Satellite Terminal GNSS Validity Extension Using Timing Advance
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Solution Overview
Problem
Satellite communication terminals face frequent disconnections due to the expiration of GNSS information, leading to continuous random access and exit from connected states, resulting in high signaling overheads and reduced communication duration.
Innovation Solution
Extend the validity duration of GNSS information by determining a longer GNSS second validity duration based on the initial duration and timing advance command (TAC), allowing terminals to maintain uplink synchronization and reduce disconnections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the terminal device continuously initiates random access to enter and exit the connected state due to GNSS information expiration, then uplink synchronization can be maintained, but signaling overheads increase and communication duration decreases
Solution Approach 1:
The network device sends a timing advance command (TAC) to the terminal device before the GNSS information expires, allowing the terminal to pre-adjust its uplink timing. This preliminary action prevents synchronization loss and avoids the need for random access procedures, thereby maintaining continuous communication without interruption.
Solution Approach 2:
The timing advance command (TAC) acts as an intermediary mechanism between the network device and terminal device. Instead of relying solely on GNSS information or requiring random access procedures, the TAC provides a direct timing adjustment mechanism that bridges the synchronization gap, enabling continuous connected state without frequent state transitions.
2Measurement precision
If the terminal device continuously initiates random access to re-enter the connected state after GNSS expiration, then uplink synchronization can be restored, but signaling overheads increase
Solution Approach 1:
The invention extracts the timing adjustment function from the random access procedure. By sending a dedicated timing advance command (TAC) separately, the timing synchronization is decoupled from the random access signaling overhead, allowing synchronization maintenance without the full burden of random access procedures.
Solution Approach 2:
The timing advance command (TAC) serves as an intermediary that directly conveys timing adjustment information from the network device to the terminal device, eliminating the need for the terminal to initiate random access procedures. This intermediary mechanism reduces signaling overhead by providing direct timing control.
3Measurement precision
If the terminal device frequently transitions between connected and idle states due to GNSS information expiration, then uplink synchronization can be maintained, but power consumption increases
Solution Approach 1:
The network device sends a timing advance command (TAC) to the terminal device before the GNSS information expires, allowing the terminal to pre-adjust its uplink timing while remaining in the connected state. This preliminary action prevents synchronization loss and avoids the energy-consuming state transitions to idle and back to connected.
Solution Approach 2:
The invention enables continuous uplink synchronization adjustment through periodic TAC commands, allowing the terminal device to maintain the connected state continuously. This continuity eliminates repeated transitions to idle state and back, reducing power consumption associated with state changes while maintaining synchronization accuracy.
Data Source
Figure 1~2b
Figure 2c~3
Figure 4a
AI summary
A satellite communication method and an apparatus are provided, and the method may be applied to the field of satellite communication. The method includes: GNSS first validity duration of a first communication apparatus is determined; a second communication apparatus sends a TAC within the GNSS first validity duration; and when receiving the TAC from the second communication apparatus within the GNSS first validity duration, the first communication apparatus determines GNSS second validity duration based on validity duration of the TAC and the GNSS first validity duration. The method can effectively increase communication duration of a terminal device.