Operation Altitude Optimization of Airborne FSO Links in the Presence of Pointing Errors

With its ultra-high capacity, free space optical (FSO) communication is an ideal backhaul solution for non-terrestrial networks (NTNs). Unlike traditional terrestrial FSO systems, airborne FSO terminals are subject to significant pointing errors. In particular, the rotational stability of a rotary-wing UAV arises from rolling, yawing, and pitching and induces altitude-dependent shifts in the center of the received beam. This motivates the optimal selection of operation altitude to minimize the effects of pointing errors. In this paper, we analyze the bit error rate (BER) of a UAV-mounted FSO link in the presence of pointing errors and determine optimal operation altitudes to minimize the BER.