Interworking Function for VoLTE Roaming SMS Interoperability
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Solution Overview
Problem
Mobile network operators face challenges in providing voice and SMS services to outbound roamers without VoLTE roaming agreements, as many visiting operators lack IMS infrastructure or refuse to offer VoLTE roaming to protect revenue, leading to the need for an interworking function between VoLTE and circuit-switched services.
Innovation Solution
The Interworking Function (IWF) enables circuit-switched voice and SMS services in a Visited Public Land Mobile Network without requiring VoLTE roaming agreements by acting as CS roaming towards the VPLMN and VoLTE roaming towards the HPLMN, utilizing a Diameter Routing Agent, virtual Home Location Register, virtual Mobility Management Entity, virtual Short Message Service Centre, and other components to intercept and route messages and establish connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If home operators shut down 2G/3G network infrastructure to save frequency bands and reduce costs, then operational costs are reduced and frequency bands are freed for 4G/5G services, but the ability to provide voice and SMS service to outbound roaming subscribers is lost when visiting operators do not have VoLTE roaming agreements
Solution Approach 1:
The patent introduces an Interworking Function (IWF) as an intermediary system that bridges the gap between VoLTE home networks and circuit-switched visited networks. The IWF translates and routes signaling messages between Diameter (VoLTE) and MAP (circuit-switched) protocols, enabling seamless service interworking without requiring direct VoLTE roaming agreements between all operator pairs.
Solution Approach 2:
The patent segments the roaming service functionality into separate virtual network functions (VNFs) including vHLR, vMME, vSMSC, and vGMSC. These virtualized components can be independently deployed and managed, allowing operators to maintain circuit-switched roaming capabilities through software rather than dedicated hardware infrastructure.
2Reliability
If home operators maintain 2G/3G network infrastructure to provide voice and SMS service to outbound roamers, then service availability is maintained, but operational costs increase and frequency bands are occupied
Solution Approach 1:
The patent merges multiple network functions (HLR, MME, SMSC, GMSC) into a single integrated IWF platform that handles both VoLTE and circuit-switched roaming. This consolidation eliminates the need for separate physical infrastructure for different roaming types, reducing operational costs while maintaining service availability.
Solution Approach 2:
The patent creates virtual copies of traditional network elements (vHLR, vMME, vSMSC, vGMSC) that replicate the functionality of physical hardware components. These virtual instances can be deployed on standard server hardware, reducing the need for specialized equipment and lowering operational costs.
3Reliability
If visiting operators do not have IMS infrastructure or refuse to provide VoLTE roaming, then their existing voice and SMS roaming revenue is protected, but home operators cannot provide VoLTE roaming service to their subscribers
Solution Approach 1:
The patent changes the protocol parameter interface at the IWF boundary, translating between Diameter protocol (used in VoLTE/IMS networks) and MAP protocol (used in traditional circuit-switched networks). This parameter transformation allows the home network to communicate with visiting operators using the protocol they support, regardless of whether they have IMS infrastructure.
Solution Approach 2:
The IWF is designed with multi-functionality to handle multiple types of roaming scenarios: it can translate VoLTE calls to circuit-switched calls, route SMS messages between different protocol domains, and manage subscriber data for both VoLTE and traditional roaming. This universal approach enables compatibility with visiting operators regardless of their infrastructure type.
Data Source
AI summary
SMS services are provided to roaming mobile devices at visiting networks. This invention implements interworking between VoLTE and circuit-switched (CS) SMS and handles roaming towards both the VPLMN (visited public land mobile network) and HPLMN (home public land mobile network). The interworking function translates CS signals from the VPLMN into IMS signals for the IMS core at the HPLMN and performs location-update registration at the HSS at the HPLMN to exchange SMS communications.