Impact of pointing error on SISO/MISO drones swarm-based free space optical system in weak turbulence regime

Applying the drone-based free space optical (FSO) technology is recent in communication systems. The FSO technology has high-security features due to narrow beamwidth, insusceptible to interferences, free license, and landline connection is not appropriate. However, these advantages face many obstacles that affect the system's performance, such as random weather conditions and misalignment. The pointing error Hp is one of the critical factors of the channel gain H. The related parameters of the Hp factor: the pointing error angles θr and the path length Z, were manipulated to extract the applicable values at various receiver diameter values. The proposed system has two topologies: single input single output (SISO) and multiple input single output (MISO), flying in weak atmospheric turbulence. The simulation was done using MATLAB software 2020. The average bit error rate (ABER) for the system versus signal-to-noise ratio (SNR) were verified and analyzed. The results showed that at θr=10−3 rad, Z increased in the range 10~100m for each one-centimeter increase of DR. At θr=10−2 rad, the applicable Z was nearly 10% of the link distance Z when θr=10−3 rad was applied. Consequently, an increase in θr must correspond decrease in Z and vice versa to maintain the system at high performance