Minimizing the Number of Dropped Users in MIMO Multicasting Channels

For multicasting applications over multiple-input multiple-output (MIMO) channels with certain kind of QoS requirement, it is more suitable to design a strategy that minimizes the number of the dropped users during one multicasting session. The immediate benefit of this strategy would be to effectively improve the outage capacity of each receiver. The major contribution of our paper is a precoded space-time block coding (STBC) strategy that can minimize the number of the dropped users for MIMO multicasting channels. We assume that the MIMO channel is narrow band with flat fading. The transmitter has full knowledge of the channel state information of every subscribed users. By approximating the indicator function with the sigmoid function and employing an iterative procedure, we are able to solve this problem using standard convex optimization techniques. Simulation results shows that this new scheme outperforms all existing methods including the open-loop STBC and beamforming.