Sequential Convolutional Recurrent Neural Networks for Fast Automatic Modulation Classification

A novel and efficient end-to-end learning model for automatic modulation classification (AMC) is proposed for wireless spectrum monitoring applications, which automatically learns from the time domain in-phase and quadrature (IQ) data without requiring the design of hand-crafted expert features. With the intuition of convolutional layers with pooling serving as front-end feature distillation and dimensionality reduction, sequential convolutional recurrent neural networks (SCRNNs) are developed to take complementary advantage of parallel computing capability of convolutional neural networks (CNNs) and temporal sensitivity of recurrent neural networks (RNNs). Experimental results demonstrate that the proposed architecture delivers overall superior performance in signal to noise ratio (SNR) range above -10 dB, and achieves significantly improved classification accuracy from 80% to 92.1% at high SNRs, while drastically reduces the training and prediction time by approximately 74% and 67%, respectively. Furthermore, a comparative study is performed to investigate the impacts of various SCRNN structure settings on classification performance. A representative SCRNN architecture with the two-layer CNN and subsequent two-layer long short-term memory (LSTM) is developed to suggest the option for fast AMC.