General Rank Beamforming Using High Order OSTBC For Multicasting Networks

This work addresses and suggests solutions to the problem of insufficient degrees of freedom in beamforming designs for single-group multicasting networks, where a group of users receives the same information. In our proposed approach we extend the known conventional rank-one, maxmin fair beamforming approach to a general rank beamforming approach. The proposed approach offers more flexibility and serves the users simultaneously with multiple beams. We broaden the concept of [1], where rank-two Alamouti space-time block coding (STBC) has been combined with beamforming by using a higher rank orthogonal space-time block code (OSTBC) instead. The increase of the rank is accompanied with an enhancement of the degrees of freedom and results in more optimal beamformers and an improved reliability. Simulations reveal that the proposed general rank beamforming approach provides a significant improvement in the bit error rate (BER) performance compared with the conventional state of the art approaches in large communication scenarios with many users.