Time Domain Propagation Characteristics with Causal Channel Model for Terahertz Band

In recent years, as more devices are connected to wireless communication systems, the demand for spectrum has increased. As conventional spectrum resources are limited, the THz band becomes an interesting option of more spectrum for wireless communication. However, the channel in THz band has different characteristics compared to the channels in typical frequency bands, and therefore, it is necessary to perform more research to understand the THz channel propagation. In this paper, we focus on the time domain THz channel model under line of sight (LoS) propagation conditions and investigate the channel propagation characteristics in time domain. Firstly, in the full frequency band (FFB) scenario, the time domain impulse responses, which correspond to the time domain THz channel model, are presented for different distances. In the impulse responses, there are significantly delayed paths due to the molecular absorption which causes significant frequency selectivity. Secondly, we extend the model to the limited frequency band (LFB) scenario by applying the root raised cosine filters. The results indicate that the richness of the delayed paths in the impulse response depends on the selected frequency band. In addition, the results indicate that the time delay and total energy strongly depend on the distance whereas the delay spread varies as a function of frequency.