IEEE Consumer Electronics Magazine - November/December 2020 - 43

adequate metric than the skin temperature,
which is subject to be dispersed during propagation and affected by the external atmosphere
(i.e., air temperature).
Every wireless device should pass compliance tests before going to the market. An international standard entitled IEC6223217 has been
acting as a key reference in compliance tests for
BSs and user equipment (UE). It focuses on
change of characteristics in radio frequency (RF)
field with distance from an RF source. Relevant
studies are also found. Exposure to RF EMF from
a UE18 and that from a BS19 are studied.

Reduction of Human EMF Exposure
Albeit not many, schemes for EMF emission
reduction in a wireless system have been studied.20,21 Note that the human exposure can be
reduced if a BS adopts a power control or adaptive beamforming technique.22 Also, the exposure level can be reduced when multiple
spectrum bands are combined for coordinated
use. The reason is that with a higher carrier frequency, a wireless system should reduce the cell
size, which leads to more severe threats to
human health.
Focus of This Article
Four points on which this article puts particular focus are highlighted as follows.
First, we discuss the human EMF exposure in
the downlink as well as the uplink. Most of the
prior work studies the uplink only, while hardly
paying attention to EMF emissions generated by
BSs in a 5G network. Recall the aforementioned
changes that the 5G adopts: 1) operation at
higher carrier frequencies; 2) reduction of cell
size (which leads to increase in number of BSs);
and 3) concentration of higher EMF energy into
an antenna beam. They all imply that in 5G,
unlike the previous-generation wireless systems,
the downlink can also be a threat to human
health as well as the uplink.
Second, we suggest that both SAR and PD
should be used to display human EMF exposure
for a wireless system. The reason is that SAR
captures an amount of EMF energy that is actually "absorbed" into human tissues, whereas PD
is an efficient metric only to present the EMF
energy being introduced to a human user.

November/December 2020

Third, we present an explicit comparison of
human EMF exposure in 5G to those in the currently deployed wireless standards. For 5G, we
adopt the system model defined in the ThirdGeneration Partnership Project (3GPP) 5G New
Radio (NR).23 Meanwhile, currently operating
technologies are represented by 4G24 and 3.9G.25
Notice that 4G represents the 3GPP's Long Term
Evolution (LTE)-Advanced, and 3.9G is the last
release by the 3GPP before 4G was deployed
(from which the name "3.9G" originated).
Fourth, we consider the maximum possible
exposure that a human user can experience. In
other words, no technique for mitigation of
received power is considered in this article's
system model. It is for advising the consumers
with most conservative perspectives in using 5G
wireless.

CASE STUDY MODELS

In order to understand how much EMF energy
is imposed on a human user in a 5G wireless system, this article suggests two "comparative" case
study models: 1) among different wireless systems-i.e., 5G, 4G, and 3.9G, and 2) between
downlink and uplink.

5G versus 4G versus 3.9G
Commonly, for all of the three systems, we
assume a fully loaded network in order to understand the "worst case" of EMF exposure. As mentioned earlier, none of the three systems is
supposed to adopt any "adaptive" techniques-
namely, power control and adaptive beamforming. That is, there is no particular method
applied to reduce the amount of EMF energy
being imposed on a user at a certain time
instant. The rationale is to provide the "most
conservative" suggestion on consumer safety,
leaving room for a safety margin.18
Figure 1 depicts the difference in the cell size
among the three wireless standards. As mentioned in the "Concern on Human EMF Exposure
in 5G" section, a 5G system adopts the smallest
cell diameter (i.e., 200 m) among the three systems, pursuing to form a small-cell network. This
difference in cell size is a significant factor differentiating the level of human EMF exposure

IEEE Consumer Electronics Magazine - November/December 2020

Table of Contents for the Digital Edition of IEEE Consumer Electronics Magazine - November/December 2020