如何选购适合半导体专用的大气机械手臂运用于EFEM设备上

从φ150mm开始Robot(机械手臂)就被广泛运用,除了有效地降低微尘颗粒的大小、允许以程序化来决定晶圆取放的路径等优点外,自动化作业的迫切需求,更是其主要原因。Robot被分为Liner与Scara两种,ScaraType在φ200mm及之后晶圆制造中运用较多。采购Robot通常有两种情况,一为只单纯买一个Robot,不需要配合其它外围做运用。二为需要搭配外围做整合蛐集成,此种方式在半导体业较为普及,但是也较为复杂。现以布鲁克斯穴Brooks雪在设备自动化整合方面的经验,与国内业界友人一同探讨选购Robot的诀窍及注意事项。     

Source behavior for ATM ABR traffic management: an explanation

The available bit rate (ABR) service has been developed to support data applications over asynchronous transfer mode (ATM) networks. The network continuously monitors its traffic and provides feedback to the source end systems. This article explains the rules that the sources have to follow to achieve a fair and efficient allocation of network resources     

在ATM网络中如何管理SLA

ATM的不断增长的需求和ATM网络的操作复杂性推动了ATM SLA（Service Level Agreement:ATM服务水平协议）的发展。ATM SLA顺应了网络管理者的要求,它包括对网络的设计、执行、监视、维护和日常管理等方面的内容。介绍了ATM网络中SLA的基本组成,并举例说明国外大公司如何将SLA应用在ATM网络中。     

Entropy of ATM traffic streams: a tool for estimating QoSparameters

For the purposes of estimating quality-of-service parameters, it is enough to know the large deviation rate-function of an ATM traffic stream; modeling procedures can be bypassed if we can estimate the rate-function directly, exploiting the analogy between the rate-function and thermodynamic entropy. We show that this proposal is soundly based on statistical sampling theory. Experiments on the Fairisle ATM network at the University of Cambridge have established that it is feasible to collect the required data in real time     

基于市场拍卖模型的ATM网络ABR业务控制

本文提出一种分布式的、基于用户竞价模型的ＡＴＭ网络ＡＢＲ业务控制机制,可为用户提供在业务传输中没价格与不同服务质量等级之间的协商。在此欺压耻我们定义了新的资源利用公平性准则。它是最大一最小准则的扩充,本文方法所用的控制和计旨易于实现,并且遵循ＡＴＭ论坛提出的ＡＢＲ业务明确位率反馈控制规范,因而此方法ＡＢＲ业务的计旨几分布式管理相集成提供了一条新思路。     

Some optimal traffic regulation schemes for ATM networks: a Markovdecision approach

Some new traffic regulation schemes are defined in terms of a relief-spacing (or spacing of the allowance for cell delivery to the network) function. The class of open-loop traffic regulators (TR's) is defined in terms of relief-spacing functions which depend on some user-state; this class may be viewed as an extension of the Spacer-Controller defined in terms of some constant (user-state independent) relief-function. The optimal open-loop TR's are derived by formulating proper optimization problems and applying a Markov decision approach. Numerical results illustrate the improved performance of the optimal open-loop TR over that of the (constant relief-spacing) Spacer-Controller. Finally, the class of closed-loop TR's is defined in terms of relief-spacing functions which depend on both some user- and some network-state information and its optimal element is derived. The improved performance under the optimal closed-loop TR over that of the optimal open-loop TR is illustrated and their difference determines the performance gain if feedback information can become available on time     

On self-similar traffic in ATM queues: definitions, overflowprobability bound, and cell delay distribution

Recent traffic measurements in corporate local-area networks (LANs), variable-bit-rate video sources, ISDN control-channels, and other communication systems, have indicated traffic behaviour of self-similar nature. This paper first discusses some definitions and properties of (second-order) self-similarity and gives simpler criteria for it. It then gives a model of self-similar traffic suitable for queuing system analysis of an asynchronous transfer mode (ATM) queue. A lower bound to the overflow probability of a finite ATM buffer is obtained, as also a lower bound to the cell loss probability. Finally, the stationary distribution of the cell delay in an infinite ATM buffer is obtained     

