In this paper, secure transmission with simultaneous information and energy multicast in the presence of multiparty eavesdropper (EVE) collusion is investigated. In the considered system, legal users simultaneously decode information and harvest energy through dynamic power splitting (PS), whereas EVEs form multiple eavesdropping-collusion parties to cooperatively decode signals. A novel optimization problem is formulated to maximize the overall achievable secure multicast capacity while satisfying the maximum transmit power constraint at the transmitter, guaranteeing the minimum harvested energy requirements at each legal user and restricting the wiretapping capability of each EVE party. Since the formulated problem is nonconvex and hence difficult to solve, it is decomposed into a power minimization subproblem and a rate optimization subproblem and then solved in a nested manner. By leveraging the properties of the objective function, it is proved that through the proposed algorithm the optimal secure multicast capacity can be achieved, with the optimal transmission strategy, i.e., optimal beamforming matrix, optimal artificial noise (AN) covariance matrix, and optimal PS factors, obtained. Moreover, the case of imperfect channel state information (CSI) is considered in which a robust secure multicast scheme is designed by considering the channel uncertainty of EVEs and maximizing the worst-case achievable secure capacity. Simulation results confirm the optimality of the proposed algorithm, show its capability of adapting to the dynamic joining and departure of multicast users and EVE parties, and verify its superiority over existing schemes for both the perfect CSI and imperfect CSI cases.
['Wenjun Xu', 'Shengyu Li', 'Chia-Han Lee', 'Zhiyong Feng', 'Jiaru Lin']
Optimal Secure Multicast With Simultaneous Wireless Information and Power Transfer in Presence of Multiparty Eavesdropper Collusion