WDM网中的分组交换技术

WDM技术为通信网络提供了巨大的带宽资源,分组交换技术提高了带宽的利用率,二才的结合即在WDM网中进行分组交换必然是下一代光网络的发展趋势。本讨论了光分组交换的分层网络模型、目前正在研究的两种分组交换技术以及实现分组交换的关键技术,最后对光分组交换技术对未来光通信网络的影响作了分析。     

WDM网中的分组交换技术

WDM技术为通信网络提供了巨大的带宽资源,分组交换技术提高了带宽的利用率,二者的结合即在WDM网中进行分组交换必然是下一代光网络的发展趋势。本文讨论了光分组交换的分层网络模型、目前正在研究的两种分组交换技术以及实现分组交换的关键技术,最后对光分组交换技术对未来光通信网络的影响作了分析。     

交换技术在信息通信中的应用

随着近年来信息通信技术的不断发展与进步,各种相应配置措施技术也在不断提高与运用,而交换技术则是信息通信技术发展的基础和关键。交换的概念在信息通信技术的不断发展过程中被越来越多地使用,实践也证明,其在信息通信技术中占据着无法取代的重要地位。文章在此背景下对交换技术在信息通信中的应用进行探讨。     

用于分组交换技术的可变速率语音编码

分组交换通信技术能有效地提高信道资源的利用率,它在通信领域中赢得了广泛的重视。在语音信号通信中,该项技术面临着因网络信道的瞬时过载而产生的分组语音数据块的丢失现象,致使分组交换通信系统的电话语音质量下降的问题。对于这个问题,人们曾提出采用填充的方法仿制那些丢失的语音信息,改善语音质量,但效果不理想。本文介绍的可变速率语音编码方法,是使分组交换通信系统避免电话语音质量明显下降的新方法,它可以在系统中重建丢失的语音信号。本文给出了利用计算机对采用该方法的分组交换系统进行系统模拟的结果。     

快速分组交换技术浅说及其帧结构

一、引言 八十年代以来,世界各国的公用和专用分组交换网蓬勃发展,现在已形成了全球性的数据通信网络。随着分组交换技术的发展,分组交换网的性能不断提高,功能不断完善,分组交换机之间的中继线速率由9.6kb/s提高到了2.048M b/s。但是到了九十年代,用户对数据通信网的速率提出了更高的要求,而采用现有的分组交换技术的分组系统的能力几乎达到了极限,因此人们开始研究新的分组交     

城域网的全光分组交换

网络业务的需求不断提高,迫使网络技术发生巨大变化,在新型的网络环境下,传统开放系统互连参考模型(OSI )的网络分层已不再适用,在光层实现像交换这样越来越智能的功能已成为必然趋势。全光分组交换正是以这样一种形式出现的,它将对下一代网络产生深远的影响。文中详细阐述了全光分组交换的实现和结构,说明全光分组交换如何运用到更灵活的下一代城域网中,最后给出与之相关的使能技术的发展情况。     

用分组交换技术实现单位内外的网络互连

用分组交换技术实现单位内外的网络互连陈守才分组交换技术是目前世界上广泛使用的数据通信技术，它具有可靠性高、灵活方便、通信费用低等优点。对于厂矿企业，采用分组交换技术实现单位内通信网络间的互连，利用国家分组交换网使本地与异地的数据终端进行数据交换、共享...     

浅析新疆民航运用现代通信技术实现自动转报系统

当今是通信网络技术不断涌现、通信领域日新月异的时代,本人根据工作中的实际经验,在此谈谈分组交换、帧中继和ATM技术在民航自动转报网中的最新应用。一、分组交换技术的实现原理分组交换是为适应计算机通信而发展起来的一种先进通信手段,可以满足不同速率、不同型号的终端与终端、终端与计算机、计算机与计算机间以及局域网间的通信,实现数据库资源共享,这也是新疆民航自动转报网使用的第一代交换网。分组交换是吸取了报文交换的优点,以分组为信息单位,采用“存储转发”的方式在网络中传输的数据交换方式。分组交换网在民航系统应用的工…     

通信传输中光交换技术的应用

随着通信技术的不断发展，以及计算机技术的不断更新，通信行业在国民经济中占有越来越重要的地位，其传输效率的不断提升和安全性能的增强，而其延伸的通信交换技术，也逐渐发展和完善。通信交换技术包含光电交换技术、分组交换技术等，本文要介绍的是交换技术中的光交换技术。     

数据通信网络

数据通信网络张旺兴数据通信是本世纪５０年代末，随着电子计算机的发展和广泛应用而开发形成的一种通信方式。自它形成以来，已经有了各种各样的数据通信网络。本文将简要介绍分组交换数据网、数字数据网、帧中继及ＡＴＭ的特点及发展现状。１．分组交换的概念分组交换也...     

