紫外Ad hoc网络中基于历史的动态公平性避退算法

本文把UV通信与Ad hoc网络相结合,利用Ad hoc网络的多跳特性来克服UV通信距离有限的弱点。为了使UV Ad hoc网络中的各个节点能够公平有效的接入信道,本文在二进制指数退避（Binary Exponential Backoff,BEB）算法的基础上,以提高公平性为目的,提出了一种基于历史的动态公平性避退算法（Uistory-Based Dynamic Fairness Backoff,HDFB）来改善节点接入信道的公平性。仿真结果表明：新算法能有效地改善信道接入的不公平性。     

认知无线Ad hoc网络的认知体系结构研究

对认知无线Ad hoc网络进行了阐述。对于认知无线Ad hoc网络,要考虑到无线Ad hoc网络的整体特点,来研究网络级认知结构。而由于认知无线Ad hoc网络是基于无线Ad hoc网络体系结构,同时鉴于无线Ad hoc网络本身特点,因此网络体系参数和网络本身特性参数共同被定义为认知信息,并在与跨层设计结合基础上进行节点级认知结构设计。认知信息的获取与传输方式将认知无线Ad hoc网络网络级与节点级结构有机地联合起来,使整个认知体系成为完整有机体。     

Ad hoc网络技术讲座第1讲Ad hoc网络的体系结构和信道接入协议

本文首先介绍Ad hoc网络的概貌，然后分析Ad hoc网络的体系结构。在介绍了信道接入协议的地位和作用后，对Ad hoc网络特有的信道共享方式。隐终端和暴露终端问题进行了介绍和分析。文章把Ad hoc网络的信道接入协议划分成基于单信道、双信道和多信道三类，最后给出了Ad hoc网络信道接入协议的发展动向。     

一种带有负载监听的多信道Ad hoc网络MAC协议

针对Ad hoc网络提出了一种新的媒体接入控制（MAC）协议——带有负载监听的多信道协议。它能够有效地解决多跳的Ad hoc网络中暴露节点的问题。在该协议中,每个节点都可以根据当前的信道负载来决定是否接入信道,并进行信道预留。在信道预留成功后,多速率的数据包就可以在指定的信道上不受干扰地进行同步传输。该机制允许一个节点同时占用多个空闲信道,不同节点间可以同时传递数据包。仿真结果显示,该机制要优于单信道的RTS／CTS模型,它提高了Ad hoc网络的吞吐量和抗干扰能力。     

Ad hoc网络中不同分布的随机功率控制

无线Ad hoc网络网络中的节能技术已经成为研究领域中的一个热点。采用随机功率控制的无线Ad hoc网络,节点之间成功传输概率及网络能耗与各节点发射功率的概率分布有关,分析并仿真了分别采用均匀分布、正线性分布、负线性分布、凸三角（类高斯）分布和凹三角分布的随机功率控制策略对Ad hoc网络通信成功概率和网络能耗的影响。结果表明采用正线性分布和类高斯分布的随机功率控制具有较优的性能。     

移动Ad hoc网络中的信道接入协议

Ad hoc网络中的信道接入是一个比较复杂的问题。本文介绍了 Ad hoc的概念 ,分析了 Ad hoc网络中实施信道接入的各种困难 ,详细讨论了隐终端和暴露终端问题。在此基础上 ,对目前提出的几种 Ad hoc环境下的信道接入协议进行了比较分析 ,并给出结论和研究方向     

基于MAODV的无线自组网设备设计

在移动Ad hoc网络技术的研究中,由于受到节点移动性、带宽和能量等的限制,传统的基于有线网络的多播路由协议无法直接应用到Ad hoc网络中。研究和设计稳定高效的多播路由协议并将其应用到实际的网络中己成为当前Ad hoc网络研究领域的热点。文中结合无线自组网节点设计的项目,论证了系统的设计方案,详细地分析了无线自组网的MAODV路由协议,设计实现了在嵌入式设备中MAODV的改进方案,并且指出了下一步工作的重点。     

