Dual-Connectivity Split-Bearer Control for In-Order PDCP Delivery
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Solution Overview
Problem
Dual-connectivity architectures in 5G networks result in out-of-order delivery and high packet re-ordering delays due to differing delays on 5G NR and LTE paths, impacting throughput, particularly for TCP-based applications.
Innovation Solution
Implement a traffic split controller in the CU-UP that estimates packet delays on LTE and NR links, selectively directing PDCP packets to minimize inter-packet delay by choosing the link with lower delay for enqueuing, switching when the delay difference exceeds, and distributing packets based on service rate ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If PDCP packets are split and transmitted through both 5G NR and LTE paths in dual-connectivity, then throughput capability is improved, but packet delivery order is compromised
Solution Approach 1:
The system performs preliminary actions by buffering packets at the PDCP entity before transmission and using sequence numbers to track expected packet order. The re-ordering buffer stores packets temporarily while the re-ordering timer monitors delivery status, allowing the system to prepare for potential out-of-order delivery and manage packet sequencing proactively.
Solution Approach 2:
The system implements feedback mechanisms through the re-ordering timer that monitors packet delivery status from both 5G NR and LTE paths. When packets arrive out-of-order, the timer provides feedback about delivery delays, enabling the system to adjust packet handling strategies and maintain reliable in-order delivery despite the parallel transmission paths.
2Reliability
If packets are buffered in the PDCP re-ordering buffer to ensure in-order delivery, then packet delivery reliability is improved, but transmission time is increased
Solution Approach 1:
The PDCP entity performs self-service by automatically managing packet re-ordering through its internal re-ordering buffer and timer mechanisms. The system monitors its own packet delivery status and autonomously handles out-of-order packets without external intervention, using sequence numbers and timing information to restore proper packet order while minimizing delay.
Solution Approach 2:
The system changes parameters dynamically by adjusting the re-ordering timer duration and buffer management strategies based on real-time packet delivery conditions. When packets arrive out-of-order, the timer parameter is activated to control the waiting period, and the buffer is managed to release packets once in-order delivery is achieved, optimizing the balance between reliability and time loss.
3Productivity
If a traffic split controller selectively directs packets to minimize inter-packet delay, then transmission efficiency is improved, but system complexity is increased
Solution Approach 1:
The traffic split controller implements dynamic packet routing decisions by continuously monitoring delay conditions on both 5G NR and LTE paths. The controller adapts its packet distribution strategy in real-time based on actual transmission delays, switching between paths or adjusting packet direction to minimize inter-packet delay, thereby optimizing transmission efficiency through dynamic adaptation rather than static rules.
Solution Approach 2:
The traffic split controller performs preliminary analysis of delay conditions and pre-determines optimal packet routing paths before packets are transmitted. By estimating delay parameters and preparing routing decisions in advance, the system can efficiently direct packets to the appropriate path without complex real-time processing, reducing the operational complexity while maintaining high transmission efficiency.
Data Source
AI summary
Systems and methods for dual-connectivity split-bearer packet management are presented. In one embodiment, a dual-connectivity, split-bearer base station, comprises: at least one centralized unit (CU) comprising a CU-CP) and at least one CU-UP; at least one DU coupled to the at least one CU-UP, wherein the at least one DU is coupled to one or more RUs configured as a first cell group to establish a first radio link for communicating with UE within a wireless coverage area; an eNodeB coupled to the at least one CU-UP, wherein the eNodeB comprises one or more RPs configured as a second cell group to establish a second radio link for communicating with UE within the wireless coverage area; and a traffic split controller configured to selectively direct PDCP packets to either the DU or the eNodeB as a function of packet delay times associated with the DU and the eNodeB.