Definition, analytical derivation and optimization of the lower credit limit in mobile user´s prepaid account for IMS services

This paper deals with prepaid charging in All IP environments. It describes Online charging prepaid system, with the main functionalities, operations and message flows. The derivation of the lower credit limit of user´s prepaid account is showed in detail, with regard to increased signalling, through the greater number of credit checks and updates, and the probability that an in-progress session is forced to terminate. It is shown how this parameters depend of the amount of granted credit units in each reserve units operations and actual credit balance in user´s account.