Reducing credit re-authorization cost in UMTS online charging system

During an online charging General Packet Radio Service (GPRS) session, a number of mid-session events, such as changes of Quality of Service (QoS), could dynamically affect the rating of the in-progress service. When such events occur, the GPRS support node needs to re-authorize the granted credit units with the Online Charging System (OCS). This paper proposes a threshold-based scheme that utilizes a threshold parameter δ to reduce the signaling traffic for the credit re-authorization procedure. By selecting an appropriate S value, the signaling overhead in the OCS can be significantly reduced while the inaccuracy of the credit information insignificantly increases. The mobile operator can choose appropriate parameter values in the threshold-based scheme based on our study.