Terminal DAPS Protocol Stack Configuration for Handover
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Solution Overview
Problem
Current LTE and NR technologies face challenges in efficiently controlling mobility during handover processes, particularly in minimizing user data interruption and improving handover robustness, with a lack of detailed operations for terminal apparatus mobility control.
Innovation Solution
The implementation of a Dual Active Protocol Stack (DAPS) mechanism in terminal and base station apparatuses, where a processing unit determines which Data Radio Bearer (DRB) to apply DAPS to and which to exclude, associating appropriate Radio Link Control (RLC) entities and Dedicated Traffic Channels (DTCH) with a target primary cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single protocol stack is used for handover, then device complexity is reduced, but user data interruption increases and handover robustness deteriorates
Solution Approach 1:
The patent divides the protocol stack into two separate instances (first protocol stack and second protocol stack) that operate simultaneously during handover. This segmentation allows independent management of source and target cell connections, enabling seamless transition without data interruption while maintaining manageable complexity through structured separation of functions.
Solution Approach 2:
The patent implements dynamic protocol stack management where the terminal can flexibly switch between single protocol stack mode (for normal operation) and dual protocol stack mode (for handover). This dynamic adaptation optimizes performance based on operational context, improving handover robustness without permanently increasing device complexity.
2Reliability
If dual active protocol stack is applied to all DRBs, then handover robustness is maximized, but device complexity and resource consumption increase
Solution Approach 1:
The patent applies DAPS selectively to specific DRBs based on their characteristics and requirements. The network can indicate which DRBs should use dual active protocol stack through RRC reconfiguration messages, allowing optimization of handover robustness for critical data bearers while maintaining simpler single-stack operation for less critical traffic, thereby reducing overall device complexity.
Solution Approach 2:
The patent introduces configurable parameters (such as daps-Indicator) that control whether DAPS is applied to each DRB. These parameters can be dynamically adjusted by the network based on traffic requirements, cell conditions, and terminal capabilities, enabling flexible optimization of handover performance without fixed complexity overhead.
3Loss of time
If handover is performed quickly, then user data interruption is minimized, but measurement precision and handover decision accuracy deteriorate
Solution Approach 1:
The patent performs preliminary measurements and preparations during the handover preparation phase. The target base station pre-configures protocol stacks and resource allocations before the actual handover executes. This preliminary action ensures that when handover occurs, the transition is rapid with minimal data interruption, while measurement accuracy is maintained through pre-handover evaluation.
Solution Approach 2:
The patent maintains continuous data transmission throughout the handover process by keeping both source and target protocol stacks active simultaneously. This continuity allows the terminal to receive data from both cells during transition, eliminating gaps in data flow and minimizing effective interruption time while allowing adequate measurement and decision time.
Data Source
AI summary
A terminal apparatus in communication with a base station apparatus includes a receiver configured to receive, from the base station apparatus, a message related to Radio Resource Control (RRC) connection reconfiguration, and a processing unit. The processing unit determines, based on information included in the message related to the RRC connection reconfiguration, a DRB to which a DAPS is to be applied and a DRB to which the DAPS is not to be applied, and associates, with a target primary cell, an RLC entity and a DTCH logical channel for the DRB to which the DAPS is not to be applied.