Dual-Protocol Stack for Zero-Mobility Interruption Handover
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Solution Overview
Problem
Current 5G radio access technologies face challenges in reducing mobility interruption time during handovers, particularly in LTE networks, where latency exceeds 50 ms, which is not sufficient for meeting the requirements of 5G networks, especially during intra-frequency and inter-frequency mobility.
Innovation Solution
Implementing dual-protocol stacks in user equipment (UE) that allow simultaneous data transmission and reception with both the source and target gNBs, enabling a seamless handover by configuring a target protocol stack with layers such as PHY, MAC, RLC, PDCP, and SDAP, and performing PDCP reordering to maintain continuous data flow and minimize interruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional handover procedure is used in LTE network, then handover can be completed with existing protocol stack, but mobility interruption time exceeds 50 ms which does not satisfy 5G requirements
Solution Approach 1:
The patent applies preliminary action by configuring the target protocol stack before actual data transmission begins. The UE receives reconfiguration messages and sets up the target protocol stack in advance, allowing seamless switching without interruption. This pre-configuration approach eliminates the traditional handover latency by preparing all necessary protocol layers (PDCP, RLC, MAC, PHY) before the handover event occurs.
Solution Approach 2:
The patent implements continuity of useful action by enabling simultaneous operation of both source and target protocol stacks. During the transition period, the UE maintains data transmission through the source protocol stack while concurrently establishing and testing the target protocol stack, ensuring uninterrupted data flow. This dual-stack operation guarantees continuous communication without mobility interruption.
2Loss of time
If make-before-break approach is used to reduce latency, then handover latency can be reduced, but interruption due to random access procedure and delivering RRCConnectionReConfiguratioComplete message cannot be avoided
Solution Approach 1:
The patent applies segmentation by dividing the protocol stack into multiple independent layers (PDCP, RLC, MAC, PHY) that can be configured and activated separately. This segmentation allows the UE to establish the target protocol stack incrementally without affecting the source stack operation. Each layer can be prepared independently, reducing the complexity of managing the overall handover process while minimizing interruption time.
3Loss of time
If dual-protocol stack is implemented for simultaneous data transmission with source and target gNB, then mobility interruption time is reduced to near zero, but device complexity increases
Solution Approach 1:
The patent applies merging by combining the source and target protocol stacks into a unified dual-stack architecture within the UE. Both stacks share common resources and control mechanisms, allowing seamless coordination between them. This merged structure enables simultaneous data transmission through both stacks without requiring completely separate communication paths, thereby reducing device complexity while achieving near-zero mobility interruption time.
Data Source
AI summary
Apparatus and methods are provided to reduce mobility interruption time through dual-protocol stacks for mobility enhancement. In novel aspect, the UE configures a target protocol stack for a target gNB upon receiving a reconfiguration message from a source gNB, performs random access procedure and establishes RRC connection with the target gNB through the target protocol stack while simultaneously maintaining data transmission and reception with the source gNB, and releases the source RRC connection with the source gNB and performs data transmission and reception with the target gNB upon detecting one or more predefined release triggering event. In one embodiment, the target protocol stack includes a PHY layer, a MAC layer, and RLC layer, a PDCP and optionally a SDAP. In one embodiment, the UE enables a PDCP reordering, wherein the PDCP reordering is performed on PDCP packet data units received from the source and the target protocol stacks.