Cell-free (CF) massive multiple-input multiple-output (MIMO) is a promising solution to provide uniform good performance for unmanned aerial vehicle (UAV) communications. In this paper, we propose the UAV communication with wireless power transfer (WPT) aided CF massive MIMO systems, where the harvested energy (HE) from the downlink WPT is used to support both uplink data and pilot transmission. We derive novel closed-form downlink HE and uplink spectral efficiency (SE) expressions that take hardware impairments of UAV into account. UAV communications with current small cell (SC) and cellular massive MIMO enabled WPT systems are also considered for comparison. It is significant to show that CF massive MIMO achieves two and five times higher 95\%-likely uplink SE than the ones of SC and cellular massive MIMO, respectively. Besides, the large-scale fading decoding receiver cooperation can reduce the interference of the terrestrial user. Moreover, the maximum SE can be achieved by changing the time-splitting fraction. We prove that the optimal time-splitting fraction for maximum SE is determined by the number of antennas, altitude and hardware quality factor of UAVs. Furthermore, we propose three UAV trajectory design schemes to improve the SE. It is interesting that the angle search scheme performs best than both AP search and line path schemes. Finally, simulation results are presented to validate the accuracy of our expressions.

翻译：无细胞(CF)大规模多输出多输出(MIMO)是提供无人驾驶航空器(UAV)通信统一良好性能的一个大有希望的解决办法。在本文中,我们提议使用无线电传输(WPT)辅助无线传输(WPT)的大规模MIMO系统进行UAV通信,从下行链路获得的能量(HE)用于支持上行链路数据和试点传输。我们从HE和上端链路效率(SE)中获取新的封闭式下行链路,将UAV的硬件缺陷考虑在内。目前与小型电池(SC)和蜂窝大型IMO启用的机动飞行器系统的UAV通信也被认为是一个比较的解决方案。重要的是,显示CFMIM大规模电传输(WPT)的无线传输(WPT)分别比SC和蜂窝大型IMO的系统高出2倍和5倍。此外,大规模脱钩式接收器接收器合作可以减少地面用户的干扰。此外,通过改变时差分法来达到最大程度的SEE(SEE)节路段。我们证明最理想的时间差分数是SEEEEF的最佳搜索轨道、高度和硬件质量计划由天线的搜索计划最终进行。我们提出。