The overall multi-ray of propagation wave between transmitter and receiver is the sum of thedirect path and the indirect paths which are from reected rays, scattered rays and diffractedrays as shown in gure 3.7 15. As explained in 15 the sum of direct and reected rays atthe receiver RX which can be generally said as the waves come from different directions. As aresult, the total combination of the waves which occurs at antenna receiver can be representedby the impulse response due to the multipath channel.3.3. RAY TRACING MODEL OF THZ PROPAGATION CHANNEL 19Figure 3.7: Wave propagation model for (a) line of sight (LoS) propagation, (b) reected raypropagation, (c) scattered ray propagation, (d) diffracted ray propagationhi( ) = hrefl( ) + hscat + hdiff (3:13)The channel overall multipath components from reection, scattering, and should be with diffrac-tion can be demonstrated by the impulse response of those conditions as showed in equation22.214.171.124 Ray Tracing Model of THz Propagation ChannelIn the multipath components (MPCs) describe the angle of arrival (AoA), angle of departure(AoD), delay ( ), and complex amplitude. The ray tracing alorithm uses to determine the rstorder and second order reection of the propagation rays, the angles both azimuth and elevation(AoA/AoD) and the delay (ToA). The proposed two dimensional (2D) and three dimensional20 CHAPTER 3. CHANNEL PROPAGATION MODEL OF THZ COMMUNICATION(3D) small office room which is depicted in gure 3.8 shows that the objects only consider thetable and the screen.However, the multipath components (MPCs) depends on the position of the transmitter(TX) and receiver (RX). Therefore in the next chapter, we also vary the TX/RX positions toexplore the impact of directivies on antenna misalignment. In this thesis, we adopt the Kirchhoffapproach for modeling the scattered ray due to the roughness of the surfaces with the Gaussianheight distribution which had been validated by 16.All the simulations are performed at frequency of 350 GHz as we are interested to explorethis frequency and still a few works on this frequency. There are some objects in the designedroom, which will show the LoS and NLoS scenario of this simulation results. Those are the twostandard work tables which are separated by a 1 cm thicked screen with 1.8 height. The screen,all 4 sides of the wall and ceiling consist of rough surface.Figure 3.8: Design of the office room3.3. RAY TRACING MODEL OF THZ PROPAGATION CHANNEL 210 0.5 1 1.5 2 2.5 3 3.5 400.511.522.533.541st order reflection0 0.5 1 1.5 2 2.5 3 3.5 400.511.522.533.54Figure 3.9: Top view of rst and second order reection for office room design scenario with TXand RX-1 by ray tracing simulationThe ray tracing set-up for each rough surface is taken by a small tile as the representation ofa surface part. This idea comes from 7 work. Figure 3.10 shows the squared tiles with the tilelength is 10xLc. Each square tile consists of 20×20 tiles which are placed around the specular22 CHAPTER 3. CHANNEL PROPAGATION MODEL OF THZ COMMUNICATIONreection point. The Kirchhoff theory needs the information of surface height standard deviation(h). As a result, the AoA/AoD, propagation delay information can be achieved correctly.Figure 3.10: Tiles of surface sample in the designed roomWe adopted the Saleh-Valenzuela channel model as it is commonly used in the modelingof indoor enviroment multi -path propagation as discussed before. The S-V model associatesthe phenomenon of clustering and the angle of arrival/departure (AoA/AoD) stochastically.Thearrival paths are composed of many clusters, which consist of several rays for each 16.