Sum-Rate Maximization for Multicell OFDMA Systems

Recently, joint subchannel allocation and (transmission) power control problems for multicell orthogonal frequency-division multiple access (OFDMA) systems have been actively studied. However, since the problems are notoriously difficult and complex, only heuristic approaches are mainly used to study them, instead of the optimal approach for achieving maximum system capacity. In this paper, we study this problem from the viewpoint of optimal subchannel allocation and power control, aiming at maximizing the sum rate of the multicell OFDMA system. By using a monotonic optimization approach, we develop an algorithm for the optimal subchannel allocation and power control that achieves the maximum sum rate of the system. In addition, we also develop an algorithm that provides both upper and lower bounds on the maximum sum rate of the system with lower computational complexity. To evaluate the tightness of the upper and lower bounds, we also study the conditions when the two bounds are close to each other so that they can be good approximations to the maximum sum rate of the system. Through numerical results, we show that the bounds provide good approximations to the maximum sum rate of the multicell OFDMA system in most cases.