Modelling for radiowave propagation in city microcells

Diffraction is one of the key radiowave propagation mechanisms in city microcell environments. This is especially true for radiowave propagation into side roads and roads parallel to the main coverage area where line-of-sight paths do not normally exist. Field experiments have shown that at 900 MHz the signal level drops by 20 dB when a mobile unit turned into a side road. The author explains the mechanism of radiowave propagation in typical city microcell environments. With this knowledge, the observed signal variation can be characterised by either using a relatively complex model based on geometrical optics and the geometrical theory of diffraction or a simple model based on piecewise linear regression. The former modelling approach enables more accurate prediction of the signal levels especially along side roads, while the latter reduces computation significantly and is more suitable for large scale cellular radio system performance simulations