Assessing realistic gains of Massive MIMO

Spectral efficiency gains of MIMO (Multiple Input Multiple Output) systems with physically realizable channels are presented. Results are based on normalized analytical channel models, using antenna theory and electromagnetic theory from the perspective that a MIMO channel model cannot be a source of energy. That is, the average received power cannot exceed the total average radiated power. The assessment of capacity/throughput calculations necessitates an accurate determination of the average received power. Analysis of MIMO systems under study show that important scaling factors are needed to render a channel model realistic, giving rise to realistic received average powers. The analysis and results are important for the assessment of realistic gains for Massive MIMO systems. Additionally, there is an upper limit on the number of receive antennas with a given aperture, where each receive antenna captures the same amount of average power. Above this limit, the conservation of energy is violated. Performance results for downlink (DL) MIMO system spectral efficiencies are presented for power normalized channel models compared with traditional channel models.