Determining the position of a jammer using a virtual-force iterative approach

Wireless communication is susceptible to radio interference and jamming attacks, which prevent the reception of communications. Most existing anti-jamming work does not consider the location information of radio interferers and jammers. However, this information can provide important insights for networks to manage its resource in different layers and to defend against radio interference. In this paper, we investigate issues associated with localizing jammers in wireless networks. In particular, we formulate the jamming effects using two jamming models: region-based and signal-to-noise-ratio(SNR)-based; and we categorize network nodes into three states based on the level of disturbance caused by the jammer. By exploiting the states of nodes, we propose to localize jammers in wireless networks using a virtual-force iterative approach. The virtual-force iterative localization scheme is a range-free position estimation method that estimates the position of a jammer iteratively by utilizing the network topology. We have conducted experiments to validate our SNR-based jamming model and performed extensive simulation to evaluate our approach. Our simulation results have showed that the virtual-force iterative approach is highly effective in localizing a jammer in various network conditions when comparing to existing centroid-based localization approaches.     

Reliable and Secure Cooperative Communication for Wireless Sensor Networks Making Use of Cooperative Jamming with Physical Layer Security

Interference is generally considered as the redundant and unwanted occurrence in wireless communication. This research work proposes a novel cooperative jamming mechanism for scalable networks like wireless sensor networks which makes use of friendly interference to confuse the eavesdropper and increase its uncertainty about the source message. The communication link is built with the help of Information theoretic source and channel coding mechanisms. The whole idea is to make use of normally inactive relay nodes in the selective Decode and Forward cooperative communication and let them work as cooperative jamming sources to increase the equivocation of the eavesdropper. In this work, eavesdropper’s equivocation is compared with the main channel in terms of mutual information and secrecy capacity.     

工业无线传感器网络物理层移动节点的抗干扰Stackelberg博弈模型

针对工业无线传感网络中物理层干扰攻击问题,研究一种移动环境下的博弈功率控制方案。为提高移动sink节点的抗干扰能力,利用Bayesion-Stackelberg博弈模拟移动sink节点和干扰节点的对抗交互行为,通过求出参与博弈的节点最优策略,即sink节点和干扰节点的最佳传输功率,达到合法节点抗干扰的最佳效果,提高通信系统物理层的安全性。Matlab仿真结果表明,相比移动sink节点的其他博弈功率控制算法,本文方案能更有效地提高合法节点抗干扰能力且能耗更低。      

基于贝叶斯深度学习的一维雷达有源干扰信号识别方法

雷达干扰信号准确识别是雷达抗干扰的前提,对于雷达生存至关重要。针对传统雷达干扰信号识别方法需要繁琐的分析计算提取特征,通用性差,泛化能力弱,难以适应复杂的雷达工作环境问题。本文考虑无需人工提取特征信息且具有较好的分类识别效果的深度学习网络。考虑到传统的深度学习网络由于使用点估计方式,不能够很好的衡量预测结果中的不确定性,本文提出了一种基于贝叶斯深度学习的干扰识别方法。首先,通过概率建模代替网络参数模型的点估计,解决了不确定性随机数据引起的网络过拟合问题。其次,考虑有效利用雷达回波信号的时序特性设计了LSTM层,同时解决训练过程中的梯度消失问题。基于线性调频雷达有源干扰实测数据完成了网络训练与测试,实验结果表明,引入贝叶斯方法可以在加快网络收敛速度的同时有效提高识别准确率。     

The Feasibility of Launching Rogue Transmitter Attacks in Indoor Visible Light Communication Networks

One of the areas in which wireless networks based on visible light communication (VLC) are considered superior to traditional radio-based communication is security. The common slogan summarizing VLC security features is: WYSIWYS—”What You See Is What You Send”. However, especially in the case of infrastructure downlink communication, security with respect to data snooping, jamming and modification must be carefully provided for. This paper examines the physical layer aspects of VLC networks with respect to possible disruptions caused by rogue transmitters. We present the theoretical system model that we use in simulations to evaluate various rogue transmission scenarios in a typical indoor environment. We use estimated bit error rate as a measure of the effectiveness of jamming and rogue data transmission. We find that it is quite easy to disrupt, and in some cases to even hijack legitimate transmission.

