Energy Consumption vs. Bit Rate Analysis Toward Massive MIMO Systems

In this paper, we provide a comprehensive study and comparison of the impact of both multiple-input multiple-output (MIMO) and massive MIMO techniques, at the base station (BS), on the energy consumption versus bit rate performance of a multi-antenna wireless handset. Both spatial diversity and spatial multiplexing (SM) are examined and compared for both known and unknown channel state information (CSI) at the transmitter. For the diversity case, our results show that for a BS with four or more receive antennas, there is little to be gained in terms of energy efficiency at the wireless handset by having more than one transmit antenna. For the SMcase with conventional MIMO, the bit rate increases linearly with Nt at the cost of additional energy consumption at the handset due to the absence of diversity gain. For massive MIMO, however, the excess receive antennas provide a diversity gain in a SM scheme thus allowing a high bit rate without sacrificing energy efficiency at the handset and even with no needs of CSI knowledge.