Performance analysis of adaptive decode-and-forward relaying in noncoherent cooperative networks

This paper studies the bit error rate (BER) performance of an adaptive decode-and-forward (DF) relaying scheme for a cooperative wireless network operating on independent and identically distributed (i.i.d.) or independent and non-identically distributed (i.n.d.) Rayleigh fading channels. The considered network is with one source, K relays, and one destination in which binary frequency-shift keying modulation is employed to facilitate noncoherent communications. A relay decodes and retransmits the received signal to the destination only if its decision variable is larger than the corresponding threshold. Depending on the availability of the information of whether a particular relay retransmits or remains silent, the destination combines the received signals from all the relays and the received signal from the source or only the received signals from the retransmitting relays and the received signal from the source to detect the transmitted information. The average end-to-end BERs are determined in closed-form expressions. The thresholds employed at the relays are investigated to minimize the end-to-end BERs. Analytical and simulation results are provided to validate our theoretical analysis. The obtained results show that the studied scheme improves the BER performance significantly compared to the previous proposed piecewise-linear (PL) scheme. In addition, the information of whether a particular relay retransmits or remains silent at the destination does not really improve the BER performance of the network.