Hybrid adaptive Beamforming Systems using programmable Metasurfaces

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To handle the growing data traffic in mobile communication networks, which will exceed roughly 335 Exabytes per year by 2020, the reduction of cell size is an ongoing process. Modern small cells, with a typical range from 10 meters to several hundred meters, enable a high spectral reuse and thus provide a much higher bandwidth per user. Hence, due to the dense arrangement of these base stations interference becomes more and more a problem. Furthermore, there is an enormous demand on cheap, compact and energy efficient mobile base stations for those small cell scenarios, for example in urban areas. To target upon these challenges, we introduce a hybrid adaptive beamforming system, which empowers us to achieve high spectral efficiency in combination with a compact and affordable hardware. The main objective of the joint project is the research on hybrid adaptive beamforming systems consisting of several digital channels in conjunction with programmable metasurfaces. A high antenna directivity as well as a reduction in hardware effort are only two of the benefits we predict.Modern wireless communication systems utilize a Multiple Input Multiple Output (MIMO) configuration to improve capacity and signal coverage. Recent studies have shown that for the fifth generations of mobile communication (5G) and beyond mmWave bands will be considered to satisfy the customer's demands on higher data rates. While going to higher carrier frequencies to obtain larger bandwidths the resulting free space path loss has to be overcome what leads to an increasing number of antenna elements and therefore digital channels. In theory, each digital channel enables the use of one particular subchannel, which can highly improve the maximum data rate. However, each digital channel needs its own analog front- or backend and a powerful analog-to-digital converter (or digital-to-analog converter at the transmitter site), which result in a large and expensive setup. Furthermore, the calculation effort in the digital signal processor increases with every added channel resulting in a high energy consumption of the system.One solution to build a more compact and efficient system is to form a hybrid beamforming system consisting of multiple digital channels in conjunction with an analog phase shifting unit as shown in. This steering of the antenna can also be integrated into the system concept by utilizing programmable metasurfaces as presented by SEU. The resulting hybrid beamforming system can achieve a high directivity, while still providing a sufficient number of digital channels to supply multiple users or to increase the channel capacity for a single user. The reduced number of digital channels has, depending on the practical scenario, no negative effects on the overall performance of the communication network. The performance comparison between the purely digital beamforming system and the hybrid approach is therefore one of the main research objectives.