MAP symbol estimation on frequency-flat Rayleigh fading channels via a Bayesian EM algorithm

Equalization of Time-Varying Channels

“…This approach can be considered an extension of the technique originally proposed by Chiavaccini and Vitetta [CV01] for a time-selective channel and trivial BEM, to doubly selective channels modeled by generic BEMs. l=0 represents the channel frequency response, which may exhibit deep and sudden nulls.…”

“…, so that the 2 K term summations in (6.97) decouple into K binary summations [CV01], greatly simplifying the evaluation of (6.97). In the general case, the 2 K -term summations do not decouple, but not all 2 K metrics {ζ coh (c;θ θ θ (i) )} c∈{0,1} K need to be calculated, because very few of them yield nonnegligible e ζ coh (c;θ θ θ (i) ) .…”

Iterative Joint Channel Estimation and Multiuser Detection for DS-CDMA in Frequency-Selective Fading Channels

“…In the same spirit of the EM-based ML estimation of [12], we develop a recursive estimator for blind channel tracking in frequency-selective time-varying channels, which turns out to be a joint stochastic MMSE channel estimator and MAP detector under additive Gaussian noise. Its complexity is much lower than the method presented in [13], [14] with no compromise in its performance. Some preliminary results in this work have been reported in [15]- [17], and a generic graphical representation of the proposed algorithm was presented in [18].…”

“…Both PSP and the methods in [13], [14] can track fast fading channels at a complexity that grows exponentially with the number of resolvable paths in multipath channels. To reduce the complexity, some modifications have been made by trading tracking performance for complexity reduction, e.g.…”

“…Pioneering work of this class is the EM-based maximum likelihood (ML) channel estimator in [12] for static channels. Other examples include the maximum a posteriori (MAP) estimators in [13], [14] for fading channels.…”