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Deep Learning Techniques for Radar-Based Continuous Human Activity Recognition

Ruchita Mehta Orcid Logo, Sara Sharifzadeh Orcid Logo, Vasile Palade Orcid Logo, Bo Tan Orcid Logo, Alireza Daneshkhah Orcid Logo, Yordanka Karayaneva

Machine Learning and Knowledge Extraction, Volume: 5, Issue: 4, Pages: 1493 - 1518

Swansea University Author: Sara Sharifzadeh Orcid Logo

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DOI (Published version): 10.3390/make5040075

Abstract

Human capability to perform routine tasks declines with age and age-related problems. Remote human activity recognition (HAR) is beneficial for regular monitoring of the elderly population. This paper addresses the problem of the continuous detection of daily human activities using a mm-wave Doppler...

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Published in: Machine Learning and Knowledge Extraction
ISSN: 2504-4990
Published: MDPI AG 2023
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa64788
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Abstract: Human capability to perform routine tasks declines with age and age-related problems. Remote human activity recognition (HAR) is beneficial for regular monitoring of the elderly population. This paper addresses the problem of the continuous detection of daily human activities using a mm-wave Doppler radar. In this study, two strategies have been employed: the first method uses un-equalized series of activities, whereas the second method utilizes a gradient-based strategy for equalization of the series of activities. The dynamic time warping (DTW) algorithm and Long Short-term Memory (LSTM) techniques have been implemented for the classification of un-equalized and equalized series of activities, respectively. The input for DTW was provided using three strategies. The first approach uses the pixel-level data of frames (UnSup-PLevel). In the other two strategies, a convolutional variational autoencoder (CVAE) is used to extract Un-Supervised Encoded features (UnSup-EnLevel) and Supervised Encoded features (Sup-EnLevel) from the series of Doppler frames. The second approach for equalized data series involves the application of four distinct feature extraction methods: i.e., convolutional neural networks (CNN), supervised and unsupervised CVAE, and principal component Analysis (PCA). The extracted features were considered as an input to the LSTM. This paper presents a comparative analysis of a novel supervised feature extraction pipeline, employing Sup-ENLevel-DTW and Sup-EnLevel-LSTM, against several state-of-the-art unsupervised methods, including UnSUp-EnLevel-DTW, UnSup-EnLevel-LSTM, CNN-LSTM, and PCA-LSTM. The results demonstrate the superiority of the Sup-EnLevel-LSTM strategy. However, the UnSup-PLevel strategy worked surprisingly well without using annotations and frame equalization.
Keywords: Human activity recognition (HAR), dynamic time warping (DTW), convolutional variational autoencoder (CVAE), mm-wave radar sensor, deep neural networks (DNNs)
College: Faculty of Science and Engineering
Funders: Coventry University
Issue: 4
Start Page: 1493
End Page: 1518