Outage performance of cognitive wireless relay network with cooperative communication

As the proliferation of wireless device and applications continues to grow; the demand for spectrum resource keeps increasing. Cognitive Radio (CR) is a promising technique to access the spectrum dynamically. It allows unlicensed (secondary) users to use the spectrum of licensed users without degrading their performance. In underlay cognitive network, secondary users can use the primary spectrum as long as interference to the primary is below certain acceptable level. We consider such a network with secondary system employing relay to forward information from source to destination. Whenever these relays are able to transmit (i.e. when the secondary relay Signal to noise ratio is above the threshold level) and it aids the source using any of the cooperative communication protocols. Considering peak power constraint and interference constraint, the analytical expression for outage probability of the system is calculated. Furthermore, the outage probability obtained by the use of Space Time Block Code (STBC) - Alamouti Scheme and Co-phasing Scheme is compared for various relay network environment. Besides, the outage probability that is being affected by the distance ratio of the interference link to the relaying link is also calculated.