Secure Transmission in Heterogeneous Networks: A Two-Level Stackelberg Game Approach.

In this paper, secure transmission in a two-tier heterogeneous network, consisting of a macrocell and a set of small cells, is considered, where an eavesdropper attempts to wiretap legitimate macrocell users. A game-theoretic framework is proposed to enhance the security of the macrocell while guaranteeing user satisfaction of the small cells. Specifically, a two-level Stackelberg game is formulated, where the macro base station as a follower employs multiple small base stations (SBSs) to jam the eavesdropper at the top level, and each employed SBS as a leader requires offloading service from multiple helping SBSs in its cluster at the bottom level if needed. Two types of objectives are investigated at the bottom level, one with the priority given to user satisfaction over the leader's profit, and the other to balance between user satisfaction and the leader's profit, respectively. The Stackelberg equilibrium of the proposed game is also derived. Numerical results verify the analysis and show that employing the existing SBSs is a promising approach to enhancing security while satisfying the user demands of the small cells.