Method for preventing overload in mobile telephone networks by using 'always-on' in the case of a call from a mobile telephone

A method for preventing overload in telecommunications networks with IMS by always-on for a call generated by a user, an IMS terminal of said user being formed by a UMTS terminal and an IMS client;

• in which process
• said user makes a PDP Context request and a GGSN of said network provides said user with a free IP address and the PDP Context becomes active;
• and wherein
• an S-CSCF of the IMS network creates a record in which an association between said IP address and a characteristic identity of the IMS network is included;
• characterized in that the process comprises the steps of:
• when the GGSN is going to deactivate said PDP Context for having been inactive for a predetermined time, an indication of such deactivation is sent to the IMS client which maintains said characteristic IMS identity-IP address association and marks it as fictitious;
• and,
• when said user generates a new call, the IMS client informs the UMTS terminal about the characteristic IMS identity-IP address association marked as fictitious, and the UMTS terminal sends a PDP Context request message, in which message the IP address of said IMS association is included in a determined field.