Robust Physical Layer Security Using Frequency Diverse Array Directional Modulation

Parallel to the rapid development of modern wireless communication technologies, the security and reliability of these systems have always been a major challenge in their design. Physical layer security is an effective solution for ensuring security in telecommunications systems, which has gained significant attention in recent years. In physical layer security based on frequency diverse array directional modulation, the beam of the transmitted signal depends on both angle and distance, in a way that the modulation scheme can only be properly received within a small range around the legitimate receiver and is intentionally degraded in other directions. While the effectiveness of this method is acceptable when accurate information about the position of the legitimate receiver is available, it suffers from a severe performance degradation in the presence of positioning estimation errors, which are highly probable in cellular wireless networks. In this paper, a novel solution against positioning estimation errors is proposed to improve the performance of physical layer security by enhancing the secrecy rate of the system. Numerical simulations demonstrate the desirable performance of this method in robustness of the secrecy rate degradation against positioning estimation errors in the legitimate receiver so that the secrecy rate is improved up to one 1 bit per second per Hertz compared to the non-robust method.