A Practical Approach for Weighted Rate Sum Maximization in MIMO-OFDM Broadcast Channels

We study the maximization of weighted sum rate in multi-input multi-output OFDM broadcast channels based on MMSE linear beamforming. The problem at hand is a well- known non-convex problem. Nevertheless, motivated by Yu\´s "zero duality gap" result in a multicarrier system, we apply dual decomposition to reduce the original problem to N independent subproblems where N denotes the number of subcarriers. For each subproblem, we propose a simple waterfilling approach that aims at iteratively solving the KKT condition. Numerical examples show that the proposed algorithm achieves near-optimal performance under a typical downlink scenario.