Asymptotic Analysis of Switching-Based Hybrid FSO/RF System with DF-Relaying

In this paper, we propose a switching scheme for a decode-and-forward (DF)-relaying-based hybrid free-space op-tics/radio frequency (FSO/RF) system. We consider two scenarios, a dual-hop (DH) scenario without direct link and a DH scenario with direct link using selection combining (SC) at the destination. The system switches between FSO and RF sub-systems based on the received SNR at the destination, where the FSO sub-system is given higher priority. The probability density function (PDF) of the FSO channel is in the form of Meijer G function and the derivation of the analytical expressions for a DH scenario involve multiple such Meijer G functions which are too complex to comprehend. Therefore, simpler asymptotic outage probability and the average symbol error rate (SER) expressions are derived for the FSO sub-system. The exact closed form expressions have been derived for the RF sub-system. The diversity order is determined using the asymptotic expressions.