Outage performance of orthogonal space-time block codes transmission in opportunistic decode-and-forward cooperative networks with incremental relaying

In this study, the authors propose an incremental opportunistic decode-and-forward (ODF) cooperation scheme employing orthogonal space-time block codes (OSTBC) under Rayleigh fading channels. Different from existing research, the authors use ODF and OSTBC together to maximise the diversity gain, while incremental relaying is implemented to improve transmission efficiency. Besides, a more practical system model is introduced where multiple geographically isolated nodes are equipped with multiple antennas and the large scale fading is taken into consideration. The exact expression of end-to-end outage probability is derived in the whole signal-to-noise ratio (SNR) region for arbitrary relay number, antenna configuration and incremental relaying trigger value. Through asymptotic analysis, the authors also obtain the closed-form expression of outage probability in high SNR region and derive the expression of diversity order. The results show that the proposed scheme outperforms traditional direct transmission and fixed ODF in arbitrary SNR region. Meanwhile, the outage probability and diversity order depend directly on the relay number, antenna configuration and incremental relaying trigger value. The analytical results can be utilised to facilitate network planning and optimisation. Simulation results are presented to verify the authors analysis.