DAPS Handover Configuration for LTE NR Mobility
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Solution Overview
Problem
Existing technologies for LTE and NR lack efficient mechanisms for controlling mobility, particularly in minimizing user data interruption during handover and improving handover robustness.
Innovation Solution
A terminal apparatus and base station apparatus system that employs a Dual Active Protocol Stack (DAPS) and a specific configuration process, including the use of RRC reconfiguration messages, timers, and protocol stack management, to efficiently manage mobility and handle handovers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a terminal apparatus performs handover between cells in existing LTE or NR systems, then mobility is achieved, but user data transmission and reception are interrupted
Solution Approach 1:
The terminal apparatus performs configuration in advance for the target primary cell before actual handover occurs. This includes receiving RRC reconfiguration messages, performing PDCP and RLC configuration, and preparing MAC settings beforehand. This preliminary configuration enables the terminal to quickly switch to the target cell without interruption when handover is triggered, as the configuration is already ready rather than being established during the handover process.
2Adaptability or versatility
If conventional handover procedures are used, then cell switching is achieved, but handover robustness is insufficient
Solution Approach 1:
The terminal apparatus establishes configuration for the target primary cell in advance, creating a buffer or cushion that protects against handover failures. By having the configuration prepared beforehand including PDCP entity setup, RLC entity configuration, and MAC parameters, the terminal can withstand potential handover challenges such as poor radio conditions or network issues without compromising reliability. This pre-prepared configuration acts as a safety cushion that ensures handover robustness.
Data Source
AI summary
A terminal apparatus for communicating with a base station apparatus includes a receiver configured to receive, from the base station apparatus, an RRC reconfiguration message including a first configuration related to a radio bearer to which a Dual Active Protocol Stack (DAPS) is applied, and a processing unit configured to perform configuration in accordance with the RRC reconfiguration message. In a case that a first timer expires, that no radio link failure is detected in a source primary cell, and that the first configuration is performed on any radio bearer, the processing units releases a configuration for a target primary cell, resets MAC for the target primary cell, discards all data of a PDCP entity for a SRB of the source primary cell, discards all data of an RLC entity for the SRB of the source primary cell, resumes the SRB suspended in the source primary cell, and transmits, to the base station apparatus, an RRC message for notifying that a DAPS handover is unsuccessful.