光纤物理网设计思路

简要阐述了光纤物理网的规划目标,详细论述了光节点、光缆路由及配纤方式的选择原则,给出了光纤物理网的环形及链形拓扑结构。     

DDBNF：一个分布式的动态蓝牙网络形成算法

提出了一个分布式的、支持节点移动性的蓝牙匹克网构造算法DDBNF,它可以有效地将随机分布在某个区域内的n个节点划分为若干个匹克网.该算法只需获得每个节点的本地拓扑信息(一跳邻居节点),基于权值大小选举主节点,允许每个普通从节点直接访问至少一个主节点,保证了每个节点对之间快速的匹克网间以及匹克网内通信.     

结合地理位置与语义聚类的P2P叠加网构建

针对目前P2P叠加网效率不高与拓扑失配问题,以基于超节点体系结构的文件共享应用为背景,提出了一种结合网络节点位置信息与语义聚类的P2P叠加网拓扑构建策略POCLS.POCLS中节点依据物理位置信息就近组成各自治域,域中节点再根据共享资源的语义形成多个语义聚类,利用域和聚类对P2P叠加网进行双重管理.仿真表明POCLS在保证查询成功率的同时,有效减少了查询延时与网络冗余流量,提高了P2P网络性能.     

高动态无线自组网路由协议设计

针对节点快速移动过程中网络建立时间较长,数据端到端传输时延无法得到可靠保 障,并且由于维护动态网络连接性造成网络开销较大等方面的问题,提出了一种无线自组网 路由协议,通过分簇算法快速将网络分为多个簇,每个簇包括簇首节点、成员节点和簇间网 关节点。该协议能够应用于快速移动节点构成的高动态无线自组织网络中,实现了先应式和 反应式路由算法进行了有机结合,能够在快速变化的拓扑结构中为未知路由提供优化的路由 结果,利用较小的网络开销实现网络快速构建和数据端到端的实时传输。     

光传输系统在接入网中的应用及常见故障处理

１基本组网方式在接入网规划中,地区千差万别,而ＳＤＨ网络的性能、可靠性和经济性很大程度上与所用的网络拓扑结构有关,如何合理地组网以达到最优的性能价格比并降低运维成本是至关重要的问题。ＳＤＨ基本网结构有链形、星形、树形、环形和网孔形５种,在此基础上组合变化又有环带链、连带环、相切环、相交环等多种拓扑结构。接入网中应用最广泛的是环形和链形。环形网有良好的自愈能力,实际中尽可能组环网。只有在极端情况下,如铁路、公路和电力干线的沿线专网,各端点之间距离较远,如果组成环形网,线路投资太大,就采用链形结构组网。２自愈…     

自适应高效无线传感器网络时间同步优化算法

针对无线传感器网络全网多跳自适应时间同步效率低的问题,在接收端与接收端同步模型基础上,该文提出一种自适应高效无线传感器网络时间同步优化算法(AEO)。首先,双节点同步时,从节点接收来自参考节点的同步消息并进行确认,在同步周期结束后通过拟合估计和数据更新完成时间修正,构建交互参数同步包,并与主节点进行信息交换完成同步过程。其次,全网同步时,建立Voronoi多边形拓扑结构,认定拓扑结构中参考节点和邻域节点身份(ID),参考节点覆盖区域间通过邻域节点交换同步信息,实现自适应多区域节点联合时间同步。仿真结果表明该算法在双节点时间同步中能够保证同步误差较小,网络能耗较低;同时,Voronoi拓扑相较于其他典型拓扑,在连通效率和收敛时间方面均有所改进。     

基于簇的无线传感器网络入侵检测系统

基于无线传感器网络的分簇结构,运用Agent技术设计了一个入侵检测系统.在网络中的每个节点部署IDS代理,其中包括本地检测Agent和全局检测Agent两个不同代理,分别完成不同的检测任务.提出采用蓝牙通信技术,引用蓝牙散射网形成算法TPSF构建传感器网络的簇节点层,完成簇的划分,进而对不同的Agent进行任务分配.通过限制节点的角色对算法进行改进,减轻节点的复杂度,从而使IDS代理能有效地工作,提高节点的安全系数.     

