Iterative channel estimation for turbo codes over fading channels

A method for coherently detecting and decoding turbo coded BPSK signals transmitted over frequency-flat fading channels is discussed. Estimates of the complex channel gain and variance of the additive noise are derived first from known pilot symbols and an estimation filter. After each iteration of turbo decoding, the channel estimates are refined using information fed back from the decoder. Both hard-decision and soft-decision feedback are considered, and simulation results compare the proposed technique with DPSK, ideal BPSK, and non-iterative PSAM based reception.