User Effects in Beam-Space MIMO

The performance and design of the novel single-RF-chain beam-space multiple-input-multiple-output (MIMO) antenna concept is evaluated for the first time in the presence of the user. First, the variations of different performance parameters are evaluated when placing a beam-space MIMO antenna in close proximity to the user body in several typical operating scenarios. In addition to the typical degradation of conventional antennas in terms of radiation efficiency and impedance matching, it is observed that the user body corrupts the power balance and the orthogonality of the beam-space MIMO basis. However, capacity analyses show that throughput reduction mainly stems from the absorption in user body tissues rather than from the power imbalance and the correlation of the basis. These results confirm that the beam-space MIMO concept, so far only demonstrated in the absence of external perturbation, still performs very well in typical human body interaction scenarios.