无线网状网与协作中继技术

无线网状网已经成为无线宽带通信领域的研究热点,但是基于交换技术的无线网状网因为其将整个网络看作是一个IP子网而无法适用于大范围的覆盖。在无线链路中采用协作中继,可以提高无线链路的传输速率及传输可靠性。同时采用基于网络层路由技术的无线网状网技术,可以实现整个无线网状网的频谱效率提升和厂域覆盖。不过,由于标准化、关键技术研究以及产业化推进方面还存在许多问题,使得协作中继技术在无线网状网中的应用面临着巨大挑战。     

无线网状网中基于干扰模型的多信道分配策略

为解决信道干扰导致无线网状网吞吐量下降的问题,本文提出一种新的基于干扰模型的多信道分配策略.首先对网络进行分层,然后按照优先级逐层进行信道分配,通过降低信道间的干扰来提高每个结点的吞吐量,进而提高整个网络的吞吐量.仿真结果表明了该策略的有效性.     

全双工窃听者主动干扰的协作NOMA网络性能分析

研究了瑞利衰落信道下协作非正交多址系统的安全性能。通信过程由一个时隙构成,源节点向中继广播叠加信号,全双工中继使用串行干扰消除技术解码信号协助用户通信。假设存在潜在全双工主动窃听者,窃听者能够从中继处截获信息并同时向用户发送人工噪声进行干扰。基于上述假设,在高信噪比条件下,推导了安全中断概率的近似表达式,分析了各节点传输信噪比与功率分配因子对系统中断概率的影响,分析结果与蒙特卡洛仿真结果吻合。     

自适应窃听下NOMA用户协作干扰的物理层安全研究

在存在一个半双工自适应窃听者的通信模型中,分析了采用非正交多址(Non-orthogonal Multiple Access,NOMA)技术合作系统的性能。提出了一种新型的合作NOMA方案,该方案在中继转发时,强用户可充当中继协助转发弱用户信号,而弱用户采用全双工技术向窃听者发送干扰信号,提高了通信链路的安全性和用户的服务质量。合法接收端采用连续干扰消除(SIC)技术,以解码来自叠加信号的各个消息。在已知窃听信道统计信道状态信息(CSI)的情况下,分别推导了2个用户的安全中断概率和中断概率的闭合表达式,并通过Monte-Carlo仿真验证。理论分析和数值模拟结果均表明所提出的NOMA用户合作方案在保密率方面优于非合作方案的性能。     

无线传感网物理层协作分集的性能分析

该文针对无线传感网中的远距传输问题,研究了一种无需网络同步和正交信道的协作分集方法的性能,给出了在两种典型信道中当解码转发存在误差传播时远程目的节点的误码率及分集指数;分析了当转发节点间为白高斯信道时增加协作节点数能够提高目的节点性能的条件。研究结果表明,当转发节点间为白高斯信道时,只要转发节点处于正常工作点,增加节点数就能提高目的节点的性能;当转发节点间为瑞利平衰落信道时,只有当转发节点处于一定位置时,协作分集相对于直接发送或传统空间分集才有性能增益;当转发节点间为瑞利平衰落信道时增加跳数性能更好,为白高斯信道时增加分支数更有效;当转发节点间为瑞利平衰落信道时,误差传播将使目的节点的分集指数为1,但在较低信噪比条件下对分集性能影响很小。     

协作SWIPT-NOMA系统的物理层安全性研究

针对协作非正交多址接入(Non-orthogonal Multiple Access,NOMA)系统中用户充当中继并存在窃听者的场景,提出了一种新型协作干扰传输方案,以提高该系统的安全性.在第一时隙,基站将混合信号进行广播,同时为了干扰窃听者,信道条件较差的用户采用全双工的工作模式,发出协作干扰信号对窃听者进行干扰.在...     

NOMA系统中基于协作干扰的物理层安全方案

针对NOMA系统中的信息安全传输问题,提出基于协作干扰的物理层安全方案,该方案利用外部协作节点发送干扰信号恶化窃听者的接收性能。本文首先利用泊松点过程对协作节点和窃听者的位置进行安全建模,然后推导了随机协作干扰方案下系统保密中断概率的闭式解,但随机协作干扰方案会同时恶化合法用户的接收信号,性能有限,因此提出一种信道增益受限的协作干扰方案,该方案选择到近端用户和远端用户的瑞利信道因子均小于一定阈值的协作节点发送干扰信号,会对窃听者造成更严重的影响。仿真结果表明,在NOMA系统中采用受限的协作干扰方案能够有效提升系统安全性能。      

非理想干扰删除下全双工中继NOMA系统的物理层安全性能研究

全双工协作中继转发信号时存在的自干扰现象会降低系统性能.本文考虑存在窃听者的下行非理想自干扰全双工协作中继非正交多址接入（NFCR-E-NOMA,Non-ideal Full Duplex Cooperative Relay in Non-Orthogonal Multiple Access system with Eavesdropper）系统,分别从系统中断概率和系统截获概率的角度分析了全双工协作中继的自干扰因素对于NFCR-E-NOMA系统安全中断性能的影响;推导了系统中断概率和截获概率的闭合表达式.仿真结果表明,全双工中继转发的自干扰因素对系统性能的影响较大,在NFCR-E-NOMA系统中,存在优化的中继转发功率,且在不同的基站发射功率和中继转发功率条件下,功率分配比对系统性能的影响也不同,在实际主链路信道条件允许的情况下,可通过设置较高的数据传输速率来抑制窃听者的截获概率.     

