Performance Analysis of HAPS-Based Relaying for Hybrid FSO/RF Downlink Satellite Communication

Abstract

Free space optics (FSO) communication has garnered significant importance to provide gigabit capacity links owing to its unique features. However, its performance is limited by the adverse effects of transmission medium such as atmospheric turbulence induced fading, wind, etc. Therefore, it is wise to backup with reliable radio frequency (RF) links to improve the performance of FSO communication. The fusion of FSO and RF technologies is a suitable candidate for future satellite communication (SATCOM) systems. In this context, the present paper proposes a novel system model for High-Altitude Pseudo-Satellite (HAPS)-based relaying for downlink scenario utilizing both FSO and RF links. The performance of the proposed hybrid FSO/RF SATCOM system is investigated through average and asymptotic symbol error probability (SEP) analyses. Further, the obtained closed-form expressions for average SEP are validated using Monte-Carlo simulation results.

Average Transmission Rate and Outage Performance of Relay-Assisted Satellite Hybrid FSO/RF Systems

“…Therefore, the hybrid FSO/RF system will be used to counteract the effect of transmission media. Recently, there have been several studies on the design of dual-hop satellite-HAP-ground systems using hybrid FSO/RF communications [3], [7]. Notably, the authors in [7] investigated the performance of the HAP relay assisted for hybrid FSO/RF downlink system was carry out using Gamma-Gamma distribution to model the FSO channel, and Rician distribution to model the RF channel.…”

“…Recently, there have been several studies on the design of dual-hop satellite-HAP-ground systems using hybrid FSO/RF communications [3], [7]. Notably, the authors in [7] investigated the performance of the HAP relay assisted for hybrid FSO/RF downlink system was carry out using Gamma-Gamma distribution to model the FSO channel, and Rician distribution to model the RF channel. In [3], the average symbol error rate and outage performance of the ground-HAP-satellite uplink system were well investigated.…”

“…The RF channel was modeled by Rician distribution, and FSO channel modeling was taken turbulence-induced fading, beam wander induced pointing error, and free-space loss into account. Aside from [3], [7], to the best of the author's knowledge, there are no other studies on the dual-hop satellite-HAP-ground with the hybrid system in the literature. However, the limitations of these studies were the costly decode-and-forward relaying solution and conventional fixed-rate hybrid FSO/RF system, which frequently switched between FSO and RF links, led to degrading the system performance.…”

On the Design of Rate Adaptation for Relay-Assisted Satellite Hybrid FSO/RF Systems

“…As a matter of fact, the dual-hop relay-assisted FSO and hybrid FSO/RF communications have been well studied for terrestrial networks [14]- [17]. In the satellite networks, the current state-of-the-art of hybrid FSO/RF systems for relayassisted satellite communication focuses on fixed users [18]- [22]. In particular, in [18], the authors studied the downlink satellite-HAP-ground with the assumption of gamma-gamma turbulence channel model for FSO link and Rician distribution for RF link.…”

“…In the satellite networks, the current state-of-the-art of hybrid FSO/RF systems for relayassisted satellite communication focuses on fixed users [18]- [22]. In particular, in [18], the authors studied the downlink satellite-HAP-ground with the assumption of gamma-gamma turbulence channel model for FSO link and Rician distribution for RF link. The impact of pointing error and atmospheric attenuation was not included in the study.…”