Legitimate Eavesdropping in Two-Way AF Relay Networks
Guojie Hu, Yueming Cai
Abstract
This letter considers a legitimate surveillance scenario, where two suspicious nodes intend to exchange their information via one suspicious amplify-and-forward relay in two phases, the process of which is under the supervision of one legitimate monitor. To achieve the effective surveillance, one novel eavesdropping strategy is designed, in which the monitor proceeds passive eavesdropping in phase 1 and then implements passive eavesdropping or simultaneous assisting and jamming in general in phase 2. Under this setup, the monitor mainly aims to design the optimal structure of the transmit signal for each specific strategy in phase 2 and then optimize the corresponding beamformers and power allocation, in order to maximize the obtained sum eavesdropping rate subject to its power constraints. Simulation results verify that, compared to the conventional schemes, the proposed adaptive eavesdropping strategy achieves significant performance gains.