The Effect of Antenna Beamforming Coverage of User Equipment: Reconfigurable intelligent surface-aided mmWave NLOS wireless scenarios

Reconfigurable intelligent surfaces (RIS) have recently received much attention to mitigate millimeter-wave (mmWave) blind spots for wireless scenarios. However, its effectiveness in conjunction with the beamforming coverage of realistic user equipment (UE) remains elusive. In this article, the challenges of mmWave blind spots that arise from insufficient beam coverage of UE, even with the incorporation of RIS, are explored through quantitative experimental results. Specifically, a mobile device configuration utilizing antenna-on-display (AoD) technology is compared and analyzed with a conventional mobile device environment composed of mmWave antenna-in-package (AiP). Through over-the-air (OTA) experiments, it is verified that the mobile device environment including AoD proves advantageous in scenarios in which the device is gripped by the human hand under identical RIS-assisted channels. It exhibits an attenuation of 3 dB or less in the forward reception, in contrast to a minimum attenuation of 7 dB in the side and back reception. The total scan patterns and cumulative distribution function (CDF) curves validate that the incorporation of AoD results in decreased attenuation of 2.04 dB under portrait mode of a hand phantom at 28 GHz, compared to the conventional case which solely incorporates AiPs, exhibiting 4.47 dB based on the CDF = 90% level.