多天线中继系统中人工噪声辅助的安全波束成形

Artificial noise aided secure beamforming for multi-antenna relay systems

针对放大转发中继系统中转发信息易被窃听者截获的问题,提出了在中继节点处采用人工噪声辅助的安全波束成形方法。该方法以系统的安全速率最大化(SRM,secrecy rate maximization)为目标,在中继节点的总功率和单个天线功率受限情况下,联合设计最优的中继波束成形矩阵和人工噪声协方差矩阵。由于该SRM问题非凸,设计了双层优化算法,其中采用一维搜索解决外层优化问题,采用半定松弛及内点法解决内层优化问题。理论推导证明,内层优化问题总存在秩为1的最优解,即所采用的松弛技术是紧的。仿真结果表明所提的方法可以显著提高系统的安全性能。

In the amplify-and-forward （AF） relay systems, the confidential information forwarded by the relay can be in- tercepted by the eavesdroppers. For guaranteeing the secure communications, an artificial noise aided secure beamform- ing method is proposed. The goal is to maximize the secrecy rate of the system by jointly designing the beamforming ma- trix and the artificial noise （AN） covariance matrix at the relay subject to the total power and the per-antenna power con- straints. This non-convex secrecy rate maximization （SRM） problem can be recast as a two-level optimization problem. The outer part can be solved by performing a one-dimensional search, and the inner part can be handled by the semidefinite relaxation （SDR） technique and interior-point methods. It is shown that there always exists a rank-one optimal solution for the SDR problem, i.e., the relaxation is tight to the original problem. Simulation results demonstrate that the proposed method can improve the security performance of the system significantly.