ISAC Delay-Doppler Processing for High-Doppler Localization
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Solution Overview
Problem
Conventional Orthogonal Frequency Division Multiplexing (OFDM) waveforms fail to maintain orthogonality and suffer performance loss in high Doppler scenarios, such as high-speed railway communications, necessitating a more effective method for accurate target parameter estimation in integrated sensing and communication (ISAC) systems.
Innovation Solution
The method converts received signals from a delay-time (DT) domain to a delay-Doppler (DD) domain, extracts a guard band region, performs 2-dimensional Fast Fourier Transform (FFT), creates a dictionary using predefined delay and Doppler values, and uses an orthogonal matching pursuit (OMP) algorithm for sparse recovery to estimate phase information and parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional OFDM waveforms are used in high Doppler scenarios, then the system structure remains simple, but orthogonality is not maintained and performance is lost
Solution Approach 1:
The patent transforms the signal processing from traditional time-frequency domain to delay-Doppler domain. By representing the channel in the delay-Doppler domain and performing processing in this alternative dimension, the system maintains orthogonality under high Doppler shifts while managing complexity through structured transformations (ISFFT and Heisenberg transforms).
Solution Approach 2:
The patent changes the fundamental parameters of waveform representation by using OTFS modulation which maps data to the delay-Doppler domain. This parameter transformation allows the system to handle high Doppler scenarios effectively by operating in a domain where Doppler shifts are explicit and manageable rather than implicit and destructive as in OFDM.
2Measurement precision
If accurate target parameter estimation is achieved using OTFS waveform, then measurement precision improves, but computational complexity increases
Solution Approach 1:
The patent segments the estimation process into distinct stages: first performing ISFFT to obtain delay estimates, then using these delay estimates to guide Doppler estimation. This segmentation allows each estimation task to be performed more accurately and independently, reducing the overall computational burden while improving precision.
Solution Approach 2:
The patent performs preliminary delay estimation using ISFFT before conducting Doppler estimation. By obtaining delay information first and using it to inform subsequent Doppler estimation, the system achieves more accurate parameter estimation with reduced computational complexity compared to simultaneous estimation methods.
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 provides accurate delay and Doppler estimation with reduced computational complexity, improving performance in high Doppler environments and enabling precise localization and velocity determination in integrated sensing and communication systems.
Implementation Method 1
performing, via the one or more hardware processors, a 2-dimensional fast Fourier transform (FFT) on the guard band region extracted from the received converted signal
Implementation Method 2
forming, via the one or more hardware processors, a sparse recovery problem for the received converted signal using an orthogonal matching pursuit (OMP) algorithm
Implementation Method 3
Orthogonal Time Frequency Space (OTFS) modulation has garnered interest recently as a potential solution to this problem. An alternate representation of the time-varying channel owing to mobility is the Orthogonal Time Frequency Space (OTFS) channel in the delay-Doppler (DD) domain
Data Source
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AI summary
Conventional Orthogonal frequency division multiplexing (OFDM) is unable to retain its orthogonality and suffers loss in performance in high Doppler circumstances. The present disclosure converts a signal received in delay-time domain into delay-Doppler domain and extracts a guard band region from the received converted signal. A 2-dimensional fast Fourier transform is performed on guard band region extracted from received converted signal. A 2-dimensional fast Fourier transform of the received converted signal is divided with the 2-dimensional fast Fourier transform of transmitted signal to extract phase information. A dictionary is created using a pre-defined set of values of delay and Doppler. A sparse recovery problem is formed for received converted signal using an orthogonal matching pursuit algorithm. One or more parameters are estimated by identifying one or more locations pertaining to the one or more columns corresponding to L significant non-zero locations comprised in sparse vector of sparse recovery problem.