CSoPS IWF Anchoring Voice Calls for Seamless Roaming
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Solution Overview
Problem
Current technologies for inter-domain handovers between packet and circuit switched sessions in LTE networks often require dual-mode terminals and IMS deployment, limiting seamless roaming and voice service continuity, especially when visiting non-CSoPS capable networks, which can result in service disruptions and reduced data rates during voice calls.
Innovation Solution
A method and apparatus for inter-domain roaming that uses a CSoPS interworking function (IWF) in the home network to anchor voice calls and trigger handovers between CSoPS and CS access legs, allowing seamless switching between IMS and CS services, even in networks without CSoPS support, by providing STN-SR parameters and using a modified MSC+ to manage call continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CSFB is used to provide voice service in LTE network, then voice service can be offered before high quality VoIP support is included, but data rates are reduced and call setup delay increases
Solution Approach 1:
The system segments the voice service handling by introducing a dedicated CSoPS IWF component that separates voice call processing from general packet switching. This allows voice services to be handled through a specialized path while data services continue through the standard LTE packet switched path, enabling simultaneous high-speed data and voice without mutual interference.
Solution Approach 2:
The CSoPS IWF acts as an intermediary between the LTE packet switched network and the circuit switched voice network. It receives voice call requests, processes them through the packet switched infrastructure, and coordinates with the MSC to maintain voice service continuity, thereby preserving data rates while ensuring voice availability.
2Reliability
If dual-mode terminals are required for inter-domain handovers, then service continuity can be maintained, but device complexity and cost increase
Solution Approach 1:
The CSoPS IWF serves as a network-side intermediary that enables single-mode LTE terminals to perform inter-domain handovers. It manages the coordination between packet switched and circuit switched domains, handling the complexity of dual-mode operation at the network level rather than requiring it in the terminal device.
Solution Approach 2:
The system enables self-service handover management where the network infrastructure (CSoPS IWF and MSC) automatically handles the complex coordination required for inter-domain handovers. The terminal simply follows network instructions without needing built-in dual-mode capabilities, as the network performs the heavy lifting of managing the handover process.
3Adaptability or versatility
If IMS deployment is required for VoIP services, then packet switched voice services can be provided, but deployment complexity and cost increase
Solution Approach 1:
The invention extracts the essential voice service functionality from the complex IMS framework by introducing a simplified CSoPS IWF component. This extracted function provides packet switched voice service capabilities without requiring full IMS deployment, reducing network infrastructure complexity while maintaining adaptability for voice services over LTE.
Data Source
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AI summary
A method for inter-domain roaming between a home network H-PLMN provided with a circuit switched over packet switched CSoPS interworking function IWF and a visited network V-PLMN supporting SRVCC mechanisms, said method comprising providing parameters (STN-SR) to the visited network, using HSS of the home network, to allow contact between MSC of the visited network and home network located MSC; said method being characterized in that it comprises the following steps: - anchoring voice call in home network using CSoPS IWF and MSC+ in the home network; - triggering handover using Sv interface from EPC to MSC in visited network; - switching between CSoPS and CS access legs in home network for call continuity.