中文摘要：

为提升存在窃听者的中继网络的安全性能,在多天线放大转发中继端采用人工噪声预编码（ANP）和特征波束形成（EB）安全传输策略,推导了ANP和EB的可达安全速率（EASR）闭合表达式。在中继配置大规模天线时,推导了ANP的EASR下界,并在高信噪比和低信噪比情况下研究了渐近性能。分析和仿真结果显示,在中高信噪比区域,ANP相比于EB可获得显著的性能增益,而在低信噪比区域,EB优于ANP。当信噪比增加时,EB的EASR接近一个与第1跳无关的常数。在高信噪比区域,ANP的最优功率分配方案是将一半左右的功率分配给人工噪声。

英文摘要：

To improve the secrecy performance of relay networks in the presence of one eavesdropper, the Artificial Noise Precoding （ANP） and Eigen-Beamforming （EB） secure transmission schemes are appilied at the multiple-antenna amplify-and-forward relay, and the new tight closed-form expressions of the Ergodic Achievable Secrecy Rate （EASR） for two schemes are derived. The lower bound of the EASR for ANP is derived with a large antenna array at the relay, and its corresponding asymptotic performance is investigated in the high SNR and low SNR regimes to show valuable intrinsic insights. Analysis and Simulation results show that, in the moderate-to-high SNR regime, ANP achieves remarkable performance gain over EB, while in the low SNR regime, EB outperforms ANP. Moreover, in the high SNR regime, it is optimal to allocate around half of total power to artificial noise for ANP.