Affine Frequency Division Multiplexing for Next Generation Wireless Communications

TL;DR

This paper introduces AFDM, a novel chirp-based multicarrier waveform utilizing the affine Fourier transform, designed to improve high mobility wireless communications by achieving full diversity and robust channel estimation.

Contribution

The paper presents AFDM, a new waveform based on DAFT, with analytical derivations, diversity analysis, low complexity detection, and embedded channel estimation, outperforming existing schemes in high mobility.

Findings

AFDM achieves full delay-Doppler domain representation.

AFDM provides significant performance gains in high mobility scenarios.

A low complexity detection and embedded channel estimation scheme is proposed.

Abstract

Affine Frequency Division Multiplexing (AFDM), a new chirp-based multicarrier waveform for high mobility communications, is introduced here. AFDM is based on discrete affine Fourier transform (DAFT), a generalization of discrete Fourier transform, which is characterized by two parameters that can be adapted to better cope with doubly dispersive channels. First, we derive the explicit input-output relation in the DAFT domain showing the effect of AFDM parameters in the input-output relation. Second, we show how the DAFT parameters underlying AFDM have to be set so that the resulting DAFT domain impulse response conveys a full delay-Doppler representation of the channel. Then, we show analytically that AFDM can achieve full diversity in doubly dispersive channels, where full diversity refers to the number of multipath components separable in either the delay or the Doppler domain, due to its full delay-Doppler representation. Furthermore, we present a low complexity detection method taking advantage of zero-padding. We also propose an embedded pilot-aided channel estimation scheme for AFDM, in which both channel estimation and data detection are performed within the same AFDM frame. Finally, simulations corroborate the validity of our analytical results and show the significant performance gains of AFDM over state-of-the-art multicarrier schemes in high mobility scenarios.