This paper investigates the second-order statistics of multipath fading channels with von Mises-Fisher (vMF) distributed scatters. Simple closed-form expressions for the mean Doppler shift and Doppler spread are derived as the key spectral moments that capture the impact of mobility and scattering characteristics on level crossings and fade durations. These expressions are then used to analyze the influence of vMF parameters on the Level-Crossing Rate (LCR) and Average Fade Duration (AFD). The results show that isotropic scattering yields the highest LCR and the lowest AFD, while fading dynamics reduce with the decreasing angular spread of scatterers. Moreover, mobile antenna motion parallel to the mean scattering direction results in a lower LCR than the perpendicular motion, with the difference between the two cases increasing with the higher concentration of scatterers.

In this article, an analysis of system loss and depolarization in body area networks (BANs) for body-to-infrastructure (B2I) communications based on a measurement campaign in the 5.8 GHz band in an indoor environment is performed. Measurements were performed with an off-body antenna transmitting linearly polarized signals and dual-polarized receiving antennas carried by the user on the body. A normal distribution with a mean of 2.0 dB and a standard deviation of 4.3 dB is found to be the best fit for modeling cross-polarization (XP) discrimination. The average correlation between the signals received by the orthogonally polarized antennas is below 0.5, showing that polarization diversity can be used. A model for the average value of the standard deviation of the XP discrimination ratio as a function of the transmitted polarization, the mobility of users, and the link dynamics is presented, together with a detailed description of the methodology being used.

In this paper, an analysis of depolarisation in Body Area Networks for Body-to-Infrastructure communications based on a measurement campaign in the 5.8 GHz band in an indoor environment is performed. Measurements were made with an offbody antenna transmitting linearly polarised signals and dualpolarised receiving antennas carried by the user on the body. A Normal Distribution with a mean of 2.0 dB and a standard deviation of 4.3 dB is found to be the best fit for modelling crosspolarisation discrimination. The average correlation between the signals received by the orthogonally polarised antennas is below 0.5, showing that polarisation diversity can be used. A model is proposed for the average value of the standard deviation of the cross-polarisation discrimination ratio as a function of the transmitted polarisation, the mobility of users and link dynamics.

This paper provides a comprehensive study on the learning models' power violation, sum-rate performance while taking into consideration power constraint, and computational efficiency in terms of training and execution times over a dynamic wireless channel. We propose a reward shaping method and modify learning models with the output scaling strategy to enforce them to fully respect the power constraints while optimizing the sum-rate performance. The proposed approach reaches close-to-optimal accuracy, i.e., up to 99.15%, while satisfying the predefined power constraint of the base station. Moreover, learning models are shown to be more computationally efficient compared to the traditional algorithm. However, solving the power allocation problem within the Orthogonal Frequency Division Multiplexing (OFDM) symbol duration of $16.7\mu \mathrm{s}$ is a remaining challenge.

This paper presents a comprehensive study on the efficiency and effectiveness of exploration policies for deep reinforcement (DRL) algorithms with applications to the power allocation problem in multi-carrier wireless systems. We propose three distinct exploration functions, i.e., linear, fast and slow, to balance exploration and exploitation in the dynamic wireless environment. We analyze the effect of exploration on the initial training length as well as learning models' sum-rate performance and power violation probabilities. Our results indicate that the DRL algorithms with the proposed exploration functions reach close-to-optimal sum-rate performance within only 1000 training episodes (i.e., equivalent to 8.01 s) while satisfying the predefined power constraint of the base station.

Hardware channel emulators are essential for developing and testing transceiver prototypes in laboratory settings. They should be able to monitor the dynamic motion of the mobile terminal. This paper presents a narrowband Multiple-Input Multiple-Output (MIMO) channel emulator implemented on Field-Programmable Gate Array (FPGA). The proposed emulator is based on Non-Line-of-Sight (NLoS) non-isotropic scattering with arbitrary motion dynamics of the mobile terminal. Its standalone hardware architecture ensures the flexibility and scalability of further hardware realization. Our proposed emulator is validated by comparing the emulated statistics of the channel gain against simulated results under a circular antenna trajectory. The Probability Density Function (PDF) of the fading envelope is observed to perfectly match the theoretical Rayleigh distribution(stationary channel) and the auto-correlation function(non-isotropic scattering) also shows a close agreement. The successful alignment of the eigenvalue of the channel gain matrix indicates our proposed emulator can perform correct MIMO characteristics.

