GNSS-Based Uplink Timing Advance for Long-Delay Satellite Links
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Solution Overview
Problem
In satellite communication systems, the long distance between a terminal device and a satellite results in high signal round trip transmission delays, leading to significant errors in timing advance (TA) value accuracy when using timing advance commands (TACs) for synchronization, which affects communication reliability.
Innovation Solution
The method involves determining a first TA value based on GNSS measurements and adjusting it using a first TA adjustment amount, with conditions set for when to correct GNSS measurement errors by accumulating previous TACs or using a preset value, thereby improving TA value accuracy and reducing error jumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a TAC is sent by the satellite to the terminal device to indicate a TA value, then the terminal device can adjust its timing, but the accuracy of the TA value becomes very low due to the long signal round trip transmission delay
Solution Approach 1:
The terminal device performs GNSS measurement to obtain timing information in advance, and calculates the TA value based on this preliminary measurement before actual communication occurs. This preliminary action allows the terminal to proactively determine timing advance without waiting for satellite feedback, thereby improving TA value accuracy despite long transmission delays.
Solution Approach 2:
The patent introduces GNSS measurement as an intermediary mechanism to obtain timing information. Instead of relying solely on direct satellite- terminal timing feedback which suffers from long delays, the GNSS system serves as an intermediary reference that provides accurate timing information that the terminal can use to calculate TA values independently.
2Measurement precision
If the terminal device continuously accumulates previous TACs to correct GNSS measurement errors, then TA value accuracy improves, but error jumps occur when GNSS measurements are updated after long periods
Solution Approach 1:
The patent implements a dynamic adjustment mechanism where the terminal device adaptively switches between two modes: accumulating previous TACs when GNSS measurements are recent (within first duration), and using preset values when GNSS measurements are outdated (after first duration). This dynamic approach allows the system to optimize TA value accuracy while preventing error jumps based on the recency of GNSS measurements.
Solution Approach 2:
The patent changes the parameter used for TA value calculation based on the timing of GNSS measurements. When the time since last GNSS measurement is within the first duration, the system uses accumulated TACs; when it exceeds the first duration, the system switches to using preset values. This parameter change strategy resolves the contradiction by adapting the correction method to the current state of measurement freshness.
Data Source
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AI summary
A communication method and a related apparatus are provided. The method includes: receiving a first timing advance TA adjustment amount from a network device; and determining a first TA value, and sending, based on the first TA value, a 1st uplink signal after global navigation satellite system GNSS measurement. When a first condition is met, the first TA value is determined based on a first GNSS measurement value obtained through the GNSS measurement, the first TA adjustment amount, and a first value. When a second condition is met, the first TA value is determined based on the first GNSS measurement value, the first TA adjustment amount, and a second value. The first value is different from the second value. The method in this application can improve accuracy of the determined TA value (that is, the first TA value), thereby improving communication reliability.