Space-time transmit diversity

• US 20030048857A1
• Filed: 04/30/2002
• Published: 03/13/2003
• Est. Priority Date: 05/01/2001
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Onggosanusi, Eko N., Dabak, Anand G.
• Granted Patent: US 7,133,459 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 7/0613 using simultaneous transmission H04B7/0686 takes precedence
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• CPC Class Codes: H04B 7/0837 using pre-detection combining H04B7/0868 takes precedence
• CPC Class Codes: H04L 1/0055 MAP-decoding
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0618 Space-time coding

Abstract

A linear transformation of parallel space-time transmit diversity encoded streams; also, asymmetrical symbol mapping of parallel streams. Separately or together, these improve error rate performance as well as system throughput. Preferred embodiments include CDMA wireless systems with multiple antennas.

Claims

1. A method of transmitting, comprising:

(a) encoding a first block of symbols {s₁(k)} with space-time transmit diversity;

(b) encoding a second block of symbols {s₂(k)} with space-time transmit diversity;

(c) simultaneously transmitting said encoded first block from step (a) and said encoded second block from step (b);

(d) wherein for an index n, the set of four symbols, s₁(n), s₁(n+1), s₂(n), s₂(n+1), are selected from at least two different symbol constellations.

2. The method of claim 1, wherein:

(a) said selected of step (d) of claim 1 adapts to transmission channel conditions.

3. The method of claim 2, wherein:

(a) said transmission channel conditions are determined from signals received from a recipient of said transmitting of step (c) of claim 1.

4. The method of claim 2, wherein:

(a) said transmission channel conditions are conveyed from a recipient of said transmitting of step (c) of claim 1.

5. The method of claim 1, wherein:

(a) said selected of step (d) of claim 1 adapts to transmission channel conditions by picking said two constellations to maximize the minimum SINR of the symbols in the constellations given a data rate constraint.

6. The method of claim 1, wherein:

(a) said selected of step (d) of claim 1 adapts to transmission channel conditions by picking said two constellations to minimize the maximum mean square error scaled by average symbol energy of symbols in the constellations given a data rate constraint.

7. The method of claim 1, wherein:

(a) said selected of step (d) of claim 1 takes s₁(n) and s₁(n+1) from a first constellation and s₂(n) and s₂(n+1) from a second constellation.

8. The method of claim 1, wherein:

(a) said selected of step (d) of claim 1 takes s₁(n) and s₂(n) from a first constellation and s₁(n+1) and s₂(n+1) from a second constellation.

9. The method of claim 1, wherein:

(a) said selected of step (d) of claim 1 takes s₁(n) and s₂(n+1) from a first constellation and s₂(n) and s₁(n+1) from a second constellation.

10. The method of claim 1, further comprising:

(a) encoding third, . . . , and P/2 blocks of symbols {s₃(k)}, . . . , {s_P/2(k)} with space-time transmit diversity, where P is an even integer greater than 3;

(b) simultaneously transmitting said encoded third, . . . , P/2 blocks with said transmitting from step (c) of claim 1.

11. The method of claim 1, further comprising:

(a) spreading said symbols with a common spreading code prior to said transmitting of step (c) of claim 1.

12. The method of claim 1, wherein:

(a) said first encoded block is transmitted from first and second antennas; and

(b) said second encoded block is transmitted from third and fourth antennas.

13. The method of claim 1, further comprising:

(a) linearly transforming said first and second encoded blocks prior to said transmitting of step (c) of claim 1, said linearly transforming determined by estimates of a transmission channel to a receiver; and

(b) wherein said transmitting of step (c) of claim 1 transmits said linearly transformed encoded blocks from four antennas.

14. A method of receiving, comprising:

(a) treating received signals as P/2 parallel STTD encoded signals from P antennas, with P an even integer greater than 3; and

(b) detecting using at least two differing constellations for symbols of said encoded signals.

15. The method of claim 14, further comprising:

(a) despreading said received signals.

16. The method of claim 14, wherein:

(a) P=4.

17. The method of claim 14, wherein:

(a) said detecting includes an interference resistance detection.

18. The method of claim 17, wherein:

(a) said detection is an iterative selected from the group consisting of zero-forcing detection and minimum mean square error detection.

19. The method of claim 18, wherein:

(a) said iterative minimum mean square error detection uses a mean square error scaled by symbol energy.

20. The method of claim 18, wherein:

(a) said iterative zero-forcing detection uses a noise variance scaled by symbol energy.

21. A transmitter, comprising:

(a) a serial-to-parallel converter;

(b) first and second symbol mappers coupled to said serial-to-parallel converter, said first and second symbol mappers with differing symbol constellations;

(c) a first space-time transmit diversity encoder coupled to said first symbol mapper;

(d) a second space-time transmit diversity encoder coupled to said second symbol mapper; and

(e) transmit antennas couple to said encoders.

22. A receiver, comprising:

(a) a channel coefficient estimator;

(b) a combiner for P/2 space-time encoded symbol streams with P an even integer greater than 3, said combiner coupled to said estimator; and

(c) a detector coupled to said combiner, said detector adaptive to asymmetric symbol constellations for said P/2 symbol streams.