Impact of energy-efficient cell-breathing on the electromagnetic radiation levels of mobile phone devices

Energy-efficient cell breathing is a mechanism that consists of adapting cell sizes and number of active Base Stations (BS) to the distribution and current levels of traffic. In this article, our goal is to analyse the effect of such a technique on the electromagnetic (EM) radiation levels for mobile phone devices. Although there exist large details in the literature of cell-breathing on energy-efficiency related to the Radio Resource Management (RRM) aspects, to the best of our knowledge, there is still a lack of work on analysing the consequences of cell-breathing and BS switching-off schemes on the EM exposure issues related to the mobile terminal. In such approaches during low-traffic, whereas there are some BSs being switched-off, there are some other BSs that must remain active expanding their cell sizes to guarantee coverage. This requires a transmission power increase for both downlink and uplink side, that for mobile devices implies an increase of the specific absorption rate (SAR) [W/kg] on the mobile user. To conduct our study, we use one of our previously proposed techniques on cell-breathing to analyse the impact of uplink transmission power increase on resulting SAR levels. Here, different BS switching-off aggressiveness levels are considered to observe the resulting exposure levels using a 3G/CDMA scenario. The results show how SAR maximum levels increase as more aggressive switching-off schemes take place as well as the uplink interference rises due to a progressive increase of network load.