How to reconstruct end-to-end traffic based on time-frequency analysis and artificial neural network

End-to-end traffic, which describes the inherent characteristics and end-to-end behaviors of communication networks, is the crucial input parameter of network management and network traffic engineering. This paper proposes a new reconstruction algorithm to develop the research on reconstruction of end-to-end traffic in large-scale communication networks. We firstly conduct the time-frequency analysis on end-to-end traffic, and then localize its features to gain its time-frequency properties before decomposing it into the low-frequency and high-frequency components. We find that if decomposing appropriately, the low-frequency component of end-to-end traffic can accurately reflect its change trend, while its high-frequency component can well show the burst and fluctuation nature. This motivates us to find a reasonable time-frequency decomposition strategy to extract the low-frequency and high-frequency components of end-to-end traffic. Moreover, this further inspires us to use the regressive model to model the low-frequency part, exploit artificial neural network to characterize the high-frequency component, and then combine these two parts according to the regressive model and artificial neural network to precisely reconstruct end-to-end traffic. Simulation results show that in contrast to previous methods our algorithm is much more effective and promising.     

Bandwidth-dependent scheduling algorithm to limit cell delayvariation for CBR traffic in ATM networks

A multiplexing control scheme is proposed for limiting the cell delay variation (CDV) caused by multiplexing of constant bit rate (CBR) traffic in asynchronous transfer mode (ATM) networks. The control scheme is based on a bandwidth-dependent scheduling algorithm. The limitation of the CDV is proved     

A VLSI sequencer chip for ATM traffic shaper and queue manager

The authors propose to control user traffic at two places in an asynchronous transfer model (ATM) network: at the user-network interface (UNI) by a traffic enforcer, and at the network-node interface (NNI) by a queue manager. The traffic enforcer adopted in this work contains a buffer to delay and reshape the violating cells that do not comply with some agreed-upon traffic parameters, and thus is also called a traffic shaper. The queue manager manages the queued cells in network nodes in such a way that higher priority cells are always served first, low-priority cells are discarded when the queue is full, and any interference between same-priority cells is prevented. Architectures for the traffic shaper and the queue manager are proposed. A key component, called the sequencer chip, has been implemented and tested to realize both architectures. The sequencer chip uses 1.2-μm CMOS technology. It contains about 150 K transistors, has a die size of 7.5 mm×8.3 mm, and is packages in a 223-pin ceramic pin-grid-array (PGA) carrier     

Scalable architectures for integrated traffic shaping and linkscheduling in high-speed ATM switches

Emerging broad-band switches must accommodate the diverse traffic parameters and quality-of-service requirements of voice, data, and video applications. End-to-end performance guarantees depend on connections complying with traffic contracts as their cells travel through the network. This paper presents a leaky-bucket shaper architecture that scales to a large number of connections with diverse burstiness and bandwidth parameters. In contrast to existing designs, the proposed architecture arbitrates fairly between connections with conforming cells by carefully integrating leaky-bucket traffic shaping with rate-based scheduling algorithms. Through a careful combination of per-connection queueing and approximate sorting, the shaper performs a small, bounded number of operations in response to each arrival and departure, independent of the number of connections and cells. When the shaper must handle a wide range of rate parameters, a hierarchical arbitration scheme can reduce the implementation overheads and further limit interference between competing connections. Through simulation experiments, we demonstrate that the architecture limits cell-shaping delay and traffic distortions, even in periods of heavy congestion. The efficient combination of traffic shaping and link scheduling results in an effective architecture for managing buffer and bandwidth resources in large, high-speed ATM switches     

A new approach for allocating buffers and bandwidth toheterogeneous, regulated traffic in an ATM node

