Outage performance of cognitive radio networks under outage constraint of multiple primary users and transmit power constraint of secondary user

In this paper, the outage performance of a cognitive radio network under the joint constraint of multiple primary users (PUs) and a secondary user (SU) is investigated. More specifically, the SU can adjust its transmit power to satisfy the outage probability constraint of multiple PUs and its own transmit power constraint for communication. The adaptive transmit power policy and closed-form expression for the outage probability are derived. On the basis of these formulas, the impact of the channel gains of the PUs and those of the interference links from the PUs to the SU on the performance of the secondary network is evaluated. Especially, our results show a relationship between the number of the active PUs on the licensed frequency bands and the outage performance of the secondary network. Also, the performance of secondary network can be improved by extending the bandwidth over a number of licensed frequency bands.