Optimal Power Allocation and CAR in Multiuser Dual‐Hop RF/FSO DF Relaying Systems With CDF‐Based Scheduling

ABSTRACT A multiuser dual‐hop RF‐FSO decode‐and‐forward (DF) relaying system with co‐channel interference (CCI) is considered. The RF channel undergoes Rayleigh fading, while the FSO channel is modeled by using Fisher‐Snedecor, ℱ distribution. A cumulative distribution function (CDF)‐based scheduling scheme is employed to effectively control the channel access ratio (CAR) and ensure fairness among users. We derive unified analytical and asymptotic expressions for the outage probability (OP), accounting for independent and non‐identically distributed (i.n.i.d) CCI with varying power and channel gain across users, relay and interferers. The asymptotic expression facilitates optimal power allocation, CAR optimization and their joint optimization to minimize the OP. Monte Carlo simulations validate the accuracy of the derived expressions. Results demonstrate that the CDF‐based scheduling system with optimized CAR outperforms proportional fairness scheduling (PFS) scheme and closely matches the performance of greedy scheduling (GS) scheme. Additionally, joint optimization of power allocation and CAR yields further improvements in outage performance compared to optimizing either power allocation or CAR alone. It is also noted that OP saturates at high SNR due to CCI.