Systems and methods for multistage signal detection in mimo transmissions and iterative detection of precoded OFDM

• US 20060059410A1
• Filed: 09/13/2005
• Published: 03/16/2006
• Est. Priority Date: 09/13/2004
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Conexant Systems Incorporated (Synaptics Incorporated)
• Inventors: Duvaut, Patrick, Santraine, Arnaud
• Granted Patent: US 7,216,267 B2
• Time in Patent Office: Days
• US Class Current: 714/785
• 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 1/0643 block codes

Abstract

Systems and methods for multi-stage signal detection in MIMO transmission including Bernoulli-Gaussian detection are provided. A multistage iterative signal decoder is provided that exploits the property that in a relatively simply decoding scheme such as mean square error (MSE) or zero-forcing (ZF) only a small portion of the total symbols are mis-detected. Therefore, an optimality test is performed on the output of a relatively low complexity decoder unit. If the symbol passes the optimality test, it is presumed to be correctly decoded. Otherwise, the symbol is sent for further processing to a relatively higher complexity decoding unit such as a sphere decoder. In this way, processing efficiency is increased, because only those symbols requiring additional processing are processed by the high complexity processing unit.

Claims

1. A multistage system for signal detection comprising:

a first relatively low complexity decoding unit configured to decode received symbols;

an optimality test unit configured to test the output of the first decoding unit; and

a second relatively high complexity decoding unit configured to reprocess those received symbols that fail a condition of the optimality test unit.

2. The system of claim 1, wherein the system is part of a multi-carrier transmission system having a plurality of different sub-channels each carrying bits of data.

3. The system of claim 1, wherein the received symbols are precoded QAM symbols.

4. The system of claim 1, wherein the first relatively low complexity decoding unit is an MSE decoding unit.

5. The system of claim 1, wherein only symbols transmitted on tones presenting a SNR above a predetermined threshold are subjected to the optimality test.

6. The system of claim 1, wherein the optimality test unit determines whether a symbol has been decoded correctly or if it needs further processing by the second decoding unit or modification as determined by the optimality test.

7. The system of claim 6, wherein the optimality test unit determines that a symbol has been decoded correctly if a syndrome value is less than zero.

8. The system of claim 7, wherein the syndrome is defined as the vector Q, where

$Q=$

A

-Γ

⊗

d2⁢

diag⁡

(RH),where {circle around (×

)}d/2diag(R_H), where {circle around (×

)} denote the element-wise product.

9. The system of claim 1, further comprising a second decoding unit interposed between an output of optimality test unit and an input of the second optimality test unit, adapted to perform reprocessing on symbol output by the first decoding unit.

10. A method of decoding signals comprising:

decoding a received signal containing at least one symbol with a first decoder;

performing an optimality test on the output of the first decoder; and

for those symbols passing the optimality test, outputting the symbols, otherwise, processing the symbols with a second decoder.

11. The method of claim 10, wherein the received signal is a symbol carried over a communication channel having a plurality of sub-carriers each carrying information.

12. The method of claim 11, wherein only symbols transmitted on sub-carriers presenting an SNR below a predetermined threshold are subjected to the optimality test.

13. The method of claim 10, wherein the received signal comprises precoded QAM symbols.

14. The method of claim 13, wherein decoding with a first decoder comprises decoding with an MSE decoding unit.

15. The method of claim 10, wherein decoding with a first decoder comprises decoding with a zero-forcing (ZF) decoding unit.

16. The method of claim 10, wherein the optimality test unit determines that a symbol has passed the optimality test if a syndrome value is less than zero.

17. The method of claim 16, wherein the syndrome is defined as the vector Q, where

$Q=$

A

-Γ

⊗

d2⁢

diag⁡

(RH),where {circle around (×

)}d/2diag (R_H), where {circle around (×

)} denote the element-wise product.

18. The method of claim 10, further comprising performing a nulling and canceling operation on symbols failing the optimality test prior to subjecting those symbols to the second optimality test.

19. An iterative method of detecting blindly precoded OFDM symbols comprising:

comprising;

performing a first iteration of a B-G algorithm approximating a joint M-L detection on received data;

iteratively running the B-G algorithm updating the data with the results of the previous iteration using update equations (37), (38) and (39).