IMS Gateway Online Charging State Machine
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Solution Overview
Problem
The existing IMS gateway systems lack a clear method for providing session control and budget control for online charging, as described in 3GPP specifications, which complicates the integration of online charging functionality and does not specify how the ISC interface, Ro interface, and S-CSCF function together to support online charging.
Innovation Solution
An IMS gateway system is implemented with a session control interface for communicating with the S-CSCF and a charging interface for the OCS, utilizing state machines to manage online charging by sending credit control messages and handling session initiation, update, and termination requests, thereby providing budget control and quota management during IMS sessions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the ISC interface is extended to support online charging functionality, then online charging can be provided through the existing service interface, but the OCS becomes overloaded with additional functionality and the interface complexity increases
Solution Approach 1:
The patent segments the online charging functionality from the OCS by introducing a dedicated charging trigger function (CTF) that handles credit control requests. This separates the charging trigger operations from the OCS core, allowing the OCS to focus on credit management while the CTF handles interface-specific charging triggers, thus reducing OCS complexity while maintaining online charging capability
Solution Approach 2:
The patent introduces an intermediary charging trigger function (CTF) that mediates between the ISC interface and the OCS. The CTF receives credit control requests from the ISC interface, processes them according to charging rules, and communicates with the OCS for credit verification and management, thereby preventing direct overloading of the OCS with interface-specific functionality
2Adaptability or versatility
If the Ro interface is used instead of the ISC interface for online charging, then online charging is supported natively, but an IMS gateway function must be introduced to translate between SIP session control and Ro credit control
Solution Approach 1:
The patent employs the IMS gateway function as an intermediary that translates between SIP session control messages and Ro credit control messages. The gateway receives SIP messages from the S-CSCF, extracts charging-related information, formulates appropriate Ro credit control requests, and manages the correlation between SIP session states and Ro charging states, enabling native Ro-based online charging while maintaining SIP compatibility
Solution Approach 2:
The patent transforms charging control parameters between different interface protocols. The IMS gateway function converts SIP session parameters (such as session initiation, modification, and termination) into corresponding Ro credit control parameters (such as initial credit control requests, update requests, and termination requests), enabling parameter compatibility across different interface standards
3Productivity
If state machines are implemented to manage online charging, then session control and budget control are provided efficiently, but the system complexity increases
Solution Approach 1:
The patent implements dynamic state machines that automatically transition between different charging control states (such as initial state, session state, update state, and termination state) based on received messages and current system conditions. This dynamic state management enables efficient automated decision-making for credit control operations, improving productivity while the state machine logic is encapsulated to manage complexity
Data Source
AI summary
IMS gateway systems and methods are disclosed for providing online charging for IMS sessions. An IMS gateway system described herein operates based on a state machine to provide charging triggers and IMS session control. For one charging trigger, the IMS gateway system transmits an initial credit control request message to an online charging system (OCS) responsive to receiving a session initiation message from a first subscriber of a session. For another charging trigger, the IMS gateway system transmits an update credit control request message to the OCS responsive to receiving a session acceptance message from a second subscriber of the session. For another charging trigger, the IMS gateway system transmits a termination credit control request message to the OCS responsive to receiving a session termination message. The IMS gateway system may trigger on other session control messages or charging messages from the OCS to provide online charging.