Energy Efficiency in Random Opportunistic Beamforming

As a step towards decreasing power consumption in mobile communication networks, we investigate the energy efficiency (EE) of a scheduler that can be utilized at the transmitter in a broadcast channel: the random opportunistic beamforming algorithm. Using the ratio of rate to power as the EE metric and considering the constant circuit power, the EE at the transmitter decreases with the number of transmit antennas M. Two approaches of optimizing the power allocation when M - 1 are introduced. We show that the optimal EE scales double-logarithmically with the number of users, which has one antenna each. The appropriate expression for EE in communications is also discussed.