Abstract:Automatic modulation recognition (AMR) is one of the essential parts in the intelligent communication system. In the underwater acoustic communication, it is a challenging work that promptly and easily recognizes the signal modulation schemes by conventional methods. The deep neural network method is a good solution to the problem, which creates a better recognition effect. The packets of data that are fed to the familiar neural network is constant. However, the packets of signal data on the communication cour… Show more
“…Kong et al [16] used IQ symbols to train a residual network. Wang et al [17] proposed a sequence convolutional network to achieve modulation classification based on signals' temporal characteristics. Liu et al [18] utilized principal component analysis technology to compress the original time-domain signals and then designed a deep heterogeneous network for modulation recognition.…”
In the process of the modulation recognition of underwater acoustic communication signals, the multipath effect seriously interferes with the signal characteristics, reducing modulation recognition accuracy. The existing methods passively improve the accuracy from the perspective of selecting appropriate signal features, lacking specialized preprocessing for suppressing multipath effects. So, the accuracy improvement of the designed modulation recognition models is limited, and the adaptability to environmental changes is poor. The method proposed in this paper actively utilizes common synchronous signals in underwater acoustic communication as detection signals to achieve passive time reversal without external signals and designs a passive time reversal-autoencoder to suppress multipath effects, enhance signals’ features, and improve modulation recognition accuracy and environmental adaptability. Firstly, synchronous signals are identified and estimated. Subsequently, a passive time reversal-autoencoder is designed to enhance power spectrum and square spectrum features. Finally, a modulation classification is performed using a convolutional neural network. The model is trained in simulation channels generated by Bellhop and tested in actual channels which are different from the training period. The average recognition accuracy of the six modulated signals is improved by 10% compared to existing passive modulation recognition methods, indicating good environmental adaptability as well.
“…Kong et al [16] used IQ symbols to train a residual network. Wang et al [17] proposed a sequence convolutional network to achieve modulation classification based on signals' temporal characteristics. Liu et al [18] utilized principal component analysis technology to compress the original time-domain signals and then designed a deep heterogeneous network for modulation recognition.…”
In the process of the modulation recognition of underwater acoustic communication signals, the multipath effect seriously interferes with the signal characteristics, reducing modulation recognition accuracy. The existing methods passively improve the accuracy from the perspective of selecting appropriate signal features, lacking specialized preprocessing for suppressing multipath effects. So, the accuracy improvement of the designed modulation recognition models is limited, and the adaptability to environmental changes is poor. The method proposed in this paper actively utilizes common synchronous signals in underwater acoustic communication as detection signals to achieve passive time reversal without external signals and designs a passive time reversal-autoencoder to suppress multipath effects, enhance signals’ features, and improve modulation recognition accuracy and environmental adaptability. Firstly, synchronous signals are identified and estimated. Subsequently, a passive time reversal-autoencoder is designed to enhance power spectrum and square spectrum features. Finally, a modulation classification is performed using a convolutional neural network. The model is trained in simulation channels generated by Bellhop and tested in actual channels which are different from the training period. The average recognition accuracy of the six modulated signals is improved by 10% compared to existing passive modulation recognition methods, indicating good environmental adaptability as well.
“…Different DL networks are selected for different shallow features. Common DL networks include the long short-term memory network [10], convolutional neural network (CNN) [11], capsule network [3], generative adversarial network [8], autoencoder network [12], and residual network [13]. With the combination of different DL networks and shallow features, DL-based methods have made considerable progress in the field of modulation recognition.…”
Deep learning (DL)-based modulation recognition methods of underwater acoustic communication signals are mostly applied to a single hydrophone reception scenario. In this paper, we propose a novel end-to-end multihydrophone fusion network (MHFNet) for multisensory reception scenarios. MHFNet consists of a feature extraction module and a fusion module. The feature extraction module extracts the features of the signals received by the multiple hydrophones. Then, through the neural network, the fusion module fuses and classifies the features of the multiple signals. MHFNet takes full advantage of neural networks and multihydrophone reception to effectively fuse signal features for realizing improved modulation recognition performance. Experimental results on simulation and practical data show that MHFNet is superior to other fusion methods. The classification accuracy is improved by about 16%.
“…[59] develops a blind signal detector for underwater acoustic signals, essentially distinguishing the signals from noise, and developing a transfer model reducing the reliance on simulated data for online testing. [60][61][62] develop a modulation classifier for underwater acoustic channels using DL techniques and validate in data from real experimental scenarios. While the results of many of these works are promising and are shown to perform with data from real underwater scenarios, they are limited in identification complexity.…”
Spectrum maps of our classifier trained on three different datasets and tested on data collected over-the-air (OTA): (Top Left) Spectrogram of data collected at 2.402 GHz (i.e., BLE advertisement channel); (Top Right): Proposed semi-augmented data generator model output; (Bottom Left): Un-augmented data model output;
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