Iterative algorithms are an attractive approach to approximating optimal, but high-complexity, joint channel estimation and decoding receivers for communication systems. We present a unified approach based on factor graphs for deriving iterative message-passing receiver algorithms for channel estimation and decoding. For many common channels, it is easy to find simple graphical models that lead directly to implementable algorithms. Canonical distributions provide a new, general framework for handling continuous variables. Example receiver designs for Rayleigh fading channels with block or Markov memory, and multipath fading channels with fixed unknown coe#cients illustrate the e#ectiveness of our approach. Keywords--- channel estimation; fading channels; iterative decoding; low-density parity check (LDPC) codes I. Introduction For many communication systems it is well-known that joint demodulation and decoding is required for optimum performance. Typically, this processing is too co..
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