Disclosed is a mobile radio communication system in which a position
registration area number is reported from a base station to a mobile
station within a radio zone, position information indicating a position
registration area in which a mobile station resides is registered in
storage means based upon position registration information that has been
transmitted from the mobile station, and when there is an incoming call
to a mobile station, a paging call is placed from a plurality of base
stations within the position registration area, in which the base station
resides, based upon position information that has been read out of the
memory means. Updating of the position registration area of a mobile
station can be performed automatically on the network side without the
mobile station transmitting position registration information to the
network side. To achieve this, a rule for predicting the manner in which
a mobile station will change a position registration area by moving is
registered beforehand on the network side. Whether a state in which the
rule is applicable has been attained is checked for every mobile station.
If such a state is attained, the position registration area of the mobile
station is updated based upon the rule.