In this work, we consider Terahertz (THz) communications with low-resolution uniform quantization and spatial oversampling at the receiver side. We compare different analog-to-digital converter (ADC) parametrizations in a fair manner by keeping the ADC power consumption constant. Here, 1-, 2-, and 3-bit quantization is investigated with different oversampling factors. We analytically compute the statistics of the detection variable, and we propose the optimal as well as several suboptimal detection schemes for arbitrary quantization resolutions. Then, we evaluate the symbol error rate (SER) of the different detectors for a 16- and a 64-ary quadrature amplitude modulation (QAM) constellation. The results indicate that there is a noticeable performance degradation of the suboptimal detection schemes compared to the optimal scheme when the constellation size is larger than the number of quantization levels. Furthermore, at low signal-to-noise ratios (SNRs), 1-bit quantization outperforms 2- and 3-bit quantization, respectively, even when employing higher-order constellations. We confirm our analytical results by Monte Carlo simulations. Both a pure line-of-sight (LoS) and a more realistically modeled indoor THz channel are considered. Then, we optimize the input signal constellation with respect to SER for 1-bit quantization. The results show that the minimum SER can be lowered significantly for 16-QAM by increasing the distance between the inner and outer points of the input constellation. For larger constellations, however, the achievable reduction of the minimum SER is much smaller compared to 16-QAM.

翻译：本文研究接收端采用低分辨率均匀量化和空间过采样的太赫兹通信系统。在保持模数转换器功耗恒定的公平前提下，我们比较了不同ADC参数配置方案。针对1-bit、2-bit和3-bit量化，研究了不同过采样因子下的检测性能。通过解析计算检测变量的统计特性，我们提出了适用于任意量化分辨率的最优检测方案及多种次优检测方案。随后，针对16进制和64进制正交幅度调制星座，评估了不同检测器的符号错误率。结果表明：当星座规模超过量化电平数时，次优检测方案相较于最优方案存在显著性能退化。值得注意的是，在低信噪比条件下，即使采用高阶星座，1-bit量化的性能分别优于2-bit和3-bit量化。通过蒙特卡洛仿真验证了解析结论，并分别考虑了纯视距信道和更贴近实际的室内太赫兹信道模型。最后，针对1-bit量化系统，以最小化SER为目标优化了输入信号星座设计。结果显示：通过增大16-QAM星座内环与外环点间距，可显著降低最小SER；但对于更大规模星座，其最小SER的降低幅度远小于16-QAM。