Breaking the Myth of RIS: Investigating the Role of User Equipment for Achieving Robust mmWave Wireless Channel Links Under NLOS Environments

Reconfigurable Intelligent Surfaces (RIS) are increasingly being explored as a solution to tackle millimeter-wave (mmWave) coverage gaps in wireless communication. However, quantitative analysis to synergize the RIS and the beamforming capacity of user equipment (UE) remains elusive. This paper delves into the challenges of mmWave blind spot resulting from insufficient terminal coverage despite the addition of RIS through empirical quantification. For in-depth investigation, a mobile configuration that employs Antenna-on-Display (AoD) technology situated on the foreside of the UE is compared with a conventional setup using mmWave Antenna-in-Package (AiP) situated on the side and backside of the UE. In the Over-the-Air (OTA) test when the device is held under consistent RIS-aided channels, the forward signal reception experiences a reduction of less than 3 dB, as opposed to a steeper reduction of at least 7 dB for side and back receptions. Comprehensive total scan patterns and cumulative distribution function (CDF) analyses further highlight the importance of foreside coverage of the terminal. Specifically, when influenced by a hand at 28 GHz, AoD integration results in a lowered attenuation of 2.04 dB, whereas the conventional AiP setup shows a 4.47 dB reduction at the 90% CDF level.