Modeling, Design, and Demonstration of IRS-Assisted FSO Communication Systems

• Applicants: Professor Dr. Bernhard Schmauss; Professor Dr.-Ing. Robert Schober
• Subject Area: Communication Technology and Networks, High-Frequency Technology and Photonic Systems, Signal Processing and Machine Learning for Information Technology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 515937276

Free-space optical (FSO) communication systems are able to provide high-rate point-to-point links. Their deployment is much cheaper and much faster compared to optical fibre links, while the data rates they are able to provide over distances of up to a few kilometers are higher than those of conventional radio-frequency (RF) communication systems at a lower cost and less equipment weight. Furthermore, because of their high directivity, FSO systems provide inherent security, do not cause interference to other links, and their operation is license free. These properties have made FSO systems an attractive option for satellite, drone/balloon, and terrestrial communications. Nevertheless, FSO systems face several challenges such as their susceptibility to atmospheric turbulence, pointing errors, and high attenuation in adverse weather conditions. Over the past years, suitable countermeasures have been developed to overcome these challenges including multiple-input multiple-output (MIMO) FSO systems and hybrid RF/FSO systems. However, the requirement of a line-of-sight (LoS) link between transmitter and receiver, which is a fundamental disadvantage of terrestrial FSO systems, cannot be overcome with these techniques. To address this challenge, in this project, we will investigate the use of optical intelligent reflecting surfaces (IRSs) to mitigate the LoS limitation of FSO systems. For an in-depth evaluation of the benefits and limitations of optical IRS, we combine communication-theoretical modeling and transmission design with experimental investigation and verification of different IRS hardware options. The specific goals of the proposed project include: 1) Development of communication-theoretical models for FSO systems employing mirrors, mirror arrays, micro-phase-shifter arrays, and meta-surfaces as optical IRS. 2) Design of IRS-assisted FSO systems including methods for dispersion mitigation, exploiting IRS to support multiple links, and optimizing MIMO FSO systems. 3) Modeling, simulation, and experimental evaluation of the optical properties of different IRS concepts including beam direction, diffraction phenomena, signal distortion, and beam parameters. 4) Demonstration of an end-to-end IRS-assisted FSO system and experimentally based verification and refinement of the proposed theoretical models and designs. To achieve these goals, we have assembled a team with significant experience in communication-theoretical modelling, analysis, and design of FSO systems as well as in hardware design and experimental evaluation of optical communication systems. The expected outcomes of this project include experimentally verified analytical models and design options for IRS-assisted FSO systems as well as a flexible testbed for optical IRS.

• DFG Programme: Research Grants