Non-pilot-aided iterative decoding for joint data recovery and channel estimation in fading

Decoding in wireless rapidly fading channels requires that the receiver has access to explicit or implicit channel-state information (CSI). This paper presents a joint channel estimation and decoding scheme for frequency-flat, time-selective Rayleigh fading with relatively high Doppler, that does not require external phase information or even pilot symbols. This system outperforms a pilot-aided iterative channel estimation algorithm that does not decode and estimate jointly. The joint decoding algorithm models the phase trajectory of the channel as a suitable Markov process, the dynamics of which depend on the Doppler rate. At each iteration it considers all possible phase trajectories to determine the maximum a posteriori probability (MAP) value for each bit. This decoding procedure is a natural extension of standard turbo decoding, but introduces a significant complexity increase. Performance is assessed via an upper bound to the capacity of a Markov-phase channel.