Performance analysis of amplify-and-forward cognitive relay networks under transmit power constraint and interference power constraint

Cooperative relaying technology has been proved to be one of the most promising techniques to improve the throughput of CR networks. In this paper, cognitive relay networks with amplify-and-forward (AF) protocol in a spectrumsharing scenario have been considered. Compared with previous studies, we further consider the transmit power constraint on secondary source node (SS). Namely, we impose both transmit power constraint and interference power constraint on SS and secondary relay node (SR). As well we obtain the exact outage probability which works as the performance measurement of CR networks. To analyze the influential factors for system performance, the closed form expression of outage probability needs to be derived. However, it is mathematical intractable. Hence, an approximate approach is adopted as a solution. Finally, Monte-Carlo simulations are conducted to verify the accuracy of our approximation, the error sources of our analytical results are discussed as well.