An iterative procedure for semi-blind symbol estimation in a multipath SISO channel context exploiting finite alphabet properties

In this paper, we present a maximum likelihood (ML) symbol detector for single-carrier block transmissions in the context of SISO channels with multipath. This ML detector is based on an iterative least squares with projection (ILSP) algorithm exploiting both finite alphabet properties of the transmitted signal and its cyclic prefixed structure in order to approach ML detection in a cheap way. Since the initial channel estimate is crucial for the convergence of the ILSP algorithm, we propose a computationally cheap stochastic method for computing an initial channel estimate using a variant of cyclic prefix only (CP-Only): the known symbol padding only (KSP-Only) technique. The resulting channel model is sufficiently accurate to be used as a starting point for the iterations. The final result is a computationally affordable direct symbol estimation method that yields promising results in terms of bit error rate (BER).