This paper considers an application of deep learning for channel estimation with imperfect frame synchronization in mobile communication systems. Without prior knowledge of the channel model and its characteristics, the proposed method can dynamically estimate and track channel transfer function variations based on received pilot symbols. Furthermore, this method is applicable in practical scenarios, as it considers imperfect frame synchronization and channel estimation for high-speed wireless communication scenarios. The performance and practical feasibility of the deep learning (DL)-based models are assessed by taking into account realistic frequency-selective fading scenarios. Numerical results demonstrate that the proposed method performs better for practical signal-to-noise ratios than the state-of-the-art approaches. In addition, the fine frame offsets are estimated and compensated in the synchronization block with a DL-based algorithm, which outperforms the traditional fine frame synchronization algorithms.

Cardiovascular events occurring in the bloodstream are responsible for about 40% of human deaths in developed countries.Motivated by this fact, we present a new global network architecture for a system for the diagnosis and treatment of cardiovascular events, focusing on problems related to pulmonary artery occlusion, i.e., situations of artery blockage by a blood clot.The proposed system is based on bio-sensors for detection of artery blockage and bio-actuators for releasing appropriate medicines, both types of devices being implanted in pulmonary arteries.The system can be used by a person leading an active life and provides bidirectional communication with medical personnel via nano-nodes circulating in the bloodstream constituting an in-body area network.We derive an analytical model for calculating the required number of nano-nodes to detect artery blockage and the probability of activating a bio-actuator.We also analyze the performance of the body area component of the system in terms of path loss and of wireless links budget.Results show that the system can diagnose a blocked artery in about 3 h and that after another 3-h medicines can be released in the exact spot of the artery occlusion, while with current medical practices the average time for diagnosis varies between 5 and 9 days.

This paper considers second-order statistics of non-stationary channels with arbitrary mobile antenna motion, by relaxing the constant velocity assumption inherent to stationary channel models. By assuming obstructed Line-of-Sight and horizontal signal propagation, analytical expressions for the Level-Crossing Rate (LCR) and Average Fade Duration are derived for non-isotropic scattering scenarios with Von Mises Distribution of angles of arrival. To demonstrate the non-stationary effects arising from non-linear motion, the obtained expressions are employed to investigate an off-body communications scenario with the user walking and the wearable antennas placed on the torso, wrist and lower leg. While the torso antenna yields an essentially stationary channel, for the latter two antenna locations the fading dynamics change periodically over the walking cycle. Two distinct phases with faster and slower signal variations are observed, with the former yielding 4.64 times higher LCR for the lower leg antenna.

In this paper, a measurement campaign for off-body communications in an indoor environment is investigated for a set of on-body antennas. The channel impulse response was measured with the user approaching and departing from an off-body fixed antenna using two user dynamics, standing at fixed positions and walking. The processing of the measurement data allowed to evaluate system loss statistics. Different antenna configurations are classified in terms of mobility and visibility depending on the on-body antenna placement. A dependence on distance is found for the antennas with the lowest mobility (chest and head), while no significant dependence is found for the antennas with the highest mobility (arms and legs). Regarding the standard deviation of system loss, higher values are found in walking scenarios (above 1.0 dB) compared to the standing ones (below 0.6 dB) showing a clear dependence on mobility.

In this paper, Body-to-Body communications in indoor and outdoor environments for different on-body antenna configurations and different mobility scenarios were studied, based on system loss measurements at 2.45 GHz. The main objective is to properly characterise the influence of the Transmitter-Receiver configuration on system loss and fast fading behaviour, the latter being modelled by the Rice Distribution. Globally, it is observed that there is no significant difference on the measured average system loss between indoor and outdoor environments, but a strong dependence is seen on the configuration of the antennas and on the mobility scenario. Concerning the Rice Factor, as expected, higher values were obtained in outdoor environments, due to the lower level of multipath, the difference to the indoor case being below 4 dB, depending on the mobility environment and on the positioning of the antennas.

