Ray-Tracing Propagation Modeling in Urban Environment at 140 GHz for 6G Wireless Networks

This paper introduces a propagation study at sub-THz frequencies in an urban environment. Deterministic simulations are carried out utilizing a software tool and a high-resolution digital map of the area. Different scenarios and antenna configurations are examined, as well as the relative propagation mechanisms are described. The simulated path loss is found to be well approximated by the close-in (CI) model, delivering path loss exponents equal to 2.1, and 3.4, and shadowing factors 2.5, and 7.2 dB, for line-of-sight (LOS) and non-line-of-sight (NLOS) conditions, respectively. Links that support high data rates are feasible even at NLOS locations but for distances up to 100-150 m. The root-mean-square (rms) delay spread is found in the range of 4.8-44.2 ns and 1.7-38.3 ns, for LOS and NLOS conditions, respectively. The simulated channel exhibits frequency selective characteristics demonstrating coherence bandwidth values between 8.9 and 161.7 MHz. Finally, a multi-cluster model is found to fit well the simulated PDPs. Up to four and two clusters are observed in LOS and NLOS locations, respectively. The cluster and ray decay factors, as well as their intra- and inter-arrivals times are all found to be regulated by the propagation environment and the adopted antenna characteristics.