C. Komninakis and R. D. Wesel: Joint Iterative Channel Estimation and Decoding in Flat Correlated Rayleigh Fading

Abstract— This paper addresses the design and performance evaluation with respect to capacity of M-PSK turbo-coded systems operating in frequency-flat, time-selective Rayleigh fading. The receiver jointly performs channel estimation and turbo decoding, allowing the two processes to benefit from each other. To this end, we introduce a suitable Markov model with a finite number of states, designed to approximate both the values and the statistical properties of the correlated flat fading channel phase, which poses a more severe challenge to PSK transmission than amplitude fading. Then, the Forward-Backward algorithm determines both the maximum a posteriori probability (MAP) value for each symbol in the data sequence, and the MAP channel phase in each iteration. Simulations show good performance in standard correlated Rayleigh fading channels. A sequence of progressively tighter upper bounds to the capacity of a simplified Markovphase channel is derived, and performance of a turbo-code with joint iterative channel estimation and decoding is demonstrated to approach these capacity bounds. Keywords— Turbo-codes, flat Rayleigh fading, capacity, Markov channels