【作者】 张立；

【导师】 付晓梅；

【作者基本信息】 天津大学 ， 通信与信息系统， 2012， 硕士

【摘要】 协作通信与信息安全是无线通信领域中的两个研究热点。在协作通信中,多个节点之间相互转发信息,共享彼此天线资源,从而在空间上形成一个分布式的虚拟MIMO系统,获得分集增益。在信息安全研究中,主要以Wyner窃听信道模型为代表,研究窃听节点对系统安全性的影响以及安全容量存在的必要条件,通常是要求主信道条件优于窃听信道条件。这种信道制约条件给物理层安全的研究带来了一定的局限性。协作与安全的结合点在于:一方面,协作促进了传输的有效性和可靠性,是否增强安全性有待研究;另一方面,协作涉及到非自身信息的转发,是否带来信息泄露,同样值得关注。本文从信息论的角度出发,将协作通信与物理层安全两个概念联系在一起,旨在探讨两者之间的相互作用关系。文章通过在Wyner窃听信道模型中引入协作中继节点,建立了协作与安全的组合模型。根据中继行为特征,将此模型分为两大类:基于可信任协作中继的外来窃听模型和基于不可信协作中继的内在窃听模型。在可信中继外来窃听模型中,给出了AF和DF协作下的安全性能分析。在不可信中继内在窃听模型中,讨论了准静态瑞利衰落环境下系统中断概率和中断安全容量的相互作用关系,以及信噪比和节点位置等因素对中断概率带来的影响,和Wyner窃听信道模型相比,中断阈值由1/2降到1/3。最后,对于上述两类模型,分别进行了基于安全容量最大化的最优功率分配。Matlab仿真结果论证了一定条件下协作对安全的促进作用,以及最优功率分配方案的有效性。更多还原

【Abstract】 Cooperation and information security are two hot issues in the area of wireless communication. In cooperative communications, multiple users share the antenna resources by forwarding each other’s information and then form a spatially distributed virtual MIMO system. For the research on information security, the impact of the eavesdropper on system security and the channel security constraints based on the wiretap channel model are investigated, where the signal-to-noise ratio(SNR) of the main channel is required to be greater than that of the eavesdropper’s channel.The combination of cooperation and security is: on the one hand, cooperation can enhance the efficiency and reliability of the transmission, whether it is conducive to security performance is what we should think; on the other hand, informations which are not related to the transmitter itself, needs to be forwarded, and this may result in the information disclosure. From the viewpoint of the information theory, this paper discussed the interrelationship between these two conceptions.According to the characteristics of the relay’s behavior, cooperative security model was divided into two categories: external eavesdropper model based on a trusted cooperative relay and internal eavesdropper model based on an untrusted cooperative relay. In the external eavesdropper model, security performance of AF and DF cooperation was investigated. In the internal eavesdropper model, security performance of AF cooperation with an untrusted relay under a quasi-static fading channel is considered. Relationship between outage probability and outage secrecy capacity is discussed and the influence of SNR and the nodes location on the outage probability is investigated. Simulation results show that the untrusted relay’s cooperation decreases the outage probability from 1/2 to 1/3 and achieves a higher outage secrecy capacity. Finally, optimum power allocations for these two models based on the security capacity maximization are formulated. Simulation results demonstrate the improvements of cooperation to the security and the efficiency of the optimum power allocations.更多还原