Uplink Alignment Timer for NTN Synchronization
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Solution Overview
Problem
In non-terrestrial network (NTN) systems, controlling uplink synchronization for a serving cell is a technical challenge due to the large propagation delays and unique communication characteristics compared to terrestrial networks.
Innovation Solution
Configuring an uplink alignment timer for terminal devices to maintain synchronization, which can be set to infinity to prevent timing misalignment and associated buffer flushes, and using indication information such as timing advance commands and frequency offset data to adjust timing advance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an uplink alignment timer is configured with a finite value to maintain synchronization, then timing alignment can be monitored and maintained within a specific duration, but the timer may expire due to large propagation delays in NTN systems, causing timing misalignment and buffer flushes that degrade communication performance
Solution Approach 1:
The patent changes the parameter of the uplink alignment timer from a finite value to infinity specifically for NTN systems. This parameter change resolves the contradiction by eliminating timer expiration issues caused by large propagation delays, while still maintaining uplink synchronization through alternative mechanisms such as timing advance commands and synchronization signal transmissions adapted for NTN conditions
2Ease of operation
If conventional terrestrial timing advance mechanisms are used in NTN systems, then existing timing control procedures can be applied, but the large propagation delays and unique NTN characteristics cause timing misalignment and require frequent synchronization updates
Solution Approach 1:
The patent applies local quality by introducing NTN-specific configurations that differ from conventional terrestrial mechanisms. It implements NTN-adapted timing advance procedures, synchronization signal transmission intervals, and random access configurations that are locally optimized for satellite communication characteristics, thereby achieving both ease of operation and reliability
Solution Approach 2:
The patent employs preliminary action by pre-configuring uplink alignment parameters and timing advance values before communication begins. The network device pre-establishes synchronization parameters and timing relationships, allowing the terminal to maintain timing alignment without frequent updates despite large propagation delays
Data Source
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AI summary
A wireless communication method, a terminal device, and a network device are provided. The method includes: a terminal device obtains a first uplink (UL) alignment timer, where the first UL alignment timer corresponds to a first timing advance group (TAG), the first TAG corresponds to a first serving cell group, the first serving cell group comprises at least one serving cell, and the first UL alignment timer is used for UL synchronization maintenance for the at least one serving cell in the first serving cell group. Thus solves the problem of how to control the uplink synchronization for the service cell in a non-terrestrial network (NTN) system.