AFDM: Evolving OFDM Towards 6G+

TL;DR

AFDM is proposed as a robust, compatible waveform for 6G+ that enhances high-mobility communication and sensing, leveraging existing OFDM infrastructure with minimal modifications.

Contribution

This paper introduces AFDM as a new waveform for 6G+ that maintains compatibility with OFDM while offering improved robustness and additional functionalities.

Findings

AFDM demonstrates intrinsic robustness in high-mobility and doubly dispersive channels.

AFDM reuses most of the OFDM pipeline with lightweight modifications.

AFDM enables advanced features like index modulation and physical-layer security.

Abstract

As the standardization of sixth generation (6G) wireless systems accelerates, there is a growing consensus in favor of evolutionary waveforms that offer new features while maximizing compatibility with orthogonal frequency division multiplexing (OFDM), which underpins the 4G and 5G systems. This article presents affine frequency division multiplexing (AFDM) as a premier candidate for 6G, offering intrinsic robustness for both high-mobility communications and integrated sensing and communication (ISAC) in doubly dispersive channels, while maintaining a high degree of synergy with the legacy OFDM. To this end, we provide a comprehensive analysis of AFDM, starting with a generalized fractional-delay-fractional-Doppler (FDFD) channel model that accounts for practical pulse shaping filters and inter-sample coupling. We then detail the AFDM transceiver architecture, demonstrating that it reuses nearly the entire OFDM pipeline and requires only lightweight digital pre- and post-processing. We also analyze the impact of hardware impairments, such as phase noise and carrier frequency offset, and explore advanced functionalities enabled by the chirp-parameter domain, including index modulation and physical-layer security. By evaluating the reusability across the radio-frequency, physical, and higher layers, the article demonstrates that AFDM provides a low-risk, feature-rich, and efficient path toward achieving high-fidelity communications in the later versions of 6G and beyond (6G+).