A hybrid attention mechanism for blind automatic modulation classification

Recently, deep leaning has been making great progress in automatic modulation classification, just like its success in computer vision. However, radio signals with harsh impairments (oscillator drift, clock drift, noise) would significantly degrade the performance of the existing classifiers. To overcome the problem and explore the depth reason, a hybrid attention convolution network is proposed to enhance the capability of feature extraction. First, a spatial transformer network module with long short‐term memory is introduced to synchronize and normalize radio signals. Second, a channel attention module is constructed to weight and assemble feature maps, exploring global feature representations with more context‐relevant information. By combining these two modules, a relatively lightweight classifier with complex convolution layer for final classification is further researched through visualization. Moreover, different structures of attention module are compared and optimized in detail. Experimental result shows that our proposed hybrid model achieves the best performance among all compared models when SNR is upper than −$$ - $$7 dB, and it peaks at 93.448%$$ \% $$ at 0 dB, 2.7% higher than that of CLDNN and 97.560%$$ \% $$ at 20 dB, 8.2% higher than that of ResNet. And our model can be more efficient after a trade‐off between accuracy and model size. In this work, we proposed a hybrid attention convolution network to classify different modulations to develop a robust automatically learning method for radio signals with harsh impairments (oscillator drift, clock drift, noise) and the lightweight network is further optimized.