Uplink Transmission Timing Management for Low-Latency Inter-Cell Mobility
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Solution Overview
Problem
Current uplink transmission timing management in communication systems experiences long latency due to the required random access channel (RACH) procedure for obtaining timing advance during inter-cell mobility, leading to impaired system performance.
Innovation Solution
A method and apparatus for uplink transmission timing management that allows a user equipment (UE) to obtain timing for a first cell based on downlink transmission timings of a second cell and an uplink transmission timing towards the second cell, and a base station to request the UE to do the same, reducing latency through mechanisms like MAC control elements and uplink control information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a full RACH procedure is used to obtain timing advance for inter-cell mobility, then timing advance can be obtained, but latency is increased
Solution Approach 1:
The UE calculates and determines the uplink transmission timing for the target cell in advance, before completing the full RACH procedure. This preliminary calculation uses downlink transmission timing information and uplink timing towards the source cell to derive the target cell's uplink timing, thereby reducing the latency of timing advance acquisition during inter-cell mobility
Solution Approach 2:
The patent uses downlink transmission timing information as an intermediary to transfer timing reference from the source cell to the target cell. By using the relationship between downlink timing and uplink timing, the system avoids the need for complete RACH procedure while still achieving accurate timing advance determination
2Reliability
If a full RACH procedure is performed during inter-cell mobility, then uplink synchronization is achieved, but system performance is impaired due to interrupt time
Solution Approach 1:
The UE performs preliminary calculation of uplink transmission timing for the target cell using available downlink timing information before mobility execution. This advance preparation ensures uplink synchronization is already established or near-established when the handover occurs, minimizing interrupt time and maintaining system performance
Solution Approach 2:
The UE autonomously calculates its own uplink transmission timing for the target cell using the relationship between downlink timing and uplink timing, without requiring the network to provide timing advance commands through the complete RACH procedure. This self-service approach reduces signaling overhead and accelerates the mobility process
Data Source
AI summary
A method of uplink transmission timing management for mobility by a user equipment (UE) includes being configured to obtain an uplink transmission timing for a first cell based on a downlink transmission timing of a second cell, a downlink transmission timing of a first cell, and an uplink transmission timing towards the second cell.