Selection combining hybrid FSO/RF system for the performance improvement of HAP to ground communication systems

HAP to Ground communication is getting high research interest as of late because of its usefulness in providing communication service during disaster management, access to remote locations, signaling to Unmanned Aerial Vehicles and drones etc. Conventional air-to-ground communication systems use Radio Frequency signals for communication. This communication access is limited by lower data rates and spectrum scarcity. Thus, as an alternative to this system, we can make use of free space optical communication (FSOC) systems for data transmission. In this paper, the FSOC technology has been used to provide communication between a ground station and a high-altitude platform which is providing communication service to remote locations. Along with the Free Space Optical (FSO) system, Radio Frequency (RF) communication service is also facilitated such that the overall system forms a hybrid FSO/RF communication system. The RF system is used as a backup for FSO under strong atmospheric turbulence fading conditions such as fog or cloud when the FSO signaling is poor, whereas the RF signal is resilient against fog or cloud. On the other hand, FSO fares better against rain when RF signals fail. Thus this hybrid system has the potential to survive throughout all weather conditions. Here, for this system, the outage probability and the bit error rate performances are derived and the results are plotted.