Beamforming in Interference Networks: Multicast, MISO IFC and Secrecy Capacity

Motivated by the two-user beamforming in multiantenna interference channels, we characterize the upper boundary of the achievable single-user gain-region. The eigenvector corresponding to the maximum eigenvalue of the weighted sum of Hermitian forms of channel vectors is shown to achieve all points on the boundary in some given direction. Thereby, we solve three different beamforming problems, namely the multicast beamforming problem, the beamforming optimization in MISO interference channels, and beamforming in MISO systems with secrecy constraints for arbitrary number of users. We are confident that the framework can be applied to beamforming problems in other interference networks as well. Numerical simulations illustrate the achievable gain-region.