Analysis and Compensation of Receiver IQ Imbalance and Residual CFO Error for AFDM

TL;DR

This paper investigates the effects of receiver IQ imbalance and residual CFO error on AFDM signals, proposing an extended LMMSE detector to mitigate these impairments and improve communication performance.

Contribution

It provides a detailed analysis of how IQ imbalance and residual CFO affect AFDM, and introduces a modified LMMSE detector for effective compensation.

Findings

IQ imbalance affects the sparsity of the AFDM channel matrix.

Residual CFO causes energy leakage in the affine domain.

Proposed LMMSE detector effectively mitigates hardware impairments.

Abstract

Affine frequency division multiplexing (AFDM) is a promising waveform for future wireless communication systems. In this paper, we analyze the impact of receiver in-phase and quadrature (IQ) imbalance and residual carrier frequency offset (CFO) error on AFDM signals. Our analysis shows that the receiver IQ imbalance may not preserve the sparsity of the AFDM effective channel matrix because of the complex-conjugate operator of the discrete affine Fourier transform (DAFT). Moreover, the residual CFO error causes energy leakage in the effective channel matrix in the affine domain. To mitigate these effects, we extend the linear minimum mean-square error (LMMSE) detector to handle the improper Gaussian noise arising from the receiver IQ imbalance. Simulation results demonstrate that the proposed LMMSE detector effectively compensates for the receiver hardware impairments.