Outage analysis of energy-harvesting based multihop cognitive relay networks with multiple primary receivers and multiple power beacons

In this paper, we propose an energy-harvesting based decode-and-forward multi-hop cognitive relay protocol, where secondary users harvest energy from the radio frequency signals transmitted by multiple dedicated power beacons (PBs) to support the information transmission. The secondary transmitters including source and relays must adjust their transmit power to satisfy interference power constraints required by multiple primary receivers (PRs). For performance evaluation, we derive exact closed-form expressions of outage probability (OP) for the proposed method over Rayleigh fading channel. Moreover, the asymptotic expressions for the outage performance at high and low signal-to-noise (SNR) are given to provide insights into the system performance. Then, Monte Carlo simulations are performed to verify the analysis results. The obtained results presented that the outage performance of the proposed system significantly depends on the number of PBs, the interference constraint as well as the position of PBs and PRs. Finally, the analytical asymptotic results show that the optimal time splitting ratio only depends on the number of hops and the number of PBs at low transmit signal-to-noise ratio (SNR).