Factor Graph Based Derivation of a Receiver for PCC Coded Transmissions over a Frequency Selective Fading Channel

In previous work, we presented a receiver to detect and decode parallel concatenated convolutional (PCC) coded transmissions over a frequency selective Rayleigh fading channel. This scheme generalized work by Valenti and Woerner to frequency selective channels. It was shown that re-estimation of the channel after each PCC decoding iteration yields significant gain. In this paper we present a detailed derivation of our receiver from factor graph theory. This illustrates the interaction between the channel estimation procedure and the message passing algorithm. In particular it is shown that, in contrast to Valenti and Woerner’s scheme, the pilot symbols appear as variables in the factor graph.