IMS Roamer Detection via I-CSCF MNC MCC Filtering
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Solution Overview
Problem
Current systems face challenges in differentiating inbound roamers from normal subscribers in IMS networks, particularly in selecting the appropriate entity for authentication and understanding the authentication vector format, due to similarities between CS and IMS authentication vectors, which limits the selection of S-CSCF capable of handling CS authentication for inbound roamers.
Innovation Solution
The proposed solution involves an I-CSCF entity that detects inbound roaming UEs based on MNC and MCC, queries an ICS-IWF entity for IMS roaming agreements, and forwards register messages with an indication for inbound roaming UEs, allowing the S-CSCF to request authentication information from the ICS-IWF acting as a HSS, ensuring appropriate authentication procedures are followed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the I-CSCF and S-CSCF use standard authentication procedures for all subscribers, then the authentication process is simplified, but the system cannot differentiate inbound roamers from normal subscribers, leading to incorrect entity selection and authentication failures
Solution Approach 1:
The I-CSCF performs preliminary detection of inbound roamers by examining the IMPI structure (comparing MNC and MCC) before the authentication process begins. This early identification allows the system to prepare the correct authentication procedure and entity selection in advance, preventing authentication failures while maintaining a streamlined process for normal subscribers
Solution Approach 2:
The I-CSCF acts as an intermediary between the MSC server and the S-CSCF, intercepting the register message and performing roamer detection. It then modifies the message by adding an indication that the UE is an inbound roamer, ensuring the S-CSCF selects the appropriate authentication entity (ICS-IWF) without complicating the overall authentication flow
2Measurement precision
If the system queries the ICS-IWF entity for every register message to check for IMS roaming agreements, then accurate roamer identification is achieved, but the authentication process time increases
Solution Approach 1:
The I-CSCF performs the MNC/MCC comparison in the IMPI structure as a preliminary action before querying the ICS-IWF. This early filter allows the system to quickly identify potential roamers without requiring extensive database queries for every subscriber, reducing overall authentication time while maintaining accuracy
Solution Approach 2:
The system applies a partial check (MNC/MCC comparison) to all subscribers, and only performs the full verification (querying ICS-IWF) for those who match the roamer criteria. This selective approach ensures accurate roamer identification while minimizing the time impact on the overall authentication process
3Productivity
If the S-CSCF is selected without considering inbound roamer status, then the authentication procedure follows the standard path, but the wrong authentication entity is selected, causing authentication failures for roamers
Solution Approach 1:
The I-CSCF adds an indication of inbound roamer status to the register message before forwarding it to the S-CSCF. This preliminary marking ensures that the S-CSCF can immediately identify roamers and select the correct authentication entity (ICS-IWF) without delays, maintaining throughput while ensuring reliability
Solution Approach 2:
The system implements feedback by modifying the register message to include information about the UE's inbound roamer status. This feedback mechanism allows the S-CSCF to adjust its entity selection based on the UE type, ensuring that roamers are directed to the appropriate authentication entity while normal subscribers follow the standard path
Data Source
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AI summary
Embodiments of this disclosure enable the I-CSCF and S-CSCF to detect inbound roaming UEs to network supporting Service Domain Centralization in IMS, so that the S-CSCF is able to select the appropriate database entity and can understand the CS authentication vector.