Analysis of a distributed coded cooperation scheme for multi-relay channels

In this paper, we consider a coded cooperation diversity scheme suitable for relay channels. The proposed scheme is based on convolutional coding, where each codeword of the source node is partitioned into two parts. The first part is transmitted from the source to the relays and destination. The second part is transmitted simultaneously from the source and relay nodes to the destination. All the relay nodes are assumed to be operating in the decode-and-forward (DF) mode. At the destination, the two replicas of the second sub-codeword are combined using maximum ratio combining (MRC). The entire codeword is decoded via the Viterbi algorithm. We analyze the proposed scheme for L-relay channels in terms of its probability of symbol error and outage probability. In that, explicit upper bounds are obtained assuming M-ary phase shift keying (M-PSK) transmission. Our analytical results show that the maximum diversity order is achieved provided that the source-relay link is more reliable than the other links. Otherwise, the diversity degrades. However, in both cases, it is shown that substantial performance improvements are possible to achieve over noncooperative coded systems. Several numerical and simulation results are presented to demonstrate the efficiency of the proposed scheme.