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

天线选择是以较低的成本和复杂性利用大型阵列的潜在增益的有力手段。在某些情况下，这需要比天线少得多的射频链，同时仍然保留了整个阵列的大部分分集潜力。考虑到天线本身简单且便宜，这似乎是一个好方法。然而，在较大的L单元阵列中选择K个天线的任意子集可能导致具有显著插入损耗的卷积RF开关电路。我们之前已经展示了如何更好地将大型阵列分成组，并为每组选择一个天线进行进一步处理。在这种所谓的两层方法中，RF交换电路要简单得多，其插入损耗大大降低，并且总体实用性能更好，即使天线的选择受到限制，因此不是最优的。另一方面，空间调制代表了一种激进的新方法，其允许由单个RF链、大量天线和适当的交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送的信息比特的一部分以非常高的比特率操作。在某些情况下，在利用大规模MIMO(多输入、多输出)链路的潜力方面，空间调制实际上可能超过经典的空间多路复用方案。然而，这些方案有两个缺点：相对复杂的接收器结构，以及易受深度衰落(缺乏发射分集)的影响。因此，研究人员将经典天线选择与空间调制相结合，以引入一定程度的分集。*本项目旨在基于两层概念推导出空间调制与天线和/或波束选择的各种新颖组合，以便所提出的架构在实践中转换良好并且具有相对简单的RF级。当在接收器处也有大阵列时，也可以在那里应用2层天线选择，以便始终隔离从其观察输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，潜在地作为一种在接收器处整形星座的手段，从而降低其复杂性。这样的技术将扩展到大规模MIMO上行链路和下行链路上下文。在后者中，由于FDMA(频分多址)，利用空间调制来减少射频链的数量是不可能的，但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这里开发的形式的空间调制的多用户检测算法。

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.