新型宽带无线网络技术——无线网状网

无线网状网技术是一种具有良好市场应用前景的新型宽带无线网络技术.本文首先简要介绍了无线网状网的产生和发展,然后针对无线网状网的定义、特点、应用以及影响网络性能的关键因素等最核心的几个问题,进行了初步的探讨和总结.     

无线网状网技术分析

无线网状网是一种全新的无线接入技术。也是一种全新的增强型体系结构。它结合了无线和有线解决方案的最佳性能特点，可以为企业和公众终端用户提供可靠的无线接入。解决方案引入了对等网状拓扑的概念。可实现接入点之间的无线通信。这个概念解决了当今面临的许多部署问题。比如进行广泛的以太网布线。支持新的部署模式等。本文介绍了无线网状网的核心技术、安全性能、网络性能等及其与无线接入同类技术的比较。     

Physical layer security performance analysis of multi-antenna full-duplex relay aided heterogeneous cellular network

To alleviate the spectrum shortage problem and security threats in heterogeneous network (HetNet),multi-antenna full-duplex relay was introduced for communication between femto base station (FBS) and legitimate user.With the aid of multi-antenna full-duplex relay in FBS network,the secrecy performance of HetNets could be improved.Under a stochastic geometry framework,the fundamental analysis model to evaluate the secrecy performance in multi-antenna full-duplex relay aided HetNet was set up.To be specific,the exact expressions for the secrecy outage probability of the typical user,serving relays and HetNet were derived respectively.Then,based on the theoretical analyses and simulation results,the influences of transmit power and antenna number of both macro base station and FBS on secrecy performance in HetNet were examined.Finally,the results show that introducing multi-antenna full-duplex relay for FBS networks improves the secrecy performance of HetNet.     

过时CSI下全双工中继辅助D2D网络的物理层安全

中继辅助终端直通（devicetodevice,D2D）网络通过与蜂窝网络共享频谱提高D2D用户的频谱效率和蜂窝用户（cellular user,CU）的物理层安全性。为进一步改善其性能,可以在基站和D2D链路的中继节点采用天线选择以及在中继节点采用全双工技术。然而,由于存在反馈时延和移动性,用于蜂窝链路和所有D2D链路天线选择的信道状态信息（channelstateinformation,CSI）均可能是过时的,针对该场景下的物理层安全性和可靠性问题,提出一种主动窃听和过时CSI场景下基站和中继节点均采用发射天线选择的全双工中继辅助D2D网络安全模型,推导CU的中断概率、遍历容量、非零安全容量概率、安全中断概率、渐近安全中断概率的解析表达式。数值计算与仿真结果均表明,基站发射天线数、中继干扰天线数越多,CU的安全性能越好;过时的CSI会降低CU的中断性能和安全性能。     

Asymptotic performance analysis of untrusted relay system with full-duplex jamming destination

The cooperative relay technique in the field of physical layer security is widely concerned by the academic community,due to the advantages of increasing the network capacity and expanding the network coverage.However,cooperative relays may play as untrusted nodes in some certain circumstances.Based on this,to enhance the secrecy performance of untrusted relay systems,a novel full-duplex destination jamming (FDJ) scheme was proposed in the Rayleigh fading channel.In order to maximize the system’s secrecy capacity,a switchable split-optimal antenna selection (OAS) scheme was proposed for a multiple-antenna destination,the power allocation optimization scheme between the source and destination was designed,and the corresponding closed-form expressions of secrecy performance were given.In the large-scale antennas analysis,the closed-form expressions of the ergodic achievable secrecy rate and the optimal power allocation factor of instantaneous secrecy capacity for the FDJ-OAS scheme were derived.Furthermore,based on different asymptotic cases,the asymptotic analyses of secrecy outage probability for the FDJ-OAS scheme were significantly analyzed.Simulation results show that the analytical curves match well with the Monte-Carlo simulation results.It is concluded that the diversity order of the FDJ-OAS scheme is proportional to the number of antennas and antenna diversity can be achieved,which reveals the advantages of the proposed FDJ-OAS scheme.     

