Performance analysis of mixed RF/FSO cooperative systems with wireless power transfer

This paper investigates the performance of mixed radio frequency-free space optical (RF/FSO) systems where the battery-limited RF nodes can harvest the required energy for information transmission. The analysis takes into account the Rayleigh fading caused by signal propagation in the RF link and Gamma-Gamma atmospheric turbulence with the effect of pointing errors in the FSO link. Two different scenarios have been considered; in the first scenario, the source uses an RF random power provided by a relay for information transmission in a dual-hop cooperative configuration; whereas in the second scenario there is also a direct RF link between the source and destination. We provide closed-form expressions for the outage probability, bit error probability and ergodic capacity for the dual-hop amplify-and-forward relaying system that performs energy harvesting. Asymptotic expressions are also provided for the high SNR regime where the diversity order of the system is calculated. The accuracy of the proposed analytical formulations is proved by means of a set of numerical results. For instance, for the second scenario, fixing the average electrical SNR of the FSO link, we show that the link diversity order is equal to one. However, when fixing the average SNR of the RF links, the link diversity order equals zero, resulting in an error floor due to the dominant effect of the RF link. (C) 2019 Elsevier B.V. All rights reserved.