Energy-Efficient Resource Allocation for Downlink MIMO-OFDMA Systems with Proportional Rates Constraints

In this paper, we address the problem of energy efficient resource allocation for the downlink multiple-input-multiple-output orthogonal frequency division multiple access (MIMO-OFDMA) system. A proportional fairness based energy efficiency optimization problem with constraints of maximum transmit power is formulated, where the object is to maximize the system energy efficiency measured by "bits/Hz/Joule". This joint subcarrier and power allocation problem turns out to be a NP-hard problem which is hard to solve. To deal with it, a two-step sub carrier assignment and power allocation method was proposed to derive the suboptimal solution of the optimization problem. Numerical results validate that the proposed algorithm brings remarkable gains to energy efficiency as well as guarantees proportional fairness to the users.