Propagation over Irregular Terrain Land mobile radio systems are used in a wide variety of scenarios. At one extreme, county police and other emergency services operate over fairly large areas using frequencies in the lower part of the VHF band. The service area may be large enough to require several transmitters, operating in a quasi-synchronous mode, and is likely to include rural, suburban and urban areas. At the other extreme, in major cities, individual cells within a 900 or 1800 MHz cellular radio telephone system can be very small in size, possibly less than 1 km in radius, and service. | 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 3 Propagation over Irregular Terrain INTRODUCTION Land mobile radio systems are used in a wide variety of scenarios. At one extreme county police and other emergency services operate over fairly large areas using frequencies in the lower part of the VHF band. The service area may Ire large enough to require several transmitters operating in a quasi-synchronous mode and is likely to include rural suburban and urban areas. At the other extreme in major cities individual cells within a 900 or 1800 MHz cellular radio telephone system can be very small in size possibly less than 1 km in radius and service has to be provided to both vehicle-mounted installations and to hand-portables which can be taken inside buildings. It is clear that predicting the coverage area of any base station transmitter is a complicated problem involving knowledge of the frequency of operation the nature of the terrain the extent of urbanisation the heights of the antennas and several other factors. Moreover since in general the mobile moves in or among buildings which are randomly sited on irregular terrain it is unrealistic to pursue an exact deterministic analysis unless highly accurate and up-to-date terrain and environmental databases are available. Satellite imaging and similar techniques are helping to create such databases and their availability makes it feasible to use prediction methods such as ray tracing see later . For the present however in most cases an approach via statistical communication theory remains the most realistic and profitable. In predicting signal strength we seek methods which among other things will enable us to make a statement about the percentage of locations within a given fairly small area where the signal strength will exceed a specified level. In practice mobile radio channels rank among the .
