Ambiguity Function Analysis of AFDM Signals for Integrated Sensing and Communications

TY - JOUR

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

N1 - Publisher Copyright: © 1983-2012 IEEE.

PY - 2026

Y1 - 2026

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.

KW - Affine frequency division multiplexing (AFDM)

KW - ambiguity function (AF)

KW - doubly selective channel (DSC)

KW - integrated sensing and communications (ISAC)

UR - https://www.scopus.com/pages/publications/105016825332

U2 - 10.1109/JSAC.2025.3611936

DO - 10.1109/JSAC.2025.3611936

M3 - Article

AN - SCOPUS:105016825332

SN - 0733-8716

VL - 44

SP - 196

EP - 211

JO - IEEE Journal on Selected Areas in Communications

JF - IEEE Journal on Selected Areas in Communications

ER -