Abstract
The main purpose in this work is to enhance relay technique in underlay cognitive radio scheme through estimating the best path between the secondary source and the secondary destination under the power interference constraint of the primary user. A protocol is proposed based on the cooperation process between the secondary relay nodes in the system in order to establish the best path at low complexity without exceeding the interference threshold of theprimary user. Performance analyses, through simulation, of the suggested protocol shows great enhancement in network outage probability when compared with direct path model and one relay node based-model.