This paper presents an analysis of the depolarization effect in off-body channels, based on a previously developed geometry-based channel model for polarized communications with dynamic users. The model considers Line-of-Sight propagation and components reflected from scatterers distributed on cylinders centered around the user. A mobility model for wearable antennas based on Fourier series is employed to take the effects of user’s motion into account. The focus is on scattered signal components, where the impact of a scatter’s position, its material properties, and the influence of user dynamics on signal depolarization are investigated. It is observed that the wearable antenna motion has a strong impact on the channel’s polarization characteristics, particularly for dynamic on-body placements, such as arms and legs. If the antenna motion is neglected, the error in cross-polarization ratio is greater than 23dB compared to a static approach. The antenna rotation during motion is found to be the dominant factor, while the corresponding displacement can be neglected, with the error not exceeding 1dB. This result justifies the channel model simplification proposed in this paper.

This paper presents an empirical validation of a polarized channel model for off-body communications with dynamic users, based on wideband indoor measurements at 5.8 GHz with a 500 MHz bandwidth. The model is based on geometrical optics, and takes the signal depolarization and influence of user dynamics into account. By considering a scenario with the user walking towards an access point with co-located vertical and horizontal dipole antennas, the simulated receiver (Rx) power is compared against measurements for wearable antenna placements on the chest, wrist and lower leg. The obtained root mean square error is found to be within 2.8 dB for the vertical off-body antenna polarization, and within 3.2 dB for the horizontal one. Fairly matching Rx power values are obtained even when only free space propagation is considered in the simulator, with the error being below 3.4 dB in most cases.

This paper analyses the impact of the human body on antenna radiation characteristics, with a focus on the polarization aspect. The effect of the body tissues on a wrist-worn ultra-wideband double loop antenna radiation characteristics is investigated at 3, 4 and 5 GHz, based on numerical full-wave simulations complemented with a voxel model of a hand. Results show a strong influence of the body on the gain and polarization characteristics; the radiation in the direction towards the body is suppressed by 20 dB or more, and the antenna polarization changes from a linear to an elliptical one. By simulating an off-body communications scenario with the user walking at a fixed distance from the off-body antenna, up to 6.5 dB lower received power is obtained by using the wearable antenna radiation pattern simulated with the hand phantom, compared to the case when the antenna in free space.

– Several frequency bands and system architectures are proposed for 5G and beyond to meet the higher data rates for point-to-point communication and point-to-area coverage. In this paper, we present radio propagation studies and models developed in typical scenarios for massive antenna deployment and body area networks, in frequency bands below 6 GHz, building entry loss and clutter loss and vehicular communication, in the millimeter wave bands, and models in the Terahertz for 5G and beyond

This paper presents an off-body channel model for polarized communications with dynamic users. The model is based on Geometrical Optics and Uniform Theory of Diffraction and accounts for free space propagation, reflections, and diffractions. It allows for arbitrary antennas’ polarizations and gain patterns and supports a number of on-body antenna placements. In order to take the influence of users’ motion into account, a mobility model for wearable antennas on dynamic users is used. Signal depolarization mechanisms are identified, and simulations are performed to analyze the influence of user dynamics on the channel. The results show that significant polarization mismatch losses occur due to wearable antenna rotations, resulting in received power variations up to 37.5 dB for the line-of-sight component and 41.4 dB for the scattered one. The importance of taking signal polarization into account is demonstrated by comparing the simulation results between polarized and nonpolarized channel models in a free space propagation scenario, where a difference up to 53 dB in between the two is observed.

This paper presents the preliminary results of a dynamic off-body channel characterisation study, based on wide-band measurements at 5.8 GHz in an indoor environment. The Channel Impulse Response (CIR) was measured for a scenario with the user approaching and departing from the off-body antenna. A CIR deconvolution procedure was performed jointly in two polarisations, and the received signal power, Cross-Polarisation Discrimination (XPD), delay mean and standard deviation were calculated based on the estimated path delays and amplitudes. The statistical analysis is performed, and the obtained results show large variations of the CIR parameters. The XPD is observed to vary up to 21.3 dB.

– Several frequency bands and system architectures are proposed for 5G and beyond to meet the higher data rates for point-to-point communication and point-to-area coverage. In this paper, we present radio propagation studies and models developed in typical scenarios for massive antenna deployment and body area networks, in frequency bands below 6 GHz, building entry loss and clutter loss and vehicular communication, in the millimeter wave bands, and models in the Terahertz for 5G and beyond

This paper presents a simple model for body-shadowing in off-body and body-to-body channels. The model is based on a body shadowing pattern associated with the on-body antenna, represented by a cosine function whose amplitude parameter is calculated from measurements. This parameter, i.e the maximum body-shadowing loss, is found to be linearly dependent on distance. The model was evaluated against a set of off-body channel measurements at 2.45 GHz in an indoor office environment, showing a good fit. The coefficient of determination obtained for the linear model of the maximum body-shadowing loss is greater than 0.6 in all considered scenarios, being higher than 0.8 for the ones with a static user.

This paper presents a general empirical system loss model for estimating propagation loss in Body Area Networks in off-body communications at 2.45 GHz in a passenger ferry environment. The model is based on measurements, which were carried out in dynamic scenarios in the discotheque passenger ferry environment. The model consists of three components: mean system loss, attenuation resulting from the variable antenna position on the human body, and attenuation due to fading. Preliminary results for system loss components in dynamic scenarios in the discotheque environment are presented. The components of mean system loss and variable antenna position attenuation are modelled by using a linear regression. The obtained root mean square error for the mean system loss is lower than 5 dB. The fading components are modelled by Lognormal and Nakagami-OT distributions.

This paper presents a mobility model for the variations in position and orientation of wearable antennas on dynamic users, considering walking and running motions. Motion is represented as a composition of a linear forward movement plus a periodic component, modeled by a Fourier series with up to two harmonics. The model is simple, yet realistic, as Motion Capture (MoCap) data are used to calculate its parameters. It is suitable for use with a variety of propagation channel models, including deterministic ray-tracing and stochastic geometry-based ones, but can also allow for analytical inference in simplified scenarios. Considering an off-body communication scenario, simulations show that the proposed mobility model provides similar received power as the skeleton-based model with MoCap data, the maximum difference in the considered scenario being below 1 dB. A significant influence of user’s motion on the channel is observed for both free-space and multipath propagation, yielding received power variations up to 28 dB in the considered scenarios.

This paper presents an analysis of the polarisation characteristics for the channel in dynamic off-body communications, and an empirical channel model, based on measurements performed at 2.45 GHz in an office environment. Body presence and propagation conditions have a strong influence on signal depolarisation. The model assumes three components for the total path loss: mean path loss, represented by a log-distance function with a path loss exponent of 1.71, Lognormal-distributed shadowing fading, and Nakagami-distributed multipath fading. The Nakagami Distribution shows a trend towards the Rice one in the co-polarised and the Rayleigh one in the cross-polarised channels.

This paper presents an approach to the estimation of mean path loss model parameters in off-body Body Area Networks channels. In this approach, the path loss exponent is constrained to a value obtained from line-of-sight (LoS) propagation in the copolarised channel, considering a generalised static scenario. The proposed approach is compared to alternative ones, by evaluating the coefficient of determination for a set of measurements obtained in an indoor environment. Compared to a traditional approach, a relative improvement of up to 0.7 and typically above 0.4 is observed in the LoS case, while the goodness of fit is unchanged for the non-LoS case.