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Of particular interest within fifth generation (5G) cellular networks are the typical levels of radiofrequency (RF) electromagnetic fields (EMFs) emitted by 'small cells', low-power base stations, which are installed such that both workers and members of the general public can come in close proximity with them. In this study, RF-EMF measurements were performed near two 5G New Radio (NR) base stations, one with an Advanced Antenna System (AAS) capable of beamforming and the other a traditional microcell. At various positions near the base stations, with distances ranging between 0.5 m and 100 m, both the worst-case and time-averaged field levels under maximized downlink traffic load were assessed. Moreover, from these measurements, estimates were made of the typical exposures for various cases involving users and non-users. Comparison to the maximum permissible exposure limits issued by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) resulted in maximum exposure ratios of 0.15 (occupational, at 0.5 m) and 0.68 (general public, at 1.3 m). The exposure of non-users was potentially much lower, depending on the activity of other users serviced by the base station and its beamforming capabilities: 5 to 30 times lower in the case of an AAS base station compared to barely lower to 30 times lower for a traditional antenna. [ABSTRACT FROM AUTHOR]

Radio frequency identification (RFID) technology attracts extensive attention for industrial applications, especially supply chain businesses and inventory management. In this article, a passive RFID localization scheme based on unmanned aerial vehicles (UAVs) or drones is established for inventory management in warehouses. In case of the major challenge of the on-board antenna tracking errors in practical scenarios, the state-of-the-art (SOTA) numerical methods rely on accurate antenna positions, such as synthetic aperture radar (SAR)-based algorithms, which will introduce large positioning errors and become unreliable. To this end, we propose a new relative RFID localization method based on phase, received signal strength indicator (RSSI), and readability, which is little affected by antenna tracking errors. In the proposed method, the tagged items on the racks are located laterally through pinpointing the minimum of the unwrapped phases, which have been unwrapped based on the hybrid random forest (RF) model. RSSI differences and the read count of each patch antenna’s beam are utilized to distinguish the rack level of tagged assets via a boosting tree classifier. The experimental results in a real warehouse show that the proposed method achieves 27.1-cm mean lateral positioning accuracy and orders the tagged items horizontally and vertically with more than 96.7% and 98.0% accuracy, respectively. [ABSTRACT FROM AUTHOR]

This paper analyses the experimentally-assessed dual-polarized (DP) mobile channel in a tunnel environment at 1.35 GHz under traffic conditions. We investigate the impact of antenna polarization and radiation pattern on the non-stationary vehicle-to-infrastructure (V2I) channel. Basic channel evaluation metrics are examined including path gain, co-polarization ratio (CPR), and cross-polarization discrimination (XPD). In addition, the stationarity region is estimated using the channel correlation function approach, and used to calculate the time-varying delay and Doppler power profiles. Statistical models are presented for parameters like CPR, XPD, RMS delay and Doppler spreads, where the lognormal distribution provides the best fit. The polarization and the opening angle of the antennas into the propagation channel are found to strongly influence the observed non-stationarity of the channel. They impact the degree of multipath richness that is captured, thus providing different path gain, delay and Doppler spreads. Based on our analysis, the directional antenna with vertical polarization provides the longest stationarity time of 400 ms at 90 km/h, as well as the highest path gain and lowest dispersion. Furthermore, the DP channel capacity is calculated and its dependence on different normalization approaches is investigated. We propose a more accurate normalization for the DP channels that takes the conservation of energy into account. Moreover, the subchannels correlation coefficients are determined. While the condition number is found to be low on average, the correlation results show high correlation among the DP subchannels. As conclusion, we show how the CPR and XPD play the main role in providing multiplexing gain for DP tunnel channels. [ABSTRACT FROM AUTHOR]

This paper introduces a novel formalism to improve the performance of an off-body system by deploying multiple ultra wideband (UWB) antennas, positioned strategically on the body. A methodology is presented for determining the optimal positions of UWB antennas on the body, necessary to provide a reliable multiband orthogonal frequency division multiplexing (MB-OFDM) UWB diversity antenna system operating in the Federal Communications Commission frequency band between 3.1 and 10.6 GHz. By evaluating the diversity metric, using simulation and measurement data, it is shown that the performance of such a system is stable throughout the entire investigated frequency band for both indoor and outdoor environments. There is a good agreement between the simulated and measured diversity values with a deviation of less than 9%. Therefore, the proposed technique optimizes the antennas’ positions for maximum diversity performance within a very broad frequency band, independent of the used wireless communication standard. Thus, the obtained diversity system might be used in any kind of wireless communication link within that frequency band, e.g., UWB-OFDM, UWB MB-OFDM, UWB, or even narrowband transmission. [ABSTRACT FROM PUBLISHER]

In this paper, we investigate multilayered lossy and heterogeneous media for wireless body area networks (WBAN) to develop a simple, fast and efficient analytical in-to-out body path loss (PL) model at 2.45 GHz and, thus, avoid time-consuming simulations. The PL model is an antenna-independent model and is validated with simulations in layered medium, as well as in a 3D human model using electromagnetic solvers. [ABSTRACT FROM AUTHOR]

