Error probability of OFDM-based hybrid relay protocols over wideband fading channels

Orthogonal frequency division multiplexing (OFDM) based relay architecture is a promising technique in modern wireless communication systems. In frequency-selective channels, different sub-carriers experience different fades. Data transmitted on the sub-carriers which experience deep fade will have a high probability of getting lost at the destination. In this paper, we propose a multicarrier-adaptive hybrid relay protocol (MC-AHRP) over frequency-selective channels to overcome this problem. In the proposed protocol, the subcarrier performs an amplify-and-forward (AF) scheme when the instantaneous SNR of the source-relay link exceeds a preset threshold value, or it utilizes the adaptive decode-and-forward (ADF) scheme as the alternative. For any subcarrier of the ADF scheme that fails to be decoded, the destination selects the respective subcarrier from the direct transmission path instead. The performance of the proposed scheme is analyzed in terms of bit error probability (BEP). Simulation and numerical results show that a significant performance gain can be achieved.