NTN UE Location Verification via Doppler Compensation
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Solution Overview
Problem
Current multi-round trip time (multi-RTT) techniques for verifying user equipment (UE) location in non-terrestrial networks (NTNs) face challenges due to signal weakness and potential tampering, especially in low earth orbit (LEO) satellite scenarios, where satellite velocity affects timing accuracy and reliability.
Innovation Solution
The method involves reporting auxiliary information such as Doppler frequency from the UE to a location management function (LMF), allowing for enhanced multi-RTT calculations that improve UE location verification accuracy without relying on global navigation satellite systems (GNSS) data, using a single satellite and providing robust location verification in NTN environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-RTT method is used for UE location verification in NTN, then location verification capability is provided, but timing accuracy deteriorates due to satellite velocity affecting DL and UL subframe timing
Solution Approach 1:
The UE performs preliminary measurements of Doppler frequency offset before the actual location verification procedure. These preliminary measurements are used to calculate compensation values that are applied to correct the timing measurements, thereby eliminating the adverse effect of satellite velocity on timing accuracy
Solution Approach 2:
The invention introduces Doppler frequency offset measurements and compensation parameters to adjust the timing relationships between DL and UL subframes. By measuring and compensating for the Doppler effect caused by satellite motion, the system maintains accurate timing measurements despite the changing satellite-UE distance
2Loss of information
If GNSS data is used for determining UE location, then location information is obtained, but reliability deteriorates due to signal weakness and potential data tampering
Solution Approach 1:
The invention introduces an intermediary location verification method that does not rely on GNSS data. Instead of using the UE's self-reported GNSS location, the system uses network-based multi-RTT measurements combined with Doppler compensation to independently verify the UE's location, thereby eliminating reliance on potentially compromised GNSS signals
Solution Approach 2:
The system implements a feedback mechanism where the network verifies UE location independently and can detect discrepancies between reported and verified locations. This feedback loop enables the network to identify and reject potentially tampered location information
3Measurement precision
If auxiliary reports with Doppler frequency measurements are implemented, then timing accuracy is improved, but device complexity increases due to additional measurement and reporting requirements
Solution Approach 1:
The Doppler frequency measurements serve multiple purposes: they compensate for timing errors in multi-RTT measurements, provide information for uplink synchronization, and enable accurate location verification. This multi-functionality justifies the additional measurement complexity by providing benefits across multiple system functions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly enhances the reliability and accuracy of UE location verification in NTN environments, addressing mobility-related challenges and ensuring precise location determination for critical services like public warning systems and emergency services without the need for multiple transmission and reception points.
Implementation Method 1
The UE may report, to an LMF, a difference between a Doppler frequency measured when receiving a PRS (or a channel state information reference signal (CSI-RS)) in DL subframe #i (or UL subframe #j) and the Doppler frequency measured when transmitting an SRS in UL subframe #k
Data Source
AI summary
A system and a method are disclosed for UE operations in an NTN. A method performed by a UE includes receiving, from a base station, a PRS in a DL subframe; determining a timestamp or subframe indices of the PRS in the DL subframe and a timestamp or subframe indices of a UE UL subframe that is closest in time to the DL subframe; determining, based on the timestamps or the subframe indices, a UE time difference from receiving the PRS to a transmission of an SRS; generating an auxiliary report including adjustment information for an LMF to calculate the UE time difference; providing the auxiliary report to the LMF; and reporting, to the LMF, the SRS based on the UE time difference.