Achievable directive antenna gain measurements and modeling for 60 GHz indoor links

Highly directive antennas may be a key component in millimeter wave links to offset their inherently high path losses. In cluttered scenarios such as Non-Line-Of-Sight (NLOS) indoor settings, antenna gain is degraded by the interaction of the channel angular spread with the antenna pattern. We conducted extensive measurements at 60 GHz indoors to evaluate the effect of angular spread on antenna gain degradation and its relation to small-scale fades. Our empirical results, obtained in corridors using five antennas with azimuthal Half-Power Beam Widths (HPBW) ranging from 6° to 60°, characterize effective gain of antennas in both Line-Of-Sight (LOS) and NLOS conditions. We find that narrow beam antennas can experience substantial gain degradation in NLOS scenarios, up to 4.4 dB at the 90th percentile for a 6° HPBW antenna. Our results confirmed this effect is less severe for wider beam antennas, which will capture a larger proportion of incident energy. We found that a Rician model can explain gain degradation to within a fraction of 1 dB for LOS links. In contrast, for NLOS links, a diffuse model with Gaussian-shaped channel angular spectrum and no dominant components yields better results, with less than 1 dB gap from 10th to 90th percentile between the empirical and simulated CDFs of azimuthal gains. Taking into account the phase profile of the antenna is particularly important when using this model, in line with the hypothesis of constructive/destructive interference of multiple wavefronts in NLOS links.