Power allocation design and optimization for secure transmission in cognitive relay networks

In this paper, physical layer security is investigated in the dual‐hop amplify‐and‐forward cognitive relay network with one secondary source, one secondary destination, multiple cognitive relays under the presence of multiple primary receivers and eavesdroppers which can be either primary receivers or secondary receivers. The power allocation method at secondary source and artificial noise at relays are utilized to secure the secondary source‐destination transmission. Two optimization problems, namely, to maximize the received signal‐to‐interference‐and‐noise ratio of secondary source in the lightly‐loaded relay cluster situation, and to minimize the relay cluster total power in the fully‐loaded relay cluster situation, are formulated. In addition, these two problems should ensure both physical‐layer security and lower interference temperature. The semi‐definite relaxation technique is used to solve the considered optimization problems. In the second problems, we further optimize the performance with the help of the bisection method. Complexity analysis shows that our proposed method is efficient and also can be solved in polynomial time. Theoretical analysis and the Monte‐Carlo simulation results validate the proposed method. Copyright © 2016 John Wiley & Sons, Ltd. In this paper, physical layer security is investigated in the dual‐hop amplify‐and‐forward cognitive relay network. By considering the relay cluster load capacity, two optimization problems, namely, to maximize the secondary source received signal‐to‐interference‐and‐noise ratio in the lightly loaded situation and to minimize the relay cluster total power in the fully loaded situation, are formulated. The semi‐definite relaxation technique is used to solve the power allocation problems, and we further optimize the performance by the bisection method in the second situation.