Patent ID: 7315576

Claim:
A method for determining soft metrics in a multiple-input multiple-output (MIMO) communication system, wherein a soft metric is determined for each bit, b i , encoded by a multi-dimensional symbol, wherein the soft metrics indicate discrepancies in the MIMO communication system, the method comprising: transmitting a sample of the multi-dimensional symbol, wherein the multi-dimensional symbol is represent-able as a complex, K-dimensional vector x, K being an integer corresponding to the number of transmit antennas in the MIMO system, wherein each vector component of the vector x represents a signal transmitted with one of the K transmit antennas, the multi-dimensional symbol being transmitted through a communication channel; receiving from the communication channel, a sample represented by a complex, N-dimensional vector y, N being an integer corresponding to the number of receive antennas in the MIMO system, and wherein vector y is related to vector x according to an equation: y=Hx+n, where H is an N×K channel matrix modeling phase shifts and amplitude changes on paths between the K transmit and N receive antennas, n is a complex N-dimensional vector representing communication channel noise; and determining a soft metric L(b i ) for each bit b i encoded by x according to the equation: L(b i )=σ −2 ·(min x j |b i =−1 ∥y−Hx j ∥ 2 −min x j |b i =+1 ∥y−Hx j ∥ 2 ), where σ is a standard deviation of the noise and/or interference, and x j represents the j-th possible value for x.