Constellation Warping-Based QAM Signal Watermarking for Secure and Reliable Wireless Communications

This paper investigates the performance of constellation warping techniques in QAM signals as a novel approach for physical layer authentication. We introduce a dynamic watermarking method that embeds subtle warping patterns into QAM constellations, enabling receivers to authenticate legitimate transmissions while detecting spoofing attacks. Our time-varying watermarking scheme employs secure key-based pattern generation to resist replay and estimation attacks. Extensive simulations analyze the system's resilience against various attack types (replay, blind spoofing, and estimation-based) across different signal-to-noise ratios. Results demonstrate that the proposed approach achieves high detection rates ($>90%$ at moderate SNRs) with minimal false alarms and negligible impact on communication performance. We further identify optimal warping strengths and authentication thresholds that maximize security while minimizing symbol error rate degradation. The findings establish constellation warping as an effective physical layer security technique for wireless communications systems that face sophisticated spoofing threats.