MOBILE UNIT TRACKING SYSTEM

摘要

A communication network keeps track of the locations of mobile units which utilize the network. On powering up, the mobile units determine their current locations using signals broadcast, for example, by overhead satellites. They then send data communication messages to the network describing their locations. The network saves the locations and returns data messages that describe borders which surround the mobile units' locations. The mobile units repetitively determine their current locations on a regular schedule. When their current locations are outside of their prescribed borders, they send other location data messages to the network to update the location data being maintained by the network and to receive a definition of a new border.