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Description
This study examines the impact of active reconfigurable intelligent surface (RIS) on radiofrequency electromagnetic field exposure in outdoor environments at mmWave frequencies. As a case study, we investigated the dose absorbed by a road user in RIS-aided vehicle-to-vehicle (V2V) communication @28 GHz. The analyzed exposure scenario resembled an urban setting with a two-lane road, buildings, and transmitting vehicles. We examined two RIS configurations: RIS placed on the door of a relaying vehicle and the infrastructure. One of the vehicles acted as a transmitter (Tx) and was equipped with a V2V antenna operating @28 GHz to communicate with another vehicle set as the Rx. The V2V communication between the Tx-Rx was obstructed by a blocking vehicle between them. The RIS was configured to reradiate the environmental electric field (E-field) generated by the Tx towards the Rx. We assessed the whole-body specific absorption rate (wbSAR [W/kg]) of a road user - an adult pedestrian – induced by the E-field generated by the Tx and reradiated by the RIS at different positions of the pedestrian and positions of the RIS. We found that the RIS enhanced the dose absorbed with a maximum wbSAR increase of 1.7 mW/kg. The median value of the dose absorbed rose by 42.5% with the implementation of the RIS. However, wbSAR remained well below ICNIRP and IEEE safety limits also with the RIS.
