共查询到20条相似文献,搜索用时 15 毫秒
1.
Chen J.S.-C. Cidon I. Ofek Y. 《Selected Areas in Communications, IEEE Journal on》1993,11(8):1183-1192
The authors present an algorithm to provide local fairness for ring and bus networks with spatial bandwidth reuse. Spatial bandwidth reuse can significantly increase the effective throughput delivered by the network. The proposed algorithm can be applied to any dual ring or bus architecture such as MetaRing. In the dual bus configuration, when transporting ATM cells, the local fairness algorithm can be implemented using two generic flow control (GFC) bits in the ATM cell header. In the performance it is shown that this local fairness algorithm can exploit the throughput advantage offered by spatial bandwidth reuse better than a global fairness algorithm. This is accomplished because it ensures fair use of network resources among nodes that are competing for the same subset of links, while permitting free access to noncongested parts of the network. The performance advantage of the local fairness scheme is demonstrated by simulating the system under various traffic scenarios and comparing the results to that of the MetaRing SAT-based global fairness algorithm. It is also shown that under certain traffic patterns, the performance of this algorithm achieves the optimal throughput result predicted by the known Max-Min fairness definition 相似文献
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《Vehicular Technology, IEEE Transactions on》1978,27(2):69-76
Bus bunching causes uneven passenger loadings and increases the average passenger waiting time. Bunching is caused by an unstable relationship between delay in the actual bus arrival time and passenger loading time requirements. An appropriate mathematical representation of this process is provided, and the general mathematical requirements for stabilizing the process is described. It is shown how if the time of arrival is known at certain locations, the traffic signals may be appropriately timed to remove this instability and enable the buses to adhere to their schedule with greater precision. An example demonstrating the performance of the algorithm on a particular bus route is provided. 相似文献
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Marsan M.A. Casetti C. Grasso S.M. Neri F. 《Selected Areas in Communications, IEEE Journal on》1993,11(8):1290-1301
Most of the medium-access control (MAC) sublayer protocols recently proposed for application in very high-speed local and metropolitan area networks (LANs and MANs) are based on a slotted transmission scheme. Slotting guarantees very good throughput efficiencies, but further gains are possible if slots can be freed after reaching their destination, thus being available for repeated use as they propagate in the network. The authors describe a simulation-based quantitative analysis of the performance gains obtained by introducing slot reuse in distributed-queue dual-bus (DQDB) and cyclic reservation multiaccess (CRMA) MANs. CRMA-II, the latest evolution of CRMA, naturally incorporates slot reuse in the MAC protocol operations and is considered in the study for comparison purposes. In the case of the standard DQDB protocol, some existing proposals are considered. In the case of CRMA, both a previous IBM proposal and a novel approach, leading to very good performances, are studied 相似文献
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Gerla M. Tai T.-Y.C. Gallassi G. 《Selected Areas in Communications, IEEE Journal on》1993,11(8):1145-1159
One of the challenges in the interconnection of LANs and MANs to asynchronous transfer mode (ATM) networks is the support of connectionless traffic in the ATM network. A commonly proposed strategy consists of maintaining a thin, low bandwidth virtual path (VP) between each pair of gateways and requesting more bandwidth whenever a burst comes in from the LAN or MAN. Unfortunately, this strategy places a heavy burden on the ATM control processors; furthermore, it is overly conservative in the use of bandwidth. An alternative solution is proposed: on the-fly tranmission of bursts without prior bandwidth reservation. The key conditions for this scheme to work are the use of the cell loss priority (CLP) bit in the ATM cell header and the knowledge of available bandwidth on the path through bandwidth advertising. An on-the-fly strategy for connectionless traffic is described and is compared with a bandwidth renegotiation strategy 相似文献
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随着公路交通日趋发达,每个交通路口方向信号指示灯在夜晚都发挥重要的作用。为了节约能源,以及不可能做到在野外的每个路口都架设220伏交流电,介绍了一种采用太阳能电板和蓄电池作为电源,使用MSP430F149超低功耗单片机和独立总线控制器SJAl000实现的CAN总线的交通导向指示灯的设计。详细介绍了控制节点的硬件电路组成,给出了CAN节点初始化以及接收和发送程序流程。 相似文献
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This paper uses measurement-based traffic models to evaluate a shared-memory ATM switch with 32×32 155 Mbit/s ports and an external multicasting engine; this is the design of Cisco System's next-generation ATM switch, the LightStream-1010 (LS-1010). Assuming that the multicast traffic can take approximately 30% of the total switch load, we find that an external multicasting engine requires a 32 (8) cell buffer at a replication rate of 16 (64) cells per cell service time. We discover that in a multimedia environment, the shared-memory architecture requires 10-30 times less total memory than the bus architecture; a 64 K cell buffer is sufficient to handle 90% utilization with the nonuniform traffic that we investigated. Multiple-priority classes are considered 相似文献
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《电子与电脑》2004,(9)
