<p>This paper proposes an unmanned aerial vehicles (UAV)-integrated reconfigurable intelligent surface (RIS)-assisted modulating retroreflector (MRR) free-space optical (FSO) communication system, enhanced with wavelength diversity (WD) and time diversity (TD) techniques, to address the challenges posed by dynamic channel conditions such as fog, gamma–gamma turbulence, and pointing errors. The integration of UAVs, programmable RISs, and passive MRRs forms a scalable and modular architecture—referred to as the UAV-integrated RIS-assisted MRR-FSO system—that significantly enhances system availability, adaptability, and energy efficiency. Analytical expressions for key performance metrics, including outage probability, average bit error rate (BER), and maximum effective bit rate, are derived and validated through Monte Carlo (MC) simulations, demonstrating a high degree of agreement with the theoretical results. Numerical evaluations show that the proposed system achieves up to 75% BER reduction and a 60% improvement in outage probability compared to conventional UAV-FSO systems. Furthermore, the incorporation of RIS and MRR components leads to up to 40% enhancement in energy efficiency, along with substantial reductions in hardware complexity and deployment cost. The WD design offers up to 2<InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11107_2025_1031_Article_IEq1.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">$\times$</EquationSource> <EquationSource Format="MATHML"><math> <mo>×</mo> </math></EquationSource> </InlineEquation> higher effective data rate and a 2–5<InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11107_2025_1031_Article_IEq1.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">$\times$</EquationSource> <EquationSource Format="MATHML"><math> <mo>×</mo> </math></EquationSource> </InlineEquation> improvement in spectral efficiency, positioning the system as a strong candidate for reliable, energy-efficient, and adaptive UAV-based optical backhaul solutions in future 6 G networks.</p>

Performance analysis of a UAV-integrated RIS-aided MRR-FSO system utilizing wavelength and time diversity techniques

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发表日期：

2025年7月2日

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Amr G. AbdElKader,
Ahmed Allam,
Kazutoshi Kato,
Hossam M. H. Shalaby

摘要

This paper proposes an unmanned aerial vehicles (UAV)-integrated reconfigurable intelligent surface (RIS)-assisted modulating retroreflector (MRR) free-space optical (FSO) communication system, enhanced with wavelength diversity (WD) and time diversity (TD) techniques, to address the challenges posed by dynamic channel conditions such as fog, gamma–gamma turbulence, and pointing errors. The integration of UAVs, programmable RISs, and passive MRRs forms a scalable and modular architecture—referred to as the UAV-integrated RIS-assisted MRR-FSO system—that significantly enhances system availability, adaptability, and energy efficiency. Analytical expressions for key performance metrics, including outage probability, average bit error rate (BER), and maximum effective bit rate, are derived and validated through Monte Carlo (MC) simulations, demonstrating a high degree of agreement with the theoretical results. Numerical evaluations show that the proposed system achieves up to 75% BER reduction and a 60% improvement in outage probability compared to conventional UAV-FSO systems. Furthermore, the incorporation of RIS and MRR components leads to up to 40% enhancement in energy efficiency, along with substantial reductions in hardware complexity and deployment cost. The WD design offers up to 2 $\times$ $\times$ higher effective data rate and a 2–5 $\times$ $\times$ improvement in spectral efficiency, positioning the system as a strong candidate for reliable, energy-efficient, and adaptive UAV-based optical backhaul solutions in future 6 G networks.