MIMO-AFDM Outperforms MIMO-OFDM in the Face of Hardware Impairments

2026-01-01

AI Summary

This study addresses the performance degradation of MIMO multicarrier systems under practical hardware impairments, including phase noise, carrier frequency offset, and nonlinear distortion. The authors systematically analyze the robustness of MIMO-AFDM by deriving a tight upper bound on the bit error rate for maximum-likelihood detection in small-scale systems and a closed-form approximation for linear minimum mean square error detection in large-scale systems, incorporating realistic channel estimation errors. For the first time, they demonstrate that AFDM preserves full diversity gain under both multiplicative and additive hardware impairments and exhibits significantly superior robustness to inter-carrier interference compared to OFDM. Both theoretical analysis and Monte Carlo simulations consistently show that, under identical hardware impairments and across varying mobility scenarios, MIMO-AFDM achieves notably better performance than MIMO-OFDM at moderate to high signal-to-noise ratios.

Technology Category

• Machine Learning: Hardware-aware ML
• Multiagent Systems: Adversarial Agents
• Cognitive Modeling & Cognitive Systems: Affective Computing

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Security and Privacy: Large-scale security measurements
• User Modeling, Personalization and Recommendation: Attacks and countermeasures in recommendation systems

Abstract

The impact of both multiplicative and additive hardware impairments (HWIs) on multiple-input multiple-output affine frequency division multiplexing (MIMO-AFDM) systems is investigated. For small-scale MIMO-AFDM systems, a tight bit error rate (BER) upper bound associated with the maximum likelihood (ML) detector is derived. By contrast, for large-scale systems, a closed-form BER approximation associated with the linear minimum mean squared error (LMMSE) detector is presented, including realistic imperfect channel estimation scenarios. Our first key observation is that the full diversity order of a hardware-impaired AFDM system remains unaffected, which is a unique advantage. Furthermore, our analysis shows that 1) the BER results derived accurately predict the simulated ML performance in moderate-to-high signal-to-noise ratios (SNRs), while the theoretical BER curve of the LMMSE detector closely matches that of the Monte-Carlo based one. 2) MIMO-AFDM is more resilient to multiplicative distortions, such as phase noise and carrier frequency offset, compared to its orthogonal frequency division multiplexing (OFDM) counterparts. This is attributed to its inherent chirp signal characteristics; 3) MIMO-AFDM consistently achieves superior BER performance compared to conventional MIMO-OFDM systems under the same additive HWI conditions, as well as different velocity values. The latter is because MIMO-AFDM is also resilient to the additional inter-carrier interference (ICI) imposed by the nonlinear distortions of additive HWIs. In a nutshell, compared to OFDM, AFDM demonstrates stronger ICI resilience and achieves the maximum full diversity attainable gain even under HWIs, thanks to its intrinsic chirp signalling structure as well as to the beneficial spreading effect of the discrete affine Fourier transform.

Problem

• hardware impairments
• MIMO-AFDM
• MIMO-OFDM
• inter-carrier interference
• bit error rate

Innovation

• MIMO-AFDM
• hardware impairments
• diversity order
• inter-carrier interference (ICI)
• chirp signaling