| 摘要 |
A soft symbol decoder for use in a multiple input multiple output (MIMO) and OFDM (orthogonal frequency division multiplexing) system. The decoder generates soft symbol values for a digital signal that represents a number of source bits. The source bits are transmitted as symbols in corresponding to points in a signaling constellation. Soft metrics are determined by searching for all possible multi-dimensional symbols that could have been transmitted. The method includes transmitting a sample of the multi-dimensional symbol using K transmit antennas. The multi-dimensional symbol is represent-able as a complex, K-dimensional vector x. Each vector component of vector x represents a signal transmitted with one of the K transmit antennas. After transmission through a communication channel, a sample corresponding to the transmitted sample is received. The received sample is represented by a complex, N-dimensional vector y, where N is the number of receive antennas in the MIMO system. After the sample is received, a soft metric L(bi) is determined for each bit bi encoded by x according to the equation: L ( b i ) = sigma - 2 · ( min x j ❘ b i = - 1 y - Hx j 2 - min x j ❘ b i = + 1 y - Hx j 2 ) , , and xj represents all possible values for x. In addition, a reduced complexity method is used for providing soft metric values in the MIMO system. This exemplary aspect reduces the complexity of the above computations from 2BK to 2B(K-1), where B is the number of bits transmitted per symbol per antenna.
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