Spectrum Sharing in Cognitive Radio Based on Robust Adaptive Beamforming

Cognitive radio is an emerging technology in wireless communication for efficient utilization of the underutilized spectrum and alleviates the spectrum scarcity. Smart antennas efficiently utilize the spectrum in cognitive radio networks. In this paper, the cognitive system consists of the secondary user, which is equipped with the multiple antennas in the form of the array and follows the steering vector of the primary users. The cognitive transmitter shares the spectrum with the primary user through generating the nulls in the direction of the primary user and maximizes the power in the direction of the secondary users. However, whenever owing to mismatch the performance tarnished, the robust beam former having the null steering algorithm, mitigate the mismatch effect and enhance the performance. Convergence of the algorithm and outage probability particularly remains low in consequence of enhancement of the array size. Moreover, for further robustness, we estimate the angle, steer the beam by using stochastic algorithms and compare with Genetic Algorithm (GA). Mathematical formulation and simulation results show the strength and competence of the proposed algorithm.