MIMO systems 5G mobile communication systems 9 Channel estimation 9 Signal to noise ratio 7 MIMO 6 Orthogonal frequency division multiplexing 6 Iterative methods 5 Massive MIMO 5 Mean square error 5 Microwave antennas 5 Reconfigurable 5 Wireless communications 5 Antenna arrays 4 Antennas 4 Channel state information 4 Communication channels (information theory) 4 Feedback control 4 MIMO radar 4 Multiple inputs 4 Multiple outputs 4 Receiving antennas 4 Wireless communication 4 5G 3 Array processing 3 Array signal processing 3 Cell-free 3 Channel capacity 3 Codes (symbols) 3 Deep learning 3 Energy efficiency 3