Satellite systems represent a cost-effective means of providing broadcast services over very large areas, but shadowing from buildings reduces availability in builtup areas. In order to provide a high quality-of-service, therefore, a hybrid network, which includes terrestrial repeaters, is attractive. The number of repeaters required depends on a large number of parameters and must therefore be analysed carefully. This paper describes a technique for achieving this by collecting building

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... ics over a small area and extending their use to the whole of the required coverage area. The approach is exemplified by determining the required number of repeaters for three satellite configurations: single GEO, dual GEO and HEO. In each case the network is required to provide high service availability over the whole of Europe to mobile receivers. It is shown, based on specified assumptions and data, including the use of time diversity, that a HEO satellite broadcast system will require close to zero terrestrial repeaters to provide ubiquitous coverage over a large part of Europe, while a GEO satellite broadcast system is likely to require up to about 4200 terrestrial repeaters for the same target coverage area.