Inter-gNB Handover RSN Allocation for PDU Session Continuity
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Solution Overview
Problem
Current 5G networks face challenges in efficiently managing inter-gNB handovers, particularly in maintaining redundant PDU sessions for ultra-reliable and low-latency communications (URLLC), which affects data transmission reliability and user experience.
Innovation Solution
The implementation of a method for inter-MN handover that includes receiving a handover request message with redundancy sequence number (RSN) information, allowing continuous allocation of PDU sessions to secondary nodes, enabling efficient redundant transmission and remapping of PDU sessions based on resource status.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inter-gNB handover is performed without RSN information, then handover procedure is simple, but PDU session allocation to secondary node cannot be maintained continuously
Solution Approach 1:
The source master node includes RSN information in the handover request message before the handover is executed. This preliminary inclusion of redundancy sequence number information allows the target master node to pre-allocate PDU sessions to secondary nodes, ensuring continuous allocation without interruption during handover, while keeping the procedure integrated within existing handover signaling.
Solution Approach 2:
The RSN (redundancy sequence number) information acts as an intermediary element that carries allocation information from the source master node to the target master node. This intermediary information enables the target node to understand and maintain the PDU session allocation pattern to secondary nodes, ensuring reliability without requiring complex re-negotiation procedures.
2Reliability
If redundant PDU sessions are maintained during handover, then data transmission reliability is improved, but signaling overhead increases
Solution Approach 1:
The handover request message from the source master node preliminarily includes RSN information that encodes the allocation pattern of PDU sessions to secondary nodes. This allows the target master node to establish redundant PDU sessions in advance, ensuring data transmission reliability during handover while avoiding the need for extensive additional signaling to negotiate session allocation after handover completion.
3Productivity
If PDU session allocation is re-negotiated after handover, then resource status can be optimized, but handover latency increases
Solution Approach 1:
The source master node determines and includes RSN information in the handover request message before handover execution. This preliminary determination allows the target master node to allocate PDU sessions to secondary nodes immediately upon receiving the handover request, maintaining resource allocation efficiency while avoiding the latency of post-handover re-negotiation. The target node can then execute handover with pre-established session allocation.
Solution Approach 2:
The system dynamically determines the RSN information based on current resource status and allocation patterns at the source master node, and this dynamic information is transferred to the target master node. This allows the target node to adapt the PDU session allocation to its own resource status while maintaining continuity, achieving both efficiency and low latency through dynamic rather than static pre-configuration.
Data Source
AI summary
A method and apparatus for supporting of inter-gNB handover in higher layer multi-connectivity is provided. A target master node (MN) of an inter-MN handover procedure receives a handover request message including information on a redundancy sequence number (RSN) from a source MN of the inter-MN handover procedure. The information on the RSN informs that a protocol data unit (PDU) session mapped to the RSN is allocated to a secondary node (SN) of the inter-MN handover procedure for redundant transmission.