  TeraHertz (THz) communications are envisioned as a promising technology,
owing to its unprecedented multi-GHz bandwidth. One fundamental challenge when
moving to new spectrum is to understand the science of radio propagation and
develop an accurate channel model. In this paper, a wideband channel
measurement campaign between 130 GHz and 143 GHz is investigated in a typical
meeting room. Directional antennas are utilized and rotated for resolving the
multi-path components (MPCs) in the angular domain. With careful system
calibration that eliminates system errors and antenna effects, a realistic
power delay profile is developed. Furthermore, a combined MPC clustering and
matching procedure with ray-tracing techniques is proposed to investigate the
cluster behavior and wave propagation of THz signals. In light of the
measurement results, physical parameters and insights in the THz indoor channel
are comprehensively analyzed, including the line-of-sight path loss, power
distributions, temporal and spatial features, and correlations among THz
multi-path characteristics. Finally, a hybrid channel model that combines
ray-tracing and statistical methods is developed for THz indoor communications.
Numerical results demonstrate that the proposed hybrid channel model shows good
agreement with the measurement and outperforms the conventional statistical and
geometric-based stochastic channel model in terms of the temporal-spatial
characteristics.
