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

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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.