Method and apparatus using coordinate interleaving to increase diversity in a MIMO system

• US 20060034381A1
• Filed: 08/12/2004
• Published: 02/16/2006
• Est. Priority Date: 08/12/2004
• Status: Active Grant

• Current Assignee: Nokia Corporation
• Original Assignee: Nokia Corporation
• Inventors: Ionescu, Dumitru Mihai, Gray, Steven
• Granted Patent: US 7,409,001 B2
• Time in Patent Office: Days
• 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: H04L 1/0047 Decoding adapted to other signal detection operation in conjunction with sequence estimation or equalization H04L25/03286
• CPC Class Codes: H04L 1/005 Iterative decoding, including iteration between signal detection and decoding operation
• CPC Class Codes: H04L 1/006 Trellis-coded modulation
• CPC Class Codes: H04L 1/0068 by puncturing
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0625 Transmitter arrangements
• CPC Class Codes: H04L 1/0631 Receiver arrangements
• CPC Class Codes: H04L 27/183 Multiresolution systems
• CPC Class Codes: H04L 27/186 in which the information is carried by both the individual signal points and the subset to which the individual signal points belong, e.g. coset coding or related schemes
• CPC Class Codes: H04L 27/2003 for continuous phase modulation frequency shift keying H04L27/10
• CPC Class Codes: H04L 27/2604 Multiresolution systems by means of multiresolution subcarriers H04L27/183, H04L27/3488
• CPC Class Codes: H04L 27/3416 in which the information is carried by both the individual signal points and the subset to which the individual points belong, e.g. using coset coding, lattice coding, or related schemes
• CPC Class Codes: H04L 27/3488 Multiresolution systems
• CPC Class Codes: H04L 5/06 the signals being represented by different frequencies combined with time-division multiplexing H04L5/26

Abstract

A method to increase diversity in MIMO fading channels interleaves coordinates of complex symbol(s) in a transmission frame after encoding and modulating. Specifically, an input signal is encoded and modulated into a codeword, jointly across at least two pipes, said pipes having space, time, frequency, or other nature, wherein the codeword spans a frame and is defined as at least one complex symbol whose complex values are all those to be transmitted during all channel uses covered by the frame. Each of the complex symbols have a first and second coordinate. After modulating, which may be combined with encoding in a signal space encoder, the coordinates are interleaved. In modulation, the complex symbols (typically two dimensional) may arise as elements of a multidimensional (typically greater than two dimensions) signal constellation, in which case those multidimensional constellation coordinates are the ones that are interleaved in the frame. The frame carrying the interleaved coordinates is transmitted by the first and at least second antennas, possible opposed sub-frames of the overall frame being transmitted separately by opposed antennas. A coset selector is used in some embodiments to maximize a minimum Hamming distance, and/or a minimum Euclidean distance, between coordinates within a coset to control diversity and/or coding gain. In some embodiments, the operation of the encoder and modulator is such as to maximize a minimum coordinate-wise Hamming distance, and/or a minimum Euclidean distance, between allowable codewords, and/or to provide additional structure for the allowable codewords. A method, transmitter, system, and mobile station are described.

Claims

1. A method for transmitting, with increased diversity in fading channels, an input signal from a plurality of transmit antennas, the method comprising:

jointly encoding, across at least two pipes, and modulating an input signal into a codeword, the codeword spanning a frame and defined as at least one complex symbol that describes all complex values to be transmitted during all channel uses covered by the frame, each complex symbol having a first and a second coordinate;

after encoding and modulating, interleaving the coordinates within a transmission frame that corresponds to a predesignated number of channel uses by said encoder; and

transmitting the frame of interleaved coordinates by L transmit antennas, wherein L is an integer greater than one.

2. The method of claim 1 wherein the encoding and modulating are performed together.

3. The method of claim 1 wherein the modulating is performed following, and separately from, the encoding.

4. The method of claim 1 wherein modulating comprises employing a signal constellation of symbols that are, in turn, each comprised of at least two real coordinates, such that a minimum Hamming distance between coordinates of symbols is maximized.

5. The method of claim 1 wherein encoding comprises partitioning a signal constellation of symbols into cosets of constellation symbols such that a minimum Hamming distance between coordinates of symbols within a coset is maximized.

6. The method of claim 1 wherein the codeword exhibits a maximized minimum Hamming distance between coordinates of all complex symbols of the codeword, the maximized minimum Hamming distance being relative to any other valid codeword.

