Design and optimization of reconfigurable intelligent surfaces for enhanced wireless communication systems

Lin, Xinyi (2024) Design and optimization of reconfigurable intelligent surfaces for enhanced wireless communication systems. PhD thesis, University of Glasgow.

Abstract

Reconfigurable intelligent surface (RIS) has been identified as a promising disruptive innovation to realize a faster, safer and more efficient communication system in the coming 6th generation (6G) era. The RIS is a meta-material composed surface comprising a large number of passive scattering unit cell (UC) elements. Each element independently controls incident signals by dynamically adjusting their amplitude and/or phase shifts. The reflected signals from all elements are coherently combined and directed towards specified directions, enabling selective electromagnetic (EM) properties. By densely deploying RISs and intelligently coordinating them within wireless propagation environments, it is possible to achieve reconfigurable and programmable end-to-end wireless channels. This innovation has the significant potential to revolutionize wireless communication by enhancing signal quality, coverage, and capacity in a cost-effective and energy-efficient manner.

This thesis aims to systematically study the design of RIS to address potential challenges in its practical deployment for wireless communication enhancement. An overview of basic technologies that may be encountered in RIS-assisted systems has been first studied. To address the inaccurate and complex channel estimation and ensure sufficient and stable power gain, a RIS-aided broadbeam design is then proposed. The design proposed in this thesis will mainly include the RIS beamforming design of generating single and multiple flat beams to cover any arbitrary sector regions. Meanwhile, the thesis also tends to define cooperation modes of base stations (BSs) concerning whether they reach an agreement on collaboratively utilising RISs and sharing resources. The resource allocation scheme between cooperative and non-cooperative BSs will be investigated. Lastly, the thesis also aims to design a RIS codebook in the wideband system leveraging the beam squint effect. The design of a codebook can largely reduce computational complexity.

To conclude, the work presented in this thesis provides insight into the design of RIS for broadbeam design, which can be viewed as an initial step towards achieving channel estimation. The investigation of non-cooperative BSs and the design of RIS codebooks also provide guidance for further theoretical study and practical implementation of RIS for enhancing wireless communication systems.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Supported by funding from the Engineering and Physical Sciences Research Council (EPSRC).
• Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering
• Colleges/Schools: College of Science and Engineering > School of Engineering
• Funder's Name: Engineering and Physical Sciences Research Council (EPSRC)
• Supervisor's Name: Imran, Professor Muhammad, Zhang, Professor Lei and Abbasi, Professor Qammer
• Date of Award: 2024
• Depositing User: Theses Team
• Unique ID: glathesis:2024-84531
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 02 Sep 2024 12:11
• Last Modified: 02 Sep 2024 12:12
• Thesis DOI: 10.5525/gla.thesis.84531
• URI: https://theses.gla.ac.uk/id/eprint/84531

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