共查询到20条相似文献,搜索用时 218 毫秒
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针对以往的网络编码应用于无线通信系统中都是采用固定的中继转发方式,提出了一种新的协作机制:网络编码—增量中继。该方案的中继节点根据两用户直传路径的发送情况来决定是否需要转发:即当两用户发送数据的直传路径都成功或都发送失败时,中继节点不转发数据;当两用户发送数据的直传路径有一个成功、一个失败时,中继节点转发经过网络编码后的数据。经过仿真表明,采用该协作机制,在不影响系统性能的情况下大大节约了时隙、功率、带宽资源。 相似文献
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为了优化多中继协作通信系统的性能,提出了一种多中继混合转发协作传输策略(Multiple-Relay Hybrid-Forwarding Cooperative Transmission Scheme,MRHF-CTS)。该策略考虑多中继协作通信系统中的译码转发与放大转发以及两种转发方式带来的性能缺陷,根据协作中继节点接收信号的译码结果选择转发方式,同时引入协作中继节点之间数据来传输对系统性能的增益。对系统中断概率性能进行了推导与分析,结果表明,该策略在消除放大转发策略噪声累积的基础上,能够有效抑制协作中继节点错误检测译码转发给系统带来的不利影响,明显提升系统性能;在大信噪比情况下,可获得多中继译码转发协作通信系统的最佳性能。 相似文献
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针对传统三节点协作通信模型虽简单易行,但其中两阶段协作传输过程中中继节点通常无偿为源节点转发数据,存在频谱效率低的缺点,基于解码转发(decode and forward,DF)协作协议,以提高系统传输速率为目标,利用链路层控制信息的交换获得链路状态信息(channel statue information,CSI),提出一种基于叠加编码的协作通信机制。协作中,允许中继节点在转发源节点数据的同时,利用叠加编码进行自身数据的发送,通过灵活调整叠加编码时的功率分配,保证系统的传输速率。仿真结果表明,该机制能有效提高系统的传输速率。 相似文献
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为了提高多群多点广播中继网络系统的性能,提出一种改进的协作中继多点广播码分多址(CDMA)系统设计。该方案利用协作中继辅助的分布式波束形成 实现单天线基站多播,获得了较好的空间分集增益。在该系统中,多个基站利用多个中继节点向多个目的地的各个小组传播消息;利用CDMA技术来减少中继节点以及目的地节点的多址干扰(MAI)障碍,同时每个中继节点作为线性预编码波束合成器,可以在合适的代码空间重塑基站信号;对线性波束形成矩阵进行优化,使得中继节点的功率最小化,从而满足QoS在信号干扰噪声比方面的要求。系统性能仿真对比实验的结果表明,提出的改进方案明显优于传统的正交复用方案(FDMA / TDMA)。 相似文献
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为提升多用户中继系统的传输效率,提出一种基于分组压缩的协作中继技术(CRCP, Coopcrativc Relaying based on Compressed Packet)。中继节点对每个接收到的分组进行协作编码后发送,减少了分组传输时间,同时可获取分集增益,以降低无线信道衰落的影响。以两跳、多接入模型为例,分析了该技术的频谱效率。结果表明,在高信噪比区域,相对于传统中继方案,CROP的频谱效率提升了1/3;在中低信噪比区域,相比于非正交复数域网络编码方案,CROP的频谱效率显著提高。 相似文献
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The security issue is critically important for wireless communications, especially for multi-hop communications. In this paper, we propose a cooperative secrecy beamforming scheme for a multi-hop MIMO communication network, in which there is a single-antenna source, multiple multi-antenna relays and a singleantenna destination. Moreover, two types of eavesdroppers exist in the network, one of which has known channel state information (CSI), while the other not. To achieve security communications, in our work null-space beamforming and artificial noise beamforming are jointly optimized to improve the secrecy rate of the multi-hop network. In nature, the joint optimization is nonconvex and challenging. Exploiting its structure, the considered optimization problem is decoupled into a series of subproblems that can be efficiently solved based on convex optimization theory. Finally, some numerical experiment results are provided to assess the performance of the proposed secrecy beamforming design. 相似文献
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The explosive development of computational tools these days is threatening security of cryptographic algorithms, which are regarded as primary traditional methods for ensuring information security. The physical layer security approach is introduced as a method for both improving confidentiality of the secret key distribution in cryptography and enabling the data transmission without relaying on higher-layer encryption. In this paper, the cooperative jamming paradigm - one of the techniques used in the physical layer is studied and the resulting power allocation problem with the aim of maximizing