Lawful Interception Continuity in SRVCC Handovers

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Solution Overview

Problem

Lawful interception continuity is not maintained during handovers from Packet Switched (PS) to Circuit Switched (CS) access networks in Single Radio Voice Call Continuity (SRVCC) procedures, posing regulatory challenges due to lack of correlation and interception in the CS domain.

Innovation Solution

The Access Transfer Control Function (ATCF) and Access Transfer Gateway (ATGW) are designated as Intercept Access Points, receiving activation messages for lawful interception, ensuring that intercept related information and media are forwarded to Mediation Functions via defined interfaces, maintaining lawful interception continuity before and after SRVCC.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If Session and Service Continuity (SSC) mechanisms are implemented to maintain service during handovers, then service continuity is improved, but lawful interception continuity deteriorates because existing ICEs cannot maintain interception across domain boundaries

Engineering Contradiction:

Improveservice continuityVSAvoidlawful interception continuity

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent introduces a Lawful Interception Continuity Function (LICF) as an intermediary component that bridges the gap between different Intercepting Control Elements (ICEs) in PS and CS domains. The LICF receives interception data from the PS domain ICE, stores it temporarily, and forwards it to the CS domain ICE, ensuring continuous lawful interception across domain handovers without requiring the existing ICEs to be modified.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent segments the lawful interception function into separate components: a PS domain ICE, a CS domain ICE, and a LICF that bridges them. This segmentation allows each component to operate independently within its domain while the LICF ensures continuity, resolving the contradiction by allowing service continuity mechanisms to operate without compromising interception reliability.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If dual mode terminals are deployed to support both PS and CS networks for smooth migration, then adaptability is improved, but device complexity increases due to multiple network interfaces and protocols

Engineering Contradiction:

Improvenetwork compatibilityVSAvoidterminal complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent enables the network infrastructure to provide the complexity management service rather than requiring the terminal to handle it. The dual-mode terminal simply connects to whichever network domain is available, while the network's LICF automatically manages the interception continuity across domains, reducing terminal complexity while maintaining adaptability.

Inventive Principle:

Principle #25Self-service

3Reliability

If SRVCC procedures are implemented to enable voice call continuity from LTE to legacy networks, then service reliability is improved, but lawful interception capability deteriorates due to lack of correlation between domains

Engineering Contradiction:

Improvevoice call continuityVSAvoidinterception correlation

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent ensures continuous lawful interception action across domain transitions by implementing the LICF that maintains interception data flow uninterrupted during SRVCC procedures. The LICF receives data from the PS domain ICE before handover, stores it, and continues forwarding to the CS domain ICE after handover, maintaining interception correlation throughout the voice call continuity process.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent performs preliminary actions by establishing the LICF and its data collection mechanisms before SRVCC handover occurs. The LICF is pre-configured to receive interception data from the PS domain ICE and is ready to immediately forward to the CS domain ICE when handover occurs, ensuring no interruption in interception correlation.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP2870788B1Lawful interception in a communications network

Publication Date: 2016.06.01 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

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AI summary

A method and apparatus for performing Lawful Interception in a communications network. An Access Transfer Control Function (ATCF) receives an activation message instructing lawful interception. The activation message includes a subject identity. The ATCF sends intercept related information to a Mediation Function at a Lawful Intercept node. The intercept related information relates to a communication session in which the subject participates.