A Convolutional-Based Distributed Coded Cooperation Scheme for Relay Channels

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Abstract
In this paper, we consider a coded cooperation diversity scheme that is suitable for L-relay channels that operate in the decode-forward mode. The proposed scheme is based on convolutional coding, where each codeword of the source node is partitioned into two frames that are transmitted in two phases. In the first phase, the first frame is broadcast from the source to the relays and destination. In the second phase, the second frame is transmitted on orthogonal subchannels from the source and relay nodes to the destination. Each relay is assumed to be equipped with a cyclic redundancy check (CRC) code for error detection. Only these relays (whose CRCs check) transmit in the second phase. Otherwise, they keep silent. At the destination, the received replicas (of the second frame) are combined using maximal ratio combining. The entire codeword, which comprises the two frames, is decoded via the Viterbi algorithm. We analyze the proposed scheme in terms of its probability of bit error and outage probability. Explicit upper bounds are obtained, assuming M-ary phase-shift keying transmission. Our analytical results show that the full 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 it is possible to achieve substantial performance improvements over noncooperative coded systems. Several numerical and simulation results are presented to demonstrate the efficacy of the proposed scheme.

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