Uplink Timing Reference in Non-Terrestrial Networks
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Solution Overview
Problem
In non-terrestrial networks (NTNs), the changing propagation delays due to satellite mobility cause inaccuracies in uplink transmission timing, leading to synchronization issues between downlink and uplink communications, which affect system performance.
Innovation Solution
A method where user equipment (UE) in NTNs receives timing advance (TA) values to synchronize uplink signaling with a reference timing based on downlink signaling and propagation delays, accounting for both UE-specific and common TA values to adjust for satellite mobility, thereby eliminating the need for predicting downlink slot boundaries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional downlink-based reference timing is used for uplink transmission in NTNs, then the system can maintain simplicity in timing reference establishment, but propagation delay variations due to satellite mobility cause uplink transmission timing inaccuracies and synchronization issues
Solution Approach 1:
The patent segments the timing advance mechanism into two distinct components: a downlink timing advance (DL-TA) for downlink reception timing adjustment and an uplink timing advance (UL-TA) for uplink transmission timing adjustment. This segmentation allows each component to be optimized independently for its specific function, resolving the contradiction by maintaining simple reference establishment through DL-TA while achieving accurate uplink timing through the separate UL-TA mechanism
Solution Approach 2:
The patent introduces a network-configured uplink timing advance (UL-TA) as an intermediary parameter that mediates between the downlink timing reference and the actual uplink transmission timing. This UL-TA acts as a correction factor that compensates for propagation delay variations due to satellite mobility, allowing the system to maintain simple downlink-based reference timing while achieving accurate uplink synchronization
2Ease of operation
If timing synchronization is maintained without accounting for satellite mobility, then the system operation remains simple, but synchronization accuracy deteriorates due to changing propagation delays
Solution Approach 1:
The patent applies preliminary action by having the network configure both DL-TA and UL-TA values in advance through RRC signaling or MAC CE messages. These timing advance values are prepared beforehand to account for expected satellite mobility effects, allowing UEs to maintain accurate synchronization without complex real-time calculations, thus preserving ease of operation while ensuring reliability
Solution Approach 2:
The patent introduces dynamic timing advance adjustment by allowing the network to update DL-TA and UL-TA values as satellite mobility conditions change. The system transitions from static timing assumptions to dynamic adjustment, where timing advance parameters are periodically updated to reflect current propagation conditions, maintaining both ease of operation through automated adjustment and synchronization accuracy through mobility-aware parameters
3Device complexity
If UE-specific timing advance values are not used, then the timing mechanism remains simple, but uplink transmission timing accuracy deteriorates for individual UEs with different propagation delays
Solution Approach 1:
The patent applies local quality by providing UE-specific uplink timing advance (UL-TA) values that are tailored to each UE's specific propagation conditions and satellite geometry. Instead of using a single common timing advance for all UEs, the system configures individualized UL-TA parameters that account for local variations in distance and angle to the satellite, ensuring each UE achieves optimal timing accuracy for its specific location while maintaining a relatively simple overall mechanism through standardized configuration procedures
Data Source
AI summary
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may receive, from a serving node associated with a non-terrestrial network (NTN), one or more timing advance (TA) values. The UE may transmit, to the serving node of the NTN, uplink signaling based at least in part on a reference timing for the uplink signaling, wherein the reference timing for the uplink signaling is based at least in part on a reference timing of a downlink signaling and the one or more TA values, wherein the one or more TA values include a UE-specific TA value, and wherein a reference timing of the UE-specific TA value is for: a first propagation delay on a service link between the UE and a satellite associated with the NTN, and a second propagation delay on the service link. Numerous other aspects are described.