OTFS分数多普勒信道估计与检测论文整理1（摘要）

写在前面：该文写于2023.6.1，整理了IEEE上最新OTFS方面（大多为2023年发表）顶刊论文，主要涉及到分数多普勒问题（一共44篇，每次更新5篇）。写文的初衷是为了理解分数多普勒的问题背景，并了解现有针对分数多普勒问题的一些成熟解决方案，因此在时间有限的前提下只针对摘要核心部分（问题背景、解决方法、简要细节）做出翻译（关于翻译的准确性仅供参考，对于不准确的地方欢迎指正），并对摘要中核心的部分进行标红或划线处理，同时对英文摘要进行拆分，方便大家快速找到所需要的内容，摘要最后写了总结，大多为概括以及本人的一些简单想法。

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一、论文1：Doppler Zero-Insert Extension for OTFS Modulation with Fractional Doppler

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Doppler Zero-Insert Extension for OTFS Modulation with Fractional Doppler
Tan, Yuanyuan and Ren, Pinyi and Xu, Dongyang
2022 Aug
2022 8th International Conference on Big Data Computing and Communications (BigCom)
原文：
背景：Orthogonal time frequency space (OTFS) modulation can better handle Doppler shift and delay issues, which is a promising modulation method in future high-mobility scenarios. In the OTFS modulation system, the channel is expressed as a constant channel by delay information and Doppler information, which poses a huge challenge to OTFS transmission based on delay-Doppler domain channel estimation. 面临问题：The accuracy of the Doppler axes is not high enough, resulting in fractional Doppler parameters in most cases, which will cause great trouble to OTFS transmission and channel estimation. 本文方法：To solve this problem, we proposed a Doppler zero-insert extension scheme. In the delayed-Doppler domain, the signal is zero-inserted and extended in the Doppler direction to increase the total transmission time, thereby improving the accuracy of the Doppler axes direction. According to the extended received signal, channel estimation can be performed on the original fractional Doppler channel. 仿真结果：We proved the feasibility of the proposed scheme for fractional Doppler channel detection through theoretical derivation, and obtained the performance improvement brought by the proposed scheme by analyzing the effect of converting fractional Doppler to integer Doppler. Finally, a relatively appropriate expansion parameter is selected through simulation, and the simulation results demonstrate the effective detection of our proposed scheme for fractional Doppler situations.

翻译：

考虑分数多普勒的多普勒插0扩展的OTFS调制 摘要：OTFS调制由于可以更好地处理多普勒频移和时延问题，成为未来高移动性场景下的理想调制方法。在OTFS调制系统中，信道的时延和多普勒信息被表示成恒定值，这给基于时延-多普勒域信道估计的OTFS传输问题带来的巨大挑战。由于多普勒轴的精确性不够高，使得在大多数场景中出现了分数多普勒的问题，这一问题为OTFS传输和信道估计方面带来挑战。为解决这一问题，提出了一个多普勒插零的扩展方案。在时延-多普勒域中，信号通过插零在多普勒维度上进行扩展以增加总的传输时间，从而增加了多普勒轴方向上的精确性。根据接收到的扩展信号，可以使用原始的分数多普勒信道进行信道估计。我们通过理论推导证明了所提方案的可行性，通过分析从分数多普勒到整数多普勒的影响获得了所提出方案的性能提升。最后，通过仿真实验选定了一个合适的扩展参数，仿真结果表明所提方案在分数多普勒问题中的有效性。

总结：论文针对分数多普勒精度不够高的问题，提出了一个通过补零的解决方案，初步来看值得精读。

二、论文2:Input-Output Relation and Performance of RIS-Aided OTFS With Fractional Delay-Doppler

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Input-Output Relation and Performance of RIS-Aided OTFS With Fractional Delay-Doppler
Bhat, Vighnesh S. and Harshavardhan, Gandhodi and Chockalingam, A.
2023 Jan
IEEE Communications Letters

原文：
内容概括：This letter presents an early investigation of reconfigurable intelligent surfaces (RIS)-aided orthogonal time-frequency space (OTFS) in high-Doppler channels. 算法细节：We derive the end-to-end delay-Doppler (DD) domain input-output relation of a RIS-aided OTFS system, considering rectangular pulses and fractional delay-Doppler values. We also consider a Zak receiver for RIS-aided OTFS that converts the received time-domain signal to DD domain in one step using Zak transform, and derive its end-to-end input-output relation. Our simulation results show that i ) RIS-aided OTFS performs better than OTFS without RIS, ii ) Zak receiver performs better than a two-step receiver, and iii ) RIS-aided OTFS achieves superior performance compared to RIS-aided OFDM.

