Optimal multiuser downlink cooperative beamforming in cognitive radio networks with SINR and power constraints

In this paper, optimal multiuser downlink cooperative beamforming in spectrum underlay based cognitive radio network is considered with target SINR and sum power constraints. In existing works, transmit beamforming vectors for maximum number of admitted secondary users are designed with fixed target SINR and sum power constraints. However, this joint optimization problem becomes infeasible as some users may absorb more power to meet the target SINR. Hence, the objective of this paper is to design optimal multiuser downlink beamforming vectors for primary and secondary base stations in a cooperative manner satisfying the practical bounded SINR. This objective is formulated as convex optimization problem and it is solved using second order cone programming method. The performance of the cognitive radio network is analyzed with the practical constraints.