Voice Service Handover in eUTRAN to GERAN for Call Continuity
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Solution Overview
Problem
The deployment of Evolved UTRAN (eUTRAN) and Evolved Packet Core (EPC) requires migrating telephony services from a traditional circuit switched (CS) system to a packet switched (PS) system, but initial IMS service deployment may not cover all eUTRAN areas, leading to potential voice call drops when users leave LTE coverage.
Innovation Solution
A method for providing voice service by initiating a PS handover from an eUTRAN cell to a GERAN/UTRAN cell within overlapping coverage areas, allowing voice service establishment in the CS domain using existing 2G/3G cells, thereby ensuring continuous service without premature call drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If telephony services are migrated from circuit switched to packet switched system, then service continuity and quality are improved, but network complexity and deployment requirements increase
Solution Approach 1:
The patent segments the voice service provision into two distinct domains: circuit switched domain for traditional voice services and packet switched domain for data and IMS services. This segmentation allows each domain to operate independently with its own infrastructure, reducing the complexity of migrating the entire telephony system while maintaining service continuity.
Solution Approach 2:
The patent implements a universal mobile telephone interface that can access both circuit switched and packet switched domains. This multi-functional interface allows a single mobile station to utilize different network domains based on service requirements, simplifying the overall network architecture by providing a unified access point for diverse services.
2Productivity
If IMS service is deployed early in eUTRAN areas, then packet switched voice service is improved, but coverage gaps and call drops occur in areas without IMS support
Solution Approach 1:
The patent introduces a media gateway as an intermediary component that bridges the circuit switched and packet switched domains. This media gateway enables seamless handover between domains, allowing voice services to be routed through the packet switched domain when available and falling back to circuit switched domain when IMS is not supported, thereby preventing call drops in coverage gaps.
Solution Approach 2:
The patent implements dynamic service selection where the network can adaptively choose between circuit switched and packet switched domains based on real-time availability and service requirements. This dynamic approach allows the system to optimize voice service delivery by selecting the most appropriate domain at any given time, improving both productivity and reliability.
3Adaptability or versatility
If handover from PS domain to CS domain is implemented, then voice service availability in overlapping areas is improved, but network configuration complexity increases
Solution Approach 1:
The patent performs preliminary actions by pre-configuring handover parameters and selecting target cells in advance. When a mobile station needs to handover from packet switched to circuit switched domain, the network already has the necessary information about suitable target cells and handover procedures prepared, reducing the complexity of real-time configuration and enabling smoother transitions.
Solution Approach 2:
The patent implements feedback mechanisms where the network continuously monitors the service status and availability of different domains. Based on this feedback, the network automatically adjusts the handover decisions and resource allocation, simplifying the configuration process by using real-time information to optimize voice service availability without requiring complex manual setup.
Data Source
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AI summary
User Equipment (UE) receiving non-voice packet switched services in an Evolved Universal Mobile Telecommunications System Terrestial Radio Access Network (eUTRAN) cell undergoes handover to a circuit switched GSM/Edge Radio Access Network (GERAN)/UTRAN cell in response to a voice service page. An eNodeB of the active eUTRAN cell uses a measurement report history for the UE to select an available circuit switched cell for handover. The voice service is established in the circuit switched domain of a GERAN/UTRAN cell to ensure service continuity regardless of UE mobility that would otherwise not be possible if the voice service was established in the eUTRAN cell. A Gs- like interface between a Mobile Switching Center (MSC) of the CS Core Network and the Mobility Management Entity (MME) of the Evolved Packet Core provides an interface for page requests and location update procedures to be performed.