Sony Ericsson Mobile Communications Ab

Sam Mullis

Scott Gordon Hicks

Bassam Jarrad

A system and method for determining if a mobile phone is in a home area that does not rely exclusively on the HPLMN data programmed into the mobile phone. To determine whether the mobile phone is in a home area or in a roaming area a processor in the mobile phone checks the PLMN control information in an over-the-air received signal. If the PLMN data matches the PLMN data stored in the mobile phone SIM card IMSI file, then the current network is a home network. Otherwise, the received LAI control data is checked to see whether it matches any LAI data in the OPL file of the SIM card in the mobile phone. If the received LAI data does not match any LAI data in the OPL file, then the network is not a home network but a roamed into network. If the received LAI data does match LAI data in the OPL file, then the OPL file is further examined to see whether the PNN record that the OPL record points to is the first record in the PNN file. If it is, then the network is a home network. If it is not, then the network is a roamed into network.

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Apex, NC, United States of America

Sam Mullis