VoLTE Interworking Function for CS Roaming
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Mobile network operators face challenges in providing voice and SMS services to roaming subscribers without VoLTE roaming agreements, as many visiting operators lack IMS infrastructure or refuse to provide VoLTE to protect revenue, leading to the need for an interworking function between VoLTE and circuit-switched services.
Innovation Solution
An Interworking Function (IWF) is introduced, which includes a Diameter Routing Agent, virtual Home Location Register, virtual Mobility Management Entity, virtual Short Message Service Centre, virtual Gateway Mobile Switching Center, and Serving Gateway, enabling circuit-switched voice and SMS services in a Visited Public Land Mobile Network without requiring VoLTE roaming agreements with the Home Public Land Mobile Network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If home operators implement VoLTE roaming, then voice and SMS service quality is improved, but the need for CS roaming infrastructure cannot be eliminated due to lack of VoLTE roaming agreements
Solution Approach 1:
The patent introduces an Interworking Function (IWF) as an intermediary system that enables circuit-switched voice and SMS services to work over VoLTE infrastructure. The IWF includes a Diameter Routing Agent that intercepts and routes Diameter S6a/s6d messages, virtual HLR that provides subscriber registration to MSC, virtual MME that performs LTE registration, virtual SMSC for SMS routing, and virtual GMSC for call delivery. This intermediary layer allows legacy CS services to function on modern VoLTE networks without requiring traditional CS roaming agreements.
Solution Approach 2:
The patent changes the operational parameters of the network by implementing virtualized network functions that operate over IP-based VoLTE infrastructure. The virtual HLR, vMME, vSMSC, and vGMSC change the state from traditional circuit-switched operation to packet-switched VoLTE operation while maintaining CS service compatibility. The Diameter routing agent modifies message routing parameters to intercept and redirect signaling between VPLMN MME and HPLMN HSS.
2Loss of energy
If visiting operators do not provide VoLTE roaming, then their voice and SMS roaming revenue is protected, but home operators cannot shutdown their 3G roaming network infrastructure
Solution Approach 1:
The IWF acts as a mediator that enables home operators to maintain VoLTE infrastructure while providing backward compatibility with circuit-switched services. The virtual network functions (vHLR, vMME, vSMSC, vGMSC) serve as intermediary components that translate between VoLTE IP-based signaling and traditional CS signaling protocols, allowing operators to phase out 3G infrastructure without losing service capability.
Solution Approach 2:
The patent creates a universal solution where the IWF can operate in multiple scenarios: it can provide CS service emulation over VoLTE for operators with VoLTE infrastructure, and it can interwork with both CS and VoLTE networks. The Diameter routing agent and virtual network functions provide multi-functional capabilities that adapt to different network configurations and roaming scenarios.
3Reliability
If operators equip CS network components for roaming, then MO and MT voice calls and SMS are supported, but the frequency bands cannot be reallocated for 4G and 5G services
Solution Approach 1:
The IWF introduces virtual network functions that mediate between the radio access network and core network services. The vMME performs LTE registration and mobility management over IP, the vHLR provides subscriber data services, and the vSMSC handles SMS routing, all without requiring dedicated CS network components. This allows frequency bands to be fully utilized for 4G/5G services while maintaining roaming capability through virtualized functions.
Solution Approach 2:
The patent replaces the mechanical/physical CS network infrastructure with virtualized software-based network functions running on IP networks. Instead of physical MSC, HLR, and SMSC components dedicated to circuit-switched operations, the system uses virtual instances of these functions that operate over the packet-switched VoLTE infrastructure, eliminating the need for separate frequency bands for CS services.
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 Circuit-switched (CS) roaming towards VPLMN, and VoLTE voice and SMS roaming towards HPLMN. The interworking function translates CS signaling with VPLMN into IMS signaling towards IMS core at HPLMN. The interworking function also performs location-update registration at HSS at HPLMN for receiving mobile-terminated voice calls and SMS.