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Reconfigurable intelligent surfaces (RISs) have attracted major attention in the last few years, due to their useful characteristics. An RIS is a nearly passive thin surface that can dynamically change the reradiated field and can therefore realize anomalous reflection, refraction, focalization, or other wave transformations for engineering the radio propagation environment or realizing novel surface-type antennas. Evaluating the performance and optimizing the deployment of RISs in wireless networks need physically consistent frameworks that account for the electromagnetic characteristics of dynamic metasurfaces. In this article, we introduce a general macroscopic model for evaluating the scattering from an RIS. The proposed method decomposes the wave reradiated from an RIS into multiple scattering contributions and is aimed at being embedded into ray-based models. Since state-of-the-art ray-based models can already efficiently simulate specular wave reflection, diffraction, and diffuse scattering but not anomalous reradiation, we enhance them with an approach based on Huygens’ principle and propose two possible implementations for it. Multiple reradiation modes can be modeled through the proposed approach using the power conservation principle. We validate the accuracy of the proposed model by benchmarking it against several case studies available in the literature, which are based on analytical models, full-wave simulations, and measurements. [ABSTRACT FROM AUTHOR]

The radiowave propagation through hollow clay brick walls, which are common in southern European construction, is analyzed. The brick walls have thicknesses of 11, 15, and 20 cm, common in both interior and exterior walls, and are bound with a portland cement, water, and sand mixture. For each brick dimension, three prototypes were assembled, varying in the type of wall finish, i.e., exposed brick, smooth painted plaster, and rough painted plaster. A 10 cm concrete wall was also included for comparison purposes. Penetration loss metrics were evaluated in an anechoic chamber at frequencies ranging from 680 MHz to 10 GHz. Results demonstrate that the brick wall internal heterogeneity, as well as the type of finish, significantly influences the propagation phenomena and thus the frequency response of the walls, with relatively high penetration losses observed at some relevant commercial frequency bands. Finally, an alternative brick design, with reduced penetration losses, is also proposed and evaluated under simulation environment only. [ABSTRACT FROM AUTHOR]

An experimental work aimed at assessing the outdoor-to-indoor propagation losses at 169 MHz is described in this paper. The building penetration loss, often considered as an additional constant value to be added to propagation losses in previous studies, is here on the contrary regarded as a random variable; its cumulative distribution is extracted from the measured data and is found to be approximately Gaussian. Moreover, in order to account for the critical installation conditions which may be experienced by indoor wireless devices in particular applications (e.g., wireless smart metering), an additional loss term, here indicated as installation loss, is introduced and its value is investigated in some reference cases. The achieved results are also embedded into a statistical procedure similar to those commonly adopted for wireless cellular networks planning. [ABSTRACT FROM PUBLISHER]

This paper presents the large scale parameters of wideband multipath channels based on extensive measurement campaigns in various indoor environments. The measurements were conducted with a wideband multiple-input multiple-output (MIMO) channel sounder having a bandwidth of 400 MHz at 11 GHz which is a challenging frequency for future mobile systems. In particular, polarization characteristics of path-loss, shadowing, cross-polarization power ratio (XPR), delay spread and coherence bandwidth are characterized. The measurement results show that the path-loss exponents range between 2.0 and 3.0 for none-line-of-sight (NLoS), 0.36 and 1.5 for LoS, respectively. Vertically and horizontally polarized transmissions have almost same path-gain, but in some corridor-room NLoS environments, the path-loss for HH is significantly large. In most cases, the RMS delay spreads are less than 20 and 50 ns for NLoS and LoS, respectively, and the average coherence bandwidth is less than 30 MHz. The Rician K-factors range between 2 and 3 dB for cross-polarization, and in large Hall environments, those for co-polarization are greater than 6.0 dB with 10% probability. Finally, some dominant propagation mechanism and site-specific behaviors are illustrated using the double-directional measurement results. [ABSTRACT FROM AUTHOR]

The effects of carrier frequency, antenna height and season on a broadband wireless access (BWA) system deployed in a rural area at 825 MHz and 3535 MHz are studied in this paper. With the aid of digital terrain information, both large scale and small scale fading effects present in the rural channel are discussed. Our investigation found that the frequency dependence of a wireless channel varies strongly with the environment. Also, the effects of the antenna height in rural areas of irregular terrains vary with the available clearance above the clutters in the regions. This paper uses extensive measurement campaigns to quantify these effects in winter and spring using a BWA system (IEEE 802.16e) deployed in Hetzwege/Abbendorf, Germany. In the study of small scale fading, the variations of the fading distributions of the wireless channel due to season changes are derived and the corresponding multipath propagations are discussed in this paper. [ABSTRACT FROM PUBLISHER]

This paper proposes the deployment of frequency selective surfaces (FSS) in indoor wireless environments and investigates their effect on radio wave propagation. FSS can be deployed to selectively confine radio propagation in indoor areas, by artificially increasing the radio transmission loss naturally caused by building walls. FSS can also be used to channel radio signals into other areas of interest. Simulations and measurements have been carried out in order to verify the frequency selectivity of the FSS. Practical considerations regarding the deployment of FSS on building walls and the separation distance between the FSS and the supporting wall have been also investigated. Finally, a controlled, small-scale indoor environment has been constructed and measured in an anechoic chamber in order to practically verify this approach through the usage of ray tracing techniques. [ABSTRACT FROM AUTHOR]

Given the trend towards a user-centric concept in mobile communications, body area networks have received increasing attention within the wireless personal and body area networks community. In this paper, an experimental investigation is presented to derive suitable radio propagation models for ultra wideband (UWB) body-centric wireless communications. The performance of the body-centric UWB radio channel is investigated by considering several on-body links, including different body postures. System-level modeling of potential multiband orthogonal frequency-division multiplexed UWB system has been conducted and system performance is measured using bit error rate (BER) and signal-to-noise ratio. The conducted system analysis demonstrated that for 78% in the static case and 75% and 61% for stable and unstable transmitter locations in the pseudodynamic in-motion scenarios (respectively) of the specified on-body radio links, the BER is equal to or less than 0.1%. This demonstrates promising applications of the proposed UWB body-centric radio system. Based on these results, clear recommendations are given for best on-body locations leading to optimal system performance. [ABSTRACT FROM AUTHOR]

This paper describes a developed wideband millimeter-wave radio channel sounder, which is based on the previously developed 2- and 5-GHz channel-sounder concept. Performance is analyzed, and examples of measurements, analysis, and comparison to lower frequencies are given. The sounder enables wideband (3-dB bandwidth of 100 MHz) measurements with continuous phase and excellent link budged without a cable connection between the transmitter and the receiver. [ABSTRACT FROM AUTHOR]