Evaluating C/N and BER in FSO Vehicular-HAP-Satellite Links Under Rain and Cloud Scattering

This letter conducts a thorough investigation into Carrier-to-Noise Ratio (C/N) and the analysis of Bit Error Rate (BER) within a Space-Air-Ground Integrated Network (SAGIN) that employs Free Space Optical (FSO) communications. The focus is particularly set on understanding the impact of attenuation on optical links to offer insights on how to mitigate its effects and support link enhancement. Rain attenuation and cloud scattering are two significant factors that influence the performance of FSO links. These links are essential for high-speed, reliable communication in SAGIN, where atmospheric conditions pose a constant challenge. To address these challenges, we have applied the Lin model and ITU model for a precise characterization of rain attenuation and incorporated theoretical models to simulate cloud scattering. This dual approach enables a detailed assessment of the factors leading to C/N degradation and their subsequent impact on BER across varying atmospheric conditions. By analyzing these effects, we aim to enhance the efficiency and reliability of communications. Our methodology involves an in-depth exploration of signal propagation and attenuation behaviors in real scenarios, leading to developing strategies to improve network resilience and performance.