Cited by 863Context-Aware Activity Recognition SystemsHuman Pose and Action RecognitionGait Recognition and Analysis

The DOI matches its Crossref record; 39 of the 40 references it cites were found in a registry or an index; none of the 10 sources its claims cite is checked for support yet.

LSTM-CNN Architecture for Human Activity Recognition

Open access

Abstract

In the past years, traditional pattern recognition methods have made great progress. However, these methods rely heavily on manual feature extraction, which may hinder the generalization model performance. With the increasing popularity and success of deep learning methods, using these techniques to recognize human actions in mobile and wearable computing scenarios has attracted widespread attention. In this paper, a deep neural network that combines convolutional layers with long short-term memory (LSTM) was proposed. This model could extract activity features automatically and classify them with a few model parameters. LSTM is a variant of the recurrent neural network (RNN), which is more suitable for processing temporal sequences. In the proposed architecture, the raw data collected by mobile sensors was fed into a two-layer LSTM followed by convolutional layers. In addition, a global average pooling layer (GAP) was applied to replace the fully connected layer after convolution for reducing model parameters. Moreover, a batch normalization layer (BN) was added after the GAP layer to speed up the convergence, and obvious results were achieved. The model performance was evaluated on three public datasets (UCI, WISDM, and OPPORTUNITY). Finally, the overall accuracy of the model in the UCI-HAR dataset is 95.78%, in the WISDM dataset is 95.85%, and in the OPPORTUNITY dataset is 92.63%. The results show that the proposed model has higher robustness and better activity detection capability than some of the reported results. It can not only adaptively extract activity features, but also has fewer parameters and higher accuracy.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

The paper proposes an LSTM-CNN architecture that feeds raw mobile sensor data into a two-layer LSTM followed by convolutional layers, with global average pooling and batch normalization to reduce parameters and speed convergence. It reports high accuracy/F1 on UCI-HAR, WISDM, and OPPORTUNITY and compares favorably with CNN and DeepConvLSTM baselines.

Key findings

  • On three public datasets, reported overall accuracy/F1 is UCI-HAR 95.78% (abstract/conclusion; experimental section says 95.80% accuracy), WISDM 95.85% (abstract/conclusion; experimental section says 95.75% accuracy), and OPPORTUNITY 92.63%; without the Null class, OPPORTUNITY accuracy is 87.58%.
  • Compared with the CNN of Yang et al. and DeepConvLSTM under the same scenario, LSTM-CNN increased about 7% on OPPORTUNITY and averaged 3% on UCI-HAR and WISDM by F1 score.
  • Replacing the fully connected layer with GAP reduced parameters: model B has 27,462 parameters versus more than 502 thousand for model A, about 94% less, with almost the same performance; adding BN raised F1 to 93.35%, and adding LSTM layers raised UCI-HAR F1 to 95.78%.
  • Hyperparameter tests on UCI-HAR found Adam was the best optimizer, batch size 192 gave the highest accuracy, and 192 filters in the second convolutional layer gave F1 96.38% (4% over 64 filters) but increased model parameters by more than 70%.

Methods

  • Architecture: preprocessed sensor data passes through two LSTM layers (32 memory cells each, 64 total), then two convolutional layers (64 filters of size 1×5 with stride 2; 128 filters of size 1×3 with stride 1), with max-pooling between them, followed by GAP, BN, and a dense Softmax output layer.
  • Data: UCI-HAR (30 subjects, 6 activities, 50 Hz, 748,406 samples), WISDM (36 subjects, 6 activities, 20 Hz, 1,098,209 samples, unbalanced), and OPPORTUNITY (4 subjects, 17 activities plus Null class, 30 Hz, 113 channels). Preprocessing used linear interpolation, 0–1 normalization, and sliding windows of length 128 for UCI/WISDM and 24 for OPPORTUNITY, with 50% overlap.
  • Training/evaluation: Keras with TensorFlow backend, cross-entropy loss, Adam optimizer, batch size 192, 200 epochs, learning rate 0.001; evaluated with accuracy and F1 score, confusion matrices, and comparisons to CNN and DeepConvLSTM.

Limitations

  • The paper states WISDM and OPPORTUNITY are imbalanced, so overall accuracy is not an appropriate measure and F1 is used; it also notes relatively poor discrimination between sitting and standing in UCI-HAR, with recall and precision in the range of 92%–93%.
  • The paper states LSTM layers slow computation because each time step depends on the previous one and cannot be computed in parallel; LSTM-CNN took 9,416 ms per epoch versus 5,156 ms for model D, and GAP can shift training pressure to convolutional layers and slow convergence, which BN was added to address.
  • Evident from the text: reported metrics are inconsistent across sections (e.g., UCI-HAR 95.78% vs 95.80%; WISDM 95.85% vs 95.75%), and OPPORTUNITY evaluation uses only four subjects, limiting generalization claims.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1109/access.2020.2982225

Cites

39 of 39 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

0 of 10 cited sources checked · 0 supported · 0 flagged

Show all 32 claims

  • It may state two separate claims as one. 28
  • Probably not a substantial claim. 10
  • The quote only partly states this claim. 1
32 of 32
  • The paper relies on this without support.

