Millimeter Wave and sub-THz Indoor Radio Propagation Channel Measurements, Models, and Comparisons in an Office Environment

This letter provides a comparison of indoor radio propagation measurements and corresponding channel statistics at 28, 73, and 140 GHz, based on extensive measurements from 2014-2020 in an indoor office environment. The empirical investigations used a wideband sliding correlation-based channel sounder with steerable horn antennas at both the transmitter and receiver to emulate futuristic electronic beam steering at both the mobile device and the access point. Side-by-side comparisons of propagation characteristics (e.g., large-scale path loss and multipath time dispersion) across a wide range of frequencies from the low millimeter wave band of 28 GHz to the sub-THz band of 140 GHz illustrate the key similarities and differences in indoor wireless channels. The measurements and models show remarkably similar path loss exponents over frequencies in both LOS and NLOS scenarios, when using a one meter free space reference distance, while the multipath time dispersion becomes smaller at higher frequencies. Results here differ from the 3GPP indoor channel model.