Interpretation of the Physical Layer Measurements of Smartphones as Measures of Exposure to Electromagnetic Fields

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.