Performance evaluation of hybrid DF-AF OFDM cooperation in Rayleigh channel

Cooperative diversity networks have been receiving a lot of attention recently as an attractive way to combat frequency-selectivity of wireless channel, as it consumes neither time nor frequency resources. In the conventional cooperative strategies, relays employ either a decode-and-forward (DF) or an amplify-and-forward (AF) relaying protocol. In this paper, we investigate a new hybrid cooperative scheme that includes both DF and AF relays. First, we propose a thresholding scheme for the division of DF and AF relays. Then, we propose a dynamic optimal combination strategy for the hybrid DF-AF cooperation and removing the unsuitable AF relays. Orthogonal Frequency Division Multiplexing (OFDM) technique is utilized to resolve the multi-path in each cooperative link. Based on space-frequency coding, the hybrid cooperative OFDM can even gain from the multi-path, and obtain the multi-path diversity. In this paper, a closed-form error probability expression for the suggested hybrid DF-AF cooperative OFDM network, under Rayleigh channel, is also provided. The resulting expression is general as it holds for an arbitrary number of cooperating DF-AF branches. Finally, the simulation results explain how diversity is improved in the hybrid cooperative diversity wireless networks.