This chapter summarizes IRACON contributions related to the application of IoT in healthcare. It consists of the following three sections. Section 8.1 presents the measurement campaigns and the related statistical analysis to obtain various channel models for wearable and implantable devices. In addition, the importance of physical human-body phantoms used for channel, Specific Absorption Rate (SAR), and Electromagnetic (EM) exposure measurements are examined. Methodologies to improve the accuracy of these phantoms for various frequency bands are also discussed. Section 8.2 outlines methodologies to improve the medium access control (MAC) and networking layers of a body area networks along with possible architectures for remote health monitoring. Several applications such as localization, activity recognition, and crowdsensing and their corresponding technical challenges are also presented in this section. Finally, Section 8.3 introduces the concept of nanocommunications which can be considered as the nano-scale limit of the IoT technology spectrum. It provides an overview of the promising mechanisms that can establish data communication at molecular levels inside the human body as well as various interfacing techniques with macro-scale devices. It also highlights the revolutionary healthcare applications that could be enabled by this technology.

This paper presents the initial results of wideband channel measurements for polarised off-body communications at 5.8 GHz in an indoor environment. Channel Impulse Response measurements were performed simultaneously for two orthogonal polarisations of a wearable antenna (several placements) and repeated for vertical and horizontal orientations of the off-body one. Four types of scenarios were considered in order to investigate the influence of user dynamics, presence of people in the environment, and body-shadowing effects from the user or other persons obstructing Line-of-Sight in between transmitter and receiver. Initial results are presented.

This paper investigates the influence of user dynamics on small-scale fading characteristics in off-body channels. A statistical channel model employing a mobility model for wearable antennas on dynamic users is presented. The model is used to analyze the effects of both user's linear forward motion and periodic wearable antenna displacement due to changes in posture, for walking and running. The time-variant Doppler shift exhibited by signals arriving from different directions is considered for wearable antennas on the chest, wrist and lower leg. A strong influence of the on-body placement is observed, with antennas on the arms and legs yielding up to a 2.2 times higher maximum Doppler frequency than with the antenna on the torso. Furthermore, the small-scale fading dynamics for these antennas vary considerably during the motion cycle, where one can distinguish between slow and fast phases. The latter is found to yield up to 4 times as high root-mean-square level-crossing rates than the former, in the case of the antenna on the lower leg. These findings imply an important effect of the periodic antenna displacement on fading dynamics in off-body channels, which is typically neglected in literature.

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.

This article investigates the impact of the user's body on wearable antenna radiation characteristics and the consequent effects on the off-body channel, with the focus on the polarization aspect. The impact on antenna gain and polarization is analyzed for different antenna placements and separations from the body, based on electromagnetic simulations with numerical phantoms at 3, 4 and 5 GHz. Results show a strong influence of the body on the antenna efficiency, gain, and polarization. The excess losses due to body-shadowing suppress the antenna radiation behind the body by more than 20 dB, while its polarization changes from vertical in free space, to an elliptical one when placed on the body. The obtained radiation characteristics are then employed for off-body channel simulations using a geometry-based polarized channel model, which employs an analytic mobility model for wearable antennas based on Fourier series. The antenna rotation due to changes in user's posture is seen as one of the main sources of off-body channel degradation. The polarization mismatch losses imposed by antennas' physical misalignment, are observed to yield periodic fades of the Line-of-Sight component, with more than 30 dB drops in the received power level.

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 indoor propagation channel model. The model is based on a Friis transmission equation to which it adds the orientation-dependent body shadowing loss by adopting a basic model derived from a cosine function. Furthermore, the developed propagation model accounts for human body dynamics and different material reflections coefficients, both implemented using a random variables with uniform distribution. Created model was evaluated against a set of measurements conducted in the indoor environment at mmWave frequency (60 GHz) gathered from the literature, showing a good fit. The difference between the slopes of the proposed model and measurements is less than 6%.

This article presents an overview of future truly personal communications, ranging from networking inside the human body to the exchange of data with external wireless devices in the surrounding environment. At the nano- and micro-scales, communications can be realized with the aid of molecular mechanisms, Förster resonance energy transfer phenomenon, electromagnetic or ultrasound waves. At a larger scale, in the domain of Body Area Networks, a wide range of communication mechanisms is available, including smart-textiles, inductive- and body-couplings, ultrasounds, optical and wireless radio transmissions, a number of mature technologies existing already. The main goal of this article is to identify the potential mechanisms that can be exploited to provide interfaces in between nano- and micro-scale systems and Body Area Networks. These interfaces have to bridge the existing gap between the two worlds, in order to allow for truly personal communication systems to become a reality. The extraordinary applications of such systems are also discussed, as they are strong drivers of the research in this area.