LTE Human Exposure Evaluation: Maximum RF Field Strength Extrapolation Technique Repeatability Analysis

The measurement of human exposure to electromagnetic fields (EMFs) is an important topic in today's scenarios where a pervasive diffusion of cellular networks, as well as short-range and personal wireless devices, negatively affects the human exposure issues. Focusing the attention on cellular systems, despite regulators and normative committees are conveying specific guidelines for the measurements of EMFs generated by cellular networks, there are several issues still to be addressed regarding the most reliable measurement procedures and the evaluation of their measurement uncertainty. In this framework, this article focuses on long-term evolution (LTE) systems by providing a large experimental analysis aimed at evaluating the repeatability of the measurement results, achieved by means of one widely recognized human exposure assessment methods, i.e., maximum RF field strength extrapolation technique, which is recommended to give worst case and time-independent estimations of the maximum electric field. To this aim, a huge amount of signal acquisitions (about 112 000 traces) is collected for several weeks, by considering two mobile network operators and two frequency bands. Results have shown how some factors, as instrument settings and the time interval in which the measurements are taken, can significantly affect the measurement results and their repeatability. Furthermore, in some cases, such effects become comparable to or even larger than typical uncertainty components of the measurement chain. To mitigate these issues, the authors also suggest some possible solutions to improve the measurement procedure's overall repeatability