HFAD: Homomorphic Filtering Adversarial Defense Against Adversarial Attacks in Automatic Modulation Classification

Deep neural networks provide intelligent solutions for Automatic Modulation Classification (AMC) tasks in the field of communication. However, their susceptibility to adversarial examples due to the interpretability problem presents a challenge as it leads to anomalous decisions. Emerging studies suggest that the high-frequency constituents within signals constitute a fundamental source of adversarial vulnerability. To address this issue, this paper introduces a Homomorphic Filtering Adversarial Defense (HFAD) algorithm that aims to effectively defend against adversarial examples by applying frequency domain filtering on the signal. This approach enhances the security and reliability of the AMC model by attenuating high-frequency components of the signal through homomorphic filtering, thereby reducing errors caused by adversarial perturbations on model outputs. The robustness of the AMC model is further enhanced through the integration of HFAD with data augmentation strategies. Experimental results demonstrate that the proposed defense algorithm not only maintains high signal recognition accuracy but also preserves communication signal transmission quality. Moreover, HFAD effectively withstands a wide range of white-box adversarial attacks and demonstrates resilience against black-box adversarial attacks, thereby enhancing the robustness of the AMC model against adversarial examples and exhibiting strong transfer performance.