Evaluating Human Electromagnetic Exposure in a UAV-aided Network
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Detemmerman, Thomas | 2020
Society relies more than ever on the availability of wireless networks. Due to the mobility of a UAV, a UAV-aided network is able to provide this necessary access in case the existing terrestrial
network gets damaged. Therefore, each UAV will be equipped with a femtocell base station. However, the public is concerned about the potential health effects of the electromagnetic radiation caused by these networks. Therefore, mobile devices and base stations have to comply to strict legislation enforced by the government. This research investigates how different scenarios influence power consumption, electromagnetic exposure and specific absorption rate. These different scenarios are defined by various flying heights, number of UAVs available and population sizes. Further, the proper microstrip patch antenna is defined and attached to the UAV. The antenna will be responsible for the communication between the UAV and the users it covers. Its performance is compared to an equivalent isotropic radiator. Thereafter, the network will be optimized towards goals like electromagnetic exposure of the average user or power consumption of the entire network; which results in conflicting requirements. To accomplish this goal, the capacity based deployment tool of the WAVES research group at Ghent University will be extended so it would be able to calculate electromagnetic exposure. Further, the tool now also provides support to optimize the networks towards electromagnetic exposure or power consumption. It looks from the results that the microstrip patch antenna with an aperture angle of 90° is a suitable starting point for an antenna. This directional antenna focusses electromagnetic radiation where it is needed. Unwanted sideways radiation is therefore reduced by design. The sufficiently large aperture angle covers enough users. The antenna is recommended to be deployed in a power consumption optimized network since less drones are required and therefore iv also less expensive. The optimal flying height for the city centre of Ghent is believed to be situated at 80 metres since lower flying heights require much more UAVs and higher flying heights have a negative influence on the electromagnetic exposure. When this configuration is applied to a network with 224 users, the average user will experience a SAR of around 0.2 µW/kg and a downlink electromagnetic exposure of 114 mV /m. The network will require on average 96 UAVs with a total power consumption of 69.5 W, which is 7.24 W per UAV.
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