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In this paper, we consider a distributed transmitter (D-TX) system, in which each TX has a dissimilar power amplifier with different maximum output power, and different number of transmit antennas. To improve energy efficiency (EE) of the D-TX system, we design a multiuser multiple-input multiple-output (MU-MIMO) precoding matrix, a transmit antenna selection (AS) matrix, and a power control (PC) matrix. A conventional zero-forcing based MU-MIMO precoding is shown to be EE optimal for given AS and PC. Optimal and heuristic PC methods are proposed for given AS and MU-MIMO precoding. For the AS, we also propose heuristic algorithms. Average transmit power, outage probability, and EE performance are evaluated to compare three AS algorithms, and to observe the performance gap between the optimal and heuristic PC methods. From the numerical results, we discuss a tradeoff between AS complexity and EE performance and provide a useful guide for energy efficient D-TX system design.
Joung et al. (Sun,) studied this question.