Best relay selection in a multi-relay nodes system under the concept of cognitive radio

In this paper we propose a simple protocol that selects the best relay node in a multi-relay nodes system that works under the cognitive radio technology. The best relay node between the secondary transmitter and the secondary receiver is selected based on the signal-to-noise ratio (SNR). This protocol is examined for many channel conditions. In addition to that, the outage probability performance for this system has been compared with the outage probability of the single-relay system model and the direct path system model. Significant enhancements in the system performance are observed. The numerical results show a noticeable reduction in outage probability when compared to the single-relay system.