Human Electromagnetic Field Exposure in Wearable Communications: A Review <s> B. Health Concern on EMF Emitted by Wearable Devices <s> This work presents a comparison of simulated and measured Specific Absorption Rate (SAR) levels of wearable antennas intended for voice communication for security applications. The compared antennas operate at UHF frequencies (360 – 420 MHz) and can be used for TETRA or TETRAPOL communication systems. Four different antenna prototypes have been considered, analyzed and SAR values simulated and measured. Two of the compared antennas are Planar Inverted F Antennas (PIFAs) and they are proposed by the authors, while the other two are dipole based antennas. One of the dipole antennas is commercially available, while the second one is reported in the literature. The antennas are modeled and simulated with a commercial software, while the measurements are performed with a special equipment intended for SAR measurements. <s> BIB001 </s> Human Electromagnetic Field Exposure in Wearable Communications: A Review <s> B. Health Concern on EMF Emitted by Wearable Devices <s> As wearable devices become more ingrained in our daily lives, traditional communication networks primarily designed for human-being-oriented applications are facing tremendous challenges. The forthcoming fifth-generation (5G) wireless systems look to support unprecedented high capacity, low latency, and massive connectivity. In this article, we examine key challenges facing wearable communication devices. A cloud/edge communication architecture that integrates the cloud radio access network (CRAN), software-defined network (SDN), device-to-device (D2D) communications, and cloud/edge technologies is presented. Computation offloading enabled by this multilayer communications architecture can offload computation-excessive and latency-stringent applications to nearby devices through D2D communications or to nearby edge nodes through cellular or other wireless technologies. Critical issues faced by wearable communications, e.g., short battery life, limited computing capability, and stringent latency, can be greatly alleviated by this cloud/edge architecture. Together with the presented architecture, current transmission and networking technologies [including nonorthogonal multiple access (NOMA), mobile edge computing (MCE), and energy harvesting] can greatly enhance the performance of wearable communications in terms of spectral efficiency, energy efficiency, latency, and connectivity. <s> BIB002 </s> Human Electromagnetic Field Exposure in Wearable Communications: A Review <s> B. Health Concern on EMF Emitted by Wearable Devices <s> Abstract At ultra-high fields, the assessment of radiofrequency (RF) safety presents several new challenges compared to low-field systems. Multi-channel RF transmit coils in combination with parallel transmit techniques produce time-dependent and spatially varying power loss densities in the tissue. Further, in ultra-high-field systems, localized field effects can be more pronounced due to a transition from the quasi stationary to the electromagnetic field regime. Consequently, local information on the RF field is required for reliable RF safety assessment as well as for monitoring of RF exposure during MR examinations. Numerical RF and thermal simulations for realistic exposure scenarios with anatomical body models are currently the only practical way to obtain the requisite local information on magnetic and electric field distributions as well as tissue temperature. In this article, safety regulations and the fundamental characteristics of RF field distributions in ultra-high-field systems are reviewed. Numerical methods for computation of RF fields as well as typical requirements for the analysis of realistic multi-channel RF exposure scenarios including anatomical body models are highlighted. In recent years, computation of the local tissue temperature has become of increasing interest, since a more accurate safety assessment is expected because temperature is directly related to tissue damage. Regarding thermal simulation, bio-heat transfer models and approaches for taking into account the physiological response of the human body to RF exposure are discussed. In addition, suitable methods are presented to validate calculated RF and thermal results with measurements. Finally, the concept of generalized simulation-based specific absorption rate (SAR) matrix models is discussed. These models can be incorporated into local SAR monitoring in multi-channel MR systems and allow the design of RF pulses under constraints for local SAR. <s> BIB003
A major concern regarding wearable communications is human biological safety under exposure to EMF generated by the wearable devices BIB002 . A human body absorbs electromagnetic radiation, which causes thermal or non-thermal heat in the affected tissues. Further, as shall be informed in Section III of this paper, the EMF energy arriving at the human skin is dominated by the distance between the EMF emitting device and the skin. This makes wearable communications as the type of wireless technology on which the most careful analysis is needed regarding human EMF exposure. For this reason, there has been surveys and tutorials on the human EMF exposure in wearable communications  BIB001 BIB003 , which provided up-to-date information that is necessary to keep general consumers informed of safe use of wearable technologies. Despite the significant contributions, the prior surveys limit their generality due to lacking enough details on: • Exact levels of EMF exposure caused by the commercial wearable products that are currently in the market • Potential impacts of technological change in future (i.e., use of mmW for wearables) on the EMF exposure