Optimal Power Allocation for Secrecy Rate Maximization in Broadcast Wiretap Channels

We investigate physical layer security in wireless communication networks, where a transmitter Alice sends a confidential message to an intended user Bob, while coexisting with a normal transmitter DT, a normal receiver DR, and a passive eavesdropper Eve. Compared with the conventional cooperative jamming (CJ) scheme, DT has dual responsibilities. One is to broadcast public information to its service subscriber DR, and the other is to confound the unauthorized eavesdropper Eve to ensure desired secure communication. Considering the secrecy outage restriction of Bob and the quality of service demand of DR, we propose an optimal resource management strategy. Users with different security requirements take hierarchical secure measures. For example, banking transaction needs to adopt high strength security measures, and personal voice communication resorts to low-level security protection strategies. Numerical simulations show that the proposed secure design outperforms the CJ scheme in terms of effective service rate and effective energy efficiency with a little secrecy rate loss, which is suitable for the low-level security real-time communication.