    LSTM is a variant of RNN that is more suitable for processing temporal sequences.

    “LSTM is a variant of the recurrent neural network (RNN), which is more suitable for processing temporal sequences.”
  • The paper relies on this without support.

    LSTM can eliminate the gradient vanishing limitation of RNN.

    “LSTM is a variety of RNN, which could eliminate this limitation.”
  • The paper relies on this without support.

    LSTM has great advantages in feature extraction of sequence data than convolutional neural networks due to its special memory cells.

    “LSTM has great advantages in feature extraction of sequence data than convolutional neural networks due to its special memory cells.”
  • The paper relies on this without support.

    RNN can take advantage of the chronological relationship between sensor readings.

    “RNN could take advantage of the chronological relationship between sensor readings.”
  • The paper relies on this without support.

    RNN has the problem of gradient vanishing, which hinders the ability of the network to model between raw sensor data and human activities in a long context window.

    “Although RNN has the ability to capture temporal information from sequential data, it has the problem of gradient vanishing, which hinders the ability of the network to model between raw sensor data and human activities in a long context window.”
  • The paper relies on this without support.

    The more convolution kernels are used, the more hidden features could be mined in the input samples.

    “Generally speaking, the more convolution kernels are used, the more hidden features could be mined in the input samples.”
  • The paper relies on this without support.

    The max-pooling layer filters interference noise caused by the unconscious jitter of the human body.

    “It serves two purposes.One is to reduce the parameters while maintaining dominant features, the other is to filter the interference noise caused by the unconscious jitter of the human body.”
  • The paper relies on this without support.

    The WISDM and OPPORTUNITY datasets are imbalanced.

    “The WISDM and OPPORTU-NITY mentioned above are both imbalanced datasets.”
  • The paper relies on this without support.

    Hyper-parameters have a great impact on classification model performance.

    “Hyper-parameters have a great impact on the classification model performance.”
  • The paper relies on this without support.

    The weight parameters of CNN mainly concentrate on the fully-connected layer.

    “The weight parameters of CNN mainly concentrate on the fully-connected layer.”
  • The paper relies on this without support.

    Recordings of activities based on mobile sensors are temporal sequences.

    “The recordings of activities based on mobile sensors are temporal sequences and LSTM has the ability to capture temporal information from sequential data.”
  • The paper relies on this without support.

    LSTM has the ability to capture temporal information from sequential data.

    “The recordings of activities based on mobile sensors are temporal sequences and LSTM has the ability to capture temporal information from sequential data.”
  • The paper relies on this without support.

    When training LSTM layers, the calculation of each time step depends on the output of the previous time step.

    “When training LSTM layers, the calculation of each time step depends on the output of the previous time step.”
13 of 13

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • UCI-HAR overall accuracy has two reported values

    Major

    The abstract reports 95.78% overall accuracy for UCI-HAR, whereas the results section reports 95.80% for the same measure.

  • WISDM waveform duration conflicts with its sampling rate

    Minor

    At the stated WISDM sampling rate of 20 Hz, 128 points span 6.4 seconds, not 2.56 seconds.

    Reported 2.56 · recomputed 6.4

  • UCI-HAR is incorrectly described as having the most volunteers

    Minor

    The paper says UCI-HAR has the largest number of volunteers at 30, but states that WISDM has 36 subjects.

  • Adding an LSTM layer to model D leaves the stated total unchanged

    Minor

    Model D is described as having two LSTM layers. The paper then says it added another layer to model D for a total of two layers.

  • WISDM overall accuracy has two reported values

    Minor

    The abstract reports 95.85% overall accuracy for WISDM, whereas the results section reports 95.75%.

5 of 5

Citations

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Metadata

Authors
Xia, K., Huang, J., & Wang, H.
Affiliations
University of Shanghai for Science and Technology (CN)
Venue
IEEE Access
Published
2020
Volume
8
Pages
56855-56866
ISSN
2169-3536 (ISSN-L)
OpenAlex
W3011785450
Cited by
851
References
40
Citations by year
2026: 68 · 2025: 169 · 2024: 169 · 2023: 185 · 2022: 136 · 2021: 83 · 2020: 14
FWCI
40.64
Type
journal article
Language
en
Open access
Locations
  • IEEE Access (publishedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
National Natural Science Foundation of China (512070901, 51637001)
Topics
  • Physical Sciences › Computer Science › Computer Vision and Pattern Recognition › Context-Aware Activity Recognition Systems
  • Physical Sciences › Computer Science › Computer Vision and Pattern Recognition › Human Pose and Action Recognition
  • Physical Sciences › Engineering › Biomedical Engineering › Gait Recognition and Analysis
Keywords
human activity recognition, long short-term memory, convolutional neural networks, mobile sensor data, wearable computing, automatic feature extraction, global average pooling, batch normalization, UCI HAR dataset, WISDM dataset, Opportunity dataset

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