Massive MIMO From a Terminal Perspective
Abstract: This thesis focuses on the terminal aspects of massive MIMO systems. Based on the degree of freedom a terminal have in a MaMi, different antenna configurations, transceiver topologies with associated transmission schemes, and the underlying algorithms are researched.The first studied topic concerns multiple-antenna terminals in a massive MIMO system for sub-6 GHz, operated at the center frequency of 3.7 GHz. Simulation environments based on fully-stochastic as well as geometric-stochastic approaches are developed and the results are compared to measured. For the measurements the Lund University Massive MIMO (LuMaMi) testbed has been used. To enable evaluation of multi-antenna terminals, modifications to the LuMaMi framework have been necessary. Real-time diversity schemes for dual antenna terminals as well as a channel capturing feature have been implemented. The latter, to enable analysis and post processing of measured channels from the multi-antenna terminals. Multi-antenna terminal prototypes with integrated antennas, based on real Sony Xperia smartphone chassis where designed for the evaluation. The three-dimensional antenna gain-patterns have been characterized in an anechoic chamber to ensure that simulations and measurements have a common ground. The second topic in this thesis relates to mm-wave massive MIMO systems. As a first step toward evaluation of handsets, a 28 GHz channel sounder has been developed for the measurement of dynamic, highly resolved, in both temporal and spatial domains, propagation channels. To enable measurements, a 256$\times$128 antenna-element system was designed together with a control program to handle the switching and the enormous amount of data.
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