Optimal Relay Placement and Power Distribution for Two Hop Hybrid FSO/MMW-RF DF Relayed System

A dual-hop relay-assisted hybrid FSO/MMW-RF system is suitable for reliable long-distance communication. Since system performance is highly distance dependent, the relay placement has a substantial impact on the system reliability, which is estimated in terms of an outage. In this work, we investigated the optimal relay position to yield minimum outage. However, due to geographical restraints, it may not be possible to install the relay at the optimal location. In this scenario, outage probability is optimized by appropriate power distribution between transmitter and relay under a total power constraint. Also, for a given fixed relay location, optimal power distribution between transmitter and relay is accomplished considering the fixed total power constraint. FSO channel is modeled as negative exponential by assuming strong turbulence, and the MMW-RF channel is modeled by Rayleigh distribution. Mathematical expressions for outage probability by assuming distance-dependent path loss are derived for DF relay which is further verified with simulation results.