Charging for Multi-grade Services in the IP Multimedia Subsystem

Flexible charging and QoS provisioning are two of the main motivations behind the IP multimedia subsystem (IMS), defined by 3GPP. We have previously proposed a call differentiation solution for 3G networks. This solution defines different grades of calls with different QoS profiles, and uses a preemptive approach to give priority to more important calls over others. This idea of multi-grade services enables the users to choose the appropriate grade of call for each of their sessions, depending on the priorities/ guarantees they require.  A suitable charging model is needed for the effective charging and billing of such services. In this paper, we focus on the charging aspects of multi-grade IMS services. The IMS online and offline charging mechanisms are leveraged and extended to tackle this issue. Furthermore, a proof-of-concept prototype, showcasing different multi-grade service charging scenarios, is presented.