LTM Early TA Acquisition for Faster Reliable Cell Switch
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Solution Overview
Problem
Existing L1/L2 Triggered Mobility (LTM) technologies face challenges in maintaining Timing Advance (TA) values and efficiently processing uplink grants for Dedicated Control Channel (DCCH) messages during cell switch, particularly in RACH-less scenarios, leading to potential delays and inefficiencies in handover processes.
Innovation Solution
Implementing a method for early Timing Advance (TA) acquisition through RRC configuration and PDCCH orders, along with maintaining TA values during LTM, and utilizing both configured and dynamic grants for transmitting DCCH messages, including RACH procedures when necessary, to ensure seamless cell switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If early RACH procedure without RAR step is used for LTM, then handover delay is reduced, but reliability of TA acquisition deteriorates
Solution Approach 1:
The patent performs RACH procedure in advance during LTM execution to acquire TA value before actual cell switch occurs. This preliminary action ensures that when handover is needed, the UE already has valid TA information, reducing actual handover delay while maintaining reliability through pre-acquisition.
Solution Approach 2:
The patent segments the TA acquisition process from the actual handover execution. The RACH procedure and TA acquisition are performed as a separate preliminary step, decoupled from the critical handover timing, allowing reliable TA acquisition without impacting handover speed.
2Device complexity
If TA is considered invalid during LTM in legacy implementation, then simplicity is maintained, but communication stability during cell switch deteriorates
Solution Approach 1:
The patent dynamically manages TA validity based on LTM state. Instead of a static invalidation rule, the system adapts TA validity according to whether LTM is executing, allowing TA to be maintained and reused during LTM when appropriate, thereby improving communication stability while adding minimal complexity through state-based logic.
3Productivity
If RACH-less LTM is used for inter-DU and intra-DU scenarios, then handover efficiency is improved, but adaptability to different grant types deteriorates
Solution Approach 1:
The patent creates a universal LTM mechanism that works across inter-DU and intra-DU scenarios with both RACH-based and RACH-less approaches. The solution provides multi-functionality by supporting multiple grant types (CG and DG) within a unified LTM framework, enhancing adaptability while maintaining efficiency through scenario-appropriate method selection.
Data Source
AI summary
Methods, devices, and systems for providing early timing advance (TA) acquisition are provided. A radio resource control (RRC) configuration of the early TA acquisition is received from a base station. A PDCCH order to trigger a random access channel (RACH) procedure toward a candidate cell is received from the base station. The RACH procedure for the early TA acquisition is initiated based on the received RRC configuration and PDCCH order. A preamble with a calculated transmission power on the candidate cell is transmitted to the base station.