用于线性调频域通信的Zadoff-Chu序列：双色散信道中的分集-复杂度权衡
Zadoff-Chu Sequences for Chirp-Domain Communication: Diversity-Complexity Tradeoffs in Doubly Dispersive Channels
浏览论文内容
中文总结 AI 辅助
本研究提出基于Zadoff-Chu（ZC）序列的线性调频域通信方案，可将双色散信道转换为单色散信道，在高速移动场景下性能优于OFDM，与AFDM、OTFS相当，揭示了分集与接收机复杂度的权衡关系。
中文摘要 AI 辅助
正交频分复用（OFDM）通过将信道划分为窄带子信道来对抗多径引起的时间色散。然而，当信道因移动性（多普勒效应）也表现出频率色散时，这些子信道会失去正交性，产生载波间干扰，降低通信系统的可靠性。本研究探讨用于线性调频域通信的Zadoff-Chu（ZC）序列，以提升时频色散信道中的可靠性。研究表明，ZC序列是唯一能将双色散信道转换为纯时间或纯频率色散的单色散信道的恒幅零自相关（CAZAC）序列。该转换由ZC根控制，其提供从延迟-多普勒域到一维线性调频域轴的几何投影，且具有闭式设计规则。由于转换后的信道为单色散信道，接收机可均衡一维卷积信道而非二维延迟-多普勒信道，并可重用生成编码系统所需软信息的基于网格的检测器。随后，本文提出基于ZC的调制方案，推导转换后的有效信道并分析分集，揭示了分集与接收机复杂度之间的潜在权衡。在车速540km/h、载波频率4GHz的条件下评估，基于ZC的调制方案表现出与仿射频分复用（AFDM）、正交时频空间（OTFS）相当的性能，较正交线性调频分复用（OCDM）增益约5dB，较OFDM增益约10dB。
英文摘要
Orthogonal frequency-division multiplexing (OFDM) combats multipath-induced time dispersion by dividing the channel into narrowband sub-channels. However, when the channel also exhibits frequency dispersion due to mobility (Doppler effect), these sub-channels lose orthogonality and cause inter-carrier interference that degrades the reliability performance of the communication system. We investigate Zadoff-Chu (ZC) sequences for chirp-domain communication to improve reliability in time-frequency dispersive channels. We show that ZC sequences are the only constant-amplitude zero-autocorrelation (CAZAC) sequences that transform a doubly dispersive channel into a singly dispersive channel that is either pure time or frequency dispersion. This transformation is controlled by the ZC root, which provides a geometric projection from the delay-Doppler domain onto a one-dimensional chirp-domain axis with a closed-form design rule. Because the transformed channel is singly dispersive, the receiver equalizes a one-dimensional convolutional channel rather than a two-dimensional delay-Doppler channel and can reuse trellis-based detectors that generate the soft information that coded systems require. Then, we present ZC-based modulations, derive the effective channel after transformation, and analyze diversity, which reveals an underlying trade-off between diversity and receiver complexity. When evaluated at a vehicle speed of 540 km/h and a carrier frequency of 4 GHz, ZC-based modulations demonstrate performance comparable to affine frequency division multiplexing (AFDM) and orthogonal time-frequency space (OTFS), with gains of about 5 dB over orthogonal chirp division multiplexing (OCDM) and 10 dB over OFDM.
