A review on pointing, acquisition, and tracking approaches in UAV-based fso communication systems

The challenge of tracking unmanned aerial vehicles (UAVs) is arising out of increasing their market and spread usage in many applications. Miscuing UAVs can lead to potential threats as they are considered an essential part of national security. One of the major issues in communication with UAVs is the enormous amount of data generated by UAVs that requires a high data rate link, making the free space optics (FSO) communication, with very high bandwidth, an appropriate choice. Consequently, current developments in UAVs have provided new horizons for establishing UAV-based FSO links. However, FSO is a narrow line of sight (LoS) technology that is highly affected by the misalignment between the transmitter and receiver. So, tracking mechanisms are of vital importance when considering UAV-based FSO communication systems. This paper addresses coarse to fine pointing, acquisition, and tracking (PAT) approaches and the recently developed tracking approaches to establish a reliable link for communication. Also, the various approaches are discussed and compared for precise alignment between the ground station and its associated UAV, highlighting their advantages and limitations. Current challenges and future research directions are addressed and integrated by combining different ideas.