A study on channel model for THz band

Abstract Impulse response of the terahertz band (0.1–10 THz) for wireless nanosensor networks is considered. For wireless communication analysis and modeling, the impulse response is very important. In the earlier works, the impulse response has been derived from the transmittance by assuming a linear phase shift. However, the linear phase shift only leads to a symmetric impulse response before and after the LoS propagation delay. Physically, it is impossible for a signal to arrive before the LoS propagation delay since this violates causality. In this paper, a phase shift function leading to an impulse response satisfying causality is derived. The validity of the derived model is shown by comparison between measurements and results predicted by the theory

Time domain channel model for the THz band

Abstract Time domain channel model based on impulse response is introduced for wireless nanosensor networks which is used in the terahertz band (THz band: 0.1—10 THz) and short range (1—100 cm). We assume two-ray ground-reflection model. In THz band, rough surface on the reflector has effect on the impulse response due to very short wavelength. This paper focuses on frequency domain and time domain channel models and, for wireless communication analysis the impulse response is very important. Both models represent molecular absorption and rough surface effect which are unique aspects in THz band. The time domain channel model has multiple delayed taps even in LoS path. Reflected path has significantly strong effect to received signal from LoS path at long distance between transmitter and receiver than at short distance, relatively. These channel models are essential for a development of THz band communication techniques

A causal channel model for the terahertz band

Abstract Impulse response is vital for wireless communication analysis and modeling. This paper considers the impulse response of the terahertz band (THz band: 0.1–10 THz) for short range (1–100 cm) wireless communication. Earlier works derived the impulse response from transmittance by assuming a linear phase, which corresponds to a line-of-sight (LoS) propagation delay to a receiver. However, the linear phase leads to a symmetric impulse response before and after the LoS propagation delay. Physically, it is impossible for a signal to arrive before the LoS propagation delay since this violates causality. To address this issue, this study derives a phase function leading to an impulse response that satisfies causality. The validity of the derived model is verified with experimental THz band measurements (up to 2 THz), which show excellent agreement with the results predicted by the theory. From the impulse response, coherence bandwidth is found for both the entire THz band and its subbands. The results show significant variations in the coherence bandwidth as a function of the center frequency. Knowledge of these variations supports selection of the proper center frequency for wireless communications in the THz band