On the performance of dual-hop mixed RF and hybrid RF-FSO relaying

In this work, we have carried out a performance analysis of the Decode and Forward (DF), dual-hop hybrid Radio Frequency-Free Space Optical Communication (RF-(RF/FSO)) link. The Source to Relay (S ? R) link is considered as an RF link, and Relay to Destination (R ? D) link is a parallel RF and FSO link. The selection combining technique is employed at the destination. The RF links are modeled by Nakagami-m distribution, and the FSO link is modeled by and Malaga channel model with pointing errors. For the FSO link, both Intensity Modulation/Direct Detection (IM/DD) and Heterodyne detection schemes are considered. The closed form expressions of Probability Distribution Function (PDF), Cumulative Distribution Function (CDF), and Moment Generating Function (MGF) of end-to-end SNR are derived in form of Meijer's G function. Utilizing the above results, The expressions for outage probability, bit error rate (BER), and ergodic capacity have been obtained. The numerical results are compared for different strengths of fading of RF links, the strength of atmospheric turbulence, the severity of pointing errors, and detection techniques. The numerical results closely match with Monte-Carlo simulations which validate the analytical work. The RF-(RF/FSO) link's performance is found to be better than the equivalent RF-FSO link. The link (S ? R or R ? D ) experiencing the stronger fading dominates the overall link performance.