Energy efficiency optimization in multiuser relay-assisted MIMO systems

The issue of energy-efficient resource allocation in a multi-user, amplify-and-forward, relay-aided MIMO system is considered. The transmit covariance matrices and the relay amplification matrix are optimized in order to maximize the systems global energy efficiency, defined as the ratio between the system achievable sum-rate and the total consumed power. In the definition of the consumed power, both the transmit power and the circuit power needed to operate the terminal are accounted for. The considered performance metric is measured in bit/Joule thus representing a measure of the efficiency with which each Joule of energy is employed. The tools of fractional programming and alternating maximization are employed to come up with a resource allocation algorithm which also considers QoS constraints.