CU-DU PDCP Sequence Reset During 5G Device Reconfiguration
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Solution Overview
Problem
Current 5G Radio Access Networks face challenges in effectively coordinating control plane traffic management during device reconfigurations, particularly in managing PDCP sequence numbers during events like intra gNB-DU handovers, leading to potential communication disruptions.
Innovation Solution
A method and system for coordinating control plane traffic management by resetting the PDCP sequence number of control plane traffic in response to events such as intra gNB-DU handovers, involving communication between a central unit (CU) and a distributed unit (DU) using F1 interface messages with indicators and flags to ensure synchronized communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PDCP sequence number is reset during intra gNB-DU handover without clear indicators, then the handover procedure can be completed, but the PDCP count may be erroneously advanced leading to handover failures
Solution Approach 1:
The patent implements a feedback mechanism where the gNB-DU sends an indicator (e.g., 'firstMessageIndicator') to the gNB-CU to signal when the first uplink RRC message from the target cell is received. This feedback enables the gNB-CU to accurately determine the timing for PDCP sequence number resetting, preventing erroneous count advancement and ensuring reliable handover completion.
Solution Approach 2:
The patent introduces an intermediary indicator message (firstMessageIndicator) that mediates between the gNB-DU and gNB-CU to convey critical timing information. This intermediary element bridges the information gap, allowing the gNB-CU to synchronize PDCP sequence number resetting with the actual receipt of the first message from the target cell, thereby resolving the timing accuracy issue.
2Device complexity
If the gNB-CU operates without clear indicators from the gNB-DU, then the system architecture remains simple, but the coordination of control plane traffic management becomes inaccurate
Solution Approach 1:
The patent applies preliminary action by having the gNB-DU prepare and send the firstMessageIndicator before the gNB-CU needs to reset the PDCP sequence number. This advance notification ensures that the timing information is available when needed, preventing information loss without requiring complex retrospective analysis or additional system architecture elements.
3Productivity
If the PDCP sequence number resetting is performed without accurate timing indicators, then the processing speed remains fast, but the coordination accuracy during device reconfiguration deteriorates
Solution Approach 1:
The feedback mechanism through the firstMessageIndicator enables the gNB-CU to accurately determine when to reset the PDCP sequence number without introducing significant processing delays. The indicator is sent as part of the existing F1AP message flow, maintaining fast processing while ensuring resetting accuracy is improved through precise timing information.
Data Source
AI summary
The present disclosure relates generally to communications, and more particularly to communication methods and related devices and nodes for control plane traffic management. Among other things, the disclosure presents a method performed by a central unit (CU) of a network node for coordination of control plane traffic management during a communication device reconfiguration in a telecommunications network. The method may, e.g., comprise receiving information from a distributed unit (DU) of the network node alerting the CU to reset a packet data convergence protocol (PDCP) sequence number of control plane traffic signaled from the communication device as a consequence of an event in the telecommunications network; and responsive to receiving the information, resetting the PDCP sequence number of the control plane traffic signaled from the communication device.