Near maximum likelihood spatial multiplexing receiver

Patent metadata

Field	Value
Publication number	US-2015341143-A1
Application number	US-201514685018-A
Country	US
Kind code	A1
Filing date	Apr 13, 2015
Priority date	Dec 31, 2013
Publication date	Nov 26, 2015
Grant date	—

Abstract

This invention is related to a low-complexity MIMO detector in a wireless communication system with near optimal performance. An initial symbol estimation is performed for a received symbol vector. The soft information of the received symbol vector can be more accurately calculated using every candidate symbol vector of a combined set of candidate symbol vectors, wherein the combined set is generated based on the initial estimation. By combining aspects of both the linear detection and the ML detection, the complexity of the proposed detector becomes orders of magnitude lower than that of a ML detector, but the performance is very close to that of an ML detector.

First claim

1 . (canceled)

2 . A method for detecting transmitted data in a received symbol vector transmitted in a communication system with multiple transmit antennas and receive antennas, wherein each symbol of the received symbol vector is from a corresponding antenna of the multiple receive antennas, wherein the received symbol vector corresponds to a transmitted symbol vector that has been modulated according to transmitted data bits using a modulation scheme, the method comprising:
performing an initial symbol estimation for each symbol of the transmitted symbol vector based on the corresponding received symbol vector; generating a candidate symbol set for each of the initially estimated symbol of the transmitted symbol vector; generating a combined set of candidate symbol vectors by using the candidate symbol sets corresponding to the initially estimated symbols; and determining the transmitted bits of the transmitted symbol vector using the candidate symbol vectors of the combined set.

3 . The method of claim 2 , wherein the number of candidate symbols in each candidate symbol set is a predetermined number.

4 . The method of claim 2 , wherein determining the transmitted data bits includes computing soft information of the transmitted symbol vector.

5 . The method of claim 2 , wherein computing soft information includes determining a log-likelihood ratio for each of the transmitted data bits.

6 . The method of claim 2 , wherein the modulation scheme is an M-QAM.

7 . The method of claim 2 , wherein the initial symbol estimation is performed using a linear detector.

8 . The method of claim 7 , wherein the linear detector is a linear MMSE detector.

9 . The method of claim 7 , wherein the linear detector is a linear Zero-Forcing detector.

10 . The method of claim 2 , wherein the initial symbol estimation comprises pre-calculating and storing intermediate variables that need to be computed only once.

11 . The method of claim 2 , wherein generating a candidate symbol set for an initially estimated symbol of the transmitted symbol vector comprises:
calculating the distance between each constellation point in the constellation and the constellation point corresponding to the initially estimated symbol; and selecting a pre-determined number of constellation points that are closest according to the calculated distance to the constellation point corresponding to the initially estimated symbol.

12 . The method of claim 11 , wherein the distance is Euclidean distance.

13 . The method of claim 11 , wherein the number of candidate symbols in each candidate symbol set is a predetermined number that is chosen based on a trade-off between performance and implementation complexity.

14 . The method of claim 13 , wherein the predetermined number is between 9 and 256.

15 . The method of claim 2 , wherein generating a candidate symbol set comprises:
identifying offline, for different set sizes and a given candidate symbol, a set of candidate symbols that are the closest to the given candidate symbol; storing the identified sets of candidate symbols for different set sizes and different candidate symbol in a look-up table; and looking up the set of candidate symbols for an initially detected symbol and the pre-determined number.

16 . The method of claim 2 , wherein generating the combined set comprises:
generating a candidate symbol vector set for each candidate symbol set that corresponds to an initially estimated symbol in the transmitted symbol vector; and forming the combined candidate set for the transmitted symbol vector by taking a union of the candidate symbol vector sets for all of the initially estimated symbols in the transmitted symbol vector.

17 . The method of claim 16 , wherein generating a candidate symbol vector set for a candidate symbol set comprises:
for each candidate symbol in the candidate symbol set, determining a corresponding candidate symbol vector; and combining all the determined candidate symbol vectors.

18 . The method of claim 17 , wherein determining a corresponding candidate symbol vector corresponding to a candidate symbol comprises:
assuming the candidate symbol is the correct transmitted symbol in the transmitted symbol vector; calculating the rest of the transmitted symbols in the transmitted symbol vector using a linear Zero-Force Decision Feedback equalizer or other similar decision feedback equalizer; and generating the candidate symbol vector by combining the candidate symbol and the calculated rest of the transmitted symbols.

19 . A MIMO detection apparatus for a wireless communication receiver having multiple receive antennas to receive a symbol vector corresponding to a transmitted symbol vector that has been modulated according to transmitted data bits, comprising:
an estimation module that performs initial symbol estimation each symbol of the transmitted symbol vector based on the corresponding received symbol vector; a candidate symbol set module that generates a candidate symbol set for each initially estimated symbol of the transmitted symbol vector, wherein the number of candidate symbols in each of the candidate symbol set is a predetermined number, a plurality of decision feedback equalizers (DFEs) that generates a combined candidate set of candidate symbol vectors, wherein each DFE uses a respective candidate symbol in the candidate symbol set, and a likelihood calculator that determines the transmitted bits of the transmitted symbol vector using the candidate symbol vectors of the combined set.

20 . The apparatus of claim 19 , further comprising a pre-processing block that generates variables for use by the estimation module using values of channel gains and channel noise associated with the receive antennas.

21 . The apparatus of claim 19 , wherein the estimation module is one of a linear MMSE detector, a linear Zero-Forcing detector and a linear zero-forcing decision-feedback equalizer.

Assignees

• Cambridge Silicon Radio Ltd

Inventors

• Wan Hong
• Tong Fei
• Lindskog Erik

Classifications

• H04B7/0413 Primary

  MIMO systems · CPC title

• H04L1/0054 Primary

  Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms · CPC title

• H04L27/2649

  Demodulators · CPC title

• H04L27/38

  Demodulator circuits; Receiver circuits · CPC title

• H04L5/0014

  Three-dimensional division · CPC title