无线mesh网络安全研究

无线mesh网络（wireless mesh networks,WMN）是下一代网络中的新型技术,和传统网络不同,它不依赖任何固定的设施,主机可以相互依赖保持网络连接,WISP可以利用它提供快速、简单、低廉的网络部署,然而存在一个主要的问题是容易遭受攻击。介绍了无线mesh网络的体系机构以及特点,分析并研究其存在的安全性威胁以及现有的关键安全解决机制。     

NOMA-D2D协作无线系统的物理层安全

针对未来海量用户设备接入的物理层安全（physical layer security，PLS）应用需求，提出了一种组合非正交多址接入（non-orthogonal multiple access，NOMA）、终端直通（device-to-device，D2D）与中继协作的NOMA-D2D协作无线系统PLS模型。该模型由采用发射天线选择（transmit antenna selection，TAS）的基站、分别作为基站和D2D发射端的NOMA远端蜂窝用户、D2D接收端以及被动窃听者组成，其中的D2D发射端承担基站的 NOMA 近端用户和解码转发中继两种角色。利用高斯—切比雪夫正交定理推导两种 TAS 方案下NOMA-D2D协作无线系统的安全中断概率、非零安全容量概率以及渐近安全中断概率的近似表达式。数值计算和仿真实验验证了NOMA-D2D协作无线系统PLS性能分析的准确性；在基站总功率恒定时增大分配给远端蜂窝用户的功率能有效提升NOMA-D2D协作无线系统的PLS性能。     

分布式多网关无线mesh网公平协作路由算法

现有的协作路由协议不能公平地分配无线网络资源,无法满足网络最小流的吞吐量需求。将多并发流的协作路由问题形式化成一个最大化网络整体效用的凸优化问题,并基于对偶分解和子梯度,提出一种分布式的多网关无线mesh网公平协作路由算法FCRMG。实验结果表明,与基于期望传输时间的非协作路由和基于竞争感知的协作路由相比,FCRMG算法在保证网络吞吐量的前提下,能显著提高最小业务流的吞吐量。     

A cross‐layer TCP for providing fairness in wireless mesh networks

The fair allocation of resources among different nodes is one of the critical problems in wireless mesh networks. Existing solutions mainly focus on rate‐limitation policies or distributed fair MAC schemes at the potential expense of total network utilization. This paper investigates a special starvation problem among TCP flows that are different hops away from the BS, as well as its recently proposed solution, the ‘Minimum Content Window’ policy based on IEEE 802.11e. It is found that the aggregate throughput degrades sharply because the effect of this policy on the TCP congestion mechanism has been overlooked. This paper proposes a priority‐based congestion control by using ‘Cross‐Layer Explicit Congestion Notification’. Analysis and simulation results demonstrate that our scheme can improve the fairness of TCP flows while the aggregate throughput is at least 20% higher than the ‘Minimum Content Window’ policy. Copyright © 2011 John Wiley & Sons, Ltd.     

Secure resource allocation in hybrid energy-harvesting relay and full-duplex receiver

Taking into account the wireless physical layer security in energy-constrained relaying systems,a secure resource allocation scheme was proposed under simultaneous wireless information and power transfer (SWIPT) protocol.The utility optimization problem was considered aiming to maximize the secrecy rate by jointly optimizing the power splitting (PS) ratio and the transmit powers under the constraint of the transmit powers of the nodes and the harvested energy of the relay.The objective problem,which is non-convex,was decoupled into two subproblems.One was to optimize the PS ratio,another was to optimize the transmit powers.The optimal solution of the subproblems can be obtained in the closed-form.Then,the suboptimal solution is obtained with the proposed convergent iterative algorithm.Simulation results show the effects of artificial noise signal,residual self-interference signal,transmit power of nodes,amplification factor of relay and other factors on the security performance.Compared with the traditional gradient descent algorithm,the proposed algorithm can reduce more than 80% of the computational load,while the algorithm has the slightly better performance.     

Fair coding for inter‐session network coding in wireless mesh networks

Because of the broadcast and overhearing capability of wireless networks, network coding can greatly improve throughput in wireless networks. However, our investigation of existing inter‐session network coding protocols found that the short‐term unfairness that existed in 802.11‐based medium access control (MAC) protocols actually decreases the coding opportunity, which in turn compromises the throughput gain of network coding. To alleviate the negative impact of this unfairness, we propose a coding‐aware cross‐layer heuristic approach to optimize the coordination of network coding and MAC layer protocol, named FairCoding, which can significantly increase coding opportunities for inter‐session network coding through a fair short‐term traffic allocation for different coding flows. Experiment evaluation shows that the proposed mechanism can bring more coding opportunities and improve the total throughput of wireless mesh networks by up to 20%, compared with the coding mechanism, without considering the negative impact of the short‐term unfairness. Copyright © 2015 John Wiley & Sons, Ltd.