Robust connectivity in time-frequency dual fading channels for the 6G satellite IoT: chirp and FRFT✩

Wenliang Lin; Xinghao Cao; Ke Wang; Zhongliang Deng; Yishan He; Kejia Cui; Yaohua Deng; Da Wan; Zhiwei He

doi:10.1016/j.dcan.2025.12.002

›› 2026, Vol. 12 ›› Issue (2) :375 -387. DOI: 10.1016/j.dcan.2025.12.002

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Robust connectivity in time-frequency dual fading channels for the 6G satellite IoT: chirp and FRFT^✩

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^a School of Electronic Engineering, Beijing University of Posts and Telecommunications, Beijing postcode, China

^b School of Information and Communication Engineering, Beijing University of Posts and Telecommunications, Beijing postcode, China

^c China Satellite Network Exploration Co. Ltd, Chongqing postcode, China

^* E-mail addresses: wangke@bupt.edu.cn (K. Wang),

dengZHL@bupt.edu.cn (Z. Deng), heyishan@live.com (Y. He).

Wenliang Lin received his B.S.degree in 2010 and Ph. D. degree in 2016 in Electronic En-gineering from the Beijing University of Posts and Telecommunications (BUPT), China. He was a doctoral candidate at BUPT in 2016. Now, he is an associate professor at BUPT. He has engaged in research on LEO satellite communications system design and testing tech-nologies. He designs a 5G-integrated air interface communication system for SIN based on hopping beam technology. He operates on-orbit testing and channel modeling for China’s LEO and GEO satellites. He proposes a multi-factor fusion decision-making satellite han-dover method and a Networked Control Systems (NCS) analytical model for radio resource management.He has authored and co-authored more than30 journal and conference pa-pers in his research areas,which include IOTJ, TCOM, CL, CHINACOM and EL.

Xinghao Cao received his B.S.degree in 2024 from BUPT, China. Now, he is working towards his M.S. degree in the school of electronic engineering, BUPT, China. He focuses on satellite communication, and 5G/6Gcommunication.

Ke Wang (Member, IEEE) received his Ph.D. degree in communication and information systems from Beijing University of Posts and Telecommu nications (BUPT), Beijing, China, in 2014. He is currently an Associate Professor with BUPT. His research interests include signal processing in satellite communications and satellite access network simulation tech-nologies. He was a recipient of the Young Scientist of the National Key Research and De-velopment Program under the Ministry of Science and Technology of China in 2024 and the Best Paper Awards from the EAI SmartGift in 2021. He served as a reviewer for several journals and conference proceedings, including IEEE COMMUNICATIONS LETTERS, IEEE TRANSACTIONS ON SIGNAL PROCESSING, IEEE Communications Magazine, and IEEE Globecom/ICC/WCNC.

ZhongLiang Deng received his M.S.degreefrom Beijing University of Aeronautics and Astronautics (BUAA) in 1991 and received his Ph. D. degreefrom Tsinghua University (THU) in Beijing, China in 1994. Since 1996, he has been a famous professor at the BUPT. He is the top future indoor navigation expert and satellite communication in China. He has gained more than 180 patents and has published 213 articles indexed by the SCI and EI.

Yishan He received the Ph.D. degree from the National Key Laboratory of Science and Technology on Communications, University of Electronic Science and Technology of China, Chengdu, China, in 2015. From 2016 to 2022, he was a Senior Engineer with Huawei Technologies Company Ltd., where he focused on 5G New Radio (NR) physical layer algorithms for Base Stations (BSs) and User Equipment (UE). He was subsequently with Southwest China Institute of Electronic Technology, Chengdu, from 2022 to 2023. He is currently with China Satellite Network Exploration Company Ltd. His research interests include satellite communications, massive MIMO, and signal processing.

Kejia Cui has been an undergraduate student at the School of Electronic Engineering, BUPT, China, since 2022. Her research mainly revolves around LEO satellite Internet of Things (IoT) technologies. She currently focuses on the performance analysis and hard-ware implementation of speech codecs for satellite-based IoT networks.

