Multi-Block UAMP Detection for AFDM under Fractional Delay-Doppler Channel

TL;DR

This paper proposes a UAMP algorithm for AFDM signal detection in fractional delay-Doppler channels, effectively mitigating energy dispersion and improving detection performance in high-mobility wireless systems.

Contribution

Introduction of a UAMP algorithm with unitary transformations and block-wise processing to enhance AFDM detection under fractional delay-Doppler channels.

Findings

UAMP outperforms GAMP in fractional delay-Doppler scenarios.

The proposed method reduces computational complexity.

Simulation confirms improved detection accuracy.

Abstract

Affine Frequency Division Multiplexing (AFDM) is considered as a promising solution for next-generation wireless systems due to its satisfactory performance in high-mobility scenarios. By adjusting AFDM parameters to match the multi-path delay and Doppler shift, AFDM can achieve two-dimensional time-frequency diversity gain. However, under fractional delay-Doppler channels, AFDM encounters energy dispersion in the affine domain, which poses significant challenges for signal detection. This paper first investigates the AFDM system model under fractional delay-Doppler channels. To address the energy dispersion in the affine domain, a unitary transformation based approximate message passing (UAMP) algorithm is proposed. The algorithm performs unitary transformations and message passing in the time domain to avoid the energy dispersion issue. Additionally, we implemented block-wise processing to reduce computational complexity. Finally, the empirical extrinsic information transfer (E-EXIT) chart is used to evaluate iterative detection performance. Simulation results show that UAMP significantly outperforms GAMP under fractional delay-Doppler conditions.