BER-Constrained Incremental Relaying with Relay Selection in Cooperative Wireless Networks

One of the main drawbacks of cooperative communication systems with half-duplex relaying is inefficient use of spectrum. Incremental relaying is an effective technique that overcomes this limitation, particularly in the high-SNR regime. In this paper, for a multi-relay cooperative network with arbitrary number of relay nodes, we propose a spectrally-efficient incremental relaying scheme that eliminates redundant relay transmissions such that an average end-to-end bit error rate (BER) constraint is satisfied. For detect-and-forward relaying, under the assumption of error propagation from the relays to the destination, we analyze the performance of the system in terms of the end-to-end BER, the average spectral efficiency and the outage probability for Rayleigh fading environment. The performance of the system depends on a single threshold employed by the relays and the destination. We optimize this threshold such that the average spectral efficiency of the system is maximized under an average end-to-end BER constraint. This optimization criterion results in a constant-BER, variable-spectral efficiency relaying scheme. The proposed scheme makes use of spectrum as efficiently as possible, while providing the required quality of service at the destination.