A Hierarchical Game for Physical Layer Security Aware Cooperative Communications with Dynamic Interchangeable Relaying and Jamming

This paper investigates a dynamic game framework for physical layer security (PLS)-aware wireless network with third-party collaborative users (TCUs). In the considered system, legitimate users (LUs) aim to transmit secret signals under the threat of eavesdroppers (EVs). There exists TCUs rationally selecting to form coalitions with LUs or EVs, strategically enhancing the secrecy transmission rates for LUs or increasing eavesdropping rates for EVs to obtain rewards. Due to the unpredictability of wireless systems (e.g., time-varying channel conditions, user mobility), coalitions among the three parties may be unfixed and dynamically changing. A hierarchical game integrating a matching subgame with a coalition formation subgame is formulated to model the interactions among LUs, EVs, and TCUs. In order to derive the optimal long-term strategies while solving the equilibrium of the hierarchical game, we first introduce a constrained Gale-Shapley algorithm which determines the optimal power, mode, and channel selections of TCUs with the known coalition partition, and then propose a coalition selection algorithm for reaching the stability of coalition partitions. Moreover, we develop a deep reinforcement learning (DRL)-based solution to concatenate the aforementioned algorithms, producing the long-term optimal strategies for LUs, EVs and TCUs over multiple time slots. Simulations evaluate the performance of the proposed scheme, and demonstrate its superiority over counterparts.