基于OPNET的校园网优化设计与仿真

为了达到优化校园网的目的,通过OPNET仿真方法,从网络拓扑结构到资源合理配置两方面进行优化设计。对多级网络和三级网络环境下网络的系统时延、服务器响应速度和吞吐量进行仿真。结果表明,控制交换级数可以有效降低系统时延,提高网络性能。建议中小型网络采用＂核心交换-汇聚交换-节点交换＂的三级交换拓扑结构。     

空载光纤数据总线的建模和仿真

根据所提出的一种空载光纤数据总线的拓扑结构,建立了空载光纤数据总线的模型,并利用模型对空载光纤数据总线系统的性能进行了仿真.分析了总线的数据吞吐速率、总线响应时间、端到端延迟和误码率等参数对系统性能的影响,仿真结果将为空载光纤总线系统的设计提供重要的依据.     

机载悬挂物EBR1553总线网络技术研究

针对小型化、低成本和批量挂载的航空机载悬挂物的网络化管理问题,首先,研究了机载悬挂物总线网络的使用特点及3种典型悬挂物总线网络;然后,对EBR1553总线网络的特点、拓扑结构、基本协议、扩展协议及其在机载悬挂物网络化中的应用等方面进行了分析与设计;最后,通过研发的仿真验证环境,验证了悬挂物EBR1553总线网络技术及应用的可行性.     

CAN总线通信控制协议的仿真与性能分析

在控制器局域网(CAN)总线通信控制协议的基础上,在MATLAB/Simulink软件Stateflow仿真环境下,利用有限状态机理论对CAN总线通信系统进行了形式化建模。通过此仿真模型,可以分析CAN总线通信系统中负载率的变化对网络吞吐量、平均信息时延、通信冲突率、网络利用率、网络效率以及负载完成率的影响。仿真结果验证了CAN总线通信控制协议的特点,同时也证明了Stateflow对CAN总线协议进行建模仿真的可行性。     

基于NS2仿真的IP网络性能分析与研究

采用网络模拟仿真方法,选用NS2仿真软件模拟IP网络运行。编程实现四种典型的网络拓扑结构:总线型、星型、环型、网型,选取网络传输中的数据包延时、延时抖动、丢包率以及吞吐量等关键性能指标为实验采集对象。通过大量的仿真实验数据分析不同拓扑类型对IP网络性能产生的不同影响。     

光纤光栅传感网络的优化研究

光纤光栅传感网络在大型复杂结构健康监测中具有广泛的应用前景,对光纤光栅传感网络优化的研究具有重要的意义。分析了结构健康监测中光纤传感网络优化布局和可靠性的研究现状,对光纤传感网络优化中的传感器优化布局与光纤传感网络可靠性两方面进行研究。通过对结构响应特性研究,提出了对结构静力响应参数监测时,传感器布局的一般规则。将概率计算引入光纤 FBG 传感网络不同拓扑结构,给出了基于不同拓扑结构的光纤传感网络形式及其可靠性数值分析。     

FC-AE-FCLP网络建模与仿真研究

光纤通道轻量协议(Fibre Channel Lightweight Protocol,FC-AE-FCLP)是光纤通道航空电子环境的5种高层协议之一。为研究FC-AE-FCLP网络性能,在研究光纤通道轻量协议的基础上,提出其在OPNET Modeler中的建模方法。采用网络层次化方法构建了节点模型、进程模型和网络模型,并对航电系统交换型拓扑结构进行了仿真。通过网络性能仿真分析得出该网络传输大数据块时具有延迟抖动小、吞吐量高的优点,因此FC-AE-FCLP网络特别适合航电系统大块数据的传输。     

机载光纤总线修复质量评估方法研究

随着武器装备信息化、智能化的不断发展,机载信息交互需求越来越高,光纤通信被普遍应用在航空电子武器系统中。通过分析机载光纤总线网络系统的关键参数,结合光纤总线各参数对任务系统的影响因子,构建了机载光纤总线修复质量评估指标体系,采用灰色关联度、熵权赋值等方法对质量进行评估,最后提出了机载光纤总线修复质量评估系统模型。     

