Multiple-output free space optical system with exponentiated gamma channel model and Greedy scheduling

This paper introduces an advanced approach to analysing atmospheric turbulence in subcarrier quadrature amplitude modulation (SC-QAM) free space optical (FSO) systems through a development and application of the exponentiated gamma channel model. The study focuses on FSO systems with multiple receivers, employing Greedy scheduling to optimize link performance. A closed-form expression for the average bit error rate (BER) is derived, leveraging the SC-QAM modulation technique and the exponentiated gamma channel model to characterise turbulence-induced fading accurately. To enhance system robustness, the use of multiple receivers is proposed, and a novel expression for the BER in a multiple-output configuration is developed. Comprehensive simulations are conducted to validate the accuracy of the derived closed-form BER expression and to investigate the influence of key system parameters on performance. The analysis examines factors such as the link distance and the refractive index structure parameter, which are critical in determining the impact of turbulence on FSO links. The results demonstrate the significant benefits of employing multiple receivers, with Greedy scheduling shown to play a pivotal role in mitigating turbulence effects and improving overall BER performance. Furthermore, the findings highlight that increasing the number of receivers substantially enhances the system resilience to fading and turbulence, leading to a robust reduction in BER. This study not only provides valuable insights into the optimization of FSO systems under turbulence but also establishes a framework for future research on advanced scheduling algorithms and modulation techniques. The results underscore the importance of system design parameters and provide practical recommendations for enhancing the reliability and efficiency of the next-generation FSO communication networks.