CSFB Paging for VoIP Call Continuity at LTE Edge
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In a radio access network, particularly when a user equipment (UE) is at the edge of the LTE RAN's VoIP service area with no adjacent LTE coverage supporting VoIP, the UE experiences poor coverage leading to potential VoIP call drops due to lack of handover options.
Innovation Solution
Implement a method where the UE is signaled to transition from the LTE RAN to a CDMA RAN via CSFB (Circuit-Switched Fallback) paging, ensuring continuous voice service by engaging the CDMA RAN to take over the voice call when the UE is determined to be at the edge of LTE coverage without adjacent LTE VoIP support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE remains on LTE RAN at the edge of coverage, then the UE can maintain LTE data service, but the UE experiences poor coverage and potential VoIP call drops
Solution Approach 1:
The patent introduces CSFB (Circuit-Switted Fallback) as an intermediary mechanism that enables the UE to transition from LTE RAN to CDMA RAN when at the edge of LTE coverage. The CSFB paging mechanism acts as a mediator that triggers the handover process, allowing the UE to maintain reliable voice service by switching to a network with stronger coverage while preserving the ability to use LTE for data services when available.
2Reliability
If the UE handovers to CDMA RAN, then the UE maintains voice service coverage, but the UE loses LTE VoIP service capability
Solution Approach 1:
The patent implements a dynamic service selection mechanism where the UE can adaptively switch between LTE and CDMA RANs based on coverage conditions and service requirements. The system dynamically determines whether to maintain LTE connectivity for VoIP services or fallback to CDMA for basic voice services, providing flexible adaptability rather than a fixed service mode.
Solution Approach 2:
The patent changes the network selection parameter dynamically based on coverage strength and service type. When the UE is at the edge of LTE coverage, the system changes the active radio access network parameter from LTE to CDMA, enabling voice service continuity. This parameter change is triggered by monitoring coverage conditions and service availability.
3Reliability
If the network implements CSFB paging to transition UE to CDMA RAN, then VoIP call drops are prevented, but network signaling complexity increases
Solution Approach 1:
The patent implements preliminary registration of the UE with the CDMA RAN while the UE is still served by LTE RAN. This preliminary action ensures that when CSFB paging is initiated, the UE is already registered and ready to quickly transition to CDMA service, reducing the complexity and time of the handover process compared to establishing a new registration at the moment of handover.
Data Source
AI summary
When a UE is served by a first radio access network (RAN) and is engaged in a voice call such as a VoIP call, a determination will be made that the UE is at an edge of coverage (e.g., threshold poor coverage) of the first RAN and that there is no other adjacent coverage of the first RAN that could support the voice call. In response, signaling will cause a second RAN to page the UE via the first RAN so as to cause the UE to transition from being served by the first RAN to being served by the second RAN. More generally, when a UE has poor coverage of its serving RAN, another RAN will pull the UE to the second RAN by paging the UE to trigger transition of the UE from to the second RAN.