NTN Timing Advance Maintenance for Uplink Synchronization

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Solution Overview

Problem

Existing wireless communication networks face challenges in maintaining timing and synchronization in non-terrestrial networks (NTN) due to varying propagation delays and satellite movements, which affect the accuracy of uplink transmissions.

Innovation Solution

Techniques for maintaining timing advance (TA) values in NTN by using UE-specific and common TA adjustments, timing drift rate updates, and beam switching mechanisms to ensure proper transmission timing and synchronization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If satellites are used as transparent network nodes in NTN, then network coverage area is expanded, but propagation delay variability increases affecting transmission timing accuracy

Engineering Contradiction:

Improvenetwork coverage areaVSAvoidtransmission timing accuracy

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent implements dynamic TA value adjustments that continuously adapt to changing satellite positions and UE movements. The timing advance values are updated in real-time based on current propagation conditions, allowing the system to maintain timing accuracy despite the dynamic nature of satellite orbits and user mobility in NTN environments.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent employs feedback mechanisms where the network monitors uplink transmission timing and sends TA adjustment commands to UEs. This closed-loop feedback system continuously corrects timing deviations caused by satellite movement and propagation delay variations, ensuring synchronized uplink transmissions across the expanding network coverage area.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If TA values are frequently updated to maintain synchronization, then transmission timing accuracy is improved, but signaling overhead and network complexity increase

Engineering Contradiction:

Improvetransmission timing accuracyVSAvoidnetwork complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies partial updates by adjusting only the necessary TA values for affected UEs rather than re-synchronizing all UEs in the network. This selective approach maintains timing accuracy for active users while minimizing unnecessary signaling overhead and network processing complexity during satellite handovers and orbital movements.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The patent performs preliminary TA value calculations and preparations before satellite handovers or significant propagation delay changes occur. By pre-computing TA adjustments and having them ready for deployment, the system maintains timing accuracy while reducing the complexity and overhead of last-minute synchronization corrections.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20250358760A1Timing advance (TA) maintenance in nonterrestrial networks (NTN)

Publication Date: 2025.11.20 APPLE INC

AI summary

Techniques discussed herein may better ensure proper timing and synchronization of transmissions within a wireless communications network that includes a terrestrial network and a non-terrestrial network (NTN). A user equipment (UE) may maintain (e.g., determine and update on an ongoing basis) a timing advance (TA) value that the UE may apply to uplink (UL) transmissions to account for propagation delays, including changes in propagation delays, between the UE, NTN, and terrestrial network. TA maintenance may be based on network broadcasts, random access channel (RACH) procedures, control messages, timing drift rates (e.g., of the UE or NTN satellite), beam switching, and more.