Beside of cryptography-the primary traditional methods for ensuring information security and confidentiality, the appearance of the physical layer security approach plays an important role for not only enabling the data transmission confidentially without relying on higher-layer encryption, but also enhancing confidentiality of the secret key distribution in cryptography. Many techniques are employed in physical layers to improve secure transmission including cooperative relaying and beamforming technique. In this paper, we consider the secrecy rate maximization problems using two techniques mentioned above with two different relaying protocols: Amplify-and-Forward and Decode-and-Forward. The optimization problems with the aim of maximizing secrecy rate subject to total and individual relay power constraints are formulated as nonconvex problems, which can be reformulated as DC (difference of two convex functions) programs and thus can be solved by DC Algorithms (DCA). The special structure of feasible set is exploited which results to an efficient DC decomposition in the sense that it leads to convex subproblems that can be explicitly solved. The numerical results show that the proposed DCA schemes are better than the existing methods in terms of both runtime and secrecy rate.

除了用于确保信息安全性和机密性的主要传统方法-密码学之外，物理层安全性方法的出现还起着重要作用，不仅可以使机密数据传输不依赖高层加密，而且还可以提高机密性。密码学中的密钥分配。在物理层中采用了许多技术来改善安全传输，包括协作中继和波束成形技术。在本文中，我们使用上述两种技术以及两种不同的中继协议（放大转发和解码转发）来考虑保密率最大化问题。以总和个别继电器功率约束为前提的最大化保密率为目标的优化问题被表述为非凸问题，可以将其重新格式化为DC（两个凸函数的差）程序，因此可以通过DC算法（DCA）解决。利用可行集的特殊结构，可以导致有效的DC分解，因为它会导致可以明确解决的凸子问题。数值结果表明，所提出的DCA方案在运行时间和保密率方面均优于现有方法。