一种基于Chord的缓存路由算法

根据small-world的研究发现,在实际的P2P拓扑结构中存在若干度数很高的节点。传统的Chord算法假定关键字的查询请求是随机分布的,没有考虑到节点之间的"短链"效应。提出一种基于Chord在一定程度上逐步找到系统节点的"短链"的方法。该方法根据关键字检索命中率动态调整路由表中记录的排序。仿真实验表明,该算法加快了关键字的查询时间,提高了路由表的查询效率。主要创新点在于针对实际P2P网络中查询请求的分布特性提出一种改进的Chord路由算法,该算法能有效改善系统的查询性能。     

一种Dijkstra优化算法的研究与实现

最短路径计算是地理信息系统应用中的重要功能之一,经典的最短路径算法是D ijkstra算法,但该算法由于结构过于复杂导致计算效率较低,无法满足实际应用需求。从实际应用需求出发,针对D ijkstra算法的不足,在拓扑存储结构、拓扑关系数据结构以及拓扑网中节点存储顺序三方面对算法进行优化,通过分析与实际应用表明提出的D ijkstra改进算法不仅结构简单易于实现,而且算法效率高,能够满足实际应用需求。     

一种非结构化P2P网络的资源搜索算法

本文针对非结构F2P网络中利用洪泛搜索机制来进行资源搜索的盲目性问题，提出一种利用节点经验积累和cache技术相结合来指导资源搜索的算法。在访搜索算法中，节点记录收到的查询主题和满足该主题的邻居节点，建立主题与邻居节点的对应关系表，当再次收到该主题时，节点就利用该表来指导资源搜索。为了加快搜索速度，将常见查询主题的记录放到cache中。该算法利用一个相似度函数来判断本地文档是否满足查询主题。仿真实验表明，该算法有效地改进了资源搜索的盲目性。减少查询带来的网络流量，提高了查询成功率。     

Bottom-Up Construction of Bluetooth Topology under a Traffic-Aware Scheduling Scheme

We propose a Bluetooth topology construction protocol that works in conjunction with a priority-based polling scheme. A master assigns a priority to its slaves including bridges for each polling cycle and then polls them as many times as the assigned priority. The slaves can spend their idle time either in a power-saving mode or perform new node discovery. The topology construction algorithm works in a bottom-up manner in which isolated nodes join to form small piconets. These small piconets can combine to form larger piconets. Larger piconets can start sharing bridge nodes to form a scatternet. Individual piconets can also discover new nodes while participating in the master-driven polling process. The shutting down of master and slave nodes is detected for dynamic restructuring of the scatternet. The protocol can handle situations when all the Bluetooth nodes are not within radio range of each other     

Distributed self-healing and variable topology optimization algorithms for QoS provisioning in scatternets

Bluetooth is an enabling technology for Personal Area Networks. A scatternet is an ad hoc network created by interconnecting several Bluetooth piconets, each with at most eight devices. Each piconet uses a different radio channel constituted by a frequency hopping code. The way the devices are grouped in different piconets and the way the piconets are interconnected greatly affect the performance of the scatternet in terms of capacity, data transfer delay, and energy consumption. There is a need to develop distributed scatternet formation algorithms, which guarantee full connectivity of the devices, reconfigure the network due to mobility and failure of devices, and interconnect them such a way to create an optimal topology to achieve gainful performance. The contribution of this paper is to provide an integrated approach for scatternet formation and quality-of-service support (called SHAPER-OPT). To this aim, two main procedures are proposed. First, a new scatternet formation algorithm called self-healing algorithm producing multihop Bluetooth scatternets (SHAPER) is developed which forms tree-shaped scatternets. A procedure that produces a meshed topology applying a distributed scatternet optimization algorithm (DSOA) on the network built by SHAPER is then defined. Performance evaluation of the proposed algorithms, and of the accordingly created scatternets, is carried out by using ns2 simulation. Devices are shown to be able to join or leave the scatternet at any time, without compromising the long term connectivity. Delay for network setup and reconfiguration in dynamic environments is shown to be within acceptable bounds. DSOA is also shown to be easy to implement and to improve the overall network performance.     

