Patent ID: 7251472

Claim:
A communication system for selecting a PLMN (Public Land Mobile Network), comprising: an MS (Mobile Station) for transmitting an MIN (Mobile Identification Number) message, an ESN (Electronic Serial Number) message and a location update request signal containing location information for registering the location of the MS and for searching for the PLMN on the basis of an HPLMN search period value corresponding to the location update request signal; an MSC (Mobile Switching Center) for performing an authentication procedure for the MS transmitting the location update request signal and extracting the location information from the location update request signal; a VLR (Visitor Location Register) for storing subscriber data of the MS provided from outside the MS and registering a location of the MS; and an HLR (Home Location Register) for updating the location information of the MS extracted from the MSC, variably setting a search period value for determining a time at which to begin a search at a time of searching for an HPLMN or higher-priority PLMN on the basis of the location information of the MS and transmitting the set search period value to the MS.