移动Ad hoc网络的单信道媒体接入协议

Ad hoc网络中的信道接入是一个比较复杂的问题，单信道接入协议是目前Ad hoc网络中应用最广泛的，本文介绍了Ad hoc网络中MAC协议需要解决的主要问题和设计要求，并列举分析了几种典型的基于CSMA／CA的由原端发起的单信道接入协议。最后总结了在MAC协议中常用的退避算法：二进制退避算法（BEB）和倍数增线性减算法（MILD），指出其中存在的问题。     

Ad hoc网络的扩频多址接入协议的研究与展望

Ad hoc网络将成为未来网络体系的基本组成部贩而扩频通信技术因其具有频带利用率高、抗干扰能力强等特点,被确认为移动通信系统首选的多址接入方式.鉴于此,本文介绍了扩频技术、Ad hoc网络以及其所面临的问题,对几种能有效解决Ad hoc网络存在的问题的扩频多址接入控制协议进行了分析比较,给出了研究过程中得出的结论.     

Ad hoc网络的体系结构及其设计

Ad hoc网络体系结构的设计问题目前仍无定论,但是有一点是可以确定的,即应采用不同于传统网络的体系结构。首先阐述Ad hoc网络的节点结构,比较了几种典型的网络结构,然后给出了一种用于Ad hoc网络的通用协议栈。接着详细地讨论了Ad hoc网络体系结构的设计策略、原则和方法,最后对全文进行了小结并给出了今后的工作方向。     

NGB管控系统研究

提出了一种面向NGB的管控系统,该系统由管控中心和部署于网络各层次的管控节点单元构成。详细分析了管控中心和管控节点单元的功能和模块架构。提出了管控网的概念,以管控网为依托部署管控系统,研究其在NGB网络上的部署方法。     

An optimal new-node placement to enhance the coverage of wireless sensor networks

Wireless sensor networks provide a wide range of applications, such as environment surveillance, hazard monitoring, traffic control, and other commercial or military applications. The quality of service provided by a sensor network relies on its coverage, i.e., how well an event can be tracked by sensors. This paper studies how to optimally deploy new sensors in order to improve the coverage of an existing network. The best- and worst-case coverage problems that are related to the observability of a path are addressed and formulated into computational geometry problems. We prove that there exists a duality between the two coverage problems, and then solve the two problems together. The presented placement algorithm is shown to deploy new nodes optimally in polynomial time.     

WSN Deployment and Localization Using a Mobile Agent

To address the problem the sensors were typically deployed in fixed positions, but the robots can be used to calibrate, deploy and maintain the surrounding wireless sensor network (WSN) in disaster relief applications, a novel framework was proposed to obtain a wide coverage of the unknown environment by the sensors, which can help the robot during the disaster recovery activities, for the concurrent deployment and localization of a WSN by means of a mobile robot. During the mission, the robot explored an unknown environment, and was equipped with both proprioceptive sensors, range finders and wireless antennas. Moreover, the robot carried a set of nodes, and it can deploy them while exploring the unknown environment. Variou experimental results showd the proposed algorithm can outperform trilateration method in unknown environment exploration and network coverage problems.     

P2P流媒体技术原理及应用

基于P2P的流媒体技术是一项非常有前途的技术,该技术有两方面的优点:不需要互联网路由器和网络基础设施的支持,因此性价比高且易于部署;流媒体用户不只是下载媒体流,而且还把媒体流上载给其他用户,因此,这种方法可以扩大用户组的规模,且由更多的需求带来更多的资源。由于P2P流媒体系统中节点存在不稳定性,因此P2P流媒体系统需要在文件定位技术、节点选择技术、容错以及安全机制方面有所突破。此外在如何管理节点并建立发布树、如何应付不可预知的节点失效、如何适应网络状态变化方面也面临着一些挑战。     

