  This paper presents LuMaMi28, a real-time 28 GHz massive multiple-input
multiple-output (MIMO) testbed. In this testbed, the base station has 16
transceiver chains with a fully-digital beamforming architecture (with
different pre-coding algorithms) and simultaneously supports multiple user
equipments (UEs) with spatial multiplexing. The UEs are equipped with a
beam-switchable antenna array for real-time antenna selection where the one
with the highest channel magnitude, out of four pre-defined beams, is selected.
For the beam-switchable antenna array, we consider two kinds of UE antennas,
with different beam-width and different peak-gain. Based on this testbed, we
provide measurement results for millimeter-wave (mmWave) massive MIMO
performance in different real-life scenarios with static and mobile UEs. We
explore the potential benefit of the mmWave massive MIMO systems with antenna
selection based on measured channel data, and discuss the performance results
through real-time measurements.
