A multicarrier-based physical layer security scheme for the multicast systems

Traditional physical layer security methods, such as artificial noise, commonly require that the sender has more antennas than that of the receivers, which is not practical in the multicasting system. To solve this problem, a multicarrier-based physical layer security scheme for the multicast systems is proposed, which takes the advantage of both space and frequency domain to form a relatively virtual multi-antenna system. Through subcarrier allocation the existence of null space in every subcarrier channel matrix is guaranteed, so that the artificial noise can be added to ensure a secure communication. Based on the Kuhn-Tucher condition, an optimal power allocation method is also proposed to maximize the security rates under the restriction of total power. Simulation results indicate that this scheme is unlimited by the amount of the sender antennas, and it improves the security rates by 2 bit/s/Hz than the average power allocation method.