Bluetooth scatternets: criteria, models and classification

Bluetooth ad hoc networks are constrained by a master/slave configuration, in which one device is the master and controls the communication with the slave devices. The master and up to seven active slave devices can form a small Bluetooth network called a piconet. In order to build larger network topologies, called scatternets, the piconets must be interconnected. Scatternets are formed by allowing certain piconet members to participate in several piconets by periodically switching between them. Due to the fact that there is no scatternet formation procedure in the Bluetooth specification, numerous different approaches have been proposed. We discuss criteria for different types of scatternets and establish general models of scatternet topologies. Then we review the state-of-the-art approaches with respect to Bluetooth scatternet formation and compare and contrast them.     

Ad hoc networking with Bluetooth: key metrics and distributed protocols for scatternet formation

Bluetooth is a promising technology for personal/local area wireless communications. A Bluetooth scatternet is composed of simple overlapping piconets, each with a low number of devices sharing the same radio channel. A scatternet may have different topological configurations, depending on the number of composing piconets, the role of the devices involved and the configuration of the links. This paper discusses the scatternet formation issue by analyzing topological characteristics of the scatternet formed. A matrix-based representation of the network topology is used to define metrics that are applied to evaluate the key cost parameters and the scatternet performance. Numerical examples are presented and discussed, highlighting the impact of metric selection on scatternet performance. Then, a distributed algorithm for scatternet topology optimization is introduced, that supports the formation of a “locally optimal” scatternet based on a selected metric. Numerical results obtained by adopting this distributed approach to “optimize” the network topology are shown to be close to the global optimum.     

BlueMesh: Degree-Constrained Multi-Hop Scatternet Formation for Bluetooth Networks

In this paper we describe BlueMesh, a new protocol for the establishment of scatternets, i.e., multi-hop wireless networks of Bluetooth devices. BlueMesh defines rules for device discovery, piconet formation and piconet interconnection so to generate connected scatternets with the following desirable properties. BlueMesh forms scatternets without requiring the Bluetooth devices to be all in each other transmission range. BlueMesh scatternet topologies are meshes with multiple paths between any pair of nodes. BlueMesh piconets are made up of no more than 7 slaves. Simulation results in networks with over 200 nodes show that BlueMesh is effective in quickly generating a connected scatternet in which each node, on average, does not assume more than 2.4 roles. Moreover, the route length between any two nodes in the network is comparable to that of the shortest paths between the nodes.     

Bluegon: a polygon-shaped scatternet formation algorithm for Bluetooth

Bluetooth is one of the cable-replacement technologies. It uses short-range radio links to replace connecting cables. Bluetooth enables portable devices to form short-range wireless ad hoc networks. A set of Bluetooth devices sharing a common channel can form a personal area network called a piconet. Several piconets can also be interconnected to establish a scatternet. Zaruba, Basaghi and Chlamtac proposed a mechanism for forming a distributed scatternet called the Bluetree. The algorithm is based on selecting an arbitrary node serving as the Blueroot. The Blueroot initiates the construction of the Bluetree. Though the algorithm is very simple, there are some weak points. For example, being a tree limits its routing choices. There are also the problems of overloading on the Blueroot and the many master/slave bridges on any routing path. In this paper, we will improve the weaknesses of Bluetree by eliminating the bottleneck in the Blueroot and by reducing the number of bridges to half for almost any path. We call the new algorithm Bluegon since polygons (cycles) will be formed in the scatternet. Simulation results indicate the efficiencies of our algorithm. Copyright © 2006 John Wiley & Sons, Ltd.     

