Propagation in Built-up Areas Having looked at how irregular terrain a ects VHF and UHF radio wave propagation and the e ects of multipath, we are now in a position to discuss propagation in built-up areas. This chapter will deal principally with propagation between base stations and mobiles located at street level; propagation into buildings and totally within buildings will be discussed later. Although losses due to buildings and other man-made obstacles are of major concern, terrain variations also play an important role in many cases. Within built-up areas, the shadowing e ects of buildings and the channelling of radio waves along streets make. | The Mobile Radio Propagation Channel. Second Edition. J. D. Parsons Copyright 2000 John Wiley Sons Ltd Print ISBN 0-471-98857-X Online ISBN 0-470-84152-4 Chapter 4 Propagation in Built-up Areas INTRODUCTION Having looked at how irregular terrain affects VHF and UHF radio wave propagation and the effects of multipath we are now in a position to discuss propagation in built-up areas. This chapter will deal principally with propagation between base stations and mobiles located at street level propagation into buildings and totally within buildings will be discussed later. Although losses due to buildings and other man-made obstacles are of major concern terrain variations also play an important role in many cases. Within built-up areas the shadowing effects of buildings and the channelling of radio waves along streets make it difficult to predict the median signal strength. Often the strongest paths are not the most obvious or direct ones and the signal strength in streets that are radial or approximately radial with respect to the direction of the base station often exceeds that in streets which are circumferential. Figure is a recording of the signal envelope measured in a vehicle travelling along two city streets. For the first 65 m the street is radial the Rayleigh fading is clearly observed along with the increase in mean level at intersections. The vehicle then turned into a circumferential street where the mean signal strength is a little lower and the fading pattern is somewhat different. In suburban areas there are fewer large buildings and the channelling effects are less apparent. However foliage effects often negligible in city centres can be quite important. Generally the effects of trees are similar to those of buildings introducing additional path losses and producing spatial fading. Estimation of the received mobile radio signal is a two-stage process which involves predicting the median signal level in a small region of the service area and .
