Abstract-A closed room environment is viewed as a lossy cavity, characterized by possibly a line of sight (LOS) component and diffuse scattering parts from walls and internal obstacles. A theory used in acoustics and reverberation chambers is applied for the electromagnetics case, and main issues related to measurement systems, antennas characteristics, diffuse energy properties, and human exposure are investigated. The goal of this paper aims first towards validation of the assessment of the reverberation time in an environment using a virtual MIMO channel system. Secondly, the reverberation time in an adjacent room is investigated and hence a measurement-based method is readily developed to assess the absorption cross section and the whole-body specific absorption rate of humans at 2.3 GHz in a realistic closed environment.

For the first time, response of personal exposimeters (PEMs) is studied under diffuse field exposure in indoor environments. To this aim, both numerical simulations, using finite-difference timedomain method, and calibration measurements were performed in the range of 880-5875 MHz covering 10 frequency bands in Belgium. Two PEMs were mounted on the body of a human male subject and calibrated on-body in an anechoic chamber (non-diffuse) and a reverberation chamber (RC) (diffuse fields). This was motivated by the fact that electromagnetic waves in indoor environments have both specular and diffuse components. Both calibrations show that PEMs underestimate actual incident electromagnetic fields. This can be compensated by using an on-body response. Moreover, it is shown that these responses are different in anechoic chamber and RC. Therefore, it is advised to use an on-body calibration in an RC in future indoor PEM measurements where diffuse fields are present. Using the response averaged over two PEMs reduced measurement uncertainty compared to single PEMs. Following the calibration, measurements in a realistic indoor environment were done for wireless fidelity (WiFi-5G) band. Measured power density values are maximally 8.9 mW/m 2 and 165.8 mW/m 2 on average. These satisfy reference levels issued by the International Commission on Non-Ionizing Radiation Protection in 1998. Power density values obtained by applying on-body calibration in RC are higher than values obtained from no body calibration (only PEMs) and on-body calibration in anechoic room, by factors of 7.55 and 2.21, respectively. Bioelectromagnetics. 2016;9999:XX-XX.

Abstract-The electromagnetic reverberation time characteristics of indoor environments are experimentally investigated from 2 to 10 GHz with bandwidths up to 900 MHz. At a given frequency, the reverberation time is observed to be approximately constant up to 900 MHz. Moreover, the reverberation time decreases for increasing frequencies. Based on the theory of electromagnetic fields in cavities, a model to predict the room quality factor, reverberation time value, and average absorption coefficient is developed for the first time in indoor environments for the investigated frequency range. The validity and robustness of the model is investigated with data obtained for various environments, central frequencies, and bandwidths. The model is applied to another room over the whole 2-10 GHz frequency band and a maximum and average relative error of 22.30% and 8.80% were obtained, respectively, with an rms error of 1.90 ns. Furthermore, good agreement is obtained with measurements reported in the literature with settings falling into the model range; scenarios for which relative errors smaller than 10% were computed. The results demonstrate that this approach is not only an accurate alternative to the reverberation time measurements and computations of indoor environments in the 2-10 GHz frequency range but also a viable route to link propagation mechanisms in indoor scenarios with reverberation chambers.

An experimental method accounting the Line-Of-sight (LOS) component and the diffuse multipath components (DMC) to assess the whole-body specific absorption rate ( wb SAR ) in a complex indoor environment was previously proposed; we validate it now by numerical simulations with the Finite-Difference Time-Domain (FDTD) method. Results show good agreement between measurements and computation at 2.8 GHz for the considered scenarios.

Abstract-An original experimental protocol is developed to assess the whole-body absorption cross section of objects with arbitrary shapes and materials in diffuse fields at any operating frequency. This approach is important for dosimetry specifically in realistic environments wherein diffuse fields can be prominent. For this application, the knowledge of the whole-body specific absorption rate is critical and can be determined from the human whole-body absorption cross section. The whole-body absorption cross section is obtained from measurements performed in a stirred-mode reverberating chamber processed with the high-resolution parameter estimator RiMAX. To validate the proposed approach and highlight its robustness, the whole-body absorption cross section of a cylindrical phantom is experimentally and numerically determined at 1800 MHz. For both methods, the whole-body absorption cross section is shown to be independent on the orientation of the transceivers, indicating that it is indeed caused by diffuse fields. A good agreement is obtained between experimental and numerical Finite-Difference Time-Domain (FDTD) results with a relative deviation of about 17 %. From the validation of this approach, the measurement protocol is applied to a real human at 1800 MHz resulting in a whole-body absorption cross section of 0.95 m 2 , 1.01 m 2 and 1.11 m 2 for a sitting, standing, and standing with stretched arms posture, respectively.

Abstract-This paper presents the channel characterization of indoor environments in the E-Band (80.5-86.5 GHz). Measurements were performed by means of mechanical steering of directive antennas at both the transmitter and receiver side, allowing a double-directional angular characterization. Specular components have been estimated by means of a detection algorithm. Characterization of the path loss, delay spread, Angle-ofDeparture and Angle-of-Arrival spreads are presented for two indoor environments.

Abstract-We present a room electromagnetics based theory which primarily models the Diffuse Multipath Components (DMC) power density with a simple circuit model, and afterwards includes the Line-Of-Sight (LOS) component to predict the total exposure in a realistic environment. Given a human absorption cross section (ACS) and its location from a transmitter (Tx), the whole-body absorption rate (SAR wb ) can be determined by the proposed circuit model for Ultra Wide Band (UWB) and Wireless Local Area Network (WLAN) systems. The SAR wb in humans in a realistic office environment for both UWB and WLAN systems is investigated as part of application. The theory is simulated with the Advanced Design System (ADS) software, and excellent agreement between theoretical and simulated values are obtained in terms of relative errors (<2%). The model may be very useful for SAR wb prediction in realistic complex indoor environments.

This paper analyzes the frequency dependency of the radio propagation channel's root mean square (rms) delay spread (DS), based on the multi-frequency measurement campaigns in the mmMAGIC project. The campaigns cover indoor, outdoor, and outdoor-to-indoor (O2I) scenarios and a wide frequency range from 2 to 86 GHz. Several requirements have been identified that define the parameters which need to be aligned in order to make a reasonable comparison among the different channel sounders employed for this study. A new modelling approach enabling the evaluation of the statistical significance of the model parameters from different measurements and the establishment of a unified model is proposed. After careful analysis, the conclusion is that any frequency trend of the DS is small considering its confidence intervals. There is statistically significant difference from the 3GPP New Radio (NR) model TR 38.901, except for the O2I scenario.