NTN UE Access Timing via RTT Estimation and Window Shifting
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Solution Overview
Problem
Current communication systems lack specific methods for determining access timing in non-terrestrial networks (NTN), particularly for terminals accessing networks through satellites with different architectures.
Innovation Solution
A method and apparatus for a user equipment (UE) to determine access timing in a mobile communication environment supporting NTN, involving the reception of synchronization signals and system information, estimation of round trip times, and transmission of messages based on the type of communication node indicated by the system information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a terminal uses typical mobile communication timing methods, then the access procedure is simple, but the access timing is inaccurate in NTN environments due to large propagation delays
Solution Approach 1:
The terminal performs preliminary estimation of the round trip time (RTT) between itself and the communication node before executing the random access procedure. This preliminary action allows the terminal to pre-calculate the appropriate timing for transmitting random access messages, ensuring accurate access timing without requiring complex real-time adjustments during the access procedure.
Solution Approach 2:
The terminal dynamically adjusts transmission timing parameters based on the estimated RTT and the specific architecture type (transparent or regenerative) of the communication node. By changing timing parameters such as the transmission time of Msg1 and the reception window for Msg2 according to the node type and distance, the system achieves accurate timing synchronization without overly complex procedures.
2Reliability
If the terminal adjusts timing based on different satellite architectures, then the access timing becomes accurate, but the determination process becomes more complex
Solution Approach 1:
The terminal changes timing parameters based on the architecture type of the communication node. For transparent architecture nodes, the terminal applies one set of timing adjustments, while for regenerative architecture nodes, it applies a different set of adjustments. This parameter-based approach ensures reliable timing for each architecture type while maintaining operational simplicity through systematic parameter selection.
Solution Approach 2:
The terminal autonomously determines the architecture type of the communication node and self-adjusts its timing parameters accordingly without requiring complex external coordination. The terminal uses the estimated RTT and node type information to automatically configure the appropriate timing for message transmission and reception, simplifying the operation while ensuring reliability.
3Measurement precision
If the terminal transmits messages at typical timing intervals, then the communication procedure is straightforward, but synchronization is lost in NTN due to propagation delays
Solution Approach 1:
The terminal performs preliminary timing calculations based on the estimated RTT before initiating message transmission. By pre-determining the transmission time of Msg1 and the expected reception time of Msg2, the terminal maintains synchronization accuracy without requiring time-consuming adjustments during the actual communication procedure.
Solution Approach 2:
The terminal adjusts timing parameters such as the transmission interval and reception window based on the estimated RTT and node architecture type. This dynamic parameter adjustment ensures that messages are transmitted and received at the correct times for NTN conditions, maintaining synchronization while minimizing timing overhead through efficient parameter selection.
Data Source
AI summary
The present disclosure provides a communication method in NTN. A method of a UE according to an exemplary embodiment of the present disclosure may comprise: receiving an SSB and SI from a first communication node of an NTN; estimating a first RTT between the UE and the first communication node; transmitting, to the first communication node, a Msg1 below a layer 2 based on a type of the first communication node indicated by the SI; in response to the type of the first communication node being a base station DU, shifting a first window for receiving a Msg2 responding to the Msg1 by the first RTT; and receiving, from the first communication node, the Msg2 including TA information based on measurement of the Msg1 and uplink grant information within the shifted first window.