Satellite Handover Pre-Synchronization for NTN Uplink Timing
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Solution Overview
Problem
In non-terrestrial networks (NTN), the long propagation delay between a terminal device and a network device can result in handover access failures due to the terminal device missing configured uplink resources during RACH-less satellite handover, as the target satellite network cannot accurately determine the terminal's actual timing advance (TA) value.
Innovation Solution
The terminal device performs first synchronization with the second satellite network based on parameters provided in a handover command before the handover, ensuring timely access to uplink resources by aligning synchronization among the first and second satellite networks and the terminal device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If RACH-less satellite handover is performed in NTN system, then handover delay is shortened, but terminal device may miss uplink resources configured by target satellite network due to long propagation delay
Solution Approach 1:
The terminal device performs synchronization with the target satellite network before the actual handover occurs. Specifically, the terminal adjusts its uplink transmission timing based on synchronization parameters (such as timing advance values) received from the target satellite network in the handover command. This preliminary timing adjustment ensures that when the handover is executed, the terminal's uplink transmissions are already properly aligned with the target network's reception window, preventing missed uplink resources despite the long propagation delay inherent in NTN systems.
2Reliability
If terminal device performs synchronization with target satellite network before handover, then uplink resource access success rate is improved, but additional synchronization procedures increase handover complexity
Solution Approach 1:
The terminal device autonomously performs the synchronization adjustment using parameters provided in the handover command from the source network. The terminal calculates the timing advance value based on the synchronization parameters received, and self-adjusts its uplink transmission timing without requiring additional interactive procedures with the target satellite network. This self-service approach achieves reliable synchronization while minimizing the increase in handover complexity, as the terminal independently completes the synchronization task using pre-provided parameters.
Data Source
AI summary
The present application provides a method for satellite handover between non-terrestrial networks, a terminal device, and a network device. One example method includes: receiving a first handover command, where the first handover command instructs a terminal device to perform satellite handover from a coverage of a first satellite network to a coverage of a second satellite network; and performing first synchronization with the second satellite network based on a first parameter before the satellite handover is performed, where the first parameter is determined based on information in the first handover command.