  With the growing interest in the deployment of massive
multiple-input-multiple-output (MIMO) systems and millimeter wave technology
for fifth generation (5G) wireless systems, the computation power to the total
power consumption ratio is expected to increase rapidly due to high data
traffic processing at the baseband unit. Therefore in this paper, a joint
optimization problem of computation and communication power is formulated for
multi-user massive MIMO systems with partially-connected structures of radio
frequency (RF) transmission systems. When the computation power is considered
for massiv MIMO systems, the results of this paper reveal that the energy
efficiency of massive MIMO systems decreases with increasing the number of
antennas and RF chains, which is contrary with the conventional energy
efficiency analysis results of massive MIMO systems, i.e., only communication
power is considered. To optimize the energy efficiency of multi-user massive
MIMO systems, an upper bound on energy efficiency is derived. Considering the
constraints on partially-connected structures, a suboptimal solution consisting
of baseband and RF precoding matrices is proposed to approach the upper bound
on energy efficiency of multi-user massive MIMO systems. Furthermore, an
oPtimized Hybrid precOding with computation and commuNication powEr (PHONE)
algorithm is developed to realize the joint optimization of computation and
communication power. Simulation results indicate that the proposed algorithm
improves energy and cost efficiencies and the maximum power saving is achieved
by 76.59\% for multi-user massive MIMO systems with partially-connected
structures.
