AFDM: A Full Diversity Next Generation Waveform for High Mobility Communications

TL;DR

AFDM is a novel chirp-based multicarrier waveform utilizing affine Fourier transform parameters to effectively handle high mobility doubly dispersive channels, achieving full diversity and outperforming existing schemes.

Contribution

Introduces AFDM, a new waveform based on DAFT, that adapts to channel conditions to provide full diversity in high mobility environments.

Findings

AFDM achieves full diversity of LTV channels.

AFDM outperforms existing multicarrier schemes in BER.

Numerical simulations validate AFDM's effectiveness.

Abstract

We present Affine Frequency Division Multiplexing (AFDM), a new chirp-based multicarrier transceiver scheme for high mobility communications in next-generation wireless systems. AFDM is based on discrete affine Fourier transform (DAFT), a generalization of discrete Fourier transform characterized with two parameters that can be adapted to better cope with doubly dispersive channels. Based on the derived input-output relation, the DAFT parameters underlying AFDM are set in such a way to avoid that time domain channel paths with distinct delays or Doppler frequency shifts overlap in the DAFT domain. The resulting DAFT domain impulse response thus conveys a full delay-Doppler representation of the channel. We show that AFDM can achieve the full diversity of linear time-varying (LTV) channels. Our analytical results are validated through numerical simulations, which evince that AFDM outperforms state-of-the-art multicarrier schemes in terms of bit error rate (BER) in doubly dispersive channels.