Robust Transmit Beamforming Using OSTBC in a Multicast Network

In multicasting networks, a multi-antenna base station (BS) transmits the same information to a single-group of users. In this paper, we investigate robust general-rank beamforming designs based on orthogonal space-time block codes (OSTBCs), taking into account imperfect channel state information. Specifically, we minimize the BS’s transmit power subject to both the users’ quality-of-service (QoS) constraints and the interference temperature constraints on the coexisting receivers. The formulated robust multicast beamforming problem is shown to be a non-convex quadratically constrained quadratic program (QCQP), which is NP-hard. As a compromise, we propose two low-complexity algorithms based on the linear approximation and the S-procedure reformulation along with a convex rank-constrained condition, respectively. Simulation results demonstrate the significant performance gain of the proposed algorithms over existing non-robust design schemes.