Spatial Fading Channel Emulation for Over-the-air Testing of mmWave Radios: Concepts and Experimental Validations

Millimeter wave (mmWave) communication is regarded
as the key enabling component for 5G cellular systems
due to the large amount of available spectrum. To make mmWave
new radio (NR) a reality, tremendous efforts have been exerted
from the industry and academia. Performance evaluation of
mmWave NR is a mandatory step and the key to ensure the
success of mmWave 5G deployment. Over-the-air (OTA) radiated
testing method for mmWave new radio (NR) in laboratory
conditions is highly attractive, since it makes possible to achieve
virtual field testing purposes of mmWave devices in realistic
propagation conditions. In this paper, we first discuss the need
and challenges for OTA measurement of mmWave 5G NR under
fading channel conditions. After that, two promising candidate
solutions: i.e. wireless cable and multi-probe anechoic chamber
(MPAC), are detailed. Their principles, applicability for mmWave
NR and main challenges are discussed. Furthermore, preliminary
experimental validations results in a frequency range (FR) 2
anechoic chamber are demonstrated for the wireless cable and
MPAC methods at 28 GHz.