Efficient Precoding in XL-MIMO-AFDM System
Jun Zhu, Yin Xu, Dazhi He, Haoyang Li, Yunfeng Guan, Wenjun Zhang, Tianyao Ma, Haozhi Yuan
TL;DR
This work tackles MUI and Doppler-induced distortion in XL-MIMO by leveraging AFDM with DAFT-domain modulation and introducing a low-complexity randomized Kaczmarz (rKA) precoding scheme. By formulating the precoding as a regularized least-squares problem and solving it with rKA, the approach achieves substantial computational savings over conventional ZF/RZF while maintaining performance. Simulations show AFDM’s robustness to Doppler and that rKA-based precoding delivers better BER and sum-rate than competitive baselines, particularly in the high-antenna-count, multi-subarray XL-MIMO regime. The results indicate practical pathways for Doppler-resilient, scalable precoding in next-generation wireless systems.
Abstract
This paper explores the potential of affine frequency division multiplexing (AFDM) to mitigate the multiuser interference (MUI) problem by employing time-domain precoding in extremely-large-scale multiple-input multiple-output (XL-MIMO) systems. In XL-MIMO systems, user mobility significantly improves network capacity and transmission quality. Meanwhile, the robustness of AFDM to Doppler shift is enhanced in user mobility scenarios, which further improves the system performance. However, the multicarrier nature of AFDM has attracted much attention, and it leads to a significant increase in precoding complexity. However, the serious problem is that the multicarrier use of AFDM leads to a sharp increase in precoding complexity. Therefore, we employ efficient precoding randomized Kaczmarz (rKA) to reduce the complexity overhead. Through simulation analysis, we compare the performance of XL-MIMO-AFDM and XL-MIMO orthogonal frequency division multiplexing (XL-MIMO-OFDM) in mobile scenarios, and the results show that our proposed AFDM-based XL-MIMO precoding design can be more efficient.