The third generation network which is vigorous nowadays will be followed by an all-IP infrastructure which is referred as NGN (Next Generation Networks) in the near future. The heterogeneity and mobility of the NGN bring many challenges to the charging system in network management. Charging should be more dynamic in an end-to-end session which includes several service components. In this paper, we firstly introduce the requirements of NGN charging and current related works in the IMS (IP Multimedia Subsystem), which led us to give our proposition which is user-centric charging with end-to-end session binding. Secondly, the experiment scenario interacting with Open IMS Core is specified. Finally, we conclude and offer perspectives.