共查询到20条相似文献，搜索用时 31 毫秒
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A novel architecture of wavelength-division multiplexing/optical code division multiplexing access-passive optical network
(WDM/OCDMA-PON) based on superstructure fiber Bragg grating (SSFBG) and wavelength re-modulation technology is proposed. In
this scheme, WDM is overlaid on OCDMA channel in a single network by virtue of a kind of SSFBG, and the total capacity of
hybrid PON can be extended by regulating the transmission power reasonably. Re-modulation technology is also a good method
to save wavelength-specific components at the optical network unit (ONU) and cost of wavelength management on the customer
side. In simulation system, 1.25 Gb/s up/downstream data are transported with good performance. In addition the crosstalk
penalties from adjacent wavelength channels (with the same OC) are found to be negligible in upstream and downstream transmissions. 相似文献
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Wavelength and bandwidth allocation is important for multicast communication in optical networks. In this paper, a new method based on scheduling theory is proposed. The proposed method formulates wavelength bandwidth capacity as a large rectangle and these multicast stream bandwidth requirements as small rectangles. It treats the wavelength and bandwidth allocation question as a rectangle packing problem. The proposed algorithm solves the problem by taking quasi-human strategy with Euclidian distance. It is an effective heuristic algorithm to quickly solve multicast stream bandwidth allocation problem in optical networks by theoretic analysis. Further simulation experiments show the bandwidth allocation algorithm can increase network utilization and have a good fairness performance for unicast stream and multicast stream in optical networks. The results indicate the effectiveness of the algorithm. 相似文献
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TCP Vegas是运输层的一种可靠算法,但是在无线网络中不能最高效率的占用网路带宽,使得数据传输受到限制,不适合在无线网络中传输。对TCP Vegas算法进行改进,提出了一种适用于异构网络的TCP New Vegas算法。该算法将diff控制在两个动态门限值a,b之间,根据a,b两个动态门限值的设定,可有效的提高算法的拥塞窗口及吞吐量。以无线传感器网络接入第三代移动通信网络为仿真背景,对该算法进行了仿真实验。仿真结果表明,改进后的TCP New Vegas算法具有较大的拥塞窗口和较高的吞吐量,更适合应用于异构网络中数据的传输。 相似文献
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由于传统卫星通信中射频链路的不足以及光通信在容量、抗干扰及保密等多方面的优势,利用激光作为链路的卫星光通信受到了广泛关注.介绍了国内外卫星光通信的发展现状,依据空间信息网络协议体系结构,从星间激光链路、信道编码和网络层三方面出发,初步探讨了卫星光网络体系结构,研究了其关键技术,提出了动态虚拓扑的路由选择算法和波分复用波长分配算法. 相似文献
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张茂华 《安顺师范高等专科学校学报》2012,(5):132-135
由于高速和高频宽网络快速发展需要,光纤通过能够提供宽频服务逐渐成为了主要的传输媒介。光纤传播过程中不仅要确保用户收到服务的品质,最重要的是需要保证不会因为光纤断点而发生通讯中断,所以说光纤断点保护机制仍是研究的重要课题。文章通过提出一种自我治愈环型-星型光纤网络拓扑结构,尝试解决光纤网络断点问题。 相似文献
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采厢EPON＋基带EOC模式对云南临沧现存有线电视网络进行双向改造,光线路终端（OLT）置于中央控制机房,ONU设备布局在集中分配的光节点位置,通过五类双绞线互连．另外,将光节点中铜轴射频信号接入到EOC局端设备,由它完成数字信号的调制,并与有线电视信号进行混合,再经原有的铜轴网络进行混合信号的传输．ONU与用户之问的连接采用EOC技术,EOC客户端设备布局在用户室内． 相似文献
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方捻 《上海大学学报(英文版)》2006,10(4):373-374
All optical network (AON) is a hot topic in recentstudies of optical fiber communications . Key tech-niques in AONinclude optical switching/routing,opti-cal cross connection ( OXC) , all optical wavelengthconversion (AOWC) ,all optical buffering,etc. Opti… 相似文献
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Based on a comprehensive study of various algorithms, the automatic recognition of traditional ocular optical measuring instruments is realized. Taking a universal tools microscope (UTM) lens view image as an example, a 2-layer automatic recognition model for data reading is established after adopting a series of pre-processing algorithms. This model is an optimal combination of the correlation-based template matching method and a concurrent back propagation (BP) neural network. Multiple complementary feature extraction is used in generating the eigenvectors of the concurrent network. In order to improve fault-tolerance capacity, rotation invariant features based on Zernike moments are extracted from digit characters and a 4-dimensional group of the outline features is also obtained. Moreover, the operating time and reading accuracy can be adjusted dynamically by setting the threshold value. The experimental result indicates that the newly developed algorithm has optimal recognition precision and working speed. The average reading ratio can achieve 97.23%. The recognition method can automatically obtain the results of optical measuring instruments rapidly and stably without modifying their original structure, which meets the application requirements. 相似文献
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LU Guang WANG Yong-chao ZHU Miao-liang 《浙江大学学报(A卷英文版)》2007,8(6):849-856
