Co~~utati~ii-~ri iiie Ei'ficient Determination of 3D Propagation Paths in Rural Area

A new deterministic 3D wave propagation model for rural area is presented, which is as accurate as the original IHE-3D-RUIUL wave propagation model but less time consuming. The 3D ray tracing proccduic is improved by using ncw and faster algoi ithnis criabling an aica covcring calculation of the channel impulse response. As a consequence, now an area covering bit-errorrate prediction Tor planning purposes of digital cominunication systems is possible. I. Introduction The IHE-3D-RURAL wave propagation model [ 1][2] provides very good prediction results for the fieldstrength and bit error rate (BER) [3]. In this ray optical model the GTDAJTD-method is used for diffraction and the Small PerturbatiodKirchhoff method for scattering calculation. The complexity of this model leads to a very high computation time restricting the number of receiver locations within an area of interest. Area covering predictions are only possible for computation grid-sizes of 1000 m and more. Hence, it is necessary to develop fast propagation models in order to provide predictions in grid sizes of 100 m or less. Since the most time consuming part within the IHE-3D-RURAL model is the determination of the scattering pixels (scatterer), efficient algorithms are implemented to minimize the necessary efforts. In this paper a new fast 3D deterministic wave propagation model is presented. It provides thc accuracy of tlic IlfB-3D-RUIZAL wavc propagation model but saves quite a lot of computation time. The time efficiency is achievcd by versatile algoritlims for thc detcnnination of the scnttcrcr locations. Scvclal difl'cicnt niclliocls nrid ulgol-itlinis ;iic picscntcd in Sections 2 and 3. In Section 4 tlic ncw ray tracing algorilhins arc tcsled and comparcd with a ieference model, which selects all possiblc scattcier locations. The goal of all presented methods is to exclude and neglect the unimportant scatterer locations - i.e. to avoid the compulation time-consuming line-or-sight (LOS) approval. 2. Algorithins for Detailed Grid In this section some ray tracing algorithms are presented, which use the same grid size as the topographical data. Algorithms using a more rough grid (macro pixel grid) are presented in Section 3. The 3D wave propagation modeling considers all those scatterers with LOS to both transmitter (T) and receiver (R). Consequently, all pixels in the computation area have to be checked whether they have LOS to T and R or not. The Reference Algorithm This algorithm checks for every pixcl in the area of interest, whether it has LOS to T and R location. Hence it is an exact but extremely time consuming algorithm those results are used as reference results. Two possibilities do exist: Since the height values of the topographical data base only exist in defined locations, tlic values in between have to be iiitcrpolaled. Dependent