Energy-efficient reconfigurable intelligent surfaces aided wireless information and power transfer.

Mohamed, Zina (2023). Energy-efficient reconfigurable intelligent surfaces aided wireless information and power transfer. Thèse. Québec, Doctorat en télécommunications, Université du Québec, Institut national de la recherche scientifique, 215 p.

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Résumé

Recently, reconfigurable intelligent surfaces (RIS) have attracted great attention from both industry and academia as a potential solution to path loss, shadowing, and multipath effects and a promising technology to enhance future network performances. RIS are planar arrays, consisting of nearly passive and low-cost reflecting elements, that control the propagation environment by reflecting the incident signal in a special direction by properly designing and adjusting the phase shift values of the reflecting elements. This dissertation aims to design a framework for RIS-aided wireless information and power transfer. We focus on assessing, designing, and enhancing the energy efficiency (EE) and reliability for different kinds of systems: wireless power transfer (WPT), wireless information transfer (WIT), and simultaneous wireless information and power transfer (SWIPT) systems. In particular, in the first part of this work, a cooperative RIS-aided WPT system with high efficiency is designed. As a starting point, we exploit the potential of cooperative energy beamforming, and we develop a design framework for a cooperative WPT system. Specifically, we focus on improving the efficiency of transmission by addressing the most important metrics characterizing the system’s performance, i.e., the WPT coverage probability and data transmission probability. The developed framework and design are then extended to the case of multiple RIS-aided WPT system. In the second part of this work, we focus on designing an energy-efficient RIS-aided WIT system for cell edge users. Particularly, we focus on designing the optimal solution in order to maximize the EE for two deployment scenarios: the single service or unicast and multiple services or the joint broadcast unicast. In the third part of this work, we focus on the design of the RIS-aided SWIPT system based on the null space. The main objective of this part is to achieve a balance between the harvested energy at energy receivers and the sum-rate of the information receivers. A framework to evaluate and optimize a multi-objective function taking into account the total harvested energy and the sum-rate, is proposed. Chapter 1 introduces the state of the art of the RIS technology focusing on comparisons with relaying technology, the optimization oriented works, channel estimation, RIS design and applica tions, and the limitations and challenges. On the other hand, the concept and the challenges of the wireless information and power transfer are also presented. The first part of this dissertation is about designing a cooperative RIS-aided WPT. In particu lar, stochastic geometry tools to model the Poisson point process (PPP) distributed network nodes (access points (APs), device, RIS) and to determine the closed-form expressions of the WPT cov erage probability and the data transmission probability for different types of devices are leveraged. The obtained expressions are a function of the extended generalized multivariate MeijerG function (EGMMGF). A new implementation of the EGMMGF is also presented. The proposed formulae in this part avoid most of the complexity and time-consumption issues already in the literature. The findings provide a guideline for deriving similar tractable formulas for different system models. The second part of this dissertation is about designing an energy-efficient RIS-aided WIT for the cell-edge users for two deployment scenarios: the single service (unicast) and multi-service (joint broadcast-unicast). In particular, a UAV equipped with RIS is leveraged to assist the downlink and uplink communication. The main objective is to maximize the EE of the cell-edge users by properly designing the active and passive beamforming matrices. Optimal solutions to solve the optimization problems are presented. Numerical results show that significant performance enhancements are achieved by the RIS-UAV compared to its counterpart but with standard relaying techniques and validate that the RIS-UAV can be leveraged to serve cell-edge users with high EE. Moreover, a framework design for joint unicast-broadcast downlink communication assisted with an aerial dual polarized RIS is proposed. Results show the superiority of leveraging polarization for the joint transmission of different kinds of traffic patterns. Unlike parts I and II which only deal with WPT or WIT, part III of this dissertation explores the SWIPT system. More specifically, a framework design for RIS-aided SWIPT based on the degree of freedom provided by the null space of the composite channel matrix between the AP and the information receivers is proposed to send additional energy signals. The main objective is to achieve a balance between the harvested energy at the energy receivers and the sum-rate of the information receivers. Based on the multi-objective optimization framework and the weighted Tchebycheff approach, the equivalent sum-rate maximization problem is formulated first. Then, an efficient two-layer algorithm is proposed to design the active information beamforming vectors at the AP and the passive beamforming matrix at the RIS. The results of this part are novel and highlight the importance of integrating RIS and exploiting the null space while designing SWIPT systems. Finally, chapter 9 concludes this dissertation and proposes future works.

Type de document:	Thèse Thèse
Directeur de mémoire/thèse:	Aïssa, Sonia
Mots-clés libres:	télécommunications
Centre:	Centre Énergie Matériaux Télécommunications
Date de dépôt:	31 août 2023 13:48
Dernière modification:	31 août 2023 13:48
URI:	https://espace.inrs.ca/id/eprint/13533

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