基坑监测系统中传感网的节点部署

基坑监测系统中,需要在各监测点部署传感器节点,系统的监测点围绕基坑工程展开,其监控区域近似圆环。在基站收集监测数据时,离基站越近的区域需要转发的数据越多,节点能量消耗速度也就越快,基站附近的节点将很快消耗完能量,系统随即瘫痪。通过研究圆环形传感网的拓扑特点,得到节点密度公式,使得各区域的总能量与能量消耗速度之比达到平衡。理论分析和仿真实验表明,按照此密度公式部署传感器节点,可显著提高系统生命周期。     

ISDN: The New,All-digital Network

The burgeoning acceptance of ISDN in the United States is leading to increased availability of ISDN equipment worldwide. This worldwide availability of equipment, in turn, will lead to increased competition and more selection as network managers deploy multinational ISDN solutions.     

航天测控设备状态配置和管理方法

针对我国航天测控网设备状态配置和管理方法现状,分析了测控设备任务准备和历史任务恢复节点的现实需要,提出了航天测控设备历史状态宏迁移、设备参数共享以及设备状态集中管理3种方法。通过分析比较,给出了设备状态集中管理和可扩展标记语言( XML)格式设备状态共享方法相结合的实现途径。该方法能够实现设备参数的快速设置和检查以及不同设备之间状态的共享,有利于提高整个测控网的自动化程度和运行效率。     

Energy Efficient Layered Cluster Head Rotation Based Routing Protocol for Underwater Wireless Sensor Networks

Energy efficiency is of paramount concern in underwater sensor networks. The very nature of underwater environment makes it difficult to deploy an energy efficient network that enhances network lifetime. The existing protocols of terrestrial networks cannot be implemented directly to underwater scenarios and as such new protocols have to be designed because of speed of signal propagation under water. Improving the energy efficiency in UWSNs is an active area of research and many protocols to that end have been proposed. The routing protocol that this paper proposes is Energy Efficient Layered Cluster Head Rotation (EE-LCHR) routing protocol. This protocol makes use of the multi sink architecture and creates virtual layers containing a number of sensor nodes such that the hop count from the sensor nodes in a particular layer to the surface sink is the same. Also each layer has a number of clusters with a cluster head that keeps on rotating depending on the fitness value of the sensor nodes. The proposed protocol as compared to other extant protocols like EE-DBR and DBR improves network lifetime. The presence of virtual layers and rotation of cluster heads together ensure that energy balance is better achieved in our proposed protocol which leads to an enhanced network lifetime.

     

A distributed lightweight Redundancy aware Topology Control Protocol for wireless sensor networks

WSN consists of a large number of sensor nodes randomly deployed, and, in many cases, it is impossible to replace sensors when a node failure occurs. Thus, applications tend to deploy more nodes than necessary to cope with possible node failures and to increase the network lifetime, which leads to create some sensing and communication redundancy. However, sensors in the same region, may collect and forward the same information, which will waste more energy. In this paper, we propose a distributed Lightweight Redundancy aware Topology Control Protocol (LRTCP) for wireless sensor networks. It exploits the sensor redundancy in the same region by dividing the network into groups so that a connected backbone can be maintained by keeping a minimum of working nodes and turning off the redundant ones. LRTCP identifies equivalent nodes in terms of communication based on their redundancy degrees with respect of some eligibility rules. Simulation results indicate that, compared with existing distributed topology control algorithms, LRTCP improves network capacity and energy efficiency.     

Introducing new Internet services: why and how

Active networks permit applications to inject programs into the nodes of local and, more important, wide area networks. This supports faster service innovation by making it easier to deploy new network services. In this article, we discuss both the potential impact of active network services on applications and how such services can be built and deployed. We explore the impact by suggesting sample uses and arguing how such uses would improve application performance. We explore the design of active networks by presenting a novel architecture, ANTS (active network transport system), that adds extensibility at the network layer and allows for incremental deployment of active nodes within the Internet. In doing so, ANTS tackles the challenges of ensuring that the flexibility offered by active networks does not adversely impact performance or security. Finally, we demonstrate how a new network service may be expressed in ANTS