GNSS Snapshot Delay and Doppler Estimation Using DFT Peaks
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Solution Overview
Problem
Conventional GNSS receivers struggle to achieve accurate estimation of delays and Doppler shifts when snapshots are not continuous, which is common in power-saving scenarios, leading to ineffective tracking by closed tracking loops.
Innovation Solution
A method that processes individual snapshots of GNSS signals to estimate delays and Doppler shifts by converting correlator outputs to frequency spectra, using discrete Fourier transforms to determine peak values in a matrix, allowing accurate estimation without continuous snapshots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed tracking loops (DLL, PLL, FLL) are used for signal tracking, then fine estimation of delays and Doppler shifts can be obtained, but continuous snapshots are required which increases power consumption
Solution Approach 1:
The patent applies periodic action by taking snapshots at specific intervals rather than continuously. The method processes individual snapshots periodically to update delay and Doppler shift estimates, allowing the receiver to enter low-power states between snapshots while maintaining estimation accuracy through sophisticated processing of each captured snapshot.
Solution Approach 2:
The patent performs preliminary action by conducting signal acquisition and coarse estimation before the actual tracking phase. This preliminary processing establishes initial delay and Doppler shift estimates that enable subsequent fine estimation from intermittent snapshots, reducing the need for continuous high-power operation.
2Reliability
If snapshots are taken continuously for signal tracking, then accurate estimation of delays and Doppler shifts is maintained, but power consumption increases
Solution Approach 1:
The system transitions from continuous snapshot acquisition to periodic snapshot acquisition. Each snapshot is processed to update tracking state, and the receiver can power down between snapshots while maintaining reliable tracking through the use of stored correlation data and efficient estimation algorithms that work effectively with intermittent data.
Solution Approach 2:
The patent implements self-service by using the correlation data and estimation results from previous snapshots to maintain tracking state during periods when no new snapshots are taken. The system serves itself by extrapolating and updating estimates from existing data, reducing the frequency of power-intensive snapshot acquisitions while maintaining tracking reliability.
3Use of energy by moving object
If individual snapshots are processed without continuous acquisition, then power consumption is reduced, but conventional tracking loops cannot effectively estimate delays and Doppler shifts
Solution Approach 1:
The patent applies dimensionality change by transforming the estimation problem from the time domain to the frequency domain using Fast Fourier Transform (FFT). This dimensional transformation enables the system to extract precise delay and Doppler shift information from individual snapshots by analyzing the frequency spectrum, overcoming the limitation of non-continuous data acquisition.
Solution Approach 2:
The patent changes parameters by using sophisticated signal processing techniques including FFT-based spectral analysis and interpolation methods. These parameter changes in the processing approach enable accurate estimation from discrete snapshots by maximizing the information extracted from each individual snapshot through advanced mathematical transformations.
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
Accurate estimation of delays and Doppler shifts is achieved, enabling precise pseudoranges and positions, even in non-continuous snapshot scenarios, without the need for conventional tracking loops, and reducing power consumption.
Implementation Method 1
obtaining a frequency spectrum by computing a K-point discrete Fourier transform, DFT, of the output sequence
Data Source
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AI summary
A method for estimating delays and Doppler shifts of GNSS signals comprises obtaining respective output sequences from N correlators for a snapshot of a received GNSS signal, wherein each sequence has K values, the N correlators correspond to N different delays of a pseudorandom noise, PRN, code sequence, the K values are correlation values at K sampling time points in each sequence, N and K are positive integers. The method further comprises, for each output sequence, obtaining a frequency spectrum by computing a K-point discrete Fourier transform, DFT, of the output sequence; obtaining a N × K matrix using the N frequency spectra; determining at least one peak value in the N × K matrix; and estimating a delay and a Doppler shift of the received GNSS signal using indices of the at least one peak value in the N × K matrix.