Uplink Time Alignment Management in LTE Wireless Systems
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Solution Overview
Problem
In LTE wireless communication systems, user equipment (UE) uplink time alignment management is inflexible, as the base station (BS) solely determines whether to maintain uplink synchronization, leading to potential interference and unsynchronized states during inactivity periods or varying UE locations and speeds.
Innovation Solution
The UE autonomously performs a random access procedure by transmitting a random access preamble to the BS, receiving a random access response, and restarting a time alignment timer (TAT) to maintain uplink time alignment, allowing for flexible management of uplink time alignment based on application needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the base station solely determines whether to maintain uplink synchronization, then the control is centralized and simple, but the flexibility and adaptability to different application needs deteriorates
Solution Approach 1:
The user equipment autonomously determines whether to perform random access procedures to maintain uplink time alignment based on its own application requirements and transmission buffer status, rather than relying solely on base station control. This self-service mechanism enables flexible adaptation to different application needs while keeping the control logic distributed and application-specific.
2Adaptability or versatility
If the UE performs random access procedure autonomously, then the flexibility and adaptability improve, but the device complexity and signaling overhead increase
Solution Approach 1:
The random access procedure is triggered locally at the user equipment based on specific conditions such as application requirements and uplink transmission buffer status. Different UEs can independently decide whether to perform random access based on their local state, enabling fine-grained control without requiring complex centralized coordination for each individual case.
3Duration of action of moving object
If the TAT timer is used to control uplink time alignment duration, then the time management is simplified, but the ability to maintain alignment during inactivity periods deteriorates
Solution Approach 1:
The user equipment performs random access procedures in advance to refresh the time alignment timer before the current alignment period expires, particularly during inactivity periods. This preliminary action ensures that uplink time alignment is maintained continuously even when there are no active transmissions, preventing synchronization loss before it occurs.
Data Source
AI summary
A method and apparatus of managing uplink time alignment in a wireless communication system is provided. A user equipment transmits a random access preamble to maintain an uplink time alignment to a base station and receives a random access response in response to the random access preamble from the base station.