基于LEACH路由协议的混合光无线传感网络研究

分析了基于低功耗自适应分簇(LEACH)路由协议的无线传感网络(WSN)在不同拓扑形状下的生命周期,并改进了长方形拓扑形状的路由协议。进而针对WSN在某些场合能量有限、易受干扰和安全性差等缺点,在长方形区域中引入分布式光纤传感结构。将传感光纤铺设在环境复杂和外界电磁波干扰大的监测区域,从而提高整个传感网络的生命周期和可靠性。理论分析和仿真结果表明,改进的拓扑和协议在提高可靠性的同时,有效地延长了光WSN的生存时间,性能优于传统LEACH协议。     

基于QualNet的数据链网络仿真研究

在数据链系统的生命周期中,仿真是不可缺少的一个环节.为了统计和分析数据链网络的重要参数指标,采用网络实时动态仿真软件QualNet的系统构架,分析了在QualNet环境下数据链系统仿真的关键技术,通过场景设计和功能设定对Link 16进行了性能参数仿真,得到了数据链网络的网络吞吐量、平均端到端时延、数据分组成功接收率等总体性能指标.仿真结果表明网络性能良好,基本满足了消息传输的实时性和可靠性,为我军进一步研究数据链系统提供了参考.     

A Fault-Tolerant Network Protocol for Real-Time Communications

We present a network access protocol suitable for use in real-time applications. It features high throughput, bounded message delay, tolerance of failed nodes, automatic resynchronization when failed nodes are revived, deadlock avoidance, and high reliability. The protocol is ideally suited for a bus topology and fiber-optic media. Measured performance data is provided from an implementation of 45 nodes operating on a 10-Mbps fiber-optic bus.     

Performance Analysis and Optimization of MAC Frame Size in IEEE 802.15.7

The IEEE 802.15.7 standard document for short-range wireless optical communication using visible light divides applications into three topologies: peer-to-peer, star, and broadcast. Among them, the star topology has the widest range of application and is the target in many researches. Unlike the peer-to-peer and broadcast, the star topology has to deal with the problem of contention. In the IEEE 802.15.7 standard, the contention problem is solved using random access mechanism, and the performance of the star topology VPAN system is greatly affected by the configuration of MAC sublayer, especially the superframe size. In this paper, we simulate a VPAN system using Matlab. Through the simulation, we analyze the impact of superframe size on the network performance in terms of network throughput and delay. Because there is a trade-off between throughput and delay, we define a new measurement for evaluating the overall system performance. Based on this measurement, we optimize the superframe size to get the optimal performance of VPAN system.     

Lightwave networks based on de Bruijn graphs

Proposes de Bruijn graphs as logical topologies for multihop lightwave networks. After deriving bounds on the throughput and delay performance of any logical topology, the authors compute the throughput and delay performance of de Bruijn graphs for two different routing schemes and compare it with their bounds and the performance of shufflenets. For a given maximum nodal in- and out-degree and average number of hops between stations, a logical topology based on a de Bruijn graph can support a larger number of stations than a shufflenet and this number is close to the maximum that can be supported by any topology. The authors also propose de Bruijn graphs as good physical topologies for wavelength routing lightwave networks consisting of all-optical routing nodes interconnected by point-to-point fiber links. The worst-case loss experienced by a transmission is proportional to the maximum number of hops (diameter). For a given maximum nodal in- and out-degree and diameter, a physical topology based on a de Bruijn graph can support a large number of stations using a relatively small number of wavelengths     

Analysis of the semisynchronous carrier sense multiple access onthe bus topology

Consider an arbitrary number of stations equally spaced on a channel configured as a bus topology. The stations access the channel according to the nonpersistent CSMA protocol, which may be with or without collision detection. Users are synchronized to the propagation delay between two adjacent users, and are thus semisynchronized. Such a system with single-buffered users and an exponential backoff strategy, is modeled. The system throughput and the mean delay are evaluated, and it is shown how to obtain the distribution of the packet interdeparture time as well as the packet delay. It is shown that the rescheduling strategy has a profound effect on the station performance, and that it can be used to eliminate the difference between the performance of different stations at any given offered load. The model is also used to accommodate finer synchronization steps, as well as arbitrary topologies     

Code-division multiple-access in an optical fiber LAN with amplified bus topology: the SLIM bus

A novel optical fiber network with a bus topology and dark signaling (the SLIM bus) using optical code-division multiple-access (CDMA) is proposed. With a new design of delay line correlator the network is shown to eliminate optical beating noise and overcome the main limitations of incoherent optical CDMA in a star topology.     

