Mobile switchboard, mobile unit, mobile communication system, and position-registration extending method

摘要

A mobile unit transmits a request for position registration to a network when moving from a first area to a second area. When the number of incoming calls does not exceed a threshold and the number of movements between the first area and the second area exceeds a threshold, a mobile switchboard combines the first area and the second area into an extended area, and informs the mobile unit of the extended area.