the sum of secrecy rates subject to power constraints is formulated as a nonconvex optimization problem. The objective function is a so-called DC (Difference of Convex functions) function, and some constraints are coupling. We propose a new DC formulation and develop an efficient DCA (DC Algorithm) to deal with this nonconvex program. The DCA introduces the elegant concept of approximating the original nonconvex program by a sequence of convex ones: at each iteration of DCA requires solution of a convex subproblem. The main advantage of the proposed approach is that it leads to strongly convex quadratic subproblems with separate variables in the objective function, which can be tackled by both distributed and centralized methods. One of the major contributions of the paper is to develop a highly efficient distributed algorithm to solve the convex subproblem. We adopt the dual decomposition method that results in computing iteratively the projection of points onto a very simple structural set which can be determined by an inexpensive procedure. The numerical results show the efficiency and the superiority of the new DCA based algorithm compared with existing approaches. 相似文献
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针对中继协同无人机(UAV)辅助的无线通信网络,提出一种基于认知无线电网络(CRN)的物理层安全通信方案。利用二次发射机协同解码转发中继向目的接收机发送机密消息,将UAV用作移动干扰器发送干扰噪声,以降低窃听者的解码能力。在不影响主用户通信的前提下,通过联合优化UAV的飞行轨迹和发射功率提高系统的平均保密率,采用基于连续凸逼近的算法求解近似凸规划的保密率最大化问题。仿真结果表明,相较于优化功率和优化轨迹这两种传统方案,该方案能够进一步提高CRN系统通信的安全性。 相似文献
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In this paper, we investigate physical layer security for simultaneous wireless information and power transfer in amplify-and-forward relay networks. We propose a joint robust cooperative beamforming and artificial noise scheme for secure communication and efficient wireless energy transfer. Specifically, by treating the energy receiver as a potential eavesdropper and assuming that only imperfect channel state information can be obtained, we formulate an optimization problem to maximize the worst-case secrecy rate between the source and the legitimate information receiver under both the power constraint at the relays and the wireless power harvest constraint at the energy receiver. Since such a problem is non-convex and hard to tackle, we propose a two-level optimization approach which involves a one-dimensional search and semidefinite relaxation. Simulation results show that the proposed robust scheme achieves better worst-case secrecy rate performance than other schemes. 相似文献
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针对中继通信中的放大转发协议,提出了一个基于最佳中继选择方案的双跳认知协作通信系统。该系统的频谱共享环境由一个主接收用户,一个次级信源,[K]个次级中继和一个次级信宿组成。并在独立非同一分布的瑞利衰落环境下对该认知协作通信系统的中断性能进行了分析,推导出了中断概率的准确闭合表达式。利用蒙特卡罗仿真实验证实了分析结果的正确性。理论分析和仿真结果都表明,分析所运用的方法降低了系统的中断概率,提高了遍历容量,从而有效地改善了系统的性能。 相似文献
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本研究旨在探讨基于云边协同的数字电网通信信息网络安全策略。首先,通过大量文献分析、调查问卷等方法,确定了数字电网通信信息网络面临的主要安全威胁和保障需求。其次,在此基础上提出以云边协同为核心的网络安全保障策略,包括资源共享、实时监测、数据加密等多层次的解决方案。接着,我们从安全性、可靠性和易用性三个角度对该策略进行评价,并通过仿真实验验证了其有效性和可行性。最后,结论表明,基于云边协同的数字电网通信信息网络安全策略可以有效地提高数字电网的安全性和稳定性,具有很强的实际应用价值。 相似文献
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基于相关的瑞利衰落信道,研究安全协作系统的安全中断性能。假定发送端知道全部信道的信道状态信息,系统中存在单个窃听节点以及多个进行协作的中继节点,某个中继节点被选择作为干扰者来发送干扰信号,合法信道与干扰节点到目的节点的信道相关,窃听信道与干扰节点到窃听节点的信道也相关。在此类协作场景中,分析了信道相关性对安全协作系统安全性能的影响,获得了安全中断概率表达式。数值结果表明信道相关对安全协作系统的安全性能存在显著影响。 相似文献