IMS Mediation Function for Real-Time VoLTE Lawful Interception
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Solution Overview
Problem
Lawful interception of VoLTE calls in IMS networks is hindered by the lack of necessary information in HI3 headers, requiring heavy post-processing by law enforcement agencies, leading to degraded service quality due to varying RTP codecs and the need for buffering.
Innovation Solution
A mediation function that receives and processes signaling and media messages from IMS networks, calculates correlation numbers, and stores mapping information to transmit media encoding names, enabling real-time handling and decoding of VoLTE calls without buffering, similar to traditional CS call interception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lawful interception of VoLTE calls is performed using standard HI3 headers, then interception can be implemented, but the service quality is degraded due to lack of media encoding information requiring heavy post-processing
Solution Approach 1:
The patent applies preliminary action by including media encoding information (payload type numbers and encoding names) directly in the HI3 headers during the interception process. This pre-inclusion of decoding information eliminates the need for complex post-processing operations, allowing law enforcement agencies to decode intercepted VoIP payloads in real-time without requiring heavy post-processing business logic.
2Adaptability or versatility
If buffering is implemented to handle varying RTP codecs, then all codec information can be collected, but the interception process becomes slower and more complex
Solution Approach 1:
The patent extracts the essential media encoding information (payload type number and encoding name) directly into the HI3 header structure. By taking out only the critical decoding information needed for real-time processing, the system achieves codec compatibility without requiring buffering of entire packets, thus eliminating interception delays while maintaining adaptability to different RTP codecs.
3Loss of information
If codec information is distributed across HI2 and HI3 interfaces, then all necessary data is captured, but real-time decoding becomes impossible without buffering
Solution Approach 1:
The patent merges the media encoding information (payload type number and encoding name) directly into the HI3 header structure. This consolidation combines all necessary decoding information into a single location accessible in real-time, eliminating the need to distribute information across multiple interfaces and buffers, thereby enabling immediate decoding without sacrificing information completeness.
Data Source
AI summary
A mediation function receives intercepted signaling and media payload messages from an IP Multimedia Subsystem, IMS. Local correlation numbers (304) are calculated and a table (300) comprising correlation numbers (304) and media payload mapping information (306) is maintained in order to enable the mediation function to provide a law enforcement agency, LEA, with intercepted media payload together with information that enables the LEA to decode the media payload in real-time.