VoLTE Interworking Function for Roaming Service Compatibility
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Solution Overview
Problem
Current technologies face challenges in providing VoLTE and SMS services in a roaming environment without the need for CS infrastructure, as VoLTE roaming agreements are often not established between operators, preventing the shutdown of 2G/3G networks and limiting service provision for LTE-only operators.
Innovation Solution
An Interworking Function (IWF) is introduced to enable VoLTE and 'SMS over SGs' services without requiring VoLTE roaming agreements, utilizing a Diameter Routing Agent, IMS Core, virtual Home Subscriber Server, and Packet Data Network Gateway to redirect IMS traffic and provide seamless voice and SMS services by behaving as VoLTE roaming towards the Visited Public Land Mobile Network and Circuit Switched roaming towards the Home Public Land Mobile Network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If VoLTE roaming is implemented without CS infrastructure, then network cost and complexity are reduced, but service compatibility and reliability deteriorate due to lack of roaming agreements
Solution Approach 1:
The patent introduces an Interworking Function (IWF) as an intermediary system that bridges the VoLTE network and legacy CS network. The IWF includes a Diameter Routing Agent (DRA) that intercepts and redirects signaling messages, and an IMS Core that handles voice and SMS services. This mediator enables LTE-only operators to provide roaming services without direct VoLTE roaming agreements, while maintaining compatibility with traditional CS-based roaming partners.
2Productivity
If 2G/3G networks are shut down to save frequency bands and reduce costs, then resource efficiency is improved, but service availability for roamers deteriorates
Solution Approach 1:
The patent creates a virtual copy of the CS network functionality through the IWF system. The DRA copies and redirects signaling messages that would traditionally go to CS network elements, and the IMS Core replicates voice and SMS service delivery. This virtual copying allows the network to maintain CS service compatibility without physical CS infrastructure, enabling LTE-only operators to serve roamers using only 4G/5G frequency bands.
3Reliability
If VoLTE roaming agreements are required, then service quality is improved, but market accessibility and operator flexibility worsen
Solution Approach 1:
The patent segments the roaming service delivery into two independent paths: a direct VoLTE path for operators with roaming agreements, and an IWF-mediated path for operators without agreements. The DRA segments the signaling flow by intercepting and redirecting messages, while the IMS Core segments the service delivery for voice and SMS. This segmentation allows operators to choose their preferred roaming approach based on their specific needs and partnerships.
Data Source
AI summary
This invention is a system and method for implementing a VoLTE and circuit switched voice and SMS interworking function to provide voice and SMS service to roaming mobile devices at visiting network based on VoLTE roaming and ‘SMS over SGs’ towards VPLMN, and circuit-switched voice and SMS towards HPLMN. The interworking function enables and redirects IMS traffic at VPLMN towards a hosted IMS core with voice connectivity to PSTN via MGCF and MGW. The interworking function also performs circuit-switched location-update registration at HLR at HPLMN for receiving mobile-terminated voice calls and SMS.