Optimal Downlink Beamforming and resource allocation in MIMO-OFDMA systems

In this paper we consider the Downlink Beamforming (DLBF) and resource allocation problem in MIMO-OFDMA systems. We consider the sum-power minimization or margin adaptive problem. This is a variable Signal to Interference and Noise Ratio (SINR), non-convex optimization problem and many aspects of this problem are not well understood. By using uplink downlink duality we first obtain the expression of target SINR values and then solve the remaining margin adaptive problem to achieve the target data rates of all the users in the system. We then develop an optimal algorithm using convex optimization theory. This algorithm provides the optimal beamformers and optimal subcarrier and power allocation for different users while achieving their target data rate constraints.