Security-Aware Codebook Design for Low-PAPR AFDM Systems

Affine frequency division multiplexing (AFDM) is regarded as a promising waveform for high-mobility wireless systems. However, the public codebook used in AFDM raises security concerns when the link is observed by an eavesdropper, and meanwhile AFDM communication suffers from a high peak-to-average power ratio (PAPR). This paper proposes a security-aware codebook design for low-PAPR AFDM systems. Specifically, the codebook is designed to minimize an eavesdropper-oriented cross-alignment metric while maintaining the legitimate user's decoding reliability and keeping the PAPR low. Since the resulting design problem is non-convex, we develop a dedicated alternating discrete coordinate descent algorithm to solve it. Simulation results show that the proposed codebook design significantly degrades the eavesdropper's decoding performance without degrading that of the legitimate receiver while maintaining the low-PAPR.