A new approach to determining the admissibility of variable bit rate (VBR) traffic in buffered digital networks is developed. In this approach all traffic presented to the network is assumed to have been subjected to leaky-bucket regulation, and extremal, periodic, on-off regulated traffic is considered; the analysis is based on fluid models. Each regulated traffic stream is allocated bandwidth and buffer resources which are independent of other traffic. Bandwidth and buffer allocations are traded off in a manner optimal for an adversarial situation involving minimal knowledge of other traffic. This leads to a single-resource statistical-multiplexing problem which is solved using techniques previously used for unbuffered traffic. VBR traffic is found to be divisible into two classes, one for which statistical multiplexing is effective and one for which statistical multiplexing is ineffective in the sense that accepting small losses provides no advantage over lossless performance. The boundary of the set of admissible traffic sources is examined, and is found to be sufficiently linear that an effective bandwidth can be meaningfully assigned to each VBR source, so long as only statistically-multiplexable sources are considered, or only nonstatistically-multiplexable sources are considered. If these two types of sources are intermixed, then nonlinear interactions occur and fewer sources can be admitted than a linear theory would predict. A qualitative characterization of the nonlinearities is presented. The complete analysis involves conservative approximations; however, admission decisions based on this work are expected to be less overly conservative than decisions based on alternative approaches     

A hybrid analysis/simulation for ATM performance with application to quality-of-service of CBR traffic

A discrete time queueing model for the performance of an ATM system is analyzed using matrix analytic methods. Time is segmented into slots with each slot equal to the transmission time of one ATM cell. The ATM system is modeled as a single server queue with Markovian arrivals and service time equal to one slot. The arrival process includes as a special case the superposition of on-off sources, possibly heterogeneous. The queueing model is of the M/G/1 type. By exploiting the structure of the M/G/1 type Markov chain, the complexity of the solution to the problem is reduced to only the inversion of a 2×2 matrix irrespective of the size of the Markov chain. This simplification allows us to investigate Constant Bit Rate (CBR) traffic performance (or quality-of-service) issues through a hybrid analysis/simulation approach. Specifically, we analyze the impact of on-off background traffic on the probability of consecutive cell losses, cell delay variation, and traffic shaper or playback buffer underflow and overflow probabilities of CBR traffic sources.     

Three-level traffic shaper and its application to source clockfrequency recovery for VBR video services in ATM networks

Studies the traffic shaping issues for VBR video services in ATM networks with stress put on the source clock frequency recovery aspect. The authors propose a “three-level traffic shaper” (TLTS) which is able to limit the minimum as well as the maximum cell rate of input VBR traffic. For a VBR video source modeled after a two-state Markov modulated Poisson process, they determine, as performance measures, the cell loss probability, the underflow probability, and the maximum delay that a cell can experience in the proposed TLTS. Then they apply the TLTS for source clock frequency recovery in VBR video services. In extending the existing CBR-based synchronous residual time stamp (SRTS) method for VBR video services, it is necessary to restrict the minimum, as well as the maximum, number of cells generated in a fixed period of time to ensure the transmission of timing information, and the proposed TLTS is tailored to meet this necessity by adopting an optimal dimensioning procedure based on the genetic algorithm (GA). Finally the authors provide some numerical examples to demonstrate the optimal dimensioning procedure of TLTS and the related performances of statistical multiplexing and source clock frequency recovery     

ATM cell delay and loss for best-effort TCP in the presence ofisochronous traffic

This paper reports the findings of a simulation study of the queueing behavior of “best-effort” traffic in the presence of constant bit-rate and variable bit-rate isochronous traffic. In this study, best-effort traffic refers to ATM cells that support communications between host end systems executing various applications and exchanging information using TCP/IP. The performance measures considered are TCP cell loss, TCP packet loss, mean cell queueing delay, and mean cell queue length. Our simulation results show that, under certain conditions, best-effort TCP traffic may experience as much as 2% cell loss. Our results also show that the probability of cell and packet loss decreases logarithmically with increased buffer size     

ATM modelling: parameterisation of 4-phase MMPP model for admissioncontrol of superposed traffic sources

A new approach is adopted to parameterise the 4-phase Markov modulated Poisson process (MMPP) to find the 4-phase arrival and transition rate parameters. This parameterisation is a major step in applying the 4-phase MMPP model to asynchronous transfer mode (ATM) modelling in the connection admission control (CAC) and in the bandwidth allocation of traffic