A Mixed SINR-Balancing and SINR-Target-Constraints-Based Beamformer Design Technique for Spectrum-Sharing Networks

We propose a transmitter beamformer design technique for a spectrum-sharing network with mixed quality-of-service requirement. In particular, the proposed algorithm has the ability to jointly design multiple beamformers, so that a specific subset of users attains certain target signal-to-interference-plus-noise ratios (SINRs) whereas the SINRs of the remaining users are balanced subject to multiple linear constraints. The design framework considered is applicable to both the overlay cognitive radio network (CRN) and the underlay CRN; however, the algorithm is described for the example of an underlay CRN to include a very general mathematical framework. We maximize the worst-case users' SINR of a particular set of users while satisfying the target SINRs of the remaining users subject to the total transmission power and the interference leakage constraints. This algorithm is solved using the uplink-downlink duality and subgradient method. The condition for convergence is analytically derived. The simulation results are provided to validate the optimality and the convergence of the proposed algorithm.