Indoor Channel Multipath Components Statistics and Spatial Correlation in 6 and 37 GHz Bands.

A large amount of spectrum is allocated for unlicensed or shared use, e.g., 1200 MHz in the 6 GHz band and 600 MHz spectrum in the lower 37 GHz band. It is being considered to provide broadband wireless access for 5G and beyond. The propagation channels determine the coverage, capacity, and wireless access network design. In this work, channel measurement data were collected in an indoor office environment at both 6 and 37 GHz using omni-directional antennas and a virtual circular array system that resolves the angle of arrival (AoA). Antenna arrays with directional coverage are considered for wireless networks to increase coverage and provide spatial multiplexing. By employing the synthetic beamwidth method in post-processing, channel characteristics with directional antenna patterns are extracted from the empirical data based on omni-directional antenna. The number of multipath components (MPCs), root-mean square (RMS) delay-spread, and RMS angular-spread at both frequencies are compared with the synthetic beamwidth set of 180°, 120°, 60°, 30° and 10°. The number of MPCs and the values of RMS delay-spread at 37 GHz are approximately half of that at 6 GHz. Spatial correlation is another channel characteristic of interest for antenna design and system design with the aim of spatial multiplexing. Our study observed the spatial correlation distance at 37 GHz is approximately $\lambda/8$, being smaller than the 6 GHz correlation which is $\lambda/4$. This allows the higher frequency arrays to pack more antenna elements in approximately the same form factor as a similar performance lower frequency array.