Performance of Incremental AF Relaying Cooperative Networks with the nth Best Relay over Rayleigh Fading Channels

Cooperative diversity networks have recently been proposed as a promising technology to improve performance over fading channels. In this paper, we consider incremental amplify-and-forward (AF) cooperative diversity networks which employ the Nth best relay when the best relay is unavailable due to issues such as scheduling or load balancing. The end-to-end performance is analyzed over independent and identical (i.i.d.) and nonidentical (i.n.d.) Rayleigh fading channels. Closed form expressions for the bit error rate and channel capacity are derived, and results are presented to illustrate the performance. According to the analysis, The incremental AF strategy can reduce BER greatly when comparing to the conventional direct communication without cooperative, although it can not get the capacity of conventional direct communication, which is with the power as the total power of soure and Nth best relay node in AF cooperative network. The incremental AF strategy with Nth best relay can improve the capacity in high SNR region comparing to the complete cooperative with Nth best relay when BER can be accepted by setting different threshold for SNR of the direct link between source node S and destination node D. The incremental Nth best relay cooperative protocol can be useful when considering improving the error rate and bandwidth efficiency at the same time comparing to the conventional direct system and complete cooperative.