Improving secrecy rate via spectrum leasing for cooperative secondary users

In cognitive radio networks, security against eavesdroppers is a critical issue. In this paper, we consider a scenario in which the primary transmitter selects one secondary transmitter to act as a relay to enhance the security of communication. And as a reward the primary transmitter allows the selected secondary transmitter to access its spectrum. We first formulate the problem as a stackelberg game with the primary transmitter and the selected secondary transmitter as the leader and the follower respectively. Next a two-level game is employed to model the interaction between the primary transmitter and secondary transmitters in which the outer framework is based on the Stackelberg game and auction theory is exploited to model the competition of secondary transmitters. Numerical results show that the proposed schemes not only improve the primary transmitter's security but also help the selected secondary transmitter maximize its own utility.