中文摘要：

中继系统可以增强物理层安全算法的系统性能,这种系统一般包含两阶段的通信过程：从信源到中继节点,在从中继节点到目的节点.通常来说,第一阶段的信息传输缺乏保护,如果窃听者距离信源节点比较近的话,系统性能就无法保证了.该文提出了一种基于混合信号的三阶段的传输方法确保整个传输过程中的保密性能,这样,当窃听者接近信源节点的时候,仍可以保证系统的安全性能.这种方法的优化解是一个复杂的非凸优化问题,该文中建议了一种低复杂度的次优解来解决其中的优化问题.理论分析以及方针结果证明,该方法可以有效确保系统的全过程的安全性能.

英文摘要：

Relay system can improve the secrecy of a wireless communication with physical layer security algorithms.Most of these algorithms include two stages： during the first stage,the source node sends coded messages to the relays,and during the second stage,the relays forward the received messages to the destination node. Usually,there is no protection during the first stage,thus most of the secrecy analysis is based on the assumption that there is no direct channel between the source and the eavesdropper. In a practical system,when the eavesdropper is located near the source,the secrecy rate of all these algorithms is down to zero. In this paper,a novel three-stage algorithm with hybrid signals is proposed,which can offer full protection on a relay system. The algorithm results in a non-convex optimal problem,and a sub-optimal solution with lowcomputational complexity is proposed. The theoretical analysis and simulation results showthat the proposed scheme can achieve much better secrecy performance than traditional algorithms when the eavesdropper is near the source node.