Integrated Sensing and Communications with Affine Frequency Division Multiplexing

TL;DR

This work proposes an AFDM-based ISAC framework that leverages the discrete affine Fourier transform (DAFT) to form chirp-based AFDM waveforms suitable for high-mobility scenarios. By embedding a pilot in an $N$-long DAFT frame with guard intervals, sensing can be performed using either the full frame or a single pilot, achieving near-identical range and velocity resolution while enabling simple analog dechirping-based self-interference cancellation. The authors derive an ML-based estimation approach for delays and Dopplers and highlight a crucial parameter setting $c_1 = rac{2 (k_f + k_{max})}{2N}$ to guarantee full delay-Doppler channel representation. Simulation results show AFDM offers comparable sensing performance to OTFS and OCDM with significantly reduced SIC complexity, reducing hardware and ADC requirements in practical ISAC deployments. Overall, the work demonstrates the practicality of one-pilot AFDM sensing with low-complexity SIC for robust, high-frequency ISAC in dynamic environments.

Abstract

Integrated sensing and communications (ISAC) is regarded as a key technology in next-generation (6G) mobile communication systems. Affine frequency division multiplexing (AFDM) is a recently proposed waveform that achieves optimal diversity gain in high mobility scenarios and has appealing properties in high-frequency communication. In this letter, we present an AFDM-based ISAC system. We first show that in order to identify all delay and Doppler components associated with the propagation medium, either the full AFDM signal or only its pilot part consisting of one discrete affine Fourier transform (DAFT) domain symbol and its guard interval can be used. Our results show that using one pilot symbol achieves almost the same sensing performance as using the entire AFDM frame. Furthermore, due to the chirp nature of AFDM, sensing with one pilot provides a unique feature allowing for simple self-interference cancellation, thus avoiding the need for expensive full duplex methods.

Figures (7)

• Figure 1: Monostatic ISAC system model
• Figure 2: Transmitted and received AFDM frame
• Figure 3: Time-frequency representation of two AFDM chirps (the pilot, $m_0$, and one chirp, $m_1$, from outside the pilot guard interval) at the transmitter (on top) and after analog dechirping at the radar receiver (on bottom)
• Figure 4: AFDM sensing receiver
• Figure 5: AFDM sensing performance as function of sensing resources