Low-Complexity Radio Frontends and Noncoherent Detection for Massive MIMO

多用户通信系统的中心基站配置了大量的接收天线，即大规模MIMO，正受到越来越多的关注。这种系统的主要挑战是获取准确的信道状态信息以及实现这种系统的努力，例如，将高质量的低电压信号分配到射频前端。这些问题可以通过应用非相干传输方案来克服，特别是如果可以使用低复杂度的前端。因此，本提案解决了多用户大规模MIMO上行系统的设计和评估问题。特别是，模拟无线电前端与所采用的联合检测算法之间的相互作用必须进行详细的研究。当联合处理这些领域时，预计会有新的见解，新的结果和新的方法。一方面，需要开发基于子空间方法的增强非相干检测方案。正如初步工作所显示的那样，在非相干情况下，天线特征（如方向图）的影响要比相干情况下明显得多，因此必须详细评估这种影响。另一方面，在大规模MIMO的背景下，必须研究低线性/低复杂度（大致量化）接收机前端的使用。Sigma-Delta转换的原理，即以速度交换分辨率，将被延续到对信道中的场进行空间采样的情况中。这种空间西格玛-三角洲采样方法的潜力，旨在使低复杂性的前端在一个仍然高性能的方案将被评估。

Multi-user communication systems with a central base station equipped with a very large number of receive antennas, so-called massive MIMO, are attaining more and more attention. The main challenges in such systems are the acquisition of accurate channel state information as well as the effort for realizing such systems, e.g., the distribuation of a high-quality LO-signal to the RF frontends. These problems can be overcome by applying noncoherent transmission schemes in particular, if low-complexity frontends may be used.Consequently, this proposal addresses the design and assessment of multi-user massive MIMO uplink systems. In particular, the interaction between the analog radio frontend and the employed joint detection algorithms has to be studied in detail. New insights, new results, and novel methods are expected, when treating these areas jointly. On the one hand, enhanced noncoherent detection schemes based on subspace methods have to be developed. Since, as preliminary work shows, the influence of the antenna characteristics like pattern is much more pronounced in the noncoherent case compared to the coherent one, this influence has to be assessed in detail. On the other hand, the use of low-linearity/low-complexity (roughly quantizing) receiver frontends has to be studied in the context of massive MIMO. The philosophy of Sigma-Delta conversion, i.e., resolution is exchanged by speed, will be carried over to the situation at hand of spatially sampling the field in the channel. The potential of such a spatial Sigma-Delta sampling approach aiming at enabling low-complexity frontends in a still high-performing scheme will be assessed.