Robust Downlink Throughput Maximization in MIMO Cognitive Network with more Realistic Conditions: Imperfect Channel Information & Presence of Primary Transmitter

Abstract: Designing an efficient scheme in physical layer enables cognitive radio (CR) users to efficiently utilize resources dedicated to primary users (PUs). In this paper in order to maximize the SU's throughput, the SU's transceivers beamforming is designed through new model considering the presence of the PU's transmitter. Since presence of primary transmitter basically degrades CR's system performance; proposed beamforming design considers intra-system interference between PUs and SUs. An optimization problem based on maximizing CR network throughput subject to controlling interference power from SU transmitter to PU receiver has been formulated. Due to limited cooperation between PU and SU network, channel state information (CSI) between two networks are assumed to be partially available, subsequently conventional CSI uncertainty model known as norm bounded error model has been employed. The proposed optimization problem, which is basically difficult to solve, has been converted to a semi definite program which can be efficiently solved by optimization toolbox software e.g., CVX-Mathlab. Furthermore, alternative time efficient and close form solutions are derived. The superiority of the proposed approach in comparison with the previous works has been confirmed through the simulation results.