Reconfigurable intelligent surfaces: beamforming, modulation, and channel shaping
Author(s)
Zhao, Yang
Type
Thesis
Abstract
Reconfigurable Intelligent Surface (RIS) is one of the most promising physical-layer technology for 6G. It adopts numerous low-power scattering elements to customize the propagation environment for improved network performance, unlocking a new potential of channel design as never before. In this dissertation, we first provide an overview of its physical structure, characteristics, applications, and scattering models, then discuss how it addresses the key issues in Simultaneous Wireless Information and Power Transfer (SWIPT) and compare it with Backscatter Communication (BackCom) in terms of functionalities and preferences. The work chapters investigate three typical use cases of RIS: Joint design with transceiver for a specific performance measure (beamforming); ride its own information over legacy networks (modulation); and manipulate the inherent properties of the wireless environment as a stand-alone device (channel shaping).
RIS-aided SWIPT: We introduce RIS into multi-antenna, multi-carrier SWIPT systems, investigating joint waveform and beamforming design. Rate-Energy (R-E) region of practical receivers are characterized under non-linear harvester and frequency-flat RIS models.
RIScatter: This novel scatter protocol integrates RIS and BackCom from an input distribution perspective. The reflection pattern is exploited simultaneously for beamforming of the primary link and modulation of the backscatter link. We propose a practical cooperative receiver and characterize the achievable rate region.
Multiple-Input Multiple-Output (MIMO) channel shaping: We exploit an advanced Beyond-Diagonal (BD)-RIS architecture for singular value redistribution in Point-to- point Channel (PC) and leakage interference minimization in Interference Channel (IC). Their implications on joint RIS-transceiver designs are also discussed. We also propose an efficient and universal BD-RIS design framework.
RIS-aided SWIPT: We introduce RIS into multi-antenna, multi-carrier SWIPT systems, investigating joint waveform and beamforming design. Rate-Energy (R-E) region of practical receivers are characterized under non-linear harvester and frequency-flat RIS models.
RIScatter: This novel scatter protocol integrates RIS and BackCom from an input distribution perspective. The reflection pattern is exploited simultaneously for beamforming of the primary link and modulation of the backscatter link. We propose a practical cooperative receiver and characterize the achievable rate region.
Multiple-Input Multiple-Output (MIMO) channel shaping: We exploit an advanced Beyond-Diagonal (BD)-RIS architecture for singular value redistribution in Point-to- point Channel (PC) and leakage interference minimization in Interference Channel (IC). Their implications on joint RIS-transceiver designs are also discussed. We also propose an efficient and universal BD-RIS design framework.
Version
Open Access
Date Issued
2024-03-30
Date Awarded
01/06/2024
License URL
Advisor
Clerckx, Bruno
Publisher Department
Electrical and Electronic Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)