Second Order Statistics of Mixed RF-FSO Relay Systems and Its Application to Vehicular Networks

This paper considers channel modeling and evaluation of second-order outage statistics of mixed radio frequency/free space optical (RF/FSO) relay systems over mixed turbulence induced fading (TIF) and non-turbulence induced fading (non-TIF) channels. The derived statistics are directly related to the performance measures. In particular, we derive fast computing closed form expressions for relevant statistics such as cumulative-distribution-function (CDF), level-crossing-rate (LCR), and average-fade-duration (AFD). Approximation through Laplace integration of the products of random processes modeled as Gamma-Gamma (G-G) and Nakagami-m (N-m) are exploited. The proposed framework is then applied to two different scenarios for vehicular networks: i) I2I (infrastructure-to-infrastructure) direct communications enabled by FSO link, ii) V2V (vehicle-to-vehicle) communications enabled by RF/FSO/RF AaF (amplify-and-forward) relay link. Moreover, we provide numerical results for various settings of RF/FSO system model parameters.