Impact of Effective Antenna Pattern on Radio Frequency Exposure Evaluation for 5G Base Station with Directional Antennas

Together with introduction of 5th generation (5G) of mobile communication system the new challenge for radio frequency (RF) exposure evaluation for base stations (BS) arises, which is mainly caused by high gain directional antennas with beamforming and beam steering. To assess RF exposure due to narrow and high gain service/traffic beams the extrapolation methods have been defined on the basis of exposure for broadcast/signaling beams which easier for determination due to theirs lower directivity. This paper indicates what is the impact on extrapolation of RF exposure for service/traffic beam if antenna gains assumed during calculations are based on nominal patterns, as measured in anechoic, instead of effective patterns determined by realistic propagation conditions. Example calculations performed for representative commercially available antenna indicate that extrapolated RF exposure for service/traffic beam can be overestimated by 1.5 dB to 2.0 dB, when power of reflected waves is dominant, i.e. BS and point of investigation are in non line of sight (NLOS) conditions.