  Current radiofrequency electromagnetic field (RF-EMF) exposure limits have
become a critical concern for fifth-generation (5G) mobile network deployment.
Regulation is not harmonized and in certain countries and regions it goes
beyond the guidelines set out by the International Commission on Non-Ionizing
Radiation Protection (ICNIRP). Using a massive multiple-input-multiple-output
(mMIMO) testbed with beamforming capabilities that is capable of mimicking
realistic 5G base station (BS) performance, this paper presents an experimental
and statistical assessment of its associated RF-EMF exposure within a
real-world indoor environment. The mMIMO testbed has up to 128 channels with
user-programmable software defined radio (SDR) capability. It could perform
zero-forcing precoding after channel state information (CSI) acquisition for
different beamforming scenarios with respect to the associated user terminal
antenna setups and positions. With 64 active mMIMO transmit antennas, 8
beamforming scenarios have been considered for single-user (SU) and multi-user
(MU) downlink communications at different locations. Using a calibrated
triaxial isotropic field-probe, the received channel power heat map for each
beamforming scenario was acquired and then converted into an RF-EMF heat map.
The relevant RF-EMF statistics was evaluated based on the variations of beam
profiles and number of users.
