  While cellular communications in millimeter wave (mmW) bands have been
attracting significant research interest, their potential harmful impacts on
human health are not as significantly studied. Prior research on human exposure
to radio frequency (RF) fields in a cellular communications system has been
focused on uplink only due to the closer physical contact of a transmitter to a
human body. However, this paper claims the necessity of thorough investigation
on human exposure to downlink RF fields, as cellular systems deployed in mmW
bands will entail (i) deployment of more transmitters due to smaller cell size
and (ii) higher concentration of RF energy using a highly directional antenna.
In this paper, we present human RF exposure levels in downlink of a Fifth
Generation Wireless Systems (5G). Our results show that 5G downlink RF fields
generate significantly higher power density (PD) and specific absorption rate
(SAR) than a current cellular system. This paper also shows that SAR should
also be taken into account for determining human RF exposure in the mmW
downlink.
