Energy Efficiency Maximization For Mimo-Ofdma Systems With Imperfect Csi

Unlike the previous work on efficiency (EE) for multiple input multiple output (MIMO) orthogonal frequency division multiple access (OFDMA) systems with assuming the availability of perfect channel state information (CSI), this paper investigates robust resource allocation to improve the system EE under imperfect CSI. Considering the estimation error and the feedback delay, we formulate a combinatorial problem involving subcarrier assignment and power allocation to maximize the EE subject to a transmit power constraint and a minimum rate constraint. By relaxing the integral constraints, we develop a joint subcarrier and power allocation algorithm which can be implemented by one-dimension search. The simulation results demonstrate that the proposed algorithm can achieve a comparable EE performance with the optimal algorithm. Moreover, with taking imperfect CSI into account, the proposed algorithm can achieve higher EE when compared with a nonrobust algorithm.