Soft decision directed MAP estimate of fast Rayleigh flat fading channels

An iterative receiver with soft decision feedback is derived to yield a maximum a posteriori (MAP) estimate of fast Rayleigh flat fading channels. The derivation is based on the expectation-maximization (EM) algorithm. Simulation results indicate that the derived receiver performs better than an iterative receiver with hard decision feedback, for both uncoded data and convolutionally coded data. The combination with turbo codes is also investigated. Three kinds of decision feedback are proposed and compared namely, re-encoder, soft decision feedback and quantizer. It is shown via simulation that soft decision feedback is the best while the quantizer has similar performance. The re-encoder, on the other hand has performance degradation