中文摘要：

当采用空域加扰实现物理层安全时，构造的多天线加权向量在合法信道上的投影具有恒模特性，窃听者能够利用这一特性截获私密信息。针对这一问题，该文设计了一种基于空频联合加扰的物理层安全算法。首先，在各个子载波上构造多天线随机加权向量，使构造的加权向量在合法信道上的投影均等于随OFDM符号快变的参考变量；然后，通过参考子载波的加权向量传递参考信息使得合法用户能够正确解调其余子载波的接收信号；而窃听者无法获得有用参考信息，从而无法解调接收信号。仿真结果表明当信噪比（SNR）达到10 dB时，合法用户的解调误比特率（BER）为510-，而窃听者无法利用盲均衡、类MUSIC等方法截获私密信息。

英文摘要：

The projection of multi-antenna weighted vector structured with spatial scrambling is of constant modulus on the legitimate channel. Eavesdropper can take the advantage of multi-antenna to intercept private information. To solve this issue, a kind of physical-layer security algorithm is designed based on the joint scrambling with spatial and frequency resource. Firstly, random multi-antenna weighted vector is constructed in each subcarrier, and the vectors projection on the legitimate channel is equal to a reference variable that changes randomly in each OFDM symbol. Secondly, the weighted vector delivering the reference variable is transmitted in the reference subcarrier, with which the legitimate user can correctly demodulate the remaining subcarriers. Whereas, eavesdropper can not obtain the useful information because of the nature difference between the legitimate channel and eavesdropper channel. The simulation results show that, when SNR achieves 10 dB, the legitimate user＇s Bit Eerror Rate （BER） is 510- , the eavesdropper can not intercept the private information using blind equalization or MUSIC-like method.