凌特公司(Linear Technology)于近日宣布推出 LTC4221 双 HotSwapTM(热插拨)控制器,它具有双电平电路断路器,并能控制低至 1V 的内核电压。该双电平电路断路器具有一个可调的滤波器以消除适量的过流错误,同时对诸如短路等灾难性的错误作出迅速反应。此电路断路器的阀值为25mV,可使新一代低压处理器内核电源的压降最小化。除主动限制浪涌电流以保证带电插入外,LTC4221 还可以保护处理器不因为电源排序问题而闭锁。通过独立的 ON 输入、 N 沟道MOSFET 独立的高端栅驱动器以及独立的电源良好输出, LTC4221 使用户能够对系统进行配置… 相似文献
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The author reviews the role of radio frequencies in the control of traffic and pedestrians. He discusses active control of traffic junctions based on vehicle actuated demands; implying a requirement for vehicles approaching junctions or waiting at junctions to be detected, and for that detection event to be notified to the junction controller. It is also desirable to know the direction of an approaching vehicle. The great advantage of this approach is that the junction control system can generate a sequence for the light signals which should optimise the prevailing traffic flow. Detectors use a wide range of frequencies within the electromagnetic spectrum, ranging from visible light range down to tens of kHz. Within the radio frequency range, and subject to the operating frequency used, traffic detection can be effected using either below ground or above-ground antennas. The author describes both of these systems and the frequencies used for the latter. The operation and implementation of these systems is then discussed 相似文献
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本文分析了目前市场上常见主流的Pci接口芯片的特点,详细介绍DSP完整系统的设计思路,包括Pcl总线接口设计,DSP系统自举,DSP与主机的通信,驱动程序等几个方面. 相似文献
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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. 相似文献
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This letter analyzes the signal-to-noise ratio (SNR) performance of a single chip-rate DS-CDMA system that supports multi-rate traffic. A user model that allows users to dynamically switch traffic rates for different connection applications is assumed. SNR results with random chip sequences are also given 相似文献
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Interdomain traffic engineering with BGP 总被引:6,自引:0,他引:6
Quoitin B. Pelsser C. Swinnen L. Bonaventure O. Uhlig S. 《Communications Magazine, IEEE》2003,41(5):122-128
Traffic engineering is performed by means of a set of techniques that can be used to better control the flow of packets inside an IP network. We discuss the utilization of these techniques across interdomain boundaries in the global Internet. We first analyze the characteristics of interdomain traffic on the basis of measurements from three different Internet service providers and show that a small number of sources are responsible for a large fraction of the traffic. Across interdomain boundaries, traffic engineering relies on a careful tuning of the route advertisements sent via the border gateway protocol. We explain how this tuning can be used to control the flow of incoming and outgoing traffic, and identify its limitations. 相似文献
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While a variety of medium access protocols have been proposed for metropolitan area networks (MANs), the problem of handling multipriority traffic effectively in these networks remains open. The authors present a simple and effective priority mechanism for an existing MAN protocol known as the p i-persistent protocol, a probabilistic scheduling scheme that has been shown to be suitable for applications requiring large bandwidth over long, repeater-free distances. The mechanism works by clipping the low-priority stations in a controlled manner, thereby increasing the bandwidth available to the high-priority stations. This mechanism operates entirely within the framework of the basic p i-persistent protocol and may be easily tailored to achieve specific performance goals by selection of a single operating parameter. A multipriority version of a distributed algorithm by which the stations can update their operating parameters and adapt to changing network conditions dynamically is also presented 相似文献
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从控制传统的测试测量仪器到基于PC的简单测量,一直发展到今天完整的测量系统平台,测量总线技术也相应经历了从GPIB到VXI直至目前主流的PXI的演变过程。近几年,PXI总线技术在国内受到大力宣传和推广,最具代表性的PXI技术倡导者是美国国家仪器公司(National Instruments—NI)以及PXI联盟旗下的众多参与企业。 相似文献
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Eles P. Doboli A. Pop P. Peng Z. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2000,8(5):472-491
In this paper, we concentrate on aspects related to the synthesis of distributed embedded systems consisting of programmable processors and application-specific hardware components. The approach is based on an abstract graph representation that captures, at process level, both dataflow and the flow of control. Our goal is to derive a worst case delay by which the system completes execution, such that this delay is as small as possible; to generate a logically and temporally deterministic schedule; and to optimize parameters of the communication protocol such that this delay is guaranteed. We have further investigated the impact of particular communication infrastructures and protocols on the overall performance and, specially, how the requirements of such an infrastructure have to be considered for process and communication scheduling. Not only do particularities of the underlying architecture have to be considered during scheduling but also the parameters of the communication protocol should be adapted to fit the particular embedded application. The optimization algorithm, which implies both process scheduling and optimization of the parameters related to the communication protocol, generates an efficient bus access scheme as well as the schedule tables for activation of processes and communications 相似文献