We study the impact of channel aging on the uplink of a cell-free massive multiple-input multiple-output system with hardware impairments. We consider a dynamic analog-to-digital converter architecture at the access points (APs), and low-resolution digital-to-analog converters at the user equipments (UEs). We derive a closed-form spectral efficiency expression by considering i) practical spatially-correlated Rician channels; ii) hardware impairments at the APs and the UEs; iii) channel aging; and iv) large-scale fading decoding (LSFD). We show that LSFD can effectively mitigate the detrimental effects of i) channel aging for both low and high UE velocities; and ii) inter-user interference for low-velocity UEs but not for high-velocity UEs.

翻译：我们研究了信道老化对存在硬件损伤的无小区大规模多输入多输出系统上行链路的影响。在接入点（APs）处考虑动态模数转换器架构，并在用户设备（UEs）处采用低分辨率数模转换器。通过考虑以下因素，我们推导出闭式频谱效率表达式：i) 实际空间相关的莱斯信道；ii) APs和UEs处的硬件损伤；iii) 信道老化；以及iv) 大规模衰落解码（LSFD）。研究表明，LSFD能够有效缓解以下有害影响：i) 低速和高速UEs下的信道老化；以及ii) 低速UEs（非高速UEs）的用户间干扰。