Yaohua Deng received the B.S. degree in Electronic Engineering from BUPT, China, in 2021. He is currently pursuing the Ph.D. degree in the School of Electronic Engineering at BUPT, China. His research interests include satellite communications, digital predistor-tion, and channel modeling.

Da Wan received the B.S. degree in Electronic Engineering from the School of Electronic Engineering, BUPT in 2020, he is currently pursuing his Ph.D. degree in the School of Electronic Engineering, BUPT. His research interests include wireless communications, modeling and estimationof wireless propagation channels, signal processing, and machine learning.

Zhiwei He received his B.S. degree in Electronic Engineering from BUPT, Beijing, China, in 2020. His research interests focus on signal measurement and channel modeling.

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Abstract

With the development of Sixth-Generation (6G) mobile communication technologies, Low Earth Orbit (LEO) satellite communication systems have become extremely important in mobile communications owing to their large coverage, high eﬃciency, and low cost. However, the high dynamic LEO satellite channels cause serious time-frequency dual selective fading, significantly impairing the performance of conventional single time or fre-quency domain synchronization algorithms and limiting their applicability. To address these challenges, this paper proposes a synchronization algorithm based on Linear Frequency Modulation (LFM) signals and the Frac-tional Fourier Transform (FRFT). Exploiting the inherent robustness of LFM signals against frequency deviations and multipath effects, coupled with their energy concentration property in the optimal fractional Fourier do-main, the proposed algorithm enables eﬃcient synchronization with enhanced resilience to time-frequency vari-ations. Furthermore, LFM preamble sequences are optimally designed for diverse channel conditions. This work presents a theoretical analysis of the time-frequency nonstationary characteristics of LEO satellite channels and discusses the performance limitations of traditional synchronization algorithms. The proposed integrated FRFT-LFM synchronization framework and sequence optimization scheme are rigorously evaluated via comprehensive simulations. The results demonstrate substantial improvements in synchronization accuracy and computational eﬃciency compared with conventional methods, particularly under time-frequency dual selective fading LEO satellite channels. The algorithm provides a robust and reliable solution for time-frequency synchronization in LEO satellite communication systems, thereby enhancing overall system performance and reliability.

Keywords

Time-frequency synchronization / Linear frequency modulation / Fractional fourier transform / Low earth orbit satellite communications / Nonstationary channel

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Wenliang Lin, Xinghao Cao, Ke Wang, Zhongliang Deng, Yishan He, Kejia Cui, Yaohua Deng, Da Wan, Zhiwei He. Robust connectivity in time-frequency dual fading channels for the 6G satellite IoT: chirp and FRFT^✩. , 2026, 12(2): 375-387 DOI:10.1016/j.dcan.2025.12.002

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Declaration of competing interest

The authors hereby declare that there are no ﬁnancial, commercial, or personal relationships that could be construed as potential conflicts of interest. All authors have reviewed and agreed upon the content of this manuscript, conﬁrming that no external influences aﬀected the re-search design, data analysis, or publication process. Any funding sources associated with this study are unrelated to entities that might have an in-terest in the outcomes, and no author holds stocks, patents, or advisory roles in organizations connected to this work. This statement is made in accordance with the ethical standards required by the journal to ensure transparency and integrity in scholarly communication.

CRediT authorship contribution statement

Wenliang Lin: Writing-review & editing, Writing-original draft, Supervision, Methodology, Data curation; Xinghao Cao: Writing-re-view & editing, Writing-original draft, Validation, Investigation; Ke Wang: Writing-review & editing; Zhongliang Deng: Writing-review & editing, Methodology, Data curation, Conceptualization; Yishan He: Writing-review & editing; Kejia Cui: Writing-review & editing; Yao-hua Deng: Writing-review & editing; Da Wan: Writing-review & editing; Zhiwei He: Writing-review & editing.

Acknowledgements

This work is supported by the Beijing Natural Science Founda-tion (4252008), the Natural Science Foundation of Chongqing Province (CSTB2024NSCQLZX0176) and the Beijing Natural Science Foundation of Undergraduate Qiyan Program (QY24197).

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