Practical large-scale antenna systems (LSAS) for high bit-rate communications based on antenna selection and spatial modulation

天线选择构成了以较低的成本和复杂性利用大阵列的潜在增益的强有力的手段。在某些情况下，这意味着可以有比天线少得多的RF链，同时仍然保留整个阵列的大部分分集潜力。考虑到天线本身既简单又便宜，这似乎是一个很好的方法。 然而，在L个元件的较大阵列中选择K个天线的任意子集可能导致具有显著插入损耗的复杂RF切换电路。我们之前已经展示了如何更好地将大型阵列划分为组，并为每组选择一个天线进行进一步处理。在这种所谓的2层方法中，RF开关电路要简单得多，其插入损耗大大降低，并且整体实际性能上级，即使天线的选择受到限制，因此不是最佳的。另一方面，空间调制代表了一种全新的方法，该方法允许由单个RF链、大量天线和适当的切换电路组成的极其简单的发射机通过使用所选天线的索引作为所发射的信息比特的一部分来以非常高的比特率操作。在某些情况下，空间调制实际上可以在利用大规模MIMO（多输入多输出）链路的潜力方面超过经典的空间复用方案。然而，这些方案有两个缺点：相对复杂的接收机结构，以及易受深度衰落（缺乏发射分集）的影响。因此，研究人员将经典的天线选择与空间调制相结合，以引入某种程度的分集。本项目旨在基于2层概念推导出空间调制和天线和/或波束选择的各种新颖组合，使得所提出的架构在实践中能够很好地转化，并且具有相对简单的RF级。当在接收器处也可获得大阵列时，也可在那里应用2层天线选择，以便始终隔离从其观察传入数据向量的最佳空间样本集合。还将探索基于波束而不是天线选择的空间调制，可能作为在接收器处形成星座的手段，从而降低其复杂性。这样的技术将被扩展到大规模MIMO上行链路和下行链路上下文。在后者中，由于FDMA（频分多址），RF链的数量的减少被认为是不可能利用空间调制的，但是将探索该缺点的解决方案。上行链路将需要仔细研究适用于空间调制的形式在这里开发的多用户检测算法。

Antenna selection constitutes a powerful means to leverage the potential gain of a large array at lesser cost and complexity. In some cases, this entails that there can be much fewer RF chains than antennas, while still conserving much of the diversity potential of the entire array. Given that antennas themselves are simple and inexpensive, this seems like a good approach. However, the selection of an arbitrary subset of K antennas in a larger array of L elements can lead to convoluted RF switching circuitry with a significant insertion loss. We have previously shown how it is better divide a large array into groups and to select one antenna per group for further processing. In this so-called 2-layer approach, the RF switching circuit is much simpler, its insertion loss considerably reduced, and the overall practical performance superior, even though the choice of antennas is constrained and therefore suboptimal.******On the other hand, spatial modulation represents a radical new approach which allows an extremely simple transmitter, comprised of a single RF chain, a large number of antennas and appropriate switching circuitry, to operate at a very high bit rate by using the index of the chosen antenna as part of the transmitted information bits. In certain cases, spatial modulation may in fact surpass classical spatial multiplexing schemes in leveraging the potential of massive MIMO (Multi-Input, Multi-Output) links. However, these schemes from 2 drawbacks: relatively complex receiver structures, and vulnerability to deep fades (absence of transmit diversity). Researchers have therefore combined classical antenna selection with spatial modulation in order to introduce some degree of diversity.******The present project aims to derive various novel combinations of spatial modulation and antenna and / or beam selection based on the 2-layer concept, so that the proposed architectures would translate well in practice and have relatively simple RF stages. When a large array is also available at the receiver, 2-layer antenna selection can also be applied there in order to isolate at all times the best set of spatial samples from which to observe the incoming data vectors. Spatial modulation based on beam instead of antenna selection will also be explored, potentially as a means to shape the constellation at the receiver and therefore reduce its complexity. Such techniques will be extended to the massive MIMO uplink and downlink contexts. In the latter, because of FDMA (Frequency Division Multiple Access), a reduction in the number of RF chains is not considered possible with spatial modulation, but solutions to this drawback will be explored. The uplink will require careful study of multiuser detection algorithms applicable to spatial modulation in the forms developed here.