Personal communications systems using multiple hierarchical cellular overlays

A personal communication system with hierarchical cellular overlays is considered. The system can include a terrestrial segment and a space segment. The terrestrial segment, consisting of microcells and macrocells, provides high channel capacity by covering service areas with microcells. Overlaying macrocells provide overflow groups of channels for clusters of microcells. At the highest hierarchical level, satellite beams overlay clusters of terrestrial macrocells and provide primary access for satellite-only subscribers. Call attempts from cellular/satellite dual subscribers are first directed to the terrestrial cellular network, with satellites providing necessary overlay. At each level of the hierarchy, hand-off calls are given priority access to the channels. The mathematical structure is that of a multi-layer hierarchical overflow system. An analytical model for teletraffic performance (including hand-off) is developed. Theoretical performance measures are calculated for users having different mobility characteristics. These show the traffic distribution, blocking, and forced termination probabilities