Secrecy transmission capacity of primary network with help of cognitive interference

The secrecy transmission performance of cognitive radio ad hoc networks is investigated in this paper. The existing work on secrecy capacity of cognitive radio networks focus on order sense results like scaling laws, however, these results only give asymptotic predictions without an exact expression. In order to overcome this limitation, we propose a new method to derive the closed-form expression of secrecy transmission capacity of the primary network. The nearest neighbour routing protocol is considered. Furthermore, we evaluate the optimal PR density maximizing the secrecy transmission capacity under constraints of the connection outage probability (COP) and the secrecy outage probability (SOP), and obtain the maximum achievable secrecy transmission capacity. Analytical results show that cognitive interference is helpful to improve the secrecy connection performance satisfying the constraint that the average channel condition of primary networks is better than that of eavesdropping networks. Numerical results indicate that there is a tradeoff between the reliability and security in cognitive radio networks.