On the heels of orthogonal time frequency space (OTFS) modulation, the recently discovered affine frequency division multiplexing (AFDM) is a promising waveform for the sixth-generation wireless network. With the superiorities of high multiplexing and diversity gain of multiple-input multiple-output (MIMO), we formulate the vectorized input-output relationship of MIMO-AFDM system. Correspondingly, we derive the diversity order of MIMO-AFDM system in doubly dispersive channels. Furthermore, we propose an efficient single pilot aided with reduced guard (SPA-RG) symbols scheme to perform channel estimation in the discrete affine Fourier transform (DAFT) domain. It is worth emphasizing that MIMO-AFDM can achieve full diversity in doubly selective channels. Simulation results show that it has the bit error ratio (BER) performance similar to MIMO-OTFS in large frame size. Additionally, compared to ideal channel state information, our proposed SPA-RG scheme is verified to induce only marginal BER performance loss with the least overhead.

翻译：紧随正方位时频空间(OTFS)的调制,最近发现的亲子频率分多路转换(AFDM)是第六代无线网络有希望的波形。随着高多路转换和多投入多输出(MIMO)系统多样性增长的优势,我们制定了MIMO-AFDM系统的矢量化输入-输出关系。相应的是,我们从双向分散的频道中得出MIMO-AFDM系统的多样性顺序。此外,我们提出一个高效的单一试点,在减少警卫(SPA-RG)符号的情况下进行频道估计。值得强调的是,MIMO-AFDM可以在双向选择性渠道实现完全多样性。模拟结果表明,其性能与IMO-OTFS大相近。此外,与理想的频道状态信息相比,我们提议的SPA-RG计划被证实只能导致最小顶部的边缘BER性能损失。