Investigations on the prediction of radiowave propagation in urban microcell environments using ray-tracing methods

Future personal and mobile radiocommunication systems may use microcells to achieve high capacity. Base station antennas will be located at low heights, below the roof height of surrounding buildings, to restrict the coverage area of each cell. The aim of the work described in the paper is to develop theoretical models which can predict the effect of buildings on radiowave propagation in urban microcells. Radiowave propagation in urban microcells is investigated using a computer ray-tracing program. Direct, reflected and diffracted rays are used to calculate signal strength predictions. Diffracted rays are calculated using the uniform theory of diffraction. The operation of the program is verified experimentally in the laboratory using the method of scaled modelling. The experiments are carried out on an aluminium ground plane, which is an idealised representation of the ground in the outdoor system. Buildings are represented in the experiment by aluminium boxes. The relative importance of different rays is investigated and only a small number of rays are found to be important at each location. This raises the possibility of more efficient ray-tracing computer programs which can calculate field strengths more quickly by pre-selecting the most significant rays.