5G移动通信系统硬件失配条件下的大规模MIMO传输技术研究

With the huge increment of mobile data requirement and the energy consumption, the future 5th generation mobile communication systems (5G) has to dramatically increase both the spectrum efficiency and the energy efficiency. As one of the key techniques in 5G physical layer, massive MIMO, which uses tens to hundreds of antennas at the base station, can significantly increase the spectrum and energy efficiency by taking advantage of the large amount of space degree of freedom and the high antenna array gain. Since the cost and the power consumption of massive MIMO grow with the number of antennas, researchers propose to use low-resolution devices which, however, bring about the problem of hardware impairment. Hardware impairment introduces extra intra-system interference, degrades the channel estimates and deteriorates the channel reciprocity between the uplink and the downlink, resulting in important constraints on the system performance. In this project, we will study different sources of hardware impairment, analyze their impact on 5G massive MIMO systems, optimize the configuration of antenna numbers and the hardware parameters, and design robust transmission techniques to suppress the negative impact of hardware impairment. Through this research, we plan to solve the hardware impairment problem in 5G massive MIMO systems to some extent and to boost its industrialization.

由于移动数据业务需求和通信产业能耗日益增长，未来的第五代移动通信系统（5G）必须大幅提高频谱利用率和能效。作为5G物理层的核心技术之一，大规模多输入多输出（MIMO）技术通过在基站侧使用几十乃至数百根天线，利用大量的空间自由度和极高的天线阵列增益，可以显著提高频谱利用率和能效。由于大规模MIMO的硬件成本和功耗随着天线数目显著增加，研究人员提出使用低精度器件的方案。然而，低精度器件会导致硬件失配（Hardware Impairment）问题，造成系统内部干扰和信道估计误差，恶化上下行链路信道互易性，严重制约着5G大规模MIMO系统的性能。本课题拟综合考虑硬件失配的不同来源，分析硬件失配对5G大规模MIMO系统的影响，优化天线数目和硬件失配参数的配置，并针对硬件失配设计上下行链路鲁棒信号传输方案。通过本项目，在一定程度上解决大规模MIMO硬件失配问题并促进5G大规模MIMO技术的产业化发展。

随着移动通信业务需求和通信产业能耗急剧增长，未来的通信系统必须大幅提高频谱利用率和能效。大规模MIMO技术通过在基站侧使用大规模天线阵列，利用大量的空间自由度和极高的阵列增益，可以显著改善频谱利用率和能效。为了控制成本和降低功耗，研究人员提出在大规模MIMO系统中使用低精度器件，这将导致硬件失配问题，进而严重制约系统性能。针对不同硬件失配来源，本项目同时考虑了IQ失衡与低精度ADC，推导了大规模MIMO系统上行链路可达速率表达式，探讨了天线数目、硬件失配参数与系统性能的关系，重点讨论了低精度ADC对系统频率利用率和能效的影响，全面对比了数字波束成形与混合波束赋形的性能；提出了低精度ADC大规模MIMO系统基于叠加导频的LMMSE信道估计方案，设计了最优的量化位数选择方法，优化了毫米波大规模MIMO系统混合波束成形天线阵列连接方式；为了降低计算复杂度，提出了基于Landweber方法的上行链路低复杂度信号检测方案，设计了基于矩阵多项式的低复杂度预编码方案，通过将信号变换到角度域并进行空间压缩，提出了毫米波大规模MIMO系统低复杂度的角度域信号检测方案。本项目的研究成果初步揭示了硬件失配对大规模MIMO系统性能的影响机制，提出了低复杂度信号处理方案，有助于促进大规模MIMO系统的实际应用。