Performance Enhancement of HAP-Based Relaying M-PPM FSO System Using Spatial Diversity and Heterodyne Detection Receiver

Abstract

In this paper, we investigate the performance of a high-altitude platform (HAP)-based relaying free-space optical communication (FSO) system, where HAP plays a role as a relay node that employs detect-and-forward relaying scheme to connect between two ground stations (GSs). $M$-ary pulse-position modulation (PPM), spatial diversity, and heterodyne detection receiver are used to improve the system’s performance. Instead of using multiple-input multiple-output (MIMO), which makes the HAP complex, multiple-input single-output (MISO) is applied to the uplink while single-input multiple-output (SIMO) is utilized for the downlink. Consequently, the HAP only needs a couple of transmit and receive aperture. The expression for the bit error rate (BER) of the proposed FSO system is derived considering the impact of atmospheric attenuation and turbulence. The achievable BER with low values has proved the feasibility of our proposed system. In addition, the advantages of using $M$-PPM, spatial diversity, and heterodyne detection are demonstrated in terms of the power gain and the geometric distance between two GSs. Other useful information for system design regarding the required transmitted power, the number of transmit/receive apertures, the modulation level, and the local oscillator power is also provided in this paper.

Improving Performance of Integrated Ground-HAPS FSO Communication Links With MIMO Application

“…The impact of environmental and FSO communication system's parameters and their optimization need to be investigated accurately to address challenges effectively and ensure maximized link availability. Recent studies have demonstrated the advantageous impact of spatial diversity techniques on enhancing the performance of FSO links, particularly in the context of HAPS-assisted FSO communication systems [31]- [33]. In [31], the BER performance of HAPS-assisted FSO communication system was investigated considering the impact of both attenuation and atmospheric turbulence.…”

“…Recent studies have demonstrated the advantageous impact of spatial diversity techniques on enhancing the performance of FSO links, particularly in the context of HAPS-assisted FSO communication systems [31]- [33]. In [31], the BER performance of HAPS-assisted FSO communication system was investigated considering the impact of both attenuation and atmospheric turbulence. Notably, the effect of pointing error was not incorporated in this particular study.…”

Improving performance of integrated ground-HAPSFSO communication links with MIMO application

“…The benefit of spatial diversity technique on the performance of FSO links has also been shown recently for HAPS-aided FSO communication systems in several studies [25], [26], [27]. In [25], the BER performance of HAPS-assisted FSO communication system was analyzed considering both attenuation and atmospheric turbulence. The effect of pointing error was not included in this study.…”

Comparison of adaptive algorithms for free space optical transmission in Málaga atmospheric turbulence channel with pointing errors

“…Diversity is a widely used and efficient technique for improving performance of communication systems. System performance for outage probability and BER when using different diversity techniques are given in [15–18].…”