Importance

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Abstract

A system for tracking the location of, and for providing cellular telephone handoff for, a mobile cellphone user as the cellphone user moves from one cellzone to another. A boundary curve B12 between a first cellzone and an adjacent second cellzone is defined in an electronic map by an equation h.sub.B12 (x,y,z)-K12=0 for points with spatial location coordinates (x,y,z) lying on the curve B12, where K12 is a selected constant. First and second quasi-boundary curves QB1 and QB2, lying within the first and second cellzones, respectively, are defined, where each point on the curve QBi (i=1,2) lies at a selected distance di from the boundary curve B12. A region CR12 of points lying between the quasi-boundary curves QB1 and QB2 and including the boundary curve B12 is defined. The present location of the cellphone user is determined using a Satellite Positioning System (SATPS) such as GPS or GLONASS. Cellular telephone service for the cellphone user is provided (1) by a first cellular service provider or (2) by a second cellular service provider, when the cellphone user is located (1) within the first cellzone, not including the overlap region CR12, or (2) within the second cellzone, not including the overlap region CR12. When the cellphone user enters the region CR12 from within the first cellzone and proceeds toward the boundary curve B12, the system carried by the cellphone user notifies at least one of the first and second cellular service providers that the cellphone user is about to leave the first cellzone and about to enter the second cellzone. The system may be extended (1) to determine the approximate location of a missing vehicle and (2) to dynamically change the boundary curves of at least one cellzone to relieve cellular service overloading that occurs within that cellzone.

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First Claim