| 摘要 |
A method for soft demapping of complex-valued symbols y(k) (k=1, 2, . . . , K) by calculation of a Logarithm of Likelihood Ratio (LogLR) such that: Log LR ( b I , q ) = ln ∑λ ∈S l , q ( 1 ) exp ( - 1 2 β y ~ ( k ) -λ 2 )∑λ ∈S q , l ( 0 ) exp ( - 1 2 β y ~ ( k ) -λ 2 ) wherein bI,q is the qth coded bit of an in-phase part of a transmitted signal,βis an asymptotic Signal-to-Interference-plus-Noise Ratio, {tilde over (y)}(k) is a standardized symbol associated with y(k),λis a reference symbol of QAM constellation associated with a M-QAM modulation, S(1)I,q and S(0)I,q are complex plane partitions that bring together, respectively, all reference symbolsλhaving a“1”at the position (I, q) and all reference symbolsλhaving a“0”at the position (I, q), a formula similar to LogLR being given for the bit bQ,p, pth coded bit of a quadrature part of the transmitted signal. The method applies to code division multiple access transmission systems. |
