P-Charging-Parameters Header Prevents Overlapping Charging in IMS
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Solution Overview
Problem
In combined network usage, particularly when IMS is used with CS/PS networks, double or overlapping charging occurs due to complex network interactions, leading to inefficiencies in charging control.
Innovation Solution
The introduction of a P-Charging-Parameters-header in SIP signalling allows for the transfer of charging information, enabling the control point to detect and prevent overlapping charging by adding specific charging details, such as FoC, CAI, ISCI, and CC information, which can be converted for use in ISUP signalling, particularly in scenarios like Voice Call Continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If IMS is combined with CS/PS networks to enable flexible network usage and handovers, then network versatility and service continuity are improved, but charging complexity increases leading to overlapping or double charging
Solution Approach 1:
The charging control function is segmented and distributed across multiple network entities (S-CSCF, AS, MRFC, OCS) with clearly defined responsibilities. Each entity handles specific charging tasks based on its role in the session, preventing centralized complexity while maintaining versatile charging control across CS/PS and IMS networks
Solution Approach 2:
The S-CSCF acts as an intermediary that receives session information from both CS/PS and IMS domains, processes charging requirements, and coordinates with the OCS. This intermediary function prevents overlapping charging by centralizing the decision logic while allowing flexible network combinations
2Reliability
If multiple charging entities (S-CSCF, AS, MRFC) perform online charging independently, then charging coverage is improved, but overlapping charging occurs
Solution Approach 1:
The S-CSCF implements feedback mechanisms by monitoring session states and charging outcomes from multiple entities. When overlapping charging is detected through session information analysis, the S-CSCF provides feedback to coordinate with the OCS to prevent duplicate charging, maintaining reliable charging coverage without harmful overlaps
Solution Approach 2:
The S-CSCF performs preliminary charging control by evaluating session establishment requests before sessions are fully established. This preliminary action includes checking charging eligibility and coordinating with the OCS in advance, preventing overlapping charging from occurring in the first place while ensuring comprehensive charging coverage
Data Source
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AI summary
For controlling charging in an Internet Protocol multimedia subsystem, it is detected whether a session initiated in the Internet Protocol multimedia subsystem is associated with a service requiring special charging control, and charging information is added to messages signalling establishment or modification of the session in the Internet Protocol multimedia subsystem in accordance with the detection result.