MAP channel estimation for Alamouti-based cooperative networks

In this paper, we consider a cooperative network with one source, one destination and two relays to bring cooperative diversity. We assume the link between the source and the destination is so bad that we do not consider it. We propose a decode-and-forward (DAF) strategy based on the Alamouti space-time (ST) code. The two relays must recover the transmitted sequence and forward it to the destination. We consider fast time varying channels between the cooperative users and the destination and our objective is to estimate these two channels in order to recover the information sequence at the destination. We propose a data-aided decision-directed Maximum A Posteriori (MAP) iterative channel estimation algorithm. It can profit from an optimum initialization by means of the MAP data-aided channel estimation. Besides, we adapt this iterative receiver to the case where the destination is equipped with two receive antennas to bring more diversity. The validity of the proposed algorithms is highlighted by simulation results.