Robust Secure Transmission of Using Main-Lobe-Integration-Based Leakage Beamforming in Directional Modulation MU-MIMO Systems

摘要

In the paper, we make an investigation of robust beamforming for securedirectional modulation in the multi-user multiple-input and multiple output(MU-MIMO) systems in the presence of direction angle measurement errors. Whenstatistical knowledge of direction angle measurement errors is unavailable, anovel robust beamforming scheme of combining main-lobe-integration (MLI) andleakage is proposed to simultaneously transmit multiple different independentparallel confidential message streams to the associated multiple distinctdesired users. The proposed scheme includes two steps: designing thebeamforming vectors of the useful confidential messages and constructingartificial noise (AN) projection matrix. Here, in its first step, thebeamforming vectors for the useful confidential messages of desired user k aregiven by minimizing the useful signal power leakage from main-lobe of desireduser k to the sum of main-lobes of the remaining desired directions plusmain-lobes of all eavesdropper directions. In its second step, the ANprojection matrix is constructed by simultaneously maximizing the AN powerleakage to all eavesdropper directions such that all eavesdroppers aredisrupted seriously, where AN is viewed by the transmitter as a useful signalfor eavedroppers. Due to independent beamforming vectors for different desiredusers, a more secure transmission is achieved. Compared with conventionalnon-robust methods, the proposed method can provide a significant improvementin bit error rate along the desired directions and secrecy-sum-rate towardsmultiple desired users without needing statistical property or distribution ofangle measurement errors.