Energy‐efficient pilot and data power allocation in massive multi‐user multiple‐input multiple‐output communication systems

Abstract

This study aims to improve the energy efficiency of time-division duplexing massive multi-user multiple-input multiple-output communication systems for both uplink and downlink transmissions. By using minimum mean square error channel estimation, two novel pilot–data power allocation schemes are proposed to minimise the total uplink and downlink transmit power under per-user signal-to-interference-plus-noise ratio (SINR) requirement and per-user power consumption constraints. The proposed schemes take into account the maximum-ratio combining and zero-forcing (ZF) detectors in the uplink transmission together with maximum-ratio transmission and ZF precoder in the downlink transmission. In order to simplify the proposed optimisation problems, lower bounds of the average SINR are derived and used in the power allocation algorithms. The key contribution of this study lies in formulating the original energy-efficient power allocation problem and converting such a complicated optimisation problem to a geometric programming problem. Computer simulation validates the tightness of the derived SINR lower bounds and shows that the proposed schemes can save up to 78% of the total power as compared with the equal power allocation among all the mobile users.