Two-Way Mixed RF/FSO Relaying System in the Presence of Co-channel Interference

Abstract

In this paper, the performance of a two-way mixed radio frequency/free space optical (RF/FSO) relaying system in the presence of co-channel interference (CCI) is investigated. The RF links are modeled as Nakagami-m distribution, and FSO links adopt Gamma-Gamma turbulence model. To improve spectral efficiency, relay exchanges the information between two terminals in three phases via RF and FSO links. Meanwhile, CCIs are considered at both relay and destination. Novel closed-form upper bounds expressions for the signal to interference plus noise ratios are derived, based on that lower bounds outage probability, average bit error rate, and outage capacity are further presented for both RF/FSO and FSO/RF links. Then, asymptotic expressions are provided to predict the diversity order. Additionally, the effect of various parameters on system performance, such as interference numbers and power, are investigated and compared including interference-free condition. Simulation results show that, in the interference-effected system, when the average signal-to-noise ratio increases, system performance enhances first and then remains unchanged. This phenomenon does not occur in the interference-free system, which implies the system performance is limited by the numbers and power of CCIs. Moreover, the effect of pointing errors on system performance is further investigated.