Parameter Design for Secure Affine Frequency Division Multiplexing Waveform

The secure affine frequency division multiplexing (AFDM) waveform design is a main concern in high-mobility networks. In this article, we employ the four key parameters in AFDM to design secure waveforms, and afterward we analyze the role of the four parameters to reveal the design guideline. We find that c1 is bounded by the Doppler shifts and preset guard. The parameter c2 exhibits a minimum periodicity of 1, with the effective range [0, 1] rather than any real number. The adjustable parameters c1 and c2 introduce additional degrees of freedom to the AFDM waveform, thereby enhancing the anti-eavesdropping performance. In addition, excessive Lmax that determines the preset guard interval leads to a security-risk interval and poses eavesdropping risks. Therefore, the optimal Lmax equals maximum delay. Numerical simulations verify the accuracy of our analysis.