     

Information leakage in bi‐directional IFD communication system with simultaneously transmitted jamming sequence

In this paper, we describe a simultaneously transmitted jamming (ST‐jamming) for bi‐directional in‐band full‐duplex (IFD) system to improve information security at the physical layer. By exploiting ST‐jamming, each legitimate user transmits data samples and jamming samples together in one orthogonal frequency division multiplexing symbol according to given traffic asymmetry. Regardless of the traffic difference in both directions in IFD communication, eavesdropping of confidential information is prevented in both directions simultaneously without the loss of data rate. We first propose an encoding scheme and the corresponding decoding scheme for ST‐jamming to be used by the legitimate users. In addition, we study a transceiver structure of the legitimate users including a baseband modem uniquely designed for the use of ST‐jamming. The leakage of confidential information at an eavesdropper is then quantified by studying the mutual information between the confidential transmit signals and the received signals of the eavesdropper. Simulation results show that the proposed ST‐jamming significantly reduces the leakage of legitimate information at the eavesdropper.     

Compromise-resilient anti-jamming communication in wireless sensor networks

Jamming is a kind of Denial-of-Service attack in which an adversary purposefully emits radio frequency signals to corrupt the wireless transmissions among normal nodes. Although some research has been conducted on countering jamming attacks, few works consider jamming attacks launched by insiders, where an attacker first compromises some legitimate sensor nodes to acquire the common cryptographic information of the sensor network and then jams the network through those compromised nodes. In this paper, we address the insider jamming problem in wireless sensor networks. In our proposed solutions, the physical communication channel of a sensor network is determined by the group key shared by all the sensor nodes. When insider jamming happens, the network will generate a new group key to be shared only by the non-compromised nodes. After that, the insider jammers are revoked and will not be able to predict the future communication channels used by the non-compromised nodes. Specifically, we propose two compromise-resilient anti-jamming schemes: the split-pairing scheme which deals with a single insider jammer, and the key-tree-based scheme which copes with multiple colluding insider jammers. We implement and evaluate the proposed solutions using Mica2 Motes. Experimental results show that our solutions have low recovery latency and low communication overhead, and hence they are suitable for resource constrained sensor networks.     

基于时频相关性的复合常规人为干扰分析方法

在军事无线通信中,对进入接收机的干扰信号进行分析、识别并提取特征参数,以支持抗干扰决策,是通信设备有效对抗蓄意人为干扰的前提。提出了基于短时傅里叶变换(STFT)的复合常规人为干扰分析方法,首先对接收的干扰信号进行STFT变换,然后将得到的三维时频域数据进行二值化处理;最后根据不同干扰样式的时域及频域特征,对二值化的时频域数据之间的关系进行分析,分别解析出多音干扰、周期脉冲干扰、扫频干扰。理论分析和仿真结果表明,通过分类搜索算法,能够较为准确地对复合人为干扰进行解析。     

A secure wireless mission critical networking system for unmanned aerial vehicle communications

A privacy-preserving secure communication in ad hoc (without infrastructure) mission critical wireless networking system suitable for unmanned aerial vehicle communication systems is introduced and analyzed. It is expected that in a critical condition, few ad hoc (without infrastructure) mission critical wireless networking systems will work together. To make the simple and low cost privacy-preserving secure communication among the same network, each transmitting mobile node generates packets in such a way that its wanted receiving mobile nodes can read the message packets easily. On the other hand, the unwanted receiving mobile nodes from other networks cannot read those message packets. In addition, the unwanted receiving mobile nodes receive ‘jamming packets’ if they try to read them. This mechanism prevents the malicious receivers (readers from other networks) from reading the packets and obtaining information from this network. Results show that the throughput is very high and does not detect any jamming packets, if the receiving nodes of a network try to read packets transmitted by the nodes from the same networks.     

Jamming sensor networks: attack and defense strategies

Wireless sensor networks are built upon a shared medium that makes it easy for adversaries to conduct radio interference, or jamming, attacks that effectively cause a denial of service of either transmission or reception functionalities. These attacks can easily be accomplished by an adversary by either bypassing MAC-layer protocols or emitting a radio signal targeted at jamming a particular channel. In this article we survey different jamming attacks that may be employed against a sensor network. In order to cope with the problem of jamming, we discuss a two-phase strategy involving the diagnosis of the attack, followed by a suitable defense strategy. We highlight the challenges associated with detecting jamming. To cope with jamming, we propose two different but complementary approaches. One approach is to simply retreat from the interferer which may be accomplished by either spectral evasion (channel surfing) or spatial evasion (spatial retreats). The second approach aims to compete more actively with the interferer by adjusting resources, such as power levels and communication coding, to achieve communication in the presence of the jammer.