Coordinated Linear Precoding in Downlink Multicell MIMO-OFDMA Networks

We consider coordinated linear precoding in downlink multicell multiple-input multiple-output orthogonal frequency-division multiple access (MIMO-OFDMA) systems, where multiple base stations (BSs) coordinate to mitigate the co-channel interference. Two nonconvex rate optimization problems with per-cell power constraints are addressed: weighted sum rate maximization (WSRM) and maximizing the weighted sum of the minimal user rates (MWSMR) of the coordinated cells. We propose two iterative algorithms to achieve suboptimal solutions for the WSRM problem. One attempts to solve the Karush-Kuhn-Tucker (KKT) conditions of the problem and the other is an alternating maximization algorithm based on the idea of the classical Blahut-Arimoto algorithm. The distributed implementations of the two algorithms are also discussed. Moreover, an iterative algorithm based on alternating maximization is proposed to solve the MWSMR problem. Finally, simulation results are presented to demonstrate the effectiveness of the proposed algorithms.