S-CSCF Reallocation via De-allocation Criteria in IMS
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Solution Overview
Problem
Current methods for reallocating Serving-Call Session Control Function (S-CSCF) in IP Multimedia Subsystem (IMS) networks are inefficient, often terminating active sessions, introducing complexity, and failing to account for unregistered services, especially when the new S-CSCF is geographically distant, leading to suboptimal signal routing and potential race conditions.
Innovation Solution
A method for reallocating S-CSCFs based on de-allocation criteria, where the S-CSCF evaluates and implements de-registration or de-assignment instructions sent via the Cx interface, allowing for seamless transition without affecting I-CSCF functionality, enabling re-allocation during both registered and unregistered service scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Administrative Deregistration procedures are used to switch user to optimal S-CSCF, then service quality is improved, but existing sessions and dialogs are terminated
Solution Approach 1:
The patent introduces a preliminary check mechanism that evaluates whether active sessions exist before executing deregistration. The I-CSCF probes the current S-CSCF to detect active sessions, and only proceeds with re-allocation if no active sessions are found, thus preventing harmful session termination while enabling optimal S-CSCF selection
2Adaptability or versatility
If re-selection procedures are initiated by I-CSCF, then S-CSCF re-allocation is achieved, but I-CSCF functionality is altered and complexity increases
Solution Approach 1:
The patent segments the re-allocation functionality into a separate logical procedure that can be triggered independently. The I-CSCF maintains its core registration handling functions while adding a distinct re-allocation probe mechanism that operates separately, avoiding entanglement of functionalities and reducing overall system complexity
3Duration of action of stationary object
If user is re-allocated to new S-CSCF in different region, then service continuity is maintained, but signal routing efficiency deteriorates
Solution Approach 1:
The patent changes the selection criteria parameter from purely geographical proximity to a composite criterion that includes S-CSCF availability and load status. This allows the system to select an optimal S-CSCF based on operational parameters rather than fixed geographical location, balancing service continuity with routing efficiency
4Adaptability or versatility
If re-allocation is performed during re-registration, then S-CSCF switching is achieved, but race conditions may arise
Solution Approach 1:
The patent introduces a feedback mechanism where the I-CSCF probes the current S-CSCF to obtain status information about active sessions before making re-allocation decisions. This feedback loop provides real-time information that prevents race conditions by ensuring re-allocation only occurs when safe, eliminating the need for complex locking mechanisms
Data Source
AI summary
The invention relates to a method of changing allocation of Serving-Call Session Control Functions (S-CSCFs) to a user of an IMS network. The user is being provided with services via a first S-CSCF allocated to the user. The method includes implementing a re-allocation instruction at the first S-CSCF. The reallocation instruction includes criteria for de-allocation of the user from the first S-CSCF. The S-CSCF determines if the criteria are met; and if the criteria are met, de-allocates the user.