Esmail zarezadeh - Department of Electrical Engineering University of Amirkabir university, Tehran, Iran
Ayaz ghorbani - Department of Electrical Engineering University of Amirkabir university, Tehran, Iran
Yaser Norouzi - Department of Electrical Engineering University of Amirkabir university, Tehran, Iran

nowadays, application of relay based networks to increase the performance of wireless communication systems is very in demand. It is expected that in near future, these networks will be implemented in the systems based on IEEE 802.16j and LTE-Advanced standards. In such networks, if there is no direct link between transceiver and receiver, in order to increase the radius of cell, telecommunication relays can be employed to transfer the data. Moreover, application of cognitive radio networks together with any other wireless networks is as established mechanism for efficiently utilizing of certified frequency ranges. One of the effective ways to measure the frequency spectrum of elementary network by cognitive radio, is the application of some secondary shared terminals.Utilizing of this method in natural environments with an intensive channel fading helps to the reduction in the probabilities of incorrect diagnostics and interferences to the primary network. Meanwhile, it solves the hidden terminal problem. A method to design a relay network along with cognitive radio is proposed in this paper. In fact we aimed to generalize the capabilities of a relay network to the cognitive radio based systems. In the proposed model, maximizing the signal to noise ratio utilizing an efficient beam shaping is designed in the distributed rely networks. This is resolved by utilizing convex optimization techniques. The proposed model so designed that the minimum requirements of elementary receiver network are satisfied and the revelation performed in both of the primary and secondary networks simultaneously with acceptable quality.

Optimal beam forming, cognitive radio, telecommunication relays, wireless communication