High hardware cost and high power consumption of massive multiple-input and multiple output (MIMO) are still two challenges for the future wireless communications including beyond 5G. Adopting the low-resolution analog-to-digital converter (ADC) is viewed as a promising solution. Additionally, the direction of arrival (DOA) estimation is an indispensable technology for beam alignment and tracking in massive MIMO systems. Thus, in this paper, the performance of DOA estimation for massive MIMO receive array with mixed-ADC structure is first investigated, where one part of radio frequency (RF) chains are connected with high-resolution ADCs and the remaining ones are connected with low-resolution ADCs. Moreover, the Cramer-Rao lower bound (CRLB) for this architecture is derived based on the additive quantization noise model approximation for the effect of low-resolution ADCs. Then, the root-MUSIC method is designed for such a receive structure. Eventually, a performance loss factor and the associated energy efficiency factor is defined for analysis in detail. Simulation results find that a mixed-ADC architecture can strike a good balance among RMSE performance, circuit cost and energy efficiency. More importantly, just 1-4 bits of low-resolution ADCs can achieve a satisfactory performance for DOA measurement.

翻译：采用低分辨率模拟数字转换器(ADC)被认为是一个很有希望的解决办法;此外,到达方向估算是大型MIMO系统光束调整和跟踪的一个不可或缺的技术;因此,本文件首先调查了DOA对大型MIMO接受混合ADC结构阵列的估算的性能,其中无线电频率链段的一部分与高分辨率ADC连接,其余部分与低分辨率ADC连接;此外,这一结构的Cramer-Rao下线(CRLB)是根据对低分辨率ADC效应的添加式四分点噪声模型近似推算出来的;然后,为这种接收结构设计了根-MUSIC方法;最后,对性能损失系数和相关能效系数进行了详细分析;模拟结果发现,公正的混合ADC结构能够为ARMSA-4的低分辨率性能、低分辨率电路路段和低分辨率测量效率取得良好平衡。