Opportunities and Challenges of OIRS-assisted UAV-based FSO Communication Systems

Free-space optical (FSO) communication is one of the most cost-effective wireless solutions that can fulfill the requirement of high quality of service (QoS) to the user in the next-generation wireless networks, i.e., beyond fifth-generation (B5G) and sixth-generation (6G). However, one of the major problems associated with the FSO-based communication system is the requirement of line-of-sight (LoS) between the transmitter and the receiver. Integration of optical intelligent reflective surface (OIRS) with FSO-based communication systems can improve the likelihood of establishing LoS links to the receivers. Furthermore, the performance of OIRS with FSO-based communication can be further improved by the utilization of unmanned aerial vehicles (UAVs) thanks to their inherent attractive attributes such as flexibility, mobility, and reconfigurable altitude. UAVs can work as mobile aerial relays and offer enhanced coverage, capacity, and QoS in next-generation wireless networks. In particular, the integration of FSO-based communication systems with an OIRS-assisted UAV could become a promising enabling technology for high-speed, ultra-reliable B5G and 6G communication. In this paper, we provide an overview and analysis of the state-of-the-art OIRS-assisted UAV-based FSO communication systems. In addition, we discuss the key design challenges related to the practical implementation of such communication systems. Furthermore, some potential research directions and open problems pertaining to OIRS-assisted UAV-based FSO communication systems are discussed.