Bayesian Semi-Blind FIR Channel Estimation Algorithms in SIMO Systems

When the transmission scenario includes a training sequence or pilots, semi-blind channel estimation techniques have shown a tendency to fully exploit the information available from the received signal if they are correctly implemented. This feature leads semi-blind channel estimation performance to exceed that of the schemes based on the blind part or the training sequence only. Moreover, in some situations they can estimate the channel when the other techniques fail. Semi-blind channel estimation techniques were developed and usually evaluated for a given channel realization, i.e. with a deterministic channel model. On the other hand, in wireless communications the channel is typically modeled as Rayleigh fading, i.e. with a Gaussian (prior) distribution expressing variances of and correlations between channel coefficients. In recent years, such prior information on the channel has started to get exploited in pilot-based channel estimation, since often the pure pilot-based (deterministic) channel estimate is of limited quality due to limited pilots. In this paper we explore a Bayesian approach to semi-blind channel estimation, exploiting a priori information on fading channels. We mainly focus on semi-blind joint ML/MAP estimation of channels and symbols on one hand, and on semi-blind ML/MAP estimation of channels with elimination of symbols on the other hand. As a consequence, a unified framework along with three novel semi-blind Bayesian estimators are introduced whose performance is compared by simulations to three, one extended and another two already existing semi-blind non-Bayesian estimators.