7. The method of claim 1 wherein jointly encoding comprises encoding the input signal into at least a first and a second sub-codeword, the first sub-codeword defined as at least one complex symbol from a first signal constellation, and the second sub-codeword defined as at least one complex symbol from at least a second signal constellation, said first and at least second signal constellations not identical to one another.

8. The method of claim 7 wherein interleaving the coordinates comprises interleaving the coordinates of the at least first and second sub-codewords within respective first and second sub-frames that are non-overlapping within the frame.

9. The method of claim 7 wherein interleaving the coordinates comprises interleaving the coordinates of the at least first and second sub-codewords with one another in the frame.

10. The method of claim 7 wherein the second signal constellation comprises the first signal constellation rotated with respect to itself.

11. The method of claim 1 wherein, for a plurality of valid codewords, each defining a codematrix that is an array of complex symbols that would be transmitted from the L antennas during the frame for the respective possible codeword, the method characterized in that a Gram matrix that has all equal nonzero eigenvalues can be identified for at least one code difference matrix that corresponds to the difference between a first and second codematrices that differ during the least number of channel uses in a frame.

12. The method of claim 11 wherein jointly encoding further comprises maximizing a minimum Euclidean distance between valid first and second codematrices that each span one frame.

13. The method of claim 11 wherein jointly encoding comprises maximizing a minimum Euclidean distance with respect to the sequence of complex symbols in a valid codeword, said maximization being carried out relative to any other codeword in the plurality of valid codewords.

14. A transmitter comprising:

an encoder for jointly encoding, across at least two pipes, an input signal into a set of at least one complex symbols that span a frame that corresponds to a predesignated number of channel uses, each complex symbol having a first and a second coordinate;

a modulator for adapting the encoder to a channel alphabet;

a coordinate interleaver, having an input coupled to an output of the encoder and the modulator, for interleaving the coordinates of the set of at least one complex symbol within the frame;

L transmit antennas having inputs coupled to an output of the coordinate interleaver for transmitting the frame, wherein L is an integer greater than one.

15. The transmitter of claim 14 wherein the encoder and modulator together comprise a signal-space encoder.

16. The transmitter of claim 14 wherein the modulator has an input coupled to an output of the encoder.

17. The transmitter of claim 14 wherein the modulator comprises a multidimensional signal constellation, each multidimensional symbol of the constellation comprising at least two real coordinates such that a minimum Hamming distance between coordinates of multidimensional symbols is maximized.

18. The transmitter of claim 14 further comprising a coset selector having an output coupled to an input of the encoder, the coset selector for partitioning a multidimensional signal constellation into cosets of multidimensional symbols such that a minimum Hamming distance between coordinates of multidimensional symbols within a coset is maximized.

19. The transmitter of claim 14 wherein the encoder operates to output sets of complex symbols such that a minimum Hamming distance between coordinates of all complex symbols in any two allowable sets is maximized.

20. The transmitter of claim 14 wherein the encoder encodes the input signal into a first set of at least one complex symbol selected from a first signal constellation, and into a second set of at least one complex symbol selected from a second signal constellation.

21. The transmitter of claim 20 further wherein the coordinate interleaver is for interleaving coordinates of the first set into a first sub-frame and coordinates of the second set into a second sub-frame, the first and second sub-frames comprising non-overlapping portions of the frame.

22. The transmitter of claim 20 further wherein the coordinate interleaver is for interleaving coordinates of the first and second set with one another in the frame.

23. The transmitter of claim 20 wherein the second signal constellation comprises the first signal constellation rotated with respect to itself.

24. The transmitter of claim 14 wherein the set of at least one complex symbol defines a first codematrix that is an array of complex symbols transmitted from the L antennas during the frame, the encoder characterized in that it outputs the set of at least one complex symbol from among a plurality of valid sets, each valid set defining a codematrix, such that a Gram matrix that has all equal nonzero eigenvalues can be identified for a code difference matrix corresponding to the difference between the first and a second codematrices that differ during the least number of channel uses in the frame.

25. The transmitter of claim 24 wherein the encoder operates to maximize a minimum Euclidean distance between valid first and second codematrices that each span one frame.

