Combined space-time decoding

• US 20040066866A1
• Filed: 10/02/2002
• Published: 04/08/2004
• Est. Priority Date: 10/02/2002
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Yu, Dong-Sheng, Tong, Wen, Ma, Jianglei, Zhu, Peiying, Jia, Ming
• Granted Patent: US 7,394,860 B2
• Time in Patent Office: Days
• US Class Current: 375/347
• CPC Class Codes: H04L 1/0618 Space-time coding

Abstract

The present invention relates to decoding space time coded (STC) signals transmitted from a number of transmit antennas. First, a separate detection technique is used to determine initial decoding solutions corresponding to the symbols transmitted from each of a number of transmit antennas at a given time. For each initial solution, a limited area about the initial solution is defined. Each of the limited areas will correspond to regions including constellation points proximate the initial solution. The initial solutions are used to define a limited, multi-dimensional space. Accordingly, the initial solutions are used to reduce the search complexity associated with joint decoding by defining a limited space about the initial solutions. Finally, a joint decoding technique is implemented within the limited space to find a final solution.

Claims

1. A method for decoding space time coded (STC) signals comprising:

a) receiving STC signals originating from a plurality of transmit antennas of a remote transmitter;

b) decoding the STC signals using a separate STC decoding technique to determine a plurality of initial solutions;

c) identifying a selected area about each of the initial solutions;

d) creating a decoding space corresponding to the selected areas; and

e) decoding the STC signals using a joint STC decoding technique to determine a final solution representing symbols transmitted from the plurality of transmit antennas.

2. The method of claim 1 wherein the limited area corresponds to a limited set of constellation points in a constellation lattice containing constellation points corresponding to possible symbols transmitted from the plurality of transmit antennas.

3. The method of claim 1 wherein the limited area corresponds to a set of four constellation points in a constellation lattice containing constellation points corresponding to possible symbols transmitted from the plurality of transmit antennas.

4. The method of claim 1 wherein the decoding space is a limited space in a multi-dimensional constellation lattice corresponding to a limited set of constellation points.

5. The method of claim 1 wherein there is an initial solution for each of the plurality of transmit antennas.

6. The method of claim 1 wherein the separate STC decoding technique is zero-forcing.

7. The method of claim 1 wherein the separate STC decoding technique is minimum mean square error decoding.

8. The method of claim 1 wherein the joint decoding technique is maximum likelihood decoding.

9. The method of claim 1 wherein the STC signals are BLAST signals.

10. A method for decoding space time coded (STC) signals comprising:

a) receiving STC signals originating from a plurality of transmit antennas of a remote transmitter;

b) decoding the STC signals using a separate STC decoding technique to determine a plurality of initial solutions;

c) selecting a group of the initial solutions associated with a group of the transmit antennas;

d) removing initial solutions outside of the group from the initial solutions associated with the group to provide modified initial solutions for the group;

e) identifying a selected area about each of the modified initial solutions;

f) creating a decoding space corresponding to the selected areas; and

g) decoding the STC signals using a joint STC decoding technique to determine a final solution representing symbols transmitted from the transmit antennas associated with the group.

11. The method of claim 10 further comprising:

h. recreating an interference cancellation signal based on the final solution; and

i. subtracting the interference cancellation signal from the STC signals to create modified STC signals.

12. The method of claim 11 wherein the modified STC signals become the STC signals and steps b through i are iteratively repeated until the final solutions are obtained for each group of transmit antennas.

13. The method of claim 10 wherein the limited area corresponds to a limited set of constellation points in a constellation lattice containing constellation points corresponding to possible symbols transmitted from the plurality of transmit antennas.

14. The method of claim 10 wherein the limited area corresponds to a set of four constellation points in a constellation lattice containing constellation points corresponding to possible symbols transmitted from the plurality of transmit antennas.

15. The method of claim 10 wherein the decoding space is a limited space in a multi-dimensional constellation lattice corresponding to a limited set of constellation points.

