PDU Session Handover Using AGF Buffering for Lossless RAN Transfer
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Solution Overview
Problem
Current techniques fail to provide seamless handover of protocol data unit (PDU) sessions between a radio access network (RAN) and an access gateway function (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 protocols like XnAP and NGAP for seamless handover, utilizing handover requests, commands, and buffering to maintain session continuity, and using end marker packets for lossless transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current handover techniques are used between RAN and AGF, then session continuity is broken, but implementing seamless handover protocols increases system complexity
Solution Approach 1:
The source AGF performs preliminary actions by buffering downlink data packets and transmitting them to the target AGF before the handover is complete. This preliminary data transfer ensures that no data is lost during the handover transition, maintaining session continuity without requiring complex retransmission protocols later.
Solution Approach 2:
The patent introduces an intermediary mechanism where the source AGF acts as a mediator that temporarily holds and forwards downlink data to the target AGF. This intermediary approach simplifies the handover process by centralizing the data transfer coordination at the source AGF, avoiding the need for complex direct coordination between multiple network elements.
2Loss of information
If seamless handover is implemented, then data loss is prevented, but resource consumption increases during the transition
Solution Approach 1:
Data buffering and pre-transfer is performed as a preliminary action before handover completion. The source AGF buffers outgoing downlink data and proactively transfers it to the target AGF, ensuring no data loss occurs during the transition. This approach prevents information loss while managing resource consumption through controlled, scheduled data transfer rather than reactive retransmission.
Solution Approach 2:
The handover process maintains continuity of useful action by ensuring uninterrupted data flow from source to target AGF. The buffering and forward transmission of downlink data creates a continuous data pipeline that bridges the handover gap, preventing data loss while efficiently utilizing network resources through sustained forward progress rather than stop-start retransmission cycles.
3Adaptability or versatility
If PDU session is reestablished during handover, then network adaptability is improved, but handover time increases
Solution Approach 1:
The target AGF performs preliminary actions by pre-establishing the PDU session context and receiving buffered data before the handover is finalized. This allows the network to adapt to the handover by having the target AGF ready with the necessary session information, reducing the actual handover time while maintaining full network adaptability through pre-configured session parameters.
Solution Approach 2:
The target AGF receives a copy of the PDU session context and buffered downlink data from the source AGF. This copying mechanism allows the target AGF to immediately assume the session without requiring time-consuming reestablishment procedures, thereby reducing handover time while maintaining network adaptability through the copied session parameters.
Data Source
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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.