Patent ID: 7092436

Claim:
A method for detecting symbols of a modulated signal received via channels of a wireless communications system, comprising: obtaining an initial estimate of a transmitted symbol via the channels from a previous channel estimate and a received symbol; updating the channel estimate; optimizing a next estimate of the transmitted symbol which maximizes an expectation of a log likelihood function by averaging a logarithm of a likelihood function over unknown parameters h of the channels; quantizing the next estimate of the transmitted symbol; comparing the quantized next estimate of the transmitted symbol with the initial estimate of the transmitted symbol to determine if the initial estimate of the transmitted symbol and the quantized next estimate of the transmitted symbol have converged; and otherwise inputting the quantized next estimate of the transmitted symbol as the initial estimate of the transmitted symbol; and repeating the updating, the optimizing, the quantizing, and the comparing until the initial estimate of the transmitted symbol and the quantized next estimate of the transmitted symbol converge; and further comprising: determining a posterior covariance matrix {circumflex over (Σ)} p of the channels using a FFT matrix W, the initial estimate of the transmitted symbol X p , the received symbol Y, and a Gaussian noise variance σ 2 as {circumflex over (Σ)} p =( W H X p H X p W/σ 2 ) −1 ; determining a posterior mean ĥ p of a channel impulse response as ĥ p ={circumflex over (Σ)} p ( W H X p H Y/σ 2 ); determining a channel update coefficients matrix C for recovering the next estimate of the transmitted symbol; and applying the coefficient matrix C to the posterior mean ĥ p , the FFT matrix W, and the received symbol Y according to {tilde over (X)} p+1 =C −1 ( ĥ p H W H Y) T to optimize the next estimate of the transmitted symbol {tilde over (X)} p+1 .