On the Aperture Efficiency of Intelligent Reflecting Surfaces

Chou, Shih-Kai; Yurduseven, Okan; Ngo, Hien Quoc; Matthaiou, Michail

doi:10.1109/lwc.2020.3039483

Cited by 12 publications

(6 citation statements)

References 14 publications

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“…In the far-field D r D F , the first-order Taylor expansion (1 + x) a ≈ 1 + ax can be applied to (18), while ignoring the quadratic terms (nd x ) 2 /D 2 r and (md y ) 2 /D 2 r . This yields…”

Section: Far-field Beamformingmentioning

confidence: 99%

“…Consequently, an IRS can provide an alternative communication link, in addition to LoS, where the Tx and Rx employ a smaller number of antennas to communicate with each other, hence saving energy. Note, though, that the suggested benefits are valid when: 1) the power expenditure of IRS elements is negligible compared to that of conventional phase shifters; 2) the Tx operates near the IRS in order to have a reasonable number of reflecting elements N ; and 3) reflection losses are small [18].…”

Section: A Energy Efficiencymentioning

confidence: 99%

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Intelligent Reflecting Surfaces at Terahertz Bands: Channel Modeling and Analysis

Dovelos

Assimonis

Ngo

et al. 2021

2021 IEEE International Conference on Communications Workshops (ICC Workshops)

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An intelligent reflecting surface (IRS) at terahertz (THz) bands is expected to have a massive number of reflecting elements to compensate for the severe propagation losses. However, as the IRS size grows, the conventional far-field assumption starts becoming invalid and the spherical wavefront of the radiated waves should be taken into account. In this work, we consider a spherical wave channel model and pursue a comprehensive study of IRS-aided multiple-input multiple-output (MIMO) in terms of power gain and energy efficiency (EE). Specifically, we first analyze the power gain under beamfocusing and beamforming, and show that the latter is suboptimal even for multiple meters away from the IRS. To this end, we derive an approximate, yet accurate, closed-form expression for the loss in the power gain under beamforming. Building on the derived model, we next show that an IRS can significantly improve the EE of MIMO when it operates in the radiating near-field and performs beamfocusing. Numerical results corroborate our analysis and provide novel insights into the design and performance of IRSassisted THz communication.

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Section: Far-field Beamformingmentioning

confidence: 99%

Section: A Energy Efficiencymentioning

confidence: 99%

Intelligent Reflecting Surfaces at Terahertz Bands: Channel Modeling and Analysis

Dovelos

Assimonis

Ngo

et al. 2021

2021 IEEE International Conference on Communications Workshops (ICC Workshops)

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“…Another feature is that RIS's HPBW will change with the incident angles. In addition, the aperture efficiency of RIS was studied in [84].…”

Section: G Hpbw and Aperture Efficiencymentioning

confidence: 99%

Reconfigurable Intelligent Surfaces: Channel Characterization and Modeling

et al. 2022

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Reconfigurable intelligent surfaces (RISs) are two dimensional (2D) metasurfaces which can intelligently manipulate electromagnetic waves by low-cost near passive reflecting elements. RIS is viewed as a potential key technology for the sixth generation (6G) wireless communication systems mainly due to its advantages in tuning wireless signals, thus smartly controlling propagation environments. In this paper, we aim at addressing channel characterization and modeling issues of RISassisted wireless communication systems. At first, the concept, principle, and potential applications of RIS are given. An overview of RIS based channel measurements and experiments is presented by classifying frequency bands, scenarios, system configurations, RIS constructions, experiment purposes, and channel observations. Then, RIS based channel characteristics are studied, including reflection and transmission, Doppler effect and multipath fading mitigation, channel reciprocity, channel hardening, rank improvement, far field and near field, etc. RIS based channel modeling works are investigated, including largescale path loss models and small-scale multipath fading models. At last, future research directions related to RIS-assisted channels are also discussed.Index Terms-6G wireless communications, reconfigurable intelligent surface (RIS), channel measurements, channel characteristics, channel modeling.

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“…The metamaterial concept also plays a fundamental role in building reflection based surfaces, particularly in the context of intelligent reflecting surfaces (IRS) [10,11,44]. An IRS consisting of ideal unit-cells is preferred (and often assumed) to have a uniform gain radiation mask within a coverage area along polar and azimuth (i.e., φ) directions [45][46][47].…”

Section: Fundamental Building Block Of Intelligent Reflecting Surfacesmentioning

confidence: 99%

Implementation of Resonant Electric Based Metamaterials for Electromagnetic Wave Manipulation at Microwave Frequencies

Assimonis

Chandravanshi

Yurduseven

et al. 2021

Sensors

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In this paper, we present the application of a resonant electric based metamaterial element and its two-dimensional metasurface implementation for a variety of emerging wireless applications. Metasurface apertures developed in this work are synthesized using sub-wavelength sampled resonant electric-based unit-cell structures and can achieve electromagnetic wave manipulation at microwave frequencies. The presented surfaces are implemented in a variety of forms, from absorption surfaces for energy harvesting and wireless power transfer to wave-chaotic surfaces for compressive sensing based single-pixel direction of arrival estimation and reflecting surfaces. It is shown that the resonant electric-synthesized metasurface concept offers a significant potential for these applications with high fidelity absorption, transmission and reflection characteristics within the microwave frequency spectrum.

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On the Aperture Efficiency of Intelligent Reflecting Surfaces

Cited by 12 publications

References 14 publications

Intelligent Reflecting Surfaces at Terahertz Bands: Channel Modeling and Analysis

Intelligent Reflecting Surfaces at Terahertz Bands: Channel Modeling and Analysis

Reconfigurable Intelligent Surfaces: Channel Characterization and Modeling

Implementation of Resonant Electric Based Metamaterials for Electromagnetic Wave Manipulation at Microwave Frequencies

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