Inbound Roaming Identity Caching for Lawful Interception Positioning
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Solution Overview
Problem
Existing systems face challenges in reducing network load while enabling accurate location requests for inbound roaming UEs in visited communications networks, particularly during lawful interception.
Innovation Solution
Implementing a Lawful Interception Mirror Management System State Function (LMISF) device that stores associations between MSISDN, IMSI, and serving MME identifiers for inbound roaming UEs, and facilitates communication with a LI-GMLC device using existing interfaces like SLh and NLh to retrieve necessary information for positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a GMLC dedicated to Lawful Interception (LI-GMLC) is implemented to enable location requests for inbound roaming UEs, then the ability to locate individuals during lawful interception is improved, but the network load and complexity increase
Solution Approach 1:
The patent introduces an Identity Caching Function (ICF) as an intermediary component that caches identity mappings between MSISDN and IMSI. This intermediary allows the LI-GMLC to retrieve subscriber information without directly querying the home network, thereby reducing network load while maintaining lawful interception capabilities. The ICF acts as a buffer between the visited network and home network, storing pre-fetched identity associations.
Solution Approach 2:
The system performs preliminary actions by pre-fetching and caching identity information (MSISDN-IMSI mappings) before they are needed for lawful interception. The ICF proactively retrieves and stores subscriber identity associations during normal network operations, so that when a location request is made, the information is already available locally without requiring real-time network queries.
2Loss of time
If identity information is cached locally in the visited network, then the response time for location requests is improved, but the memory requirements and data storage needs increase
Solution Approach 1:
The patent applies local quality by implementing caching specifically for identity information (MSISDN-IMSI mappings) in the visited network's ICF, rather than caching all types of subscriber data. This targeted approach stores only the essential identity associations needed for lawful interception, minimizing storage requirements while achieving the goal of faster location request processing.
3Measurement precision
If the LI-GMLC queries the home network for each location request, then the accuracy of subscriber identification is improved, but the network load and signaling overhead increase
Solution Approach 1:
The patent uses copying by creating and storing local copies of identity information (MSISDN-IMSI mappings) in the ICF of the visited network. Instead of repeatedly querying the home network for the same subscriber identity data, the LI-GMLC uses these pre-cached copies, which maintain identification accuracy while dramatically reducing signaling overhead and network load.
Data Source
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AI summary
An LMISF device (310), a LI-GMLC device (410), methods, and computer programs are disclosed. The LMISF device (310) for lawful interception and data retention in a visited communications network (220) for one or more inbound roaming UEs (210, 215), is configured to: receive signalling (315) related to the one or more inbound roaming UEs (210, 215), the signalling (315) comprises an MSISDN, and an IMSI, corresponding to each of the one or more inbound roaming UEs (210, 215), and a serving MME identifier for each of the one or more inbound roaming UEs (210, 215); store an association among the MSISDN, the corresponding IMSI, and the serving MME identifier for each of the one or more inbound roaming UEs (210, 215); receive, from an LI-GMLC, device (410), a query message (420) containing a MSISDN of a target inbound roaming UE and requesting an associated IMSI and a serving MME identifier corresponding to the MSISDN; and transmit, to the LI-GMLC device (410), a response message (430) comprising the associated IMSI and the serving MME identifier corresponding to the MSISDN for the target inbound roaming UE, if the MSISDN of the target inbound roaming UE is stored in the LMISF device (310).