This paper proposes a novel non-orthogonal affine frequency division multiplexing (nAFDM) waveform for reliable high-mobility communications with enhanced spectral efficiency (SE). The key idea is to introduce a bandwidth compression factor into the AFDM modulator to enable controllable subcarrier overlapping. We first detail the proposed nAFDM transceiver and derive the corresponding input-output signal relationship. Then, an efficient nAFDM signal generation method based on the inverse discrete Fourier transform (IDFT) is proposed, enabling practical implementation using existing inverse fast Fourier transform (IFFT) modules without additional hardware complexity. Next, to characterize the impact of non-orthogonal modulation, we derive a closed-form expression of inter-carrier interference (ICI), showing its dependence on the bandwidth compression factor. To mitigate the resulting interference, we propose a soft iterative detection algorithm and a low-complexity implementation approach that leverages the distribution characteristics of ICI. Simulation results demonstrate that 1) in terms of bit error rate (BER), the proposed nAFDM can achieve near identical BER compared to conventional AFDM, while outperforms other waveform counterparts; 2) nAFDM is capable of striking higher SE compared to other existing waveforms; and 3) the proposed nAFDM achieves an attractive BER vs. SE trade-off, and the proposed soft iterative detection (ID) scheme can attain a trade-off between BER and complexity.

翻译：本文提出了一种新型非正交仿射频分复用（nAFDM）波形，旨在以增强的谱效实现可靠的高移动性通信。其核心思想是在AFDM调制器中引入带宽压缩因子，以实现可控的子载波重叠。我们首先详细阐述了所提出的nAFDM收发机结构，并推导了相应的输入-输出信号关系。随后，提出了一种基于离散傅里叶逆变换（IDFT）的高效nAFDM信号生成方法，该方法可利用现有的快速傅里叶逆变换（IFFT）模块实现，无需额外的硬件复杂度。接着，为表征非正交调制的影响，我们推导了载波间干扰（ICI）的闭式表达式，揭示了其与带宽压缩因子的依赖关系。为减轻由此产生的干扰，我们提出了一种软迭代检测算法以及一种利用ICI分布特性的低复杂度实现方案。仿真结果表明：1）在误码率（BER）方面，所提出的nAFDM能够达到与传统AFDM近乎相同的BER，同时优于其他对比波形；2）与现有其他波形相比，nAFDM能够实现更高的谱效；3）所提出的nAFDM实现了具有吸引力的BER与谱效权衡，且所提出的软迭代检测（ID）方案能够在BER与复杂度之间取得良好折衷。