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，这需要有比天线少得多的射频链，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，这似乎是一个好方法。然而，在较大的L元素阵列中选择K天线的任意子集可能导致具有显著插入损耗的复杂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，射频开关电路要简单得多，其插入损耗大大降低，整体实际性能优越，尽管天线的选择受到限制，因此不是最优的。

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.