自适应调制MIMO无线系统的物理层安全

Physical layer security of MIMO wireless systems with adaptive modulation

针对主动窃听场景下单输入单输出(single-input single-output,SISO)自适应调制频谱效率低和物理层安全(physical layersecurity,PLS)性能差的问题,提出了一种多输入多输出(multiple-input multiple-output,MIMO)安全自适应调制(secure adaptive modulation,SAM)无线系统PLS模型。其设计思路是:通过在发送端采用发送天线选择(transmit antenna selection,TAS)、在合法接收端采用最大比合并(maximal ratio combining,MRC)的天线分集技术来提高主信道的信噪比,以改善频谱效率;同时,限制主动窃听者的误比特率,使之无法解调出主信道发送的机密信息,从而保证合法接收端的PLS。在平均发射功率和PLS的联合约束下,推导SAM-MIMO系统的最佳切换门限和频谱效率以及窃听者的平均误比特率的解析表达式。数值计算与仿真结果表明:与SAM-SISO系统相比,采用TAS/MRC技术的SAM系统既可以提高主信道的频谱效率,又可以确保对主动窃听者的PLS。

To solve the problems of low spectral efficiency and poor performance of physical layer security(PLS)in single-input single-output(SISO)wireless systems with adaptive modulation in the presence of an active eavesdrop-per,multiple-input multiple-output(MIMO)wireless systems with secure adaptive modulation(SAM)were proposed.The design idea was to improve the spectral efficiency of the main channel by antenna diversity technology,which used the transmit antenna selection(TAS)at the transmitter and the maximal ratio combining(MRC)at the legitimate receiver to improve the signal-to-noise ratio.Simultaneously,the PLS of the legitimate receiver was guaranteed by limiting the bit error rate of the active eavesdropper so that it could not demodulate the confidential information from the main channel.With the joint constraints of the average transmission power and PLS,the optimal switching thre-sholds and the analytical expressions of spectral efficiency and the eavesdropper’s average bit error rate of the SAM-MIMO systems were derived.Numerical and simulation results show that SAM systems using TAS/MRC technology can not only improve the spectral efficiency of the main channel,but also ensure the PLS against the ac-tive eavesdropper,compared with the SAM-SISO systems.