Intelligent reflecting surface (IRS) consisting of a plane including many passive components can control even-t signals and create a programmable wireless environment by reconfigurable passive components. Passive components are typically composed of electronic components such as positive intrinsic-negative (PIN) diodes, field effect transistors, and micro electromechanical system switches, whose inherent characteristics show without active circuitry. Given that intelligent reflecting surfaces can strengthen the property of wireless transmission channels by adjusting the phase of incident signals, we investigate a multi-input single-output smart home model for downlink multi-users in this paper. An alternating optimization (AO) algorithm is proposed to cope with the challenge of maximizing the weighted sum of objectives of multiple users. To increase the sum rate, the beamforming vector at the access point and the phase shift matrix at the IRS are jointly tuned. In perfect channel state information, the AO approach is employed to achieve the effect of user maximization. Typically, fractional programming is utilized to optimize the beamforming vector at AP, while the Riemannian conjugate gradient approach is used to design the phase shift at IRS. Compared with the baseline methods, our proposed method can significantly improve convergence of the system.

Multi-Device Rate Maximization for IRS-Based Smart Home

This study introduces a novel algorithm for precisely characterizing dielectric properties in clothing materials, which is crucial for wireless body area networks (WBANs) and 5G technology. Our hybrid technique combines the open-ended coaxial probe (CP) method with an enhanced two-transmission-line approach, enabling accurate measurement of complex permittivity from 0.5 to 20 GHz. Our method, augmented by the extended Jonscher model (EJM), significantly improves the dielectric property assessment, especially at low frequencies, where previous studies and conventional models are inadequate. EJM exhibits a power-law relationship for both the dielectric constant (DK) and loss factor (LF) with respect to frequency, a relationship validated by the Kramers–Kronig (KK) relation, which ensures a constant ratio between the real and imaginary parts of the electric susceptibility across frequencies. Importantly, our research clarifies the previously debated behavior of LF within the 0.5–6-GHz range, demonstrating that the LF decreases as frequency increases. This study represents a significant advancement in antenna engineering and wearable technology.

Enhancing Dielectric Characterization of Clothing Materials: An Extended Jonscher Model Supported by the Kramers-Kronig Relations

This paper presents a hybrid method for determination of continuous dielectric properties of clothing materials. The dielectric constant and loss tangent of three types of materials are firstly investigated using open-ended coaxial probe from 0.5 to 20 GHz. The average measured values are input into the CST simulation of two CPW lines to obtain the two-port S-parameters. Finally, more reasonable yet reliable results are obtained by using two retrieval algorithms (TRACE and ABCD) for validation and comparative purposes. 

Determination of Continuous Dielectric Properties of Clothing Materials Using Hybrid Method

This paper presents a modified two-line method for determination of continuous dielectric properties of unknown dielectric materials at a frequency range of 0.5 to 20 GHz. The dielectric constant and loss tangent of three types of different-thick dielectric materials: (i) Microfiber (ii) FR4-like substrate, (ii) non-stretch denim are investigated. The results have demonstrated that the initial values can be arbitrary, and accurate broadband properties can be obtained by using the modified retrieval algorithms based on the TRACE algorithm. Finally, the reliable and convergent results can be obtained after a few iterative simulations.

A Modified Two-Line Method for Determining Dielectric Properties of Unknown Materials

Due to the broadcast nature of multi-hop channels, the information security of intelligent reflecting surface (IRS) assisted wireless communication remains an open issue to be resolved, which is even more urgently in the case that the passive eavesdropper is directly linked with the transmitter of a single-input single-output (SISO) transmission system. To deal with this, in this paper, we propose a transmitter perturbation injection and IRS reflection based physical-layer security scheme, such that the secure transmission of wireless SISO can be guaranteed comprehensively no matter the reflection based jamming from IRS to the eavesdropper is blocked or not. Upon considering this, two different eavesdropping scenarios, which are referred to as the ideal and worst eavesdropping, are considered and investigated. In addition, we propose element-wise and group-wise phase-alignment based reflection strategies respectively, so as to attain different trade-offs between the achievable performance and implementation complexity. In order to evaluate the achievable performance limits, we analyze the ergodic secrecy rate (ESR) of the proposed system. Simulation and numerical results verify the accuracy of performance evaluations. Finally, the effectiveness of our proposed secure transmission scheme is demonstrated by comparing the ESR performance achievable by it with that by the random-phase reflection based counterpart. 

IRS-Enabled Physical Layer Secure Transmission

In recent years, reconfigurable intelligent surface (RIS) technologies have been proposed due to its ability in shaping propagation environment for future 6G network development. Existing RIS technologies mainly include the active reconfigurable intelligent surface (ARIS) and the passive reconfigurable intelligent surface (PRIS). In this paper, according to the characteristics of RIS and demands of lower costs, we present a new strategy on the cross-deployment of ARIS and PRIS that meets the beneficial maximization in both capital cost and running cost.

Cross Deployment of Active and Passive Reconfigurable Intelligent Surfaces (RISs) for Next-Generation Communications

This paper presents a new performance metric of filtering antennas known as radiation suppression index (RSI). Researchers often use the term “high selectivity” when reporting filtering antenna designs, however, it is a descriptive term. High selectivity cannot quantify the radiation roll-off and thus, no comparison can be made with other designs. A metric of RSI based on radiation efficiency is proposed here through a design of dual-polarized filtering magnetoelectric dipole antenna. The purpose is to promote a measurement standard for RSI in such a way that the radiation roll-off rates can be (i) gauged, and (ii) compared between filtering antennas.

Radiation Suppression Index of Filtering Antennas

A broadband dielectric characterization of textile fabrics for clothing antenna designs is presented in this paper. The dielectric properties of four types of textile fabrics were investigated, where the measurements of complex permittivity were undertaken from 0.5 to 20 GHz. Frequency dispersion of these properties were also examined with standard deviations.

Broadband Dielectric Characterization of Textile Materials for Clothing Antenna Applications

A broadband $\boldsymbol{(0.5\sim 20 \text{GHz})}$ dielectric characteri-zation of textile materials for clothing antennas is presented in this paper. The dielectric properties of four types of textile fabrics were investigated, where the measurements of complex permittivity were undertaken using open-ended coaxial probe. Frequency dispersion of these properties over 20 GHz were studied with standard deviations.

Measurement of Broadband Dielectric Properties of Textile Fabrics for Clothing Antennas

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Papers

Cross Deployment of Active and Passive Reconfigurable Intelligent Surfaces (RISs) for Next-Generation Communications

Radiation Suppression Index of Filtering Antennas

Broadband Dielectric Characterization of Textile Materials for Clothing Antenna Applications

Measurement of Broadband Dielectric Properties of Textile Fabrics for Clothing Antennas