Distributed coded cooperation for relay channels operating in the decode-and-forward mode

We introduce coded cooperation diversity using relay nodes in the decode-and-forward (DF) mode, in which the codewords of the source node are partitioned and transmitted through independent fading channels to both relay and destination nodes, to achieve remarkable gains over a noncooperative system. The main difference between the distributed and the noncooperative space-time coding is that the link between the source and the relay node is not error-free in the distributed case, as opposed to the noncooperative case. In this work, we take into account the errors in the source-relay link and derive upper bounded expression for the symbol error rate on DF relaying in the case of 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. This is unlike the case when the relay nodes operating in the DF mode are based on symbol-by-symbol decoding and forwarding. We present several numerical examples to support our analytical expression.