An efficient wavelength reusing/migrating/sharing protocol for dualbus lightwave networks

High-speed lightwave networks employing linear fiber bus topology have become attractive with the emergency of erbium-doped optical amplifiers. Moreover, the huge network capacity in a dual bus lightwave network is obtained by several parallely transmitting channels (wavelengths) on each bus. By applying the wavelength reusing concept, nonoverlapping traffic in the network can be serviced simultaneously to achieve high network throughput. It is also possible that a new incoming request is blocked even the bandwidth between the source and the destination is available. Nevertheless, this request may be accommodated by migrating some existing connections. Due to the number of wavelengths is limited, some requests may further share the same wavelength to improve the network throughput. In this paper, an efficient distributed wavelength reusing/migrating/sharing protocol (WRMSP) for the dual bus lightwave networks (DBLN) is proposed. This protocol consists of three efficient schemes for carrying out the wavelength reusing, migration and sharing, respectively. Simulation results show that for a limited number of wavelengths and tunable receivers, the proposed protocol substantially improve the network throughput and access delay under general traffic demands     

Active star coupler based fiber-optic local area network

A 50-MBd active star fiber optical Iocal area network (LAN) and its optical combiner and mixing rod splitter are presented. The limited power budget and relatively large tapping losses of lightwave technology, which limit the use of fiber optics in tapped bus LAn topologies, are examined and proven tolerable in optical star topologies. The optical combiner and splitter, compononets necessary for such a network, have been fabricated and evaluated. The optical combiner, consisting, of a fiber bundle couled to a large-area p-i-n photodetector, and the mixing rod splitter, which had an insertion lodd of 19.8dB±1.4dB (including splitting loss), are shown to have suitable characteristics for the 50-MBd 32-node active optical star network. This star topology. proposed as an internetwork gateway which uses token-passing or polling protocol for packet switched data transmission, could be enhanced with wavelength-division multiplexing to provide both packet switched data and frequency division circuit switched real-time video and voice services network. Applications suggested for such a gateway or netwrok include health car information systems and factory automation.     

Design of logical topologies for wavelength-routed optical networks

The problem of designing a logical topology over a wavelength-routed all-optical network (AON) physical topology is studied. The physical topology consists of the nodes and fiber links in the network. On an AON physical topology, we can set up lightpaths between pairs of nodes, where a lightpath represents a direct optical connection without any intermediate electronics. The set of lightpaths along with the nodes constitutes the logical topology. For a given network physical topology and traffic pattern, our objective is to design the logical topology and the routing algorithm so as to minimize the network congestion while constraining the average delay seen by a source-destination pair and the amount of processing required at the nodes (degree of the logical topology). Ignoring the delay constraints can result in fairly convoluted logical topologies with very long delays. On the other hand, in all our examples, imposing it results in a minimal increase in congestion. While the number of wavelengths required to imbed the resulting logical topology on the physical all optical topology is also a constraint in general, we find that in many cases of interest this number can be quite small. We formulate the combined logical topology design and routing problem described above as a mixed integer linear programming problem which we then solve for a number of cases of a six-node network. This programming problem is split into two subproblems: logical topology design, and routing. We then compare the performance of several heuristic topology design algorithms against that of randomly generated topologies, as well as lower bounds     

Achieving 100% Throughput in Reconfigurable Optical Networks

We study the maximum throughput properties of dynamically reconfigurable optical network architectures having wavelength and port constraints. Using stability as the throughput performance metric, we outline the single-hop and multi-hop stability regions of the network. Our analysis of the stability regions is a generalization of the BvN decomposition technique that has been so effective at expressing any stabilizable rate matrix for input-queued switches as a convex combination of service configurations. We consider generalized decompositions for physical topologies with wavelength and port constraints. For the case of a single wavelength per optical fiber, we link the decomposition problem to a corresponding Routing and Wavelength Assignment (RWA) problem. We characterize the stability region of the reconfigurable network, employing both single-hop and multi-hop routing, in terms of the RWA problem applied to the same physical topology. We derive expressions for two geometric properties of the stability region: maximum stabilizable uniform arrival rate and maximum scaled doubly substochastic region. These geometric properties provide a measure of the performance gap between a network having a single wavelength per optical fiber and its wavelength-unconstrained version. They also provide a measure of the performance gap between algorithms employing single-hop versus multi-hop electronic routing in coordination with WDM reconfiguration.