In the Terahertz frequency a multi-ray model needs to be detailly developed to get an accuratecharacteristic of such line-of-sight (LoS), reected, scattered, and diffracted ray in the multipathpropagation channel. The lower frequency band in 60 GHz for example, does not consider wellthe high loss of reection and atmospheric attenuation or molecular absorption. Moreover,the decrease of wavelength in THz band, reection and scattering losses on propagation pathsare much higher than the millimeter-wave. Therefore, we only consider up to double (second)reections. Due to the fewer paths of THz channel than milimeter-wave, the gap between line ofsight (LoS) and non line-of-sight (NLoS) are signicant. As a result, the transmit power shouldbe mainly focused on the LoS as dominant paths and the strongest rays of NLoS paths.Figure 3.1 shows the modelling approach of a general wireless channel and in this thesis thedeterministic approach is considered as the rst step to model the THz multipath channel. TheSaleh Valenzuela takes many apart on this channel model as he had done the measurements aswell as for indoor multipath propagation. Therefore the clustering of rays is considered as thechannel model results.3.1 Line of Sight ScenarioIn this Thesis we propose a 3D Ray tracing model for the THz channels which accounts for theline of sight (LoS), single reection (rst reection) and double reection (second reection) raysas multipath components (MPCs). The geometrical 3D model ray tracer has been developed inanother work. The Ray Tracing methods have been proved a very well approximation capabilitiesat Terahertz frequency 8. The material properties for Non Line of Sight have been consideredand validated in the Ray Tracing work according to references 12. The LoS or free space directray consists of absorption loss and spreading loss, while the absorption coefficient of medium1112 CHAPTER 3. CHANNEL PROPAGATION MODEL OF THZ COMMUNICATIONdepends on the composition of the medium, such as plaster, wood, glass material. compared tothe LoS, particularly the power of rst reection (single reection) paths are attenuated by 5 to10 dB averagely and more than 15 dB for the second reection (second reection).Figure 3.1: Modeling approaches of wireless channels3.2 Multipath Propagation EffectsThe non line-of-sight (NLoS) is the rays of radio transmissions across a path that is partiallyobstructed, usually by a physical object in the Fresnel zone between transmitter and receiver. Ina point of rough surfaces for example, the backscattered Electromagnetic (EM) wave is basicallyconsist of reected ray in specular direction and diffusely scattered in all direction.