翻译：

RIS辅助的带有分数时延-多普勒的OTFS输入输出关系域性能 摘要：论文呈现了关于RIS（可重构智能反射表面）辅助的大多普勒信道中的OTFS方面的早期研究。首先推导了一个RIS辅助下OTFS系统的端到端的时延-多普勒域输入输出关系，同时考虑了矩形脉冲和分数多普勒值。此外，推导了RIS辅助的OTFS的Zak接收机，通过Zak变换仅需1步可以将接收到的时域信号转换到DD域中，同时推导了一个端到端的输入输出关系。仿真结果表明：1.引入RIS的OTFS在性能方面更优。2.Zak接收机比两步接收机性能更好。3.与RIS辅助的OFDM系统相比，RIS辅助的OTFS系统性能更优。

三、论文3：Fractional Delay and Doppler Estimation for OTFS Based ISAC Systems

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Fractional Delay and Doppler Estimation for OTFS Based ISAC Systems
Zacharia, Olivia and Vani Devi, M
2023 March
2023 IEEE Wireless Communications and Networking Conference (WCNC)

原文：
问题背景：In this paper, we consider an orthogonal time frequency space (OTFS) modulation |based single input single output (SISO) radar |for integrated sensing and communication (ISAC) |where the transmitter sends OTFS frames |and the radar receiver co-located with the transmitter leverages the transmit frame along with the reflected signal |for the estimation of the target range and velocity. 本文算法：We present a novel radar channel model| that is capable of capturing both integer as well as fractional delays and Doppler shifts accounted for by the targets in the channel. 算法细节：A two-step modified orthogonal matching pursuit with fractional refinement (OMPFR) algorithm is also proposed to estimate the delays and Doppler shifts that can be non-integer multiples of the system delay and Doppler resolutions respectively. 仿真结果：We show that our algorithm has much lower complexity than the traditional orthogonal matching pursuit (OMP) algorithm if used in estimating the fractional delays and Dopplers, as the latter requires a colossal dictionary matrix. Target profiles and the root mean square error (RMSE) plots for range and velocity estimates validate the effectiveness of the proposed OMPFR algorithm.

翻译：

基于ISAC系统的OTFS分数时延和多普勒估计 摘要：这篇论文主要解决了分数多普勒和时延问题在通信感知一体化中的应用（论文简称为ISAC）。论文提出了一个全新的雷达信道模型，该模型能够同时捕捉整数和分数时延和多普勒的偏移。在算法方面，论文引入了一个改进的两阶段OMP算法（正交匹配追踪）用来分别估计非整数倍的时延和多普勒频移。仿真结果表明，在估计分数时延和多普勒方面，该算法复杂度更低。

四、论文4:Channel and Radar Parameter Estimation With Fractional Delay-Doppler Using OTFS

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Channel and Radar Parameter Estimation With Fractional Delay-Doppler Using OTFS
Muppaneni, Sai Pradeep and Mattu, Sandesh Rao and Chockalingam, A.
2023 May
IEEE Communications Letters

原文：
背景：Orthogonal time frequency space (OTFS) waveform is suited for both communication as well as radar sensing. 本文算法：In this letter, we propose an algorithm for efficient channel estimation at the receiver and range/velocity estimation at the transmitter using OTFS. 算法细节：The algorithm processes received pilot frames for channel estimation at the receiver |and data frames echoed from the target/user for range and velocity estimation at the transmitter. A key component in the proposed algorithm is the cancellation of inter-path interference (IPI) in the DD domain. The algorithm works for fractional delay-Doppler which is a source of IPI. 仿真结果：The proposed algorithm outperforms other channel estimation schemes and also achieves good root mean square error performance of range and velocity estimation.

翻译：

基于分数时延-多普勒OTFS的信道和雷达参数估计 摘要：该论文提出一个算法可以实现接收机的有效信道估计以及使用OTFS在发射机的距离/速度估计（关于雷达方面的问题未曾涉猎，翻译可能不准确望理解）。该算法可以处理接收机处用于信道估计的导频帧信号，同时数据帧通过响应从而估计出发射机出的距离与速度。该算法的核心部分在于IPI算法（即路径间干扰消除算法），该算法可以在分数时延-多普勒下工作。所提算法与其他算法性能更优，同时在不同距离和速度下具有较好的均方根性能。

五、论文5:DNN-Based Fractional Doppler Channel Estimation for OTFS Modulation

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DNN-Based Fractional Doppler Channel Estimation for OTFS Modulation
Guo, Lin and Gu, Peng and Zou, Jun and Liu, Guangzu and Shu, Feng
2023
IEEE Transactions on Vehicular Technology

原文：
本文方法：In this paper, we proposed a deep neural network (DNN) based fractional Doppler channel estimation scheme for orthogonal time frequency space (OTFS) modulation in the air-to-ground communication scenario with high-dynamic Doppler. 算法细节：Based on the zero-padded OTFS structure, the traditional pilot pattern with guard symbols is adopted. The received pilots in the OTFS domain are used as the inputs of the network to estimate the channel parameters which are used in the MRC algorithm to demodulate the signal.仿真结果： In our proposed method, it can achieve the similar performance with 14 dB boost of pilot energy comparing with the ideal channel estimation case, while the conventional method requires 30 dB higher. Both the accuracy and generalization ability of the DNN network are validated.

翻译：

OTFS调制下基于DNN分数多普勒信道估计方法 摘要：论文提出了一个基于DNN的分数多普勒信道估计方案，用于空地通信场景下的OTFS调制。该算法基于零填充OTFS结构，引入了带有保护符号的传统导频方案。在OTFS域中接收到的导频符号用作网络的输入用来估计信道参数，这些信道参数用在MRC算法中来解调信号。仿真结果表明，与理想CSI相比，导频能量增加了14dB，然而传统方法需要的导频能量更高（大约有30dB）,最后验证了在精确性和泛化能力方面DNN网络更优。

总结：该论文也引入了补零的思想，可以和论文1结合起来阅读，同时，思考DNN在论文中取代了什么算法，其优势是什么？