Migrating the Subscribers of a Prepaid Service

When migrating a service from a legacy system to a target platform, the tasks associated to the introduction of the new platform should be distinguished from the subscriber data migration itself. Migrating the subscriber data of a Prepaid service is a complex operation because data at Application level is checked in real-time when the service is triggered, and further influences the actual behaviour of the service delivered to the end-subscriber. In most cases, telcos want to avoid service interruption for end-subscribers. But the migration steps take some time, so there is always a delay between the moment when subscriber data is dumped from the legacy system and the moment when it can be actually uploaded onto the target platform. Consequently, updates during migration windows cannot be taken into account. In order to avoid any credit loss for the end-subscribers, recharges should be blocked in that time frame. Besides, the routing of the calls and the subscriber location information need to be updated in the customer environment too. A detailed migration procedure involving all the steps on the legacy system, on the target platform, and on the Core Network needs to be designed. Two examples of successful Prepaid Migration are given, one at KPNMobile, one at Vodafone. In the context of the IMS architecture, the current issues with Migration could eventually be simplified in the future.