The Internet evolves to incorporate very-high-bandwidth optical links and more large-delay satellite links. TCP faces new challenges in this unique environment. Theory and experiments showed that TCP becomes inefficient and is prone to be unstable as the per-flow product of bandwidth and latency increases, regardless of the queuing scheme. Variable-structure congestion Control Protocol (VCP) is proposed to address these problems. However, VCP has problem in terms of convergence time, i.e., it takes a long time for a new VCP flow to achieve fair bandwidth allocation if the existing VCP flows have large con- gestion windows. This paper proposed an Extended Variable-structure congestion Control Protocol (EVCP), which adopted a convergence controller. The basic idea of convergence controller is that if a flow has larger window than its fair window, its congestion window should be decreased more aggressively than usual in Multiplicative Decrease (MD) phase. Simulations showed that EVCP has better performance in terms of convergence time while keeping the advantages of VCP. 相似文献
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把波分复用技术应用于计算机光互连网络 ,通过分析波长和网络路由之间的关系 ,提出了采用波长作为 IP寻径“网络地址”,实现网络间路由寻径的新概念 ,使网络具有非常好的可扩展性 .介绍了实验室利用双波长环网构成机群系统验证波长路由的工作进展及关键单元设计 .性能测试表明 ,光互连技术的应用 ,是解决网络带宽不足的理想技术 . 相似文献
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本文针对MPEG VBR多媒体流量的特征,结合小波和卡尔曼滤波的特点,在新的网络流量预测模型的基础上,提出了一种新的多媒体流自适应带宽分配算法,并在NS仿真平台中实现该算法。结果表明,该算法能够有效避免网络拥塞,降低网络传输时延,减少数据丢包率,明显地提高了带宽利用率,具有较好的实时性,支持QOS。 相似文献
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High-speed train communication system is a typical high-mobility wireless communication network. Resource allocation problem has a great impact on the system performance. However, conventional resource allocation approaches in cellular network cannot be directly applied to this kind of special communication environment. A multidomain resource allocation strategy was proposed in the orthogonal frequency-division multiple access （OFDMA） of high-speed. By analyzing the effect of Doppler shift, sub-channels, antennas, time slots and power were jointly consid- ered to maximize the energy efficiency under the constraint of total transmission power. For the purpose of reducing the computational complexity, noisy chaotic neural network algorithm was used to solve the above optimization problem. Simulation results showed that the proposed resource allocation method had a better performance than the traditional strategy. 相似文献
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In this paper, we propose a novel optimal quality adaptation algorithm for MPEG-4 fine granular scalability (FGS) stream over wired network. Our algorithm can maximize perceptual video quality by minimizing video quality variation and increasing available bandwidth usage rate. Under the condition that the whole bandwidth evolution is known, we design an optimal algorithm to select layer. When the knowledge of future bandwidth is not available, we also develop an online algorithm based on the optimal algorithm. Simulation showed that both optimal algorithm and online algorithm can offer smoothed video quality evolution. 相似文献
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针对AdHoc网络的视频传输,提出了一种新的网络带宽预测及控制方案．该方案基于跨层、接收端反馈以及贝叶斯网络等技术．对视频传输过程进行公式化描述,从而推导出影响视频传输质量的几个主要因素,这些因素可以通过跨层机制或接收端反馈的方式获取．根据这些影响因素,确定变量集和贝叶斯网络拓扑结构,从而构建贝叶斯网络预测模型．预测结果作为AdHoc网络带宽,根据该带宽值来控制视频编码器,动态调节输出的实时视频流码率．为验证该方案,对整个视频通信系统进行了仿真．结果显示,跟传统的传输方案相比较,夺方案能更好地利用网络带宽,减少了数据包的丢失,提高了实时视频质量． 相似文献
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In order to improve the transmission accuracy and efficiency of sensing and actuating signals in Internet of Things(IoT) and ensure the system stability,an adaptive resource allocation algorithm is proposed,which dynamically assigns the network bandwidth and priority among components according to their signals’ frequency domain characteristics.A remote sensed and controlled unmanned ground vehicle(UGV) path tracking test-bed was developed and multiple UGV’s tracking error signals were measured in the simulation for performance evaluation.Results show that with the same network bandwidth constraints,the proposed algorithm can reduce the accumulated and maximum errors of UGV path tracking by over 60% compared with the conventional static algorithm. 相似文献
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Nonlinear errors always exist in data obtained from tracker in augmented reality （AR）, which badly influence the effect of AR. This paper proposes to rectify the errors using BP neural network. As BP neural network is prone to getting into local extrema and convergence is slow, genetic algorithm is employed to optimize the initial weights and threshold of neural network. This paper discusses how to set the crucial parameters in the algorithm. Experimental results show that the method ensures that the neural network achieves global convergence quickly and correctly. Tracking precision of AR system is improved after the tracker is rectified, and the third dimension of AR system is enhanced. 相似文献
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为提高大型网络的 FlexRay 动态段带宽利用率,采用时隙复用的方法对 FlexRay 动态段消息调度进行优化。在深入分析 FlexRay 动态段带宽利用率表达式及整体消息最坏响应时间的基础上,确定影响动态段带宽利用率的关键因素,并根据可调度分析方法建立动态调度模型。该模型以优化动态段带宽利用率为目标,采用启发式调度算法构建消息的动态调度方案,从而得出最优的动态段长度配置和帧 ID 配置,以降低负载、提升网络带宽利用率。最后,以 FlexRay 底盘综合控制与安全系统为对象,对上述算法进行验证。实验结果证明,启发式调度算法可以优化动态段帧 ID 配置,动态段带宽利用率在总线速率为 5Mbit/s、10Mbit/s 时分别提高了6.22%与 10.23%。 相似文献