This work presents an analysis of dense multipath components (DMC) in an industrial workshop. Radio channel sounding was performed with a vector network analyzer and virtual antenna arrays. The specular and dense multipath components were estimated with the RiMAX algorithm. The DMC covariance structure of the RiMAX data model was validated. Two DMC parameters were studied: the distribution of radio channel power between specular and dense multipath, and the DMC reverberation time. The DMC power accounted for 23% to 70% of the total channel power. A significant difference between DMC powers in line-of-sight and nonline-of-sight was observed, which can be largely attributed to the power of the line-of-sight multipath component. In agreement with room electromagnetics theory, the DMC reverberation time was found to be nearly constant. Overall, DMC in the industrial workshop is more important than in office environments: it occupies a fraction of the total channel power that is 4% to 13% larger. The industrial environment absorbs on average 29% of the electromagnetic energy compared to 45%–51% for office environments in literature: this results in a larger reverberation time in the former environment. These findings are explained by the highly cluttered and metallic nature of the workshop. [ABSTRACT FROM PUBLISHER]

Occupational exposure to non-ionising electromagnetic radiation emitted by train protection (TP) systems operating at ∼27 MHz is investigated in situ. In total, five TP systems of two different types, i.e. KVB (Contrôle de Vitesse par Balises) and TBL1+ (Transmission Balise-Locomotive), are considered. For each type, the boundaries outside which the field levels are in compliance with the International Commission on Non-Ionizing Radiation Protection guidelines for occupational exposure (‘compliance boundaries’) are determined. Maximal fields of 4.7 A m−1 and 0.2 kV m−1 for KVB, and 51 A m−1 and 1.5 kV m−1 for TBL1+ are measured, at distances between 10 and 25 cm from the respective antennas. Compliance boundaries for occupational exposure are maximally 0.6 m for KVB to 1 m for TBL1+, while no specific compliance boundary is needed for the general public. [ABSTRACT FROM AUTHOR]

In this paper, the transmission between two small antenna coils for wireless body area networks (WBANs) operated at 10.8 MHz is characterized in free space and near a phantom filled with water. In order to investigate the influence of the flat conducting medium, measurements are performed at different separations between the coils and at different heights above the medium. The voltage ratio |V2/V1| of the received voltage to the input voltage is studied as a function of the distance between the coils. Also, the influence of the medium and the height of the coils above the medium is determined. Transmission models are derived for the voltage ratio in free space and near the flat conducting medium, and a physical explanation is given. The measurements and models agree very well. Circuit equivalent models representing the physical transmission between coupled coils are proposed. The measurement results are compared with simulations of the presented circuit model and excellent agreement is obtained. [ABSTRACT FROM AUTHOR]

In this paper, the scattering parameters of two dipoles placed closely to a flat, homogeneous, biological tissue are characterized in the 2.4-GHz band. The impact of the presence of a flat phantom and of the height of a dipole above the phantom on the reflection coefficient is analyzed through measurements and simulations. The effect of the type of tissue on the reflection coefficient is also investigated by performing simulations for a range of relative permittivity and conductivity combinations spanning the whole range of human tissues at 2.4 GHz. A semiempirical path loss model, validated by measurements and simulations, is presented for wireless communication, for antenna heights from 2 mm up to 5 cm and antenna separations from 10 to 50 cm. Also, the influence of the relative permittivity and conductivity on the path loss is modeled, leading to a range of possible values and lower and upper boundaries for the path loss as a function of the antenna height. The combination of the range with the boundaries results in a best-case and worst-case path loss model for wireless body area networks. The models are validated with measurements on the torso of a human. [ABSTRACT FROM AUTHOR]

A correction factor dependent upon frequency, type of phantom, and incident polarization, which should be applied to the measured specific absorption rate is proposed for homogeneous phantoms. It is shown for an application of occupational exposure in the neighborhood of a base station antenna that this correction factor not underestimates realistic exposure of workers. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 652–655, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22249 [ABSTRACT FROM AUTHOR]

The disturbance caused by a measurement probe close to a ground plane is characterized. A trade-off must be made between disturbance and sensitivity. An optimal probe for electromagnetic exposure measurements above a ground plane in the neighborhood of a base station antenna is selected. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1610–1613, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21694 [ABSTRACT FROM AUTHOR]

A low-cost measurement method for the extraction of the relative phases of the field of base station and broadcast antennas is presented. Our purpose is to determine the polarization of the field at a measurement site using magnitude measurements only. By determining six amplitude components using a spectrum analyzer, the polarization ellipse of the field can be obtained. This low-cost method can be used for outdoor measurements, which is not possible with network analyzers. Using this method and thus knowing the polarization of the incident field we are able to determine more accurately the actual electromagnetic power absorbed in people at a measurement site. [ABSTRACT FROM AUTHOR]