors configured to process a plurality of received signals to provide a plurality of symbol streams,

at least one receive processor coupled to the front-end processors and configured to process the symbol streams in accordance with a successive cancellation receiver processing scheme to provide a plurality of decoded data streams, and to further derive channel state information (CSI) indicative of characteristics of a MIMO channel used to transmit the data streams, and

a transmit data processor operatively coupled to the receive processor and configured to process the CSI for transmission back to the transmitter unit; and

a transmitter unit comprising

at least one demodulator configured to receive and process one or more signals from the receiver unit to recover the transmitted CSI, and

a transmit data processor configured to adaptively process data for transmission to the receiver unit based on the recovered CSI.

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

a plurality of front-end processors configured to process a plurality of received signals to provide a plurality of received symbol streams;

at least one receive processor coupled to the front-end processors and configured to process the received symbol streams to provide a plurality of decoded data streams, each receive processor including a plurality of processing stages, each stage configured to process input symbol streams to provide a respective decoded data stream and channel state information (CSI) associated with the decoded data stream, and to selectively provide modified symbol streams for a succeeding stage, wherein the input symbol streams for each stage are either the received symbol streams or the modified symbol streams from a preceding stage; and

a transmit processor configured to receive and process the CSI associated with the decoded data streams for transmission from the receiver unit, wherein the data streams are adaptively processed prior to transmission based in part on the CSI.

49. The receiver unit of claim 48, wherein each processing stage except a last stage includes

a channel processor configured to process the input symbol streams to provide a decoded data stream, and

an interference canceller configured to derive the modified symbol streams based on the decoded data stream and the input symbol streams.

50. The receiver unit of claim 49, wherein each channel processor includes

an input processor configured to process the input symbol streams to provide a recovered symbol stream, and

a data processor configured to process the recovered symbol stream to provide the decoded data stream.

51. The receiver unit of claim 50, wherein each input processor includes

a first processor configured to process the input symbol streams in accordance with a linear or non-linear receive processing scheme to provide the recovered symbol stream, and

a channel quality estimator configured to estimate a quality of the recovered symbol stream.

52. The receiver unit of claim 51, wherein the estimated quality comprises a signal-to-noise-plus-interference-ratio (SNR).

53. The receiver unit of claim 51, wherein the channel quality estimator is further configured to provide an indication of a data rate supported for the recovered symbol stream based on the quality estimate.

54. The receiver unit of claim 51, wherein the channel quality estimator is further configured to provide an indication of a particular processing scheme to be used at a transmitter unit for the recovered symbol stream based on the quality estimate.

55. The receiver unit of claim 51, wherein the estimated quality comprises an error signal indicative of detected noise plus interference level at the output of the receiver unit.

56. The receiver unit of claim 51, wherein the first processor performs linear spatial processing on the input symbol streams.

57. The receiver unit of claim 51, wherein the first processor performs space-time processing on the input symbol streams.