16. The method of claim 10 wherein there is an initial solution for each of the plurality of transmit antennas.

17. The method of claim 10 wherein the separate STC decoding technique is zero-forcing.

18. The method of claim 10 wherein the separate STC decoding technique is minimum mean square error decoding.

19. The method of claim 10 wherein the joint decoding technique is maximum likelihood decoding.

20. An apparatus for receiving space time coded (STC) signals comprising:

a) receiver circuitry adapted to receive and demodulate modulated STC signals to provide STC signals;

b) an STC decoder adapted to;

i) receive the STC signals originating from a plurality of transmit antennas of a remote transmitter;

ii) decode the STC signals using a separate STC decoding technique to determine a plurality of initial solutions;

iii) identify a selected area about each of the initial solutions;

iv) create a decoding space corresponding to the selected areas; and

v) decode the STC signals using a joint STC decoding technique to determine a final solution representing symbols transmitted from the plurality of transmit antennas.

21. The apparatus of claim 20 wherein the limited area corresponds to a limited set of constellation points in a constellation lattice containing constellation points corresponding to possible symbols transmitted from the plurality of transmit antennas.

22. The apparatus of claim 20 wherein the limited area corresponds to a set of four constellation points in a constellation lattice containing constellation points corresponding to possible symbols transmitted from the plurality of transmit antennas.

23. The apparatus of claim 20 wherein the decoding space is a limited space in a multi-dimensional constellation lattice corresponding to a limited set of constellation points.

24. The apparatus of claim 20 wherein there is an initial solution for each of the plurality of transmit antennas.

25. The apparatus of claim 20 wherein the separate STC decoding technique is zero-forcing.

26. The apparatus of claim 20 wherein the separate STC decoding technique is minimum mean square error decoding.

27. The apparatus of claim 20 wherein the joint decoding technique is maximum likelihood decoding.

28. The apparatus of claim 20 wherein the STC signals are BLAST signals.

29. An apparatus for receiving space time coded (STC) signals comprising:

a) receiver circuitry adapted to received and demodulate modulated STC signals to provide STC signals;

b) an STC decoder adapted to;

i) receive the STC signals originating from a plurality of transmit antennas of a remote transmitter;

ii) decode the STC signals using a separate STC decoding technique to determine a plurality of initial solutions;

iii) select a group of the initial solutions associated with a group of the transmit antennas;

iv) remove initial solutions outside of the group from the initial solutions associated with the group to provide modified initial solutions for the group;

v) identify a selected area about each of the modified initial solutions;

vi) create a decoding space corresponding to the selected areas; and

vii) decode the STC signals using a joint STC decoding technique to determine a final solution representing symbols transmitted from the transmit antennas associated with the group.

30. The apparatus of claim 29 wherein the STC decoder is further adapted to:

viii) recreate an interference cancellation signal based on the final solution; and

ix) subtract the interference cancellation signal from the STC signals to create modified STC signals.

31. The apparatus of claim 30 wherein the modified STC signals become the STC signals and steps ii) through ix) are iteratively repeated until final solutions are obtained for each group of transmit antennas.

32. The apparatus of claim 29 wherein the limited area corresponds to a limited set of constellation points in a constellation lattice containing constellation points corresponding to possible symbols transmitted from the plurality of transmit antennas.

33. The apparatus of claim 29 wherein the limited area corresponds to a set of four constellation points in a constellation lattice containing constellation points corresponding to possible symbols transmitted from the plurality of transmit antennas.

34. The apparatus of claim 29 wherein the decoding space is a limited space in a multi-dimensional constellation lattice corresponding to a limited set of constellation points.

35. The apparatus of claim 29 wherein there is an initial solution for each of the plurality of transmit antennas.

36. The apparatus of claim 29 wherein the separate STC decoding technique is zero-forcing.

37. The apparatus of claim 29 wherein the separate STC decoding technique is minimum mean square error decoding.

38. The apparatus of claim 29 wherein the joint decoding technique is maximum likelihood decoding.