标题： 预啁啾域索引调制用于6G的全分集仿射频分复用 显示英文标题

标题： Pre-Chirp-Domain Index Modulation for Full-Diversity Affine Frequency Division Multiplexing towards 6G

摘要： 自适应频分复用（AFDM），作为一种利用线性调频信号的优越多载波技术，专为高速移动通信设计，被视为第六代（6G）无线网络的有前途的候选技术。 AFDM基于离散自适应傅里叶变换（DAFT），具有两个可调参数的线性调频信号，分别称为预线性调频参数和后线性调频参数。 我们表明，预线性调频对应项可以灵活操控以获得额外的自由度（DoF）。 因此，本文提出了一种新颖的AFDM方案，采用预线性调频索引调制（PIM）理念（AFDM-PIM），可以通过动态预线性调频参数分配隐式地传输额外的信息比特，从而提高频谱和能量效率。 具体而言，我们首先证明，在AFDM调制过程中，通过对不同子载波应用不同的预线性调频参数，子载波正交性仍然得以保持。 受此特性的启发，每个AFDM子载波根据输入比特构成一个唯一的预线性调频信号。 通过这种安排，可以在不增加额外能量消耗的情况下，将额外的二进制比特嵌入到预线性调频参数分配的索引模式中。 为了进行性能分析，我们推导了所提方案在最大似然（ML）检测下的平均误比特率（BER）的渐近紧致上界，并验证了所提的AFDM-PIM在双扩散信道下可以实现最优分集阶数。 基于推导结果，我们进一步提出了一个最优的预线性调频字母表设计，通过智能优化算法来提升BER性能。 仿真结果表明，在双扩散信道下，所提出的AFDM-PIM优于经典基准。 显示英文摘要

摘要： Affine frequency division multiplexing (AFDM), tailored as a superior multicarrier technique utilizing chirp signals for high-mobility communications, is envisioned as a promising candidate for the sixth-generation (6G) wireless network. AFDM is based on the discrete affine Fourier transform (DAFT) with two adjustable parameters of the chirp signals, termed as the pre-chirp and post-chirp parameters, respectively. We show that the pre-chirp counterpart can be flexibly manipulated for additional degree-of-freedom (DoF). Therefore, this paper proposes a novel AFDM scheme with the pre-chirp index modulation (PIM) philosophy (AFDM-PIM), which can implicitly convey extra information bits through dynamic pre-chirp parameter assignment, thus enhancing both spectral and energy efficiency. Specifically, we first demonstrate that the subcarrier orthogonality is still maintained by applying distinct pre-chirp parameters to various subcarriers in the AFDM modulation process. Inspired by this property, each AFDM subcarrier is constituted with a unique pre-chirp signal according to the incoming bits. By such arrangement, extra binary bits can be embedded into the index patterns of pre-chirp parameter assignment without additional energy consumption. For performance analysis, we derive the asymptotically tight upper bounds on the average bit error rates (BERs) of the proposed schemes with maximum-likelihood (ML) detection, and validate that the proposed AFDM-PIM can achieve the optimal diversity order under doubly dispersive channels. Based on the derivations, we further propose an optimal pre-chirp alphabet design to enhance the BER performance via intelligent optimization algorithms. Simulations demonstrate that the proposed AFDM-PIM outperforms the classical benchmarks under doubly dispersive channel.