Physical-layer security has become a critical technique in current wireless networks.The existing conventional physical layer security techniques,e.g. artificial-noise-aided transmit beamforming,do not apply well to multicast transmission from large multicast user and eavesdropper user numbers.To address this problem,an enhanced secure multicast algorithm based on user clustering scheme was proposed.Firstly,the multicast users with close channel vectors were divided into a cluster and different clusters were served on different channels.Secondly,a heuristic joint power allocation and beamforming design algorithm based on this user clustering scheme were proposed to maximize the globally achievable secure multicast rate.Finally,to reduce the overall computation complexity,the new searching method was put forward to solve power allocation and beamforming design jointly.Simulation results showed that the enhanced secure multicast algorithm can support a much higher secure transmission rate than conventional secure multicast (CSM) schemes,and the proposed joint power allocation and beamforming design algorithm outperform existing CSM schemes with the ergodic searching method greatly in terms of computation complexity.
