PDU Session Handover via AGF Buffering for Traffic Continuity
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Solution Overview
Problem
Current standards fail to provide seamless handover of protocol data unit (PDU) sessions between radio access networks (RAN) and access gateway functions (AGF), leading to dropped subscriber traffic, resource consumption, and multiple network changes due to reconnecting and reestablishing sessions.
Innovation Solution
Implementing an access gateway function (AGF) that supports Xn application protocol (XnAP) or next generation application protocol (NGAP) for session and service continuity mode 3, enabling seamless handover of PDU sessions between wireless and wireline networks through buffering and end marker packets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current standards are used for handover between RAN and AGF, then the handover process can be completed, but subscriber traffic is dropped and multiple network changes occur due to reconnecting and reestablishing sessions
Solution Approach 1:
The patent applies preliminary action by performing data buffering and sequence number status transfer before the actual handover occurs. The AGF receives and buffers downlink data packets from the RAN prior to the handover command, ensuring data is ready for seamless transfer. This prevents traffic drops by having data waiting in the buffer while the handover transitions, eliminating the need to reestablish sessions and reducing network resource consumption.
Solution Approach 2:
The patent uses an intermediary approach by introducing the AGF as a mediating entity between the RAN and the data network. The AGF acts as a buffer and protocol translator, receiving data from the RAN, maintaining sequence numbers, and forwarding data to the appropriate destination after handover. This intermediary function enables seamless handover by decoupling the data path from the control path, allowing continuous data flow during network transitions without dropping subscriber traffic.
2Productivity
If seamless handover is implemented between RAN and AGF, then resource consumption is reduced, but requires support for XnAP or NGAP protocols and buffering capabilities
Solution Approach 1:
The patent applies universality by designing the AGF to support multiple protocols (XnAP and NGAP) within a single device architecture. The AGF can handle both XnAP-based handovers (for 5G NR networks) and NGAP-based handovers (for LTE networks), making it a multi-functional entity that can serve different network types. This universal capability allows the system to achieve resource-efficient seamless handover while maintaining protocol flexibility, as the AGF can adapt to different network scenarios without requiring separate dedicated devices for each protocol type.
3Reliability
If PDU session is reestablished during handover, then network connectivity can be restored, but causes dropped traffic and multiple network changes
Solution Approach 1:
The patent implements continuity of useful action by maintaining the PDU session context and data buffer throughout the handover process. Instead of tearing down and reestablishing the session, the AGF preserves the existing session state, sequence numbers, and buffered data. The handover simply changes the access path from RAN to AGF while the session remains active and continuous. This eliminates traffic drops because data flows continuously through the buffer during the transition, and no session reestablishment is needed to restore connectivity.
Data Source
AI summary
A device may receive a handover request to handover a protocol data unit (PDU) session of a network device from a radio access network (RAN) to the device, and may provide, to the RAN, a handover request acknowledgment message acknowledging receipt of the handover request. The device may receive, from the RAN, a sequence number status transfer indicating provision of a handover command by the RAN to the network device, and may receive, from the RAN, uplink data packets and downlink data packets associated with the PDU session. The device may receive, from the network device, a request to establish the PDU session, and may establish the PDU session of the network device based on the request to establish the PDU session.