Three types of widely used radio redundancy coverage schemes are thoroughly inspected in terms of system reliability,disaster recovery,frequency utilization efficiency,anti-interference ability and the impact on handover.This comparison provides a theoretical basis for engineering design in the choice of a redundancy scheme.Path loss modeling for several typical environments is done using Hata model in high-speed scenario.Cell coverage radiuses are calculated with different base station antenna height satisfying train control needs.On this basis,the formula for calculating the length of overlap zone is derived,which provides a way to research the impact of train speed,length of handover zone,handover margin and handover time on the overlap zone.Lengths of overlap designed for different maximum speeds are compared with results derived from C/I requirement,proves the former is better in C/I ratio. Finally,the distance between the base stations is planned and compared with the required minimum distance imposed by the error free period(Qos parameter),which leads to the conclusion that small and medium-sized city is not a suitable environment for high-speed trains.
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