Affine frequency division multiplexing (AFDM) is a promising new multicarrier technique based on discrete affine Fourier transform (DAFT). By properly tuning pre-chirp parameter and post-chirp parameter in the DAFT, the effective channel in the DAFT domain can completely avoid overlap of different paths, thus constitutes a full representation of delay-Doppler profile, which significantly improves the system performance in high mobility scenarios. However, AFDM has the crucial problem of high peak-to-average power ratio (PAPR) caused by phase randomness of modulated symbols. In this letter, an algorithm named grouped pre-chirp selection (GPS) is proposed to reduce the PAPR by changing the value of pre-chirp parameter on sub-carriers group by group. Specifically, it is demonstrated first that the important properties of AFDM system are maintained when implementing GPS. Secondly, we elaborate the operation steps of GPS algorithm, illustrating its effect on PAPR reduction and its advantage in terms of computational complexity compared with the ungrouped approach. Finally, simulation results of PAPR reduction in the form of complementary cumulative distribution function (CCDF) show the effectiveness of the proposed GPS algorithm.

翻译：仿射频分复用（AFDM）是一种基于离散仿射傅里叶变换（DAFT）的新型多载波技术。通过适当调整DAFT中的预啁啾参数和后啁啾参数，DAFT域中的等效信道可完全避免不同路径间的重叠，从而构成时延-多普勒剖面的完整表示，显著提升了高移动性场景下的系统性能。然而，AFDM存在因调制符号相位随机性导致的高峰均功率比（PAPR）这一关键问题。本文提出一种名为分组预啁啾选择（GPS）的算法，通过逐组改变子载波上的预啁啾参数值来降低PAPR。具体而言，研究首先论证了实施GPS时AFDM系统的重要特性得以保持；其次详细阐述了GPS算法的操作步骤，说明了其降低PAPR的效果，以及与未分组方法相比在计算复杂度方面的优势；最后通过互补累积分布函数（CCDF）形式的PAPR降低仿真结果验证了所提GPS算法的有效性。