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Conventional methods for exposure assessment cannot provide comprehensive and continuous monitoring. A crowdsourcing-based approach relying on the signal strength measurements of common smartphones could be a potential solution. This paper deals with the evaluation of measurement data collected with smartphones under conditions similar to crowdsourcing. Kriging is used to interpolate and smooth the noisy measurement data. The smartphone measurement data is analyzed for three LTE cells and compared with codeselective measurements of a field strength meter. It is shown that areas with high and low exposure can be distinguished and that local hot spots can also be detected. Furthermore, it becomes clear that at least a rough estimate of the electric field strength can be derived from the signal strength measurements, provided that enough smartphone readings are available for this area.

Current extrapolation procedures for the assessment of theoretical maximum RF-EMF exposure to 5G massive MIMO base stations consider the antenna gain difference between SSB and traffic beams. The procedure strongly relies on the provided antenna patterns obtained under ideal conditions, but being distorted and smoothed in practice. In this paper, we investigate the impact of ground reflections (for different ground materials) as well as the vertical sweeping of the measurement antenna (in order to find the local maximum exposure) on the effective base station antenna pattern. It shows that for base station antenna heights ≥30 m, ground reflection dominates the impact and leads to an increase of null levels in the normalized antenna pattern to around -30 dB in case of concrete ground and furthermore, to a slight increase of side lobe levels. Both ground reflection and vertical antenna sweeping additionally lead to a broadening of the side lobes.

The roll-out of the 5G standard with novel functionalities brings with it the urgent need to evaluate the human exposure to massive-MIMO base stations. This paper discusses concepts for the measurement of instantaneous and maximal exposure in the sub-6 GHz frequency range (FR1). The concepts have been implemented with the NARDA SRM-3006 selective radiation meter. For instantaneous exposure, the Safety Evaluation mode with an averaging over multiple frequency sweeps has been identified appropriate. First results with provoked data traffic revealed exposures below 0.25 % of the ICNIRP 1998 power density reference levels. For maximal possible exposures, the exposure to the synchronization signal and physical broadcast channel block (SSB) should be measured in the Level Recorder mode and extrapolated to the signal bandwidth considering a measurement point-specific gain difference between traffic and broadcast beams. As another outcome of our studies, we argue that code-selective devices for SSB measurements are urgently needed.

The monitoring of the exposure to electromagnetic fields emitted by mobile radio networks is necessary for a responsible operation of these networks. A possible alternative to classical exposure assessment methods for the realization of a time-continuous and area-wide exposure monitoring is a crowdsourcing-based approach that relies on the use of ordinary smartphones. This paper discusses the interpretation of the signal strength indicators measured by mobile phones in LTE networks when connected to the base station and explains how the instantaneous or maximum exposure is related to them. Longterm measurements of a smartphone and a field strength meter are presented in comparison, which show the time-dependent variation of the utilization of the radio cell during the day. In addition, it is demonstrated how the measurement data of the smartphone have to be adjusted due to the measurement characteristics resulting from the considered signal components in order to correspond correctly with the exposure. The results show that RSSI is suitable for tracing variations in exposure over the day.

Mobile communication for vehicles is a promising technology to increase road safety and traffic efficiency. Advanced driver assistance systems (ADAS) basing on mobile communication have to be validated properly before being deployed in commercial vehicles. Basing on an existing test facility, we have set up an urban intersection aiming to reproduce real world propagation effects. In recent studies, requirements for the building properties were derived in simulations assuming an omnidirectional radiator on the vehicle rooftop for a vehicle-to-vehicle (V2V) blind corner communication. In this paper, a measured radiation pattern of an antenna mounted on a vehicle's rooftop is used for the investigation of wave propagation and compared to the omnidirectional radiator. The measured vehicular antenna is mainly radiating in the upper hemisphere. The horizontal cut shows some distinct nulls and especially in the front half of the car two symmetric lobes. In spite of the large differences in the radiation patterns, the simulations results of wave propagation for the measured antenna pattern are similar to the omnidirectional antenna due to multiple reflections from the surrounding building walls and the roadway.

The usage of driving assistance systems that are based on V2X communication technologies as ITS-G5 are a promising technology to increase road safety as well as traffic efficiency. To allow for communication even in challenging propagation scenarios (such as busy urban intersection), we investigated a new concept for rooftop mounted beam-steerable vehicular antennas which is a 2-element monopole array (parallel and orthogonal to direction of travel) and a switchless reconfigurable antenna. It shows that the monopole array configurations give the best propagation results in any scenario and time step. However, the beams have to be steered dynamically to ensure the best possible communication.

Safety assessment of exposure caused by cellular base stations based on calculation methods is often performed using free space propagation in order to include the worst case. For prospective technologies (e.g. small cells in the vicinity of people), this approach might lead to a high exploitation of exposure limits. This paper investigates the overestimation of downlink exposure being predicted with a free space propagation model in comparison to a deterministic 2D knife edge diffraction model in an exemplary urban environment for a rooftop mounted base station. The results show that overestimation is quite low in the vicinity of the base station, particularly in LOS regions. In a distance between 100 and 200 m the overestimation is constantly rising, whereas for distances larger than 200 m it stays nearly constant.

Radio based communication and driving assistance systems for vehicular applications aim to increase traffic safety, energy and comfort. To ensure a holistic functionality, upcoming systems must be - particularly in an early development stage - validated in a real world environment without using public roads. For this reason, in this paper we present a new vehicular test environment for urban purposes that offers a challenging validation of communication systems by providing a facility which is adapted close to reality. We offer communication infrastructure dedicated for V2X (ITS-G5) and for cellular mobile radio (LTE). Buildings constructed from modular concrete bricks guarantee realistic propagation effects and flexible creation of various building types in terms of inter-building distance, height and facade heterogeneity.