Global shadowing margins for 3G networks

The purpose of this paper is to study the impact of shadowing effects at the network level of an UMTS-FDD system. As we show, shadowing phenomena engender an increase of the total amount of interference, which may lead to coverage and capacity limitations. To account for the interference increase we introduce global shadowing margins added to path losses, whose values depend on the probability of macro-diversity of a mobile. A theoretical uplink study is presented and numerically validated using the FTR&D fast modelling tool. It is then extended to the downlink. Besides, a sensitivity analysis shows that these margin values remain relatively unchanged with the load. A direct application of these results is to simplify 3G network-dimensioning studies and to reduce the amount of Monte Carlo runs necessary for a network-planning tool to correctly account for shadowing randomness.