Optimal Constant-Envelope Jamming Waveform Design Against M-QAM Modulation

Recently, unmanned aerial vehicles and Internet-of-Things devices have significantly facilitated daily life, but they can also pose serious threats to public security if maliciously used. An effective way to counteract these threats is to transmit interference signals to disrupt their wireless communication links. However, excessively complex jamming waveforms are difficult to be realized. In addition, due to the limited jamming power budget and the long distance between jammer and receiver, the jamming-to-noise-ratio (JNR) at the receiver may be low. Thus, the efficiency of jamming power is vital. The constant-envelope jamming waveform appears to be a promising solution to both problems. Therefore, we consider the commonly-used quadrature amplitude modulation (QAM) wireless system, and optimize the constant-envelope jamming waveform to maximize the error probability when JNR < signal-to-noise-ratio (SNR). This is a complicated non-convex problem that is difficult to solve directly. As a compromise, we seek a closed-form solution for a simplified version of it, which demonstrates that the simple binary phase shift keying (BPSK) is optimal. Numerical results confirm its superiority.