Performance Analysis of Dual-Hop Mixed FSO/mmWave Systems

The combination of free-space optical (FSO)-based backhaul links and millimeter wave (mmWave)-based access links is considered as a key enabling technique to provide enhanced mobile broadband in ultra dense networks. In this paper, the generalized end-to-end performance of a dual-hop mixed FSO/mmWave relaying system is evaluated. The FSO link is assumed to follow the Gamma-Gamma fading with pointing error impairments, while the mmWave link experiences the fluctuating two-ray fading. Both heterodyne detection and indirect modulation/direct detection are accounted for in the FSO link. Using both amplify-and-forward and decode-and-forward relaying schemes, novel closed-form expressions for the outage probability and average bit error probability (BER) are derived in terms of bivariate Fox's H-functions. Furthermore, an asymptotic analysis for the outage probability and the average BER is provided to show the diversity order and other important engineering insights. Finally, the accuracy of our derived results is validated through Monte-Carlo simulations.