Abstract— In cognitive radio, the received signal to interference noise ratio (SINR) of the secondary users (SUs) should be at certain level to protect primary users (PUs) from harmful interference for reliable communication. Therefore, firstly, a new beamforming problem has been formulated in this paper considering few new constraints in addition to the only constraint of the conventional minimum variance beamformer and secondly, a solution has been provided using Lagrange multiplier method and complexmatrix calculus to reduce the interference due to the presence of SUs. The simulation results show that our proposed solution has placed a deeper null towards the direction of the PUs than the conventional beamformer. Furthermore, the response of the presented beamformer has been examined with different number of array elements and inter-element spacing.

Index Terms—Cognitive radio, SINR, beamforming, optimization, Lagrange multiplier method, sidelobes

Cite: Z. Hossain, U. Habiba, and M A Matin, "Efficient Beamforming Technique for Cognitive Radio Networks," Journal of Advances in Information Technology, Vol. 4, No. 3, pp. 111-115, August, 2013.doi:10.4304/jait.4.3.111-115