Full-rate general rank beamforming in single-group multicasting networks using non-orthogonal STBC

In this paper, we propose a novel single-group multicast beamforming technique using non-orthogonal space-time block coding (STBC). In the system, a multi-antenna base station broadcasts its information to a large group of single-antenna users. We introduce a modified max-min fair beamforming optimization problem, which maximizes the worst user's modified Euclidean distance instead of the conventional worst user's signal-to-noise ratio. Our beamforming formulation extends the traditional max-min fair problem, by taking the pairwise error probability of the employed STBC into consideration, which in turns improves the overall system performance. For the resulting non-convex quadratically constrained quadratic program, an iterative inner convex approximation method is devised, in which the non-convex part of the problem is linearized and a sequence of inner convex optimization problems is solved. Simulation results demonstrate considerable improvement for networks with a large number of users.