Correlation Levels for Measured Indoor 21.5 GHz Channels With a User-Held Handset

Adaptive beamforming (BF) is essential when mm-wave bands are utilized for mobile communications, where it is important that the channel experienced when BF is applied is as similar as possible to the estimated channel. This work investigates the similarity of the channel at different time-instants using estimates of auto-correlation functions for the instantaneous channel coefficients, based on 21.5 GHz measurements with a smartphone-like mock-up in different indoor corridor scenarios, with and without a user holding the mock-up. The correlation is found to be relatively independent of the location and orientation, with a reduced correlation with a person present. Further, BF is studied based on the 7-element handheld array with a 8.8-24.6 dB gain found for the 1st amplitude percentile obtained with ideal channel state information (CSI). Non-ideal CSI typically reduces both the correlation and the BF gain.