Secrecy capacity in two-way energy harvesting relay networks with a friendly jammer

This paper considers secure two-way relay communications in the presence of an eavesdropper. Two users without a direct link between them communicate via an energy harvesting two-way relay. A friendly jammer is employed to reduce information leakage to the eavesdropper. The relay relies on the signals received to harvest energy and forward signals to the users. The power splitting factor and transmit power at the users and jammer are jointly optimized using geometric programming to maximize the secrecy capacity of the system. The imperfect cancellation of the jamming signal is interpreted as noise at the users which decreases the secrecy capacity. Further, it is shown that the secrecy capacity with a jammer is greater than without a jammer. The effect of the relay, jammer, and eavesdropper locations on the performance is studied. It is shown that the secrecy capacity is greater when the relay is equidistant from the users. In addition, having the jammer closer to the eavesdropper results in a higher secrecy capacity.