NTN Propagation Delay Estimation Using Doppler Without GNSS
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Solution Overview
Problem
Existing methods for estimating signal propagation delay between non-terrestrial nodes and user equipment in cellular systems, such as satellites and HAPS, are inadequate, especially when the user equipment lacks GNSS capabilities or experiences GNSS outages, leading to degraded accuracy and system performance.
Innovation Solution
Estimating Doppler frequency shifts at different time instances to calculate the signal propagation delay between non-terrestrial nodes and user equipment, allowing compensation for uplink and downlink transmissions without relying on GNSS.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GNSS is used to estimate propagation delay, then location accuracy is improved, but the system becomes unreliable when GNSS is unavailable or malfunctioning
Solution Approach 1:
The patent changes the measurement parameter from GNSS-based location to Doppler frequency shift-based distance estimation. By measuring the Doppler shift of signals from multiple NTN nodes and using geometric relationships, the system estimates propagation distance and delay without relying on GNSS, thus maintaining reliability when GNSS is unavailable while achieving adequate measurement precision for timing compensation
Solution Approach 2:
The patent introduces Doppler frequency shift measurement as an intermediary method to bridge the gap between signal transmission and timing synchronization. Instead of directly using GNSS location data, the system uses Doppler shifts from NTN nodes as an intermediate measurement that can be converted into distance and delay estimates, providing a reliable alternative path when GNSS fails
2Reliability
If Doppler frequency shift estimation is used to calculate propagation delay, then GNSS dependency is reduced, but measurement precision may be affected
Solution Approach 1:
The patent makes the Doppler measurement system multi-functional by using the same Doppler frequency shift measurements for both frequency compensation and propagation delay estimation. The Doppler shift data serves dual purposes: correcting frequency offsets in communication signals and calculating distance/delay through geometric relationships with multiple NTN nodes, thereby achieving reliable GNSS-independent operation with adequate precision
Solution Approach 2:
The patent transitions from two-dimensional GNSS location estimation to a different dimensional approach using Doppler frequency shifts in the frequency domain. By measuring Doppler shifts from multiple NTN nodes at different geometries and using temporal variations, the system extracts distance and delay information through a different measurement dimension that does not depend on GNSS satellite signals
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
Enables accurate timing of wireless communications by compensating for propagation delays, improving system performance even when GNSS is unavailable or malfunctioning.
Implementation Method 1
estimate a first Doppler frequency shift in a signal received from a non-terrestrial network (NTN) node at a first time instance; estimate a second Doppler frequency shift in the signal at a second time instance
Data Source
AI summary
A user equipment (UE) includes one or more non-transitory computer-readable media having computer-executable instructions embodied thereon, and at least one processor coupled to the one or more non-transitory computer-readable media, and configured to execute the computer-executable instructions to: estimate a first Doppler frequency shift in a signal received from a non-terrestrial network (NTN) node at a first time instance, estimate a second Doppler frequency shift in the signal at a second time instance, estimate a signal propagation delay between the NTN node and the UE based on the first Doppler frequency shift and the second Doppler frequency shift, and apply the signal propagation delay to compensate for an uplink transmission from the UE to the NTN node.