Uplink Time Synchronization in Non-Terrestrial Networks
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Solution Overview
Problem
The existing PRACH design in 3GPP New Radio systems is impractical for Non-Terrestrial Networks (NTN) due to high differential propagation delays, leading to critical uplink synchronization challenges, and requires a method to minimize PRACH duration and timing advance estimation errors while ensuring compatibility with terrestrial networks.
Innovation Solution
A system and method for uplink time synchronization in NTN, where the UE estimates Timing Advance (TA) using satellite location information broadcast by the NTN-Base Station, applying a quantized TA value based on predefined step sizes and minimizing TA margin to reduce signaling overhead and errors, with the NTN-Base Station providing final corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing PRACH design in 3GPP New Radio systems is used for NTN, then terrestrial network compatibility is maintained, but uplink synchronization performance deteriorates due to high differential propagation delays
Solution Approach 1:
The patent applies local quality by introducing NTN-specific parameters (satellite location, ephemeris data, differential propagation delay compensation values) that are locally adapted to NTN conditions while maintaining the overall PRACH framework. The gNB provides NTN-specific configuration information including satellite location and timing advance compensation parameters that are tailored to the specific NTN scenario, allowing the system to maintain terrestrial compatibility while addressing NTN-specific synchronization challenges.
Solution Approach 2:
The patent changes key parameters including timing advance values, PRACH configuration parameters, and synchronization signal timing to account for NTN-specific propagation delays. The system adjusts timing advance compensation parameters based on satellite location and relative velocity, modifying the temporal characteristics of uplink transmissions to compensate for the high and variable propagation delays inherent in NTN scenarios while maintaining compatibility with terrestrial network protocols.
2Reliability
If PRACH duration is extended to accommodate high differential propagation delays in NTN, then uplink synchronization coverage is improved, but signaling overhead and system complexity increase
Solution Approach 1:
The patent applies preliminary action by having the gNB broadcast satellite location information, ephemeris data, and timing advance compensation parameters before the UE performs uplink synchronization. The UE uses this pre-provided information to calculate and apply appropriate timing advance values before transmitting PRACH, thereby achieving synchronization without requiring extended PRACH duration or complex post-processing at the gNB.
Solution Approach 2:
The patent enables self-service by allowing the UE to autonomously calculate timing advance values using broadcast satellite ephemeris data and location information. The UE independently determines the appropriate timing advance compensation based on the provided satellite parameters and its own location, reducing the need for extensive gNB processing and complex signaling mechanisms while achieving adequate synchronization coverage.
3Loss of information
If UE performs autonomous TA estimation using satellite location information, then signaling overhead is reduced, but timing estimation accuracy deteriorates due to UE limitations
Solution Approach 1:
The patent implements feedback by having the gNB measure the actual uplink reception timing and compare it with the expected timing based on UE-reported parameters. The gNB then provides feedback in the form of timing advance correction commands to refine the UE's autonomous estimation. This closed-loop feedback mechanism allows the system to maintain low signaling overhead while progressively improving timing estimation accuracy through iterative corrections.
Solution Approach 2:
The patent applies partial action by having the UE perform autonomous TA estimation using a subset of available information (broadcast satellite location and ephemeris data) rather than requiring complete and precise measurements. The UE uses the provided parameters to make an initial estimation, which is then refined by gNB feedback, achieving adequate accuracy without requiring the UE to perform complex or excessive measurements that would increase its processing burden and signaling overhead.
Data Source
AI summary
A system and a method for performing uplink (UL) time synchronization in non-terrestrial networks (NTN) include Performing Downlink (DL) synchronization SSB signals. At least one information is received by a UE 102 from an NTN BS 104. A location information of a satellite is obtained using the at least one information received by the UE 102. Location of the UE 102 is estimated using one of GNSS receiver of the UE 102 and by processing at least one reference signal received by the UE 102 from multiple NTN-BS 104, using at least one multilateration technique and RTK. Timing Advance (TA) estimate is determined using the location of the satellite and location of the UE 102. TA applied is determined using the TA estimate and TA margin. PRACH is transmitted based on the TA applied and an information related to the TA applied is reported to the NTN-BS 104. Residual TA is estimated using the reported information related to the TA applied and the detected PRACH. The residual TA is indicated to the UE 102 for subsequent UL transmissions, in order to achieve the UL time synchronization in the NTN based communication network.