摘要： Simulation data from a ray-tracing tool applied in specific urban environments in the 28-GHz band suggest that the utilization of arbitrary base station (BS) angles in a directional search procedure may not be of maximum benefit for users located in non-line-of-sight positions, because certain angles restrict the radio frequency illumination to a lower maximum power than from others. An appropriate selection of BS angles offers a potential power level benefit of greater than 2 dB in a defined number of consecutive measurements; however, this performance improvement appears to be conditioned by the severity of the existing street canyon propagation and the probability of the angle used. A simple ray tracing method is proposed to approximately identify the most effective BS angles that avoid power emissions in directions largely blocked by nearby buildings. The results indicate that prior site-specific information may be helpful, particularly for systems using analog beamforming.