Relay Selection Based Hybrid RF/FSO Transmission over Double Generalized Gamma Channels under Outdated CSI and Pointing Errors

This paper analyzes the performance of dual-hop amplify-and-forward hybrid radio-frequency/free-space optical (RF/FSO) transmissions with partial relay selection based on outdated channel state information estimates. The FSO channel modeling accounts for turbulence-induced fading, path loss, and pointing errors as well. Essential statistics of the system end-to-end signal-to-noise ratio (SNR) are derived in closed-form, yielding novel expressions for its cumulative distribution function and probability density function. Afterwards, novel closed-form expression for the system outage probability is obtained. High SNR approximation is applied to the obtained expression, yielding simple and easily tractable results, that, additionally, offer useful insights into the system performance. The analysis is unified, applying to both types of detection techniques, i.e., intensity modulation/direct direction and heterodyne detection. Monte Carlo simulation results corroborate the proposed analysis, and provide additional insights on the system performance.