Empirical Investigation of Antenna Beamwidth Effects on the ITU-R Building Entry Loss (BEL) Model Based on 32 GHz Measurements

Recently, the ITU-R developed a building entry loss (BEL) propagation model covering millimeter-wave (mmWave) frequency bands, assuming omnidirectional antenna reception. Anticipating the application of directional beamforming (or antennas) employment in mmWave systems, this paper investigates the antenna beam width effects on the BEL based on 32 GHz measurements. We conducted the measurements with three antennas (Omni, 10° horn and 30° horn) at two building sites. These two buildings were specifically selected as candidates in that they followed the ITU - R building classifications of traditional type and thermally-efficient type. In both buildings, the BEL variations with respect to beam angle rotation were observed to be at least 17 dB (up to 50 dB); therefore, precise beam alignment is required. We also observed that the BEL increases as the beamwidth gets narrower, which is due to the fact that the narrower beamwidth antenna captures fewer multipath components while beamforming gain is normalized when calculating the propagation loss.