In a method of providing cellular telephone service to a mobile telephone located in an off-load cellular telephone system adjacent to a main cellular telephone system, the mobile telephone is registered with the off-load cellular telephone system upon the mobile telephone entering the off-load cellular...http://www.google.com/patents/US5862483?utm_source=gb-gplus-sharePatent US5862483 - Mobility management method for delivering calls in a microcellular network
