From OFDM to AFDM: Enabling Adaptive Integrated Sensing and Communication in High-Mobility Scenarios

TL;DR

This paper reviews AFDM-ISAC, a waveform designed for high-mobility scenarios, highlighting its advantages over OFDM in terms of Doppler resilience, and discusses its performance limits and sensing algorithms.

Contribution

It provides a comprehensive overview of AFDM-ISAC, analyzing its fundamentals, performance limits, and sensing algorithms for high-mobility applications.

Findings

AFDM exhibits Doppler resilience and FMCW-like characteristics.

Analysis of AFDM's diversity order, ambiguity function, and CRB.

Presentation of effective sensing algorithms for AFDM-ISAC.

Abstract

Integrated sensing and communication (ISAC) is a key feature of next-generation wireless networks, enabling a wide range of emerging applications such as vehicle-to-everything (V2X) and unmanned aerial vehicles (UAVs), which operate in high-mobility scenarios. Notably, the wireless channels within these applications typically exhibit severe delay and Doppler spreads. The latter causes serious communication performance degradation in the Orthogonal Frequency-Division Multiplexing (OFDM) waveform that is widely adopted in current wireless networks. To address this challenge, the recently proposed Doppler-resilient affine frequency division multiplexing (AFDM) waveform, which uses flexible chirp signals as subcarriers, shows great potential for achieving adaptive ISAC in high-mobility scenarios. This article provides a comprehensive overview of AFDM-ISAC. We begin by presenting the fundamentals of AFDM-ISAC, highlighting its inherent frequency-modulated continuous-wave (FMCW)-like characteristics. Then, we explore its ISAC performance limits by analyzing its diversity order, ambiguity function (AF), and Cramer-Rao Bound (CRB). Finally, we present several effective sensing algorithms and opportunities for AFDM-ISAC, with the aim of sparking new ideas in this emerging field.