Dynamic Programming based Time-Delay Estimation (TDE) Technique for Analysis of Time-varying Time-delay

TL;DR

This paper introduces a dynamic programming-based time-delay estimation method that significantly improves frequency response and is validated through simulations and application to tokamak plasma data, revealing zonal flows.

Contribution

The paper presents a novel dynamic programming approach for time-delay estimation that outperforms existing methods in frequency response and is applicable to plasma diagnostics.

Findings

Frequency response 5-10 times higher than previous methods

Transfer function decreases with noise, independent of spectrum shape

Successful application to tokamak data reveals zonal flows

Abstract

A new time-delay estimation (TDE) technique based on dynamic programming is developed, to measures the time-varying time-delay between two signals. Dynamic programming based TDE technique provides a frequency response 5 to 10 times higher than previously known TDE techniques, namely those based on time-lag cross-correlation or wavelet analysis. Effects of frequency spectrum, signal-to-noise ratio and amplitude of time-delay on response (represented as transfer function) of TDE technique is studied using simulated data signals. Transfer function for the technique decreases with increase in noise in signal; however it is independent of signal spectrum shape. Dynamic programming based TDE technique is applied to the Beam-Emission-Spectroscopy (BES) diagnostic data to measure poloidal velocity fluctuations, which led to the observation of theoretically predicted zonal flows in high-temperature tokamak plasmas.