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Performance Improvement of Wireless Communication Using Reconfigurable Intelligent Surfaces

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Thesis embargoed until 29th April 2026(33.79 MB)

Date

2024

Authors

Farashahi, Mohammadreza

Supervisor

Seet, Boon-Chong
Li, Jack

Item type

Thesis

Degree name

Doctor of Philosophy

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Publisher

Auckland University of Technology

Abstract

Wireless communication systems are rapidly evolving to meet the ever-increasing demands for enhanced capacity and ubiquitous connectivity. As we progress towards Sixth-Generation networks, novel technologies are essential to overcome the limitations of traditional communication paradigms. Reconfigurable Intelligent Surfaces (RISs) have emerged as a promising solution, offering a wide range of applications to improve signal quality, extend coverage, and mitigate interference in wireless environments. These metasurface-based structures can dynamically manipulate electromagnetic waves, providing unprecedented control over the propagation environment. This thesis focuses on three critical aspects of RIS technology: (i) unit cell design; (ii) phase distribution optimization; and (iii) propagation modeling using ray tracing (RT) techniques. The thesis begins with a comprehensive literature review of state-of-the-art RIS structures, followed by an examination of optimization approaches for RIS-based communications. Additionally, a thorough review of RT-based propagation modeling platforms and methods for wireless communication systems, including those involving RIS structures, is presented. Following the literature review, the thesis delves into a detailed RIS design procedure, proposing a novel, dual-polarized RIS unit cell with an operating center frequency of 5.2 GHz. The study then presents an efficient optimization method for space-time-coding RIS structures, followed by the optimization of the proposed RIS's phase distribution based on the transmission power of two antennas interacting with the RIS, utilizing a genetic algorithm. Finally, the focus shifts to RT-based propagation modeling of RIS-assisted wireless communications, proposing a novel approximation method for simulation speed enhancement. This is complemented by the introduction of a comprehensive simulation platform, WiPy-RT, developed entirely in Python. This study makes a concerted effort to examine RIS technology from multiple perspectives, encompassing both hardware and system development. By addressing the challenges in RIS design, optimization, and propagation modeling, this thesis contributes to the advancement of RIS-assisted wireless communications. The proposed methods and tools provide valuable insights for researchers and engineers working towards the realization of efficient and reliable RIS-enhanced wireless networks, paving the way for future innovations in this rapidly evolving field.

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http://hdl.handle.net/10292/19124

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