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Precoder design for dual-stream MIMO multicasting

In this paper, we investigate the precoder design for MIMO multicasting, where two data streams are sent from the transmitter and the minimum mean-squared-error decision feedback equalizer is performed at all users. To improve the receiving quality of data streams, we focus on maximizing the minimal signal-to-interference-plus-noise ratio (SINR) for all streams via precoding. Considering that the precoder is composed of a transformation matrix and a rotation matrix, we separate the precoder design into two stages. Firstly we calculate the transformation matrix under the criterion of maximizing the throughput of the multicast channel. Then, by deriving the relationship between the rotation matrix and the SINR, we transform the original problem into a real-valued optimization problem, and moreover, a Lozano's algorithm is proposed to compute the rotation matrix. In particular, for the special case of two users, a constructive method can be applied to directly calculate the rotation matrix. The simulation results show that the proposed design outperforms the existing ones in both the achievable rate and symbol error rate.