Frequency diverse array- (FDA-) based directional modulation (DM) is a promising technique for physical layer security, due to\nits angle-range dependent transmit beampattern. However, the existing schemes are not suitable for the broadcasting scenario,\nwhere there are multiple legitimate users (LUs) to receive the confidential message. In this paper, we propose a novel random\nfrequency diverse array- (RFDA-) based DM scheme to realize the point to multi-point broadcasting secure transmission in both\nangle and range dimension. In the first stage, the beamforming vector is designed to maximize the artificial noise (AN) power,\nwhile satisfying the power requirement of LUs for transmitting the confidential message simultaneously. In the second stage, the\nAN projection matrix is obtained by maximizing signal-to-interference-plus-noise ratio (SINR) at the LUs. The proposed scheme\nonly broadcasts the confidential message to the locations of LUs while the other regions are covered by AN, which promotes the\nsecurity of the wireless broadcasting system. Moreover, it is energy efficient since the power of each LU is under accurate control.\nNumerical simulations are presented to validate the performance of the proposed scheme.
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