Joint iterative detection and decoding in the presence of phase noise and frequency offset
Alan Barbieri, Giulio Colavolpe, Giuseppe Caire · 2005
In this paper, we present an iterative decoding algorithm for turbo and LDPC codes transmitted over channels affected by a time-varying phase noise and an uncompensated frequency offset. The proposed algorithm is obtained as an application of the sum-product algorithm to the factor graph representing the joint a posteriori distribution of the information symbols and the channel parameters given the channel output. The resulting algorithm employs the soft-output information on the coded symbols provided by the decoder and performs forward-backward recursions taking into account the joint probability distribution of phase and frequency offset. We present numerical results for binary LDPC codes and LDPC-coded modulation schemes, showing that, despite its low complexity, the algorithm is able to cope with a strong phase noise and a significant uncompensated frequency offset, thus avoiding the use of complicated data-aided frequency estimation schemes operating on a known preamble.