26. A system for communicating over fading channels with high diversity comprising a transmitter and a receiver, wherein the transmitter comprises:

an encoder for jointly encoding, across at least two pipes, an input signal into a set of at least one complex symbols that span a frame that corresponds to a predesignated number of channel uses, each complex symbol having a first and a second coordinate;

a modulator for adapting the encoder to a channel alphabet;

a coordinate interleaver, having an input coupled to an output of the encoder and the modulator, for interleaving the coordinates of the set of at least one complex symbol within the frame;

L transmit antennas having inputs coupled to an output of the coordinate interleaver for transmitting the frame;

and the receiver comprises;

M receive antennas for receiving the frame over a multi-path channel;

a coordinate de-interleaver having an input coupled to an output of the receive antenna for de-interleaving coordinates in the frame;

a demodulator for demodulating the received frame; and

a decoder for decoding the de-interleaved coordinates;

a mechanism for performing one or more iterations between demodulator and decoder;

wherein L is an integer greater than one and M is an integer at least equal to one.

27. The system of claim 26 wherein the encoder and modulator of the transmitter together comprise a signal-space encoder.

28. The system of claim 26 wherein the transmitter further comprises:

a coset selector having an output coupled to an input of the encoder, the coset selector for partitioning a multidimensional signal constellation into cosets of multidimensional symbols such that a minimum Hamming distance between coordinates of multidimensional symbols within a coset is maximized.

29. The system of claim 26 wherein,

in the transmitter, the encoder operates to encode the input signal into a first sub-set of at least one complex symbol selected from a first signal constellation, and into a second sub-set of at least one complex symbol selected from a second signal constellation.

30. The system of claim 29 wherein the coordinate interleaver operates to interleave coordinates of the first set into a first sub-frame and coordinates of the second set into a second sub-frame, the first and second sub-frames comprising non-overlapping portions of the frame.

31. The system of claim 30 further wherein the coordinate de-interleaver operates to separate the first sub-frame from the second sub-frame and separately de-interleave coordinates in the separated sub-frames.

32. The system of claim 30 further wherein the coordinate de-interleaver operates to de-interleave coordinates of the first and second set that are interleaved together within the frame.

33. The system of claim 26 wherein the set of at least one complex symbols defines a first codematrix that is an array of complex symbols transmitted during the frame, the encoder characterized in that it outputs the set of at least one complex symbols from among a plurality of valid sets, each set defining a codematrix such that a Gram matrix that has all equal nonzero eigenvalues can be identified for a code difference matrix corresponding to the difference between the first and a second codematrices that differ during the least number of channel uses in the frame.

34. A mobile station comprising:

an encoder for jointly encoding, across at least two pipes, an input signal into a set of at least one complex symbols that span a frame that corresponds to a predesignated number of channel uses, each complex symbol having a first and a second coordinate;

a modulator for adapting an output of the encoder to a channel alphabet;

a coordinate interleaver, having an input coupled to an output of the encoder and the modulator, for interleaving the coordinates of the set of at least one complex symbol within the frame; and

L transmit antennas having inputs coupled to an output of the coordinate interleaver for transmitting the frame;

wherein L is an integer greater than one.

35. The mobile station of claim 34 wherein the encoder and modulator of the transmitter together comprise a signal-space encoder.

36. The mobile station of claim 34 further comprising a coset selector having an output coupled to an input of the encoder, the coset selector for partitioning a multidimensional signal constellation into cosets of multidimensional symbols such that a minimum Hamming distance between coordinates of multidimensional symbols within a coset is maximized.

37. The mobile station of claim 34, wherein

the encoder operates to encode the input signal into a first set of at least one complex symbol selected from a first signal constellation, and into a second set of at least one complex symbol selected from a second signal constellation.

38. The mobile station of claim 37 wherein the coordinate interleaver operates to interleave coordinates of the first set into a first sub-frame and coordinates of the second set into a second sub-frame, the first and second sub-frames comprising non-overlapping portions of the frame.

39. The mobile station of claim 37 wherein the coordinate interleaver operates to interleave coordinates of the first and second sets together in the frame.

40. The mobile station of claim 34 wherein the set of at least one complex symbol defines a first codematrix that is an array of complex symbols transmitted from the L antennas during the frame, the encoder characterized in that it outputs the set of at least one complex symbol from among a plurality of valid sets, each valid set defining a codematrix, such that a Gram matrix that has all equal nonzero eigenvalues can be identified for a code difference matrix corresponding to the difference between the first and a second codematrices that differ during a least number of channel uses in the frame.