Joint subcarrier pairing and resource allocation for adaptive hybrid relay protocol in OFDM systems

Orthogonal frequency division multiplexing (OFDM) has been adopted as a promising technique to mitigate multi-path fading and provides high spectral efficiency in broadband communications. In this paper, we investigate resource allocation and sub-carrier permutation in OFDM-based hybrid relay protocol over frequency-selective channels. Selective multicarrier-adaptive hybrid relay protocol (MC-AHRP), involves the sub-carrier utilizing an amplify-and-forward (AF) scheme when the instantaneous signal-to-noise ratio (SNR) is larger than threshold value and an adaptive decode-and-forward (ADF) scheme when the instantaneous SNR is less than threshold value. The proposed protocol exploits the benefits of adaptive hybrid relay protocol, OFDM, resource allocation, and sub-carrier permutation to provide a substantial enhancement in the system performance. The simulation results show that when the protocol performs resource allocation (RA) and sub-carrier permutation (SP) can provide an excellent improvement in the capacity of the system. It also demonstrate that the proposed protocol can achieve a significant improvement in throughput compared with conventional protocols.