GPRS Subscriber Tracking via Cross-Interface Correlation
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Solution Overview
Problem
In GPRS networks, it is challenging to correlate and track related packets exchanged across different interfaces due to varying parameters, making it difficult to monitor and manage subscriber sessions, especially when multiple subscribers share the same IP address.
Innovation Solution
A system of monitoring probes captures signaling units and data packets across various GPRS interfaces, correlating subscriber information into a single record using parameters like IMSI, TLLI, and authentication keys, even when these parameters are not present in all messages, and prioritizes message processing to ensure accurate record creation and updating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If dynamic IP address allocation is used to maximize network resource utilization, then IP address pool efficiency is improved, but subscriber identification and session tracking become difficult
Solution Approach 1:
The patent introduces an intermediary correlation system that uses persistent identifiers (IMSI, TLLI) as mediators between the dynamic IP addresses and subscriber identities. The correlation entity maintains mapping records that link temporary IP addresses to permanent subscriber identifiers, enabling accurate tracking despite IP reuse. This intermediary layer resolves the contradiction by decoupling the IP address allocation mechanism from subscriber identification.
Solution Approach 2:
The patent implements a nested structure where multiple layers of identification are embedded within each other: IP address → PDP context → TLLI → IMSI. Each layer provides additional identification context, with the innermost layer (IMSI) serving as the ultimate persistent identifier. This nested approach allows the system to track subscribers through multiple IP address changes by following the nested identification hierarchy.
2Quantity of substance
If multiple subscribers share the same IP address, then network resource utilization is improved, but packet correlation and session tracking across different interfaces become complex
Solution Approach 1:
The patent segments the packet correlation process into distinct functional components: interface-specific message capture, correlation key extraction, mapping record maintenance, and query processing. Each network interface (Gn, Gp, Gi) is handled independently with its own message capture logic, while the correlation entity coordinates them through standardized mapping records. This segmentation reduces complexity by localizing interface-specific logic while maintaining centralized correlation state.
Solution Approach 2:
The patent creates a universal correlation entity that handles multiple functions: correlating packets across different interfaces (Gn, Gp, Gi), maintaining mapping records for multiple subscribers, supporting both active and inactive session tracking, and providing query services. This multi-functional design reduces overall system complexity by consolidating correlation logic into a single universal component rather than requiring separate correlation mechanisms for each interface or subscriber.
3Measurement precision
If comprehensive subscriber monitoring is implemented across all GPRS interfaces, then session tracking accuracy is improved, but system complexity and message processing overhead increase
Solution Approach 1:
The patent extracts only the essential correlation keys (IMSI, TLLI, IP address, PDP context ID) from the complex stream of GPRS interface messages, separating these critical identification elements from the rest of the message data. The correlation entity maintains only these extracted keys in mapping records, rather than processing and storing complete message contents. This extraction approach maintains high tracking accuracy while significantly reducing system complexity and processing overhead.
Solution Approach 2:
The patent performs preliminary message processing at each interface level, where correlation keys are extracted and preliminary mapping records are created before messages reach the central correlation entity. Interface-specific preprocessing filters and organizes data in advance, so the central correlation entity receives pre-processed, structured information rather than raw messages. This preliminary action reduces the processing burden on the central system while maintaining comprehensive monitoring accuracy.
Data Source
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AI summary
A system and method for subscriber tracking and creating subscriber records in a GPRS or UMTS network is disclosed. A local mapping record is created on a probe monitoring a Gi interface upon the detection of Access Start messages. Additional information is sent from a probe monitoring a Gn/Gp interface, and this information is added to the local mapping record. The processing of captured messages and the creation of local mapping record is prioritized to ensure that records for different subscribers who used the same IP address are not improperly combined. Finally, Gi traffic is tagged with unique subscriber information, such as the International Mobile Subscriber Identity (IMSI), not previously present on the Gi network.