This paper presents a method to determine transmission power based on power amplifier\n(PA) operations in order to improve the energy efficiency (EE) of a large-scale (LS) Multiple Input\nMultiple Output (MIMO)-OFDM system, which is a multi-carrier multiple antenna system with a\nlarge amount of transmitter (TX) antennas. Regarding the EE improvement, we propose two kinds\nof PA operation schemes: increasing the effective TX power (ITXP) and reducing the PA power\nconsumption (RPC) assuming that a reduction of peak-to-average power ratio is applied in the\nappropriate manner. Closed-form expressions of relative EE are derived for both schemes, and the\nrelative EE of the ITXP scheme is shown to depend on the precoding method that is applied to\nreduce the inter-user interference, while that of the RPC scheme is independent of the precoding\nmethod. The relative EE difference between the ITXP and the RPC schemes is also shown to rely on\nthe occupation ratio of the PA power consumption over the total power consumption. Thus, the EE\ncan remarkably improve by selecting the appropriate scheme based on the circumstances. The results\nof a simulation also validate the derived closed-form expression of the relative EE.
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