LAUSR

Abstract Large-scale (LS) MIMO antenna systems use excessive amount of TX antennas and serve limited number of users to make very high channel gain, and it is obvious that the channel gain increases spectral efficiency of the system. The transmission power of LS-MIMO systems also can be reduced from the increment of channel gain to increase energy efficiency (EE). In this situation, a determination of transmission power which is reduced from total available transmission power can be an important scheme to achieve high EE. This paper proposes a determination scheme of the EE optimum transmission power for LS-MIMO systems. The approximated optimum transmission power is derived analytically as a closed-form function based on various parameters, such as number of TX antennas, number of users, system bandwidth, interference, and so on. Using the closed-form function with the measurable parameters, we can easily get the optimum EE transmission power in real-time. The effectiveness of proposed scheme is validated with numerical simulations. According to the results, the proposed scheme can significantly increase the EE with fairly small loss of channel capacity, compared with ordinary LS-MIMO systems.