Uplink Alignment Timer for LTE Synchronization
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Solution Overview
Problem
In LTE communication systems, maintaining uplink synchronization is challenging due to differences in signal propagation delays among terminals, leading to inconsistent uplink signal arrival times and potential interference, especially when one terminal loses synchronization while others maintain it.
Innovation Solution
A method and terminal implementation that triggers an uplink alignment timer and receives a timing advance command within a specified duration, with mechanisms to reconfigure and re-establish synchronization by clearing HARQ buffers and PUCCH resources, and transmitting uplink time alignment requests to notify target cells for re-adjustment, ensuring synchronization is maintained even when the original timer fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the terminal uses a single time alignment timer (TAT) to maintain uplink synchronization, then the synchronization management is simple, but the uplink synchronization may be lost when the timer expires without receiving timing advance commands
Solution Approach 1:
The patent divides the single time alignment timer (TAT) into two separate timers: TAT (Time Alignment Timer) for monitoring uplink synchronization status and UAT (Uplink Alignment Timer) for receiving timing advance commands. This segmentation allows independent management of synchronization monitoring and command reception, preventing unnecessary synchronization loss when commands are delayed while maintaining simple timer management mechanisms.
2Productivity
If the terminal immediately loses uplink synchronization when TAT expires, then the synchronization state is quickly updated, but the signaling overhead and delay for re-establishing synchronization increase
Solution Approach 1:
The patent triggers the UAT timer when TAT expires, performing preliminary action to extend the synchronization maintenance period. This allows the terminal to continue using the current timing advance value temporarily while waiting for the network to send new timing advance commands, avoiding immediate synchronization loss and reducing the time needed to re-establish synchronization.
3Stability of the object's composition
If the terminal maintains uplink synchronization with extended timer duration, then the synchronization stability is improved, but the response time to actual synchronization loss increases
Solution Approach 1:
The patent introduces UAT as an intermediary timer between the network and the terminal's uplink transmission. This intermediary mechanism allows the terminal to maintain synchronization stability during the extended UAT period while still providing timely detection of synchronization loss through the original TAT expiration, balancing stability and response time.
Data Source
AI summary
Embodiments of the present disclosure disclose a method and a terminal for maintaining uplink synchronization of a terminal, the method including: triggering, by the terminal, an uplink alignment timer UAT, and receiving a timing advance command TAC within a duration of the UAT; and losing uplink synchronization in the case where the terminal does not receive the TAC within the duration of the UAT.