Physics-Based Modeling and Scalable Optimization of Large Intelligent Reflecting Surfaces
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In this paper, a physics-based model and a scalable optimization framework for large RISs were developed to optimize a large number of sub-wavelength RIS elements for online transmission.Abstract:
Intelligent reflecting surfaces (IRSs) have the potential to transform wireless communication channels into smart reconfigurable propagation environments. To realize this new paradigm, the passive IRSs have to be large, especially for communication in far-field scenarios, so that they can compensate for the large end-to-end path-loss, which is caused by the multiplication of the individual path-losses of the transmitter-to-IRS and IRS-to-receiver channels. However, optimizing a large number of sub-wavelength IRS elements imposes a significant challenge for online transmission. To address this issue, in this article, we develop a physics-based model and a scalable optimization framework for large IRSs. The basic idea is to partition the IRS unit cells into several subsets, referred to as tiles, model the impact of each tile on the wireless channel, and then optimize each tile in two stages, namely an offline design stage and an online optimization stage. For physics-based modeling, we borrow concepts from the radar literature, model each tile as an anomalous reflector, and derive its impact on the wireless channel for a given phase shift by solving the corresponding integral equations for the electric and magnetic vector fields. In the offline design stage, the IRS unit cells of each tile are jointly designed for the support of different transmission modes, where each transmission mode effectively corresponds to a given configuration of the phase shifts that the unit cells of the tile apply to an impinging electromagnetic wave. In the online optimization stage, the best transmission mode of each tile is selected such that a desired quality-of-service (QoS) criterion is maximized. We consider an exemplary downlink system and study the minimization of the base station (BS) transmit power subject to QoS constraints for the users. Since the resulting mixed-integer programming problem for joint optimization of the BS beamforming vectors and the tile transmission modes is non-convex, we derive two efficient suboptimal solutions, which are based on alternating optimization and a greedy approach, respectively. We show that the proposed modeling and optimization framework can be used to efficiently optimize large IRSs comprising thousands of unit cells.read more
Citations
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References
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Journal ArticleDOI
Intelligent Reflecting Surface Enhanced Wireless Network via Joint Active and Passive Beamforming
Qingqing Wu,Rui Zhang +1 more
TL;DR: Simulation results demonstrate that an IRS-aided single-cell wireless system can achieve the same rate performance as a benchmark massive MIMO system without using IRS, but with significantly reduced active antennas/RF chains.
Journal ArticleDOI
Channel Estimation and Hybrid Precoding for Millimeter Wave Cellular Systems
TL;DR: An adaptive algorithm to estimate the mmWave channel parameters that exploits the poor scattering nature of the channel is developed and a new hybrid analog/digital precoding algorithm is proposed that overcomes the hardware constraints on the analog-only beamforming, and approaches the performance of digital solutions.
Journal ArticleDOI
Convergence of a block coordinate descent method for nondifferentiable minimization
TL;DR: In this article, the convergence properties of a block coordinate descent method applied to minimize a non-convex function f(x1,.., x 2, N 3 ) with certain separability and regularity properties were studied.
Journal ArticleDOI
Reconfigurable Intelligent Surfaces for Energy Efficiency in Wireless Communication
TL;DR: In this article, the authors developed energy-efficient designs for both the transmit power allocation and the phase shifts of the surface reflecting elements subject to individual link budget guarantees for the mobile users.
Journal ArticleDOI
Smart radio environments empowered by reconfigurable AI meta-surfaces: an idea whose time has come
Marco Di Renzo,Merouane Debbah,Dinh-Thuy Phan-Huy,Alessio Zappone,Mohamed-Slim Alouini,Chau Yuen,Vincenzo Sciancalepore,George C. Alexandropoulos,Jakob Hoydis,Haris Gacanin,Julien de Rosny,Ahcène Bounceur,Geoffroy Lerosey,Mathias Fink +13 more
TL;DR: This paper overviews the current research efforts on smart radio environments, the enabling technologies to realize them in practice, the need of new communication-theoretic models for their analysis and design, and the long-term and open research issues to be solved towards their massive deployment.
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