Maximum SINR transmit beamforming for multiuser MIMO systems with limited feedback

The Lloyd´s vector quantization method is adopted to design a codebook for multiuser transmit beamforming vectors over multiple-input multiple-output (MIMO) channels which only allow limited feedback. The beamformer code-book is designed to maximize the post-processing signal-to-interference-plus-noise ratio (SINR), and the resulting codebook is called maximum SINR (MSINR) codebook. The MSINR cooperative beamforming algorithm proposed in our previous work under the assumption that the instant channel information of all users is perfectly known to each user as well as the receiver is modified to obtain the code for a given set of channel samples, which is the key step in the Lloyd´s method. The obtained codebook, as revealed by the numerical results, is robust to a wide range of deviation of the actual transmit SNR from that associated with a codebook..