Personal communication systems using multiple hierarchical cellular overlays

A personal communication system with multiple hierarchical cellular overlays is considered. The system can include a terrestrial segment and a space segment. The terrestrial trail segment, consisting of microcells and macrocells, provides high channel capacity by covering service areas with microcells. Overlaying macrocells cover spots that are difficult in radio propagation for microcells and provide overflow groups of channels for clusters of microcells. At the highest hierarchical level, communications satellites comprise a space segment. The 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 multilayer 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 carried traffic, traffic distribution, blocking, and forced termination probabilities