On feasible SNR region for multicast downlink channel: Two user case

In this paper, we address the problem of the feasible SNR region for a multicast MIMO downlink channel. We characterize the feasible SNR region for a multicast group consisting of two mobile users. Based on this characterization, we propose solving the max-min SNR problem over the smallest convex and downward comprehensive superset of the feasible SNR region. We show, that the max-min SNR transmit beamformer is achievable via maximization of a weighted sum of SNRs. Both transmitter and the receivers are equipped with multiple antenna elements. The receive beamformers are fixed but arbitrary and each transmission is a single-mode transmission (no multiplexing and parallel transmissions of symbols).