SRVCC Handover in 5G Networks via AMF Intermediary
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Solution Overview
Problem
The Next Generation Core Network (NGCN) faces challenges in enabling voice service continuity without adding CS interworking functionality, particularly in supporting SRVCC handovers to UTRAN/GERAN/CDMA networks, due to the coexistence of legacy CS networks with EPC and NGCN, which complicates the transition to 5G technology.
Innovation Solution
The solution involves a method where a gNB or eLTE eNB connected to the NGCN orders a UE to handover to an EUTRAN-connected eNB that supports SRVCC, based on indications of SRVCC capability and VoLTE sessions, ensuring seamless voice over IP continuity by anchoring the user plane in the NGCN while performing the handover to an SRVCC-capable EPC network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NGCN anchors user plane for VoLTE sessions and hands over UE to EPC for SRVCC, then voice service continuity is maintained, but core network complexity increases due to dual connectivity management
Solution Approach 1:
The patent introduces the AMF as an intermediary entity that mediates between the NGCN and EPC networks. The AMF receives SRVCC handover requests from the NGCN, manages the handover process to EPC, and coordinates the user plane anchor relocation. This intermediary role simplifies the overall system complexity by centralizing the handover management logic in a dedicated component rather than distributing it across multiple network elements.
Solution Approach 2:
The patent segments the core network functions by separating the control plane (handled by AMF in NGCN) from the user plane (anchored in EPC during SRVCC). This segmentation allows each network to operate independently in its optimized domain while maintaining service continuity through coordinated handover management.
2Adaptability or versatility
If gNB orders UE to handover to EUTRAN eNB for SRVCC support, then SRVCC capability is enabled, but radio access network complexity increases due to multi-RAT coordination
Solution Approach 1:
The patent implements dynamic handover decision-making where the gNB evaluates UE capabilities, current session status, and network conditions to determine whether to initiate SRVCC handover. The handover target selection is also dynamic, allowing the system to adapt to changing radio conditions and network availability, thereby managing complexity through intelligent adaptation rather than static configuration.
3Device complexity
If NGCN does not add CS interworking functionality, then network simplicity is maintained, but support for legacy CS networks is reduced
Solution Approach 1:
The EPC network acts as an intermediary that provides the CS interworking functionality on behalf of the NGCN. The EPC's MSC server handles the circuit-switched voice calls and coordinates with the NGCN's AMF for control plane functions. This allows the NGCN to maintain its simplified architecture without direct CS network interfaces while still supporting legacy CS networks through the EPC's established interworking capabilities.
Solution Approach 2:
The EPC network performs multiple functions including both packet-switched data routing and circuit-switched voice call handling. By leveraging the EPC's existing multi-functionality, the system avoids duplicating CS interworking capabilities in the NGCN, thereby maintaining network simplicity while preserving support for legacy CS networks.
Data Source
Figure 1~2A
Figure 2B~2C
Figure 3A~3B
AI summary
Apparatus and methods relating to enabling a wireless device to perform SRVCC when connected to a 3GPP specified gNB and a 5G core network that does not support SRVCC are disclosed. In some embodiments, a method of operation of a wireless device comprises providing an indication to the 5G core network that the UE support SRVCC in EPC mode and receiving instruction to connect to an eNB in EUTRAN and EPC that supports SRVCC to a circuit switched network. In this manner, the gNB and the 5G Core network is not required to support SRVCC. Related embodiments in gNB and a control plane entity in the G core network are also provided.