Ambiguity Function Analysis of AFDM Signals for Integrated Sensing and Communications

Haoran Yin; Yanqun Tang; Yuanhan Ni; Zulin Wang; Gaojie Chen; Jun Xiong; Kai Yang; Marios Kountouris; Yong Liang Guan; Yong Zeng

doi:10.1109/JSAC.2025.3611936

Ambiguity Function Analysis of AFDM Signals for Integrated Sensing and Communications

Haoran Yin
, Yanqun Tang^*
, Yuanhan Ni
, Zulin Wang
, Gaojie Chen
, Jun Xiong
, Kai Yang
, Marios Kountouris
, Yong Liang Guan
, Yong Zeng

^*此作品的通讯作者

Sun Yat-Sen University
Guangdong Provincial Key Laboratory of Sea-Air-Space Communication
Beihang University
National University of Defense Technology
Beijing Institute of Technology
University of Granada
Communication Systems Department
Nanyang Technological University
Southeast University, Nanjing
Purple Mountain Laboratories

科研成果: 期刊稿件 › 文章 › 同行评审

18 引用（Scopus）

摘要

Affine frequency division multiplexing (AFDM) is a promising chirp-based waveform with great flexibility and resilience, making it well suited for next-generation wireless networks, particularly in high-mobility scenarios. In this paper, we investigate the ambiguity functions (AFs) of AFDM signals, which fundamentally characterize their range and velocity estimation capabilities in both monostatic and bistatic scenarios. Specifically, we first derive the auto-ambiguity function (AAF) of an AFDM chirp subcarrier, revealing its “spike-like” local and “periodic-like” global properties along the rotated delay and Doppler dimensions. This structure naturally forms a parallelogram for each localized pulse in the AAF of an AFDM chirp subcarrier, enabling unambiguous target sensing. Then, we study the cross-ambiguity function (CAF) between two different AFDM chirp subcarriers, which exhibits the same local and global properties as the AAF but with an additional shift along the Doppler dimension. We then extend our analysis to the AF of typical AFDM frames, considering both deterministic pilot symbols and random data symbols. In particular, we demonstrate that inserting guard symbols in AFDM facilitates interference-free sensing. Simulation results confirm our theoretical findings, highlighting AFDM’s strong potential for ISAC applications.

源语言	英语
页（从-至）	196-211
页数	16
期刊	IEEE Journal on Selected Areas in Communications
卷	44
DOI	https://doi.org/10.1109/JSAC.2025.3611936
出版状态	已出版 - 2026
已对外发布	是

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title = "Ambiguity Function Analysis of AFDM Signals for Integrated Sensing and Communications",

abstract = "Affine frequency division multiplexing (AFDM) is a promising chirp-based waveform with great flexibility and resilience, making it well suited for next-generation wireless networks, particularly in high-mobility scenarios. In this paper, we investigate the ambiguity functions (AFs) of AFDM signals, which fundamentally characterize their range and velocity estimation capabilities in both monostatic and bistatic scenarios. Specifically, we first derive the auto-ambiguity function (AAF) of an AFDM chirp subcarrier, revealing its {\textquotedblleft}spike-like{\textquotedblright} local and {\textquotedblleft}periodic-like{\textquotedblright} global properties along the rotated delay and Doppler dimensions. This structure naturally forms a parallelogram for each localized pulse in the AAF of an AFDM chirp subcarrier, enabling unambiguous target sensing. Then, we study the cross-ambiguity function (CAF) between two different AFDM chirp subcarriers, which exhibits the same local and global properties as the AAF but with an additional shift along the Doppler dimension. We then extend our analysis to the AF of typical AFDM frames, considering both deterministic pilot symbols and random data symbols. In particular, we demonstrate that inserting guard symbols in AFDM facilitates interference-free sensing. Simulation results confirm our theoretical findings, highlighting AFDM{\textquoteright}s strong potential for ISAC applications.",

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T1 - Ambiguity Function Analysis of AFDM Signals for Integrated Sensing and Communications

AU - Yin, Haoran

AU - Tang, Yanqun

AU - Ni, Yuanhan

AU - Wang, Zulin

AU - Chen, Gaojie

AU - Xiong, Jun

AU - Yang, Kai

AU - Kountouris, Marios

AU - Liang Guan, Yong

AU - Zeng, Yong

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N2 - Affine frequency division multiplexing (AFDM) is a promising chirp-based waveform with great flexibility and resilience, making it well suited for next-generation wireless networks, particularly in high-mobility scenarios. In this paper, we investigate the ambiguity functions (AFs) of AFDM signals, which fundamentally characterize their range and velocity estimation capabilities in both monostatic and bistatic scenarios. Specifically, we first derive the auto-ambiguity function (AAF) of an AFDM chirp subcarrier, revealing its “spike-like” local and “periodic-like” global properties along the rotated delay and Doppler dimensions. This structure naturally forms a parallelogram for each localized pulse in the AAF of an AFDM chirp subcarrier, enabling unambiguous target sensing. Then, we study the cross-ambiguity function (CAF) between two different AFDM chirp subcarriers, which exhibits the same local and global properties as the AAF but with an additional shift along the Doppler dimension. We then extend our analysis to the AF of typical AFDM frames, considering both deterministic pilot symbols and random data symbols. In particular, we demonstrate that inserting guard symbols in AFDM facilitates interference-free sensing. Simulation results confirm our theoretical findings, highlighting AFDM’s strong potential for ISAC applications.

AB - Affine frequency division multiplexing (AFDM) is a promising chirp-based waveform with great flexibility and resilience, making it well suited for next-generation wireless networks, particularly in high-mobility scenarios. In this paper, we investigate the ambiguity functions (AFs) of AFDM signals, which fundamentally characterize their range and velocity estimation capabilities in both monostatic and bistatic scenarios. Specifically, we first derive the auto-ambiguity function (AAF) of an AFDM chirp subcarrier, revealing its “spike-like” local and “periodic-like” global properties along the rotated delay and Doppler dimensions. This structure naturally forms a parallelogram for each localized pulse in the AAF of an AFDM chirp subcarrier, enabling unambiguous target sensing. Then, we study the cross-ambiguity function (CAF) between two different AFDM chirp subcarriers, which exhibits the same local and global properties as the AAF but with an additional shift along the Doppler dimension. We then extend our analysis to the AF of typical AFDM frames, considering both deterministic pilot symbols and random data symbols. In particular, we demonstrate that inserting guard symbols in AFDM facilitates interference-free sensing. Simulation results confirm our theoretical findings, highlighting AFDM’s strong potential for ISAC applications.

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Ambiguity Function Analysis of AFDM Signals for Integrated Sensing and Communications

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