Characterisation of Frequency Selective Reflections off Indoor Surfaces for 92–110 GHz

Terahertz Channel Propagation Phenomena, Measurement Techniques and Modeling for 6G Wireless Communication Applications: A Survey, Open Challenges and Future Research Directions

“…This means that measurements at THz frequencies may be limited by substantial practical difficulties requiring a trade off between accuracy and feasibility, or otherwise, requiring costly high precision positioning equipment. A similar process in measurement as such, has been recently adopted in [98] in order to observe PtP variations in multipath distribution by reflections off indoor surfaces. In the case where the Doppler spectra are measured using a sliding correlator dynamic channel sounder where we essentially transmit a maximum length, m-sequence, the maximum Doppler frequency can be obtained as 1/2km𝜏 where k represents the scaling factor of the sliding correlator, and 𝜏 is the clock period, leading to,…”

“…1) Diffuse Particle Scattering: The issue of diffuse particle scattering at THz frequencies, where we get rough surfaces due to the Rayleigh criterion, becomes crucially important when it comes to accurate modeling for use cases applicable in indoor environments and within devices. Multipath resulting from the layers in the 'smooth looking' composite materials as well as interactions where the surface height varies the order of the wavelength, cause cluster formation and broadened peaks, which are some of the effects caused when surfaces with different roughness levels and dielectric constants interact with the THz wave [98]. These effects, cause variations in the received power levels from point to point and over different angles, as well as increased delay spreads that may affect system design as observed from the analysis conducted in Section VII, and it is therefore of great importance to study these effects for accurate channel modeling.…”

Angular scattering measurements and modelling from building surfaces at sub‐THz frequencies between 92‐110 GHz

“…Deterministic models are either based on full‐wave methods such as method of moments (MoM) and finite‐difference time domain (FDTD) [12] that directly solve Maxwell's equations without any simplifications, or based on approximations such as uniform theory of diffraction (UTD) [13], and mathematical formulations like the Fresnel equations that are used to derive coefficients for reflection and transmission of electromagnetic (EM) waves at dielectric interfaces [14]. On the other hand, stochastic methods employ statistical approaches and require extensive measurements, with samples taken relative to the wavelength [10].…”

“…The high path loss and highly directive beams formed at sub‐THz give value to non‐line‐of‐sight (NLoS) fixed link propagation, such as a path around a corner with a single reflection, to combat blockages and challenges in extending fiber optic deployment. However, the wideband nature of communications at sub‐THz emphasizes the need to integrate the frequency‐selective characteristics of scattered communication channels resulting from small‐scale reflections comparable to the wavelength [10].…”

Autoregressive modelling for Sub‐THz spatio‐temporal wideband scattered reflection coefficient measurement of complex structures

“…This, however, is only true for the specular reflected path. In reality, scattered wave distributions resulting from propagation through “smooth” looking complex structures that contain features such as metallic reinforcement studs and insulating material are highly complex, as they vary significantly from one point to another within the structure [7]. Attempting to model such complex wave distributions solely based on geometric considerations becomes inadequate.…”