Secure Transmission Aided by Orbital Angular Momentum Jamming with Imperfect CSI

In order to deal with the power leakage of side lobes in physical layer security, this paper investigates a secure transmission system aided by Orbital Angular Momentum (OAM) jamming. The receiver, located at the center of the beam, remains unaffected due to the power null of OAM radio wave. Based on its distinctive power null, a secure transmission system with imperfect Channel State Information (CSI) and random eavesdroppers is proposed in this paper. To be specific, the artificial noise and the desired information signal are transmitted by the radio wave with OAM and without OAM respectively. Meanwhile, a power allocation optimization algorithm is designed to acquire the target secrecy capacity. Simulations are implemented to evaluate the effectiveness of the proposed algorithm compared with other methods. Furthermore, we find that there is a secrecy capacity upper bound in the presence of imperfect angle measurement and random eavesdroppers. Moreover, the proposed power allocation algorithm leads to a higher secrecy capacity upper bound.