Effects of terrain and buildings on path loss in urban environments for wireless communication applications

In modern wireless systems, the radio links are about 20 kilometersor less, the antennas that create the links lie near to or among thebuildings, and the wavelength is small compared to buildingdimensions. As a result, the channel signal characteristics, whichare most significant for wireless communication systems, arestrongly influenced by the buildings as well as by vegetation andgeographical conditions. In this environment, signals propagatefrom one antenna to the other over multiple paths that involve theprocesses of reflection and transmission at walls and by the groundand process of diffraction at building edges and terrain obstacles. Inthis thesis, electromagnetic wave propagation over buildings isexamined when the buildings are located on flat terrain and hills.The buildings, which are represented by a series of absorbing half-screens, are assumed to lie in rows that are equally spaced alongparallel streets, with the streets running perpendicular to the terrainslope. Phenomenological methods based on non-linear ray opticsfor diffraction investigated and the results are evaluated throughcomputer simulation programs and some results are comparedmeasurements and other some path loss models. Furthermore, pathloss to subscribers located in a forest and on roads or in clearingsin a forest are examined using refraction and diffraction concepts.