Adaptive Robust Null-Space Projection Beamforming Scheme for Secure Wireless Transmission with AN-aided Directional Modulation
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In this paper, an adaptive robust secure null-space projection (NSP) synthesis scheme is proposed for wireless transmission networks with artificial noise (AN) aided directional modulation (DM). This scheme is composed of three steps: direction of arrival (DOA) and signal-to-noise ratio (SNR) estimation, prediction of error range, and robust secure beamforming. In the first step, the direction angles of desired user and eavesdropping user are found by the Root-MUSIC algorithm, and their SNRs are estimated by the ratio of the corresponding eigenvalue to minimum eigenvalue. Then, by using the estimated DOA and SNR, the error range is predicted. Finally, those estimated parameters are used to design the robust secure NSP beamforming DM system. Simulation results show that the proposed adaptive robust NSP method performs much better than conventional non-adaptive robust scheme and unrobust NSP one in terms of bit error rate (BER) and secrecy rate (SR). Especially, the BER and SR performance gains of the proposed adaptive robust NSP over conventional methods increase gradually as the DOA error range increases.
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