Indoor Wireless Channel Properties at Millimeter Wave and Sub-Terahertz Frequencies

Abstract

This paper provides indoor reflection, scattering, transmission, and large-scale path loss measurements and models, which describe the main propagation mechanisms at millimeter wave and Terahertz frequencies. Channel properties for common building materials (drywall and clear glass) are carefully studied at 28, 73, and 140 GHz using a wideband sliding correlation based channel sounder system with rotatable narrow-beam horn antennas. Reflection coefficient is shown to linearly increase as the incident angle increases, and lower reflection loss (e.g., stronger reflections) are observed as frequencies increase for a given incident angle. Although backscatter from drywall is present at 28, 73, and 140 GHz, smooth surfaces (like drywall) are shown to be modeled as a simple reflected surface, since the scattered power is 20 dB or more below the reflected power over the measured range of frequency and angles. Partition loss tends to increase with frequency, but the amount of loss is material dependent. Both clear glass and drywall are shown to induce a depolarizing effect, which becomes more prominent as frequency increases. Indoor propagation measurements and large-scale indoor path loss models at 140 GHz are provided, revealing similar path loss exponent and shadow fading as observed at 28 and 73 GHz. The measurements and models in this paper can be used for future wireless system design and other applications within buildings for frequencies above 100 GHz.

Millimeter Wave and Sub-Terahertz Spatial Statistical Channel Model for an Indoor Office Building

“…A wideband pseudorandom noise (PN) sequence of length 2047 was generated at baseband, then upconverted to a center frequency of 28 and 142 GHz, and transmitted through a directional and steerable horn antenna at the transmitter (TX). The receiver (RX) captured the RF signal [11], [42]. [39].…”

“…The 28 GHz channel has about three more TCs than the 140 GHz channel in both NLOS and LOS scenarios, which can be attributed to the higher partition loss at 140 GHz (e.g., 4-8 dB higher than 28 GHz for different materials [42]). The channel sparsity at 140 GHz should be considered in the channel estimation and beamforming algorithms for sub-THz frequencies.…”

Power-efficient beam tracking during connected mode DRX in mmWave and sub-THz systems

“…We form clusters of reflectors based on their proximity [47] and select up to N Cluster clusters in increasing order of the gNB → cluster → UE path length [48], in addition to the line-of-sight path. The reflection loss suffered by the signal is taken to be 7 (10) dB at 28 (140) GHz [49] 12 .…”

An Overview of Signal Processing Techniques for Terahertz Communications

“…For example, by developing a wideband channel sounder system at 140 GHz, indoor wideband propagation and penetration measurements for common building material are reported in [74]. In [75], indoor measurements and models for reflection, scattering, transmission, and large-scale path loss are also provided by the same group, for mmWave and sub-THz frequencies. Lower reflection loss is noted at higher frequencies in indoor drywall scenarios (stronger reflections).…”