Interference modeling and performance of Bluetooth MAC protocol

The emergence of Bluetooth as a default radio interface has allowed handheld electronic devices to be instantly interconnected as ad hoc networks. These short-range ad hoc wireless networks, called piconets, operate in the unlicensed 2.4-GHz ISM (Industrial-Scientific-Medical) band where devices may be used to configure single or overlapping piconets, known as scatternet. As all piconets operate in the same frequency band, the presence of multiple piconets in the vicinity may create interference on signal reception. This paper employs a signal capture model to study the piconet MAC performance, taking inter-piconet interference into consideration. This model leads to several important mathematical relationships for Bluetooth networks, including successful packet transmission probability. Furthermore, our model and anticipated throughput are validated using extensive simulation. These results indicate that Bluetooth throughput is affected by multiple piconet interference. Definitely, our model can be considered to provide a solid foundation for future interference aware Bluetooth protocols.     

A New Bluetooth Scatternet Formation Protocol

A Bluetooth ad hoc network can be formed by interconnecting piconets into scatternets. The constraints and properties of Bluetooth scatternets present special challenges in forming an ad hoc network efficiently. In this paper, we present and analyze a new randomized distributed protocol for Bluetooth scatternet formation. We prove that our protocol achieves O(logn) time complexity and O(n) message complexity. The scatternets formed by our protocol have the following properties: (1) any device is a member of at most two piconets, and (2) the number of piconets is close to be optimal. These properties can help prevent overloading of any single device and lead to low interference between piconets. We validate the theoretical results by simulations, which also show that the scatternets formed have O(logn) diameter. As an essential part of the scatternet formation protocol, we study the problem of device discovery: establishing multiple connections simultaneously with many Bluetooth devices. We investigate the collision rate and time requirement of the inquiry and page processes. Our simulation results indicate that the total number of packets sent is O(n) and that the maximum number of packets sent by any single device is O(logn).     

Load-adaptive inter-piconet scheduling in small-scale Bluetooth scatternets

Bluetooth enables wireless communication via ad hoc networks. The basic topology (piconet) is a collection of slaves controlled by a master. A scatternet is a multihop network of piconets. We anticipate that most scatternets will be composed of only a few piconets. However, even in small scatternets, efficient data flow requires the design of inter-piconet scheduling algorithms. Thus, this article presents and evaluates a load adaptive scheduling algorithm tailored for small-scale scatternets. The main advantage of this algorithm is the use of the Bluetooth low-power hold mode, which allows greater flexibility than other low-power modes. A simulation model has been developed in order to evaluate the performance of the algorithm. We show that the results obtained by the model are very close to the analytic results. Then we evaluate the performance of various intra-piconet scheduling algorithms. Finally, we present simulation results regarding inter-piconet scheduling, and compare the proposed algorithm to algorithms using the sniff mode.     

A Bluetooth scatternet-route structure for multihop ad hoc networks

Bluetooth scatternets, integrating polling, and frequency hopping spread-sprectrum in their medium access control protocol, provide a contention-free environment for Bluetooth devices to access the medium and communicate over multihop links. Currently, most available scatternet formation protocols tend to interconnect all Bluetooth devices at the initial network startup stage and maintain all Bluetooth links thereafter. Instead of this "big scatternet" approach, we propose a scatternet-route structure to combine the scatternet formation with on-demand routing, thus eliminating unnecessary link and route maintenances. To the best of our knowledge, this is the first effort to address on-demand scatternet formation with every detail. We introduce an extended ID (EID) connectionless broadcast scheme, which, compared with original Bluetooth broadcast mechanism, achieves very much shortened route discovery delay. We also propose to synchronize the piconets along each scatternet route to remove piconet switch overhead and obtain even better channel utilization. Furthermore, we present a route-based scatternet scheduling scheme to enable fair and efficient packet transmissions over scatternet routes. Network performance analysis and simulations show that scatternet routes can provide multihop wireless channels with high network utilization and extremely stable throughput, being especially useful in the transmission of large batches of packets and real time data in wireless environment.