  This paper designs a novel hybrid (a mixture of analog and digital)
beamforming and examines the relation between the hybrid and digital
beamformings for downlink multiuser massive multiple input multiple output
(MIMO) systems. We assume that perfect channel state information is available
only at the transmitter and we consider the total sum rate maximization
problem. For this problem, the hybrid beamforming is designed indirectly by
considering a weighed sum mean square error (WSMSE) minimization problem
incorporating the solution of digital beamforming which is obtained from the
block diagonalization technique. The resulting WSMSE problem is solved by
applying the theory of compressed sensing. The relation between the hybrid and
digital beamformings is studied numerically by varying different parameters,
such as the number of radio frequency (RF) chains, analog to digital converters
(ADCs) and multiplexed symbols. Computer simulations reveal that for the given
number of RF chains and ADCs, the performance gap between digital and hybrid
beamformings can be decreased by decreasing the number of multiplexed symbols.
Moreover, for the given number of multiplexed symbols, increasing the number of
RF chains and ADCs will increase the total sum rate of the hybrid beamforming
which is expected.

Optimization and Control