Affine frequency division multiplexing (AFDM) and orthogonal AFDM access (O-AFDMA) are promising techniques based on chirp signals, which are able to suppress the performance deterioration caused by Doppler shifts in high-mobility scenarios. However, the high peak-to-average power ratio (PAPR) in AFDM or O-AFDMA is still a crucial problem, which severely limits their practical applications. In this paper, we propose a discrete affine Fourier transform (DAFT)-spread AFDMA scheme based on the properties of the AFDM systems, named DAFT-s-AFDMA to significantly reduce the PAPR by resorting to the DAFT. We formulate the transmitted time-domain signals of the proposed DAFT-s-AFDMA schemes with localized and interleaved chirp subcarrier allocation strategies. Accordingly, we derive the guidelines for setting the DAFT parameters, revealing the insights of PAPR reduction. Finally, simulation results of PAPR comparison in terms of the complementary cumulative distribution function (CCDF) show that the proposed DAFT-s-AFDMA schemes with localized and interleaved strategies can both attain better PAPR performances than the conventional O-AFDMA scheme.

翻译：仿射频分复用（AFDM）与正交仿射频分多址接入（O-AFDMA）是基于啁啾信号的前沿技术，能够抑制高移动性场景中多普勒频移引起的性能恶化。然而，AFDM或O-AFDMA中较高的峰均功率比（PAPR）仍是制约其实际应用的关键问题。本文基于AFDM系统特性，提出一种离散仿射傅里叶变换（DAFT）扩展的AFDMA方案（命名为DAFT-s-AFDMA），通过利用DAFT显著降低PAPR。我们构建了采用局部化与交织啁啾子载波分配策略的所提DAFT-s-AFDMA方案时域发射信号模型，进而推导出DAFT参数设置准则，揭示PAPR降低的内在机理。最后，基于互补累积分布函数（CCDF）的PAPR仿真对比结果表明，采用局部化与交织策略的DAFT-s-AFDMA方案相比传统O-AFDMA方案均能获得更优的PAPR性能。