Impact of Indoor Distributed Antenna System on RF-EMF Global Exposure

Abstract

The deployment of Distributed Antenna Systems (DAS) in poorly covered indoor areas has been a strategy to improve and extend radio-frequency (RF) coverage. However, this may imply a rise in the risk perception related to human exposure to electromagnetic fields (EMF), despite the existence of protection limits. Therefore, the objective of the current study is to analyze the overall impact of the installation of indoor DAS on the global human exposure. This analysis takes into account both downlink exposure, which includes exposure from outdoor base stations and indoor DAS, as well as uplink exposure induced by mobile phones. To this end, we carried out measurement campaigns in the premises of an organization and two subway stations in France, with the capability to selectively activate or deactivate the DAS antennas. The global exposure is evaluated using the ‘Exposure Index (EI)’ metric, which was developed as part of the European project LEXNET. The EI metric takes into consideration the exposure induced by both base stations and mobile devices, as well as the specific usage service (such as data or voice calls). The results have shown that deploying indoor DAS implies a reduction in the global EMF exposure while improving the quality of the cellular network connectivity. In addition to the impact of the usage service of mobile phones, the extent of EMF decrease is heavily influenced by the presence of additional RF sources. Specifically, significant reductions in EMF exposure have been observed in locations with minimal additional RF sources, whereas relatively lower reduction factors have been observed in locations with additional RF sources.

Keywords

• Distributed antenna system
• radio-frequency electromagnetic field (RF-EMF)
• human exposure
• exposure index
• indoor coverage
• measurements