Energy Efficient Power Control for Distributed Transmitters with ZF-Based Multiuser MIMO Precoding

Distributed transmitter (D-TX) system with multiple distributed TXs is considered. To support multiple users, the D-TX system employs a zero-forcing based multiuser multiple-input multiple-output precoding. An energy efficiency (EE) maximization problem is formulated under constraints on {per-user data rate} and per-antenna instantaneous transmit power. The latter constraint is to avoid severe distortion of transmit signals at a power amplifier, i.e., the clipping effects. A low-complexity and performance-effective power control method is then proposed by solving the modification of the original, intractable optimization problem. Transmit antenna selection is elucidated with respect to the EE. Numerical results verify the efficacy of D-TX system employing the proposed EE-aware power control and antenna selection with respect to both system EE and outage performance, and also impart the importance of equal power output capability, i.e., equal maximum output power of the distributed TXs, for energy efficient D-TX systems.