Patent ID: 8121220

Claim:
A method of estimating a plurality of transmit symbols s i , i=1 to n, in a transmit symbol vector s of a multiple-input multiple-output (MIMO) communication system, where n is a size of the transmit symbol vector s, the method comprising: calculating a plurality of permuted MIMO channel matrices H i , i=1 to n, wherein a rightmost column of each permuted MIMO channel matrix H i is an i th column of an estimated MIMO channel matrix H; determining a QR decomposition of each permuted MIMO channel matrix H i in the plurality of permuted MIMO channel matrices H i , i=1 to n, to generate a plurality of unitary matrices Q i , i=1 to n, and a plurality of upper triangular matrices R i , i=1 to n; determining a plurality of modified receive symbol vectors y i , i=1 to n, each modified receive symbol vector y i calculated using a receive symbol vector z and a conjugate transpose of the unitary matrix Q i ; estimating each transmit symbol s i , i=1 to n, of the transmit symbol vector s using the modified receive symbol vector y i and the upper triangular matrix R i ; and using a receiver, determining a soft decision reliability metric for a bit of the transmit symbol s i of the transmit symbol vector s using a plurality of symbol values as candidates for the estimated transmit symbol s i , each symbol value σ j taken from a subset of a signal constellation, wherein determining the soft decision reliability metric for a bit of the estimated transmit symbol s i further comprises: calculating a set of error distances, one error distance for each different symbol value σ j in the subset of the signal constellation, by estimating the transmit symbol s i as the symbol value σ j ; calculating an error distance of the estimated transmit symbol vector s containing the estimated transmit symbol s i set to the symbol value σ j using the modified receive symbol vector y i and the upper triangular matrix R i ; determining a minimum error distance for a bit value of “one” for the bit of the estimated transmit symbol s i and a minimum error distance for a bit value of “zero” for the bit of the estimated transmit symbol s i from the set of calculated error distances; and determining the soft decision reliability metric based on a difference between the minimum error distance with the bit value of “one” and the minimum error distance with the bit value of “zero”.