Experimental Demonstration of Passive Channel Sounding in 28-GHz-band 5G Systems

This paper experimentally investigates passive channel sounding in millimeter-wave (mmWave)-band fifth-generation (5G) mobile communication systems. A mmWave-band base station (BS) generally steers narrow beams, leading to a significant impact on radio propagation channels. Taking advantage of the fact that the BS transmits channel state information reference signals (CSI-RSs) over the entire band with changing beam patterns, a passive channel sounder estimates multipath component (MPC) parameters for each beam. In addition, the frequency-domain space-alternating generalized expectationmaximization (FD-SAGE) algorithm is employed to analyze the MPC parameters. Passive channel sounding for a commercial 28 GHz -band 5 G BS is experimentally demonstrated in indoor environments. The experimental results reveal the effect of the different BS beams on the radio propagation channel in both line-of-sight (LOS) and non-line-of-sight (NLOS) environments.