## 3 Methodology
### RF-EMF Exposure Assessment Modeling and Measurements  
The RF-EMF exposure assessment includes both modeling and measurements of the experimental setup (dosimetry), RF-EMF levels inside and outside the human body, and environmental RF-EMF levels in indoor and outdoor scenarios (Figure 2). **Multi-Scale Model-Based Assessment of RF-EMF Exposure in the Human Body:** The scope of this activity is a multiscale approach to RF-EMF exposure assessment by simulation and/or measurements from the small (cells and small organisms) to medium (human body) and large scale (cities, buildings). Initially, the unperturbed RF-EMF distribution generated by the radiating source will be calculated (or measured) at every point of interest in the indoor/outdoor environment (city, workplace, school, home). This information will be used as input to the RF-EMF software tool for the exposure conditions in the experiments to calculate the fields outside/inside a human body. The various simulations and experiments will take place in parallel and will be used bidirectionally to improve computational models and experimental conclusions to compare the results. The RF-EMF software will be used with exposure source properties, the radiated region's CAD model, the human body's electromagnetic properties, and the human body's CAD model. **Exposure Compliance Assessment and Environmental Protection:** RF-EMF exposure assessment is particularly challenging in 5G due to its high flexibility with respect to the antenna technologies employed, such as beamforming capabilities and/or different MIMO implementations, as well as its sophisticated energy-efficient signaling structure. NextGEM will develop novel measurement techniques for different antenna technologies (such as continuous beamforming, a grid of beams, SU-MIMO, MU-MIMO, and Ma-MIMO, based on maximum power extrapolation (MPE)). MPE techniques have been proposed and successfully applied in past-generation cellular systems but require a generalization from a \"passive\" determination of what is on air in a certain moment to an \"active\" measurement forcing the system under test to assume the most suitable configuration. In NextGEM, novel statistical models will be developed for realistic exposure assessment in both indoor and outdoor scenarios measurements. A possible approach [30] relies on the normalized  
Figure 2: Multi-scale approach to RF-EMF exposure assessment. average power pattern (NAPP), which seems particularly suitable to compare different antenna technologies and scenarios, and is easy to integrate with stochastic models of user distributions, as well as with ray-tracing algorithms. Channel power measurements will be performed with a spectrum analyzer, whereas measurements in the code domain will be performed with a signal analyzer with 5G NR decoding capabilities. Both directive and omnidirectional antennas will be used. Both line of sight (LOS) and non-LOS will be tested with one or more user devices. **RF-EMF exposure paradigms and self-monitoring:** 5G NR technology makes intensive use of MIMO technologies, and the user's exposure is related to the EM coupling in the body. For these reasons, a body-worn portable exposure meter can mimic real scenarios obtaining reliable data to monitor RF-EMF exposure. The NextGEM project will develop multiple body-wearable portable exposure meters to be employed in real-life use-case scenarios. To achieve this novel wearable sensing device, the current sensing node, operating at 27.5 GHz, will be redesigned using planar antennas with plastic lenses (easier to integrate into a wearable device), providing higher spatial selectivity. The newly developed sensor will be tested in the ADome TU Delft characterization facility, allowing the identification of the critical electrical specification of the sensor and adequate design of the sensor-carrying west with full spatial coverage. The single sensors and the west's first prototypes will be tested in the TU Delft Green Village.