N＊DPT／D／1排队系统分析

多路离散周期串到达，单个服务台定长服务排队系统，是在研究ＣＢＲ业务下ＡＴＭ网络中间节点性能时所遇到的一种排队模型，在有线ＡＴ 的ＣＢＲ精力接进无线ＡＴＭ网时也会遇到这种排模型，本文分析了这一排队系统，得到 队长剩余分布的计算公式     

ATM网络中CBR业务排队性能分析

分析了ATM网络中CBR业务排队性能,给出了一种简单的计算信元丢失率和信元平均时延的表达式.分析结果表明,一方面在较小的缓冲区容量下,即使CBR业务被分配的带宽大于等于其峰值速率,也还存在着较大的信元丢失;另一方面,当复用的CBR业务源数目很大时,只需要分配相对较小的缓冲区容量就可以满足十分低的信元丢失率要求.该结果对于ATM设备中相应的缓冲区设计、带宽分配以及连接允许控制机制的研究具有重要的意义.     

ATM通信量管理技术及其在视频点播中的应用

ATM现有的5种通信量业务类型,即：恒定比特率（CBR）、可变比特率（VBR）、可用比特率（ABR）、不定比特率（UBR）和可保证帧速率（GFR）业务,在应用中各有所长。阐述了将ATM ABR业务运用于视频点播系统时,客户端和服务器端的缓存尺寸设置方法,为ABR业务在视频点播系统中的实际应用提供了有力的理论基础。     

信元率可调的ATM网络技术

现在,当用户使用异步传送模式(ATM)网络时,它必须从4类传送业务中选择一类业务。第一类业务是恒定比特率(CBR),其数据率是固定不变的。ATM网必须保证这类传送业务,并控制网络连接的业务量,以保证用户不至于超过其所分配的业务量。这类业务主要用于传送类似数据租用线传送的数据流。 第二类业务是更灵活的可变比     

突发业务环境下CBR业务性能的实验分析

CBR业务是一类极为重要的实时业务,能否有效地传递这类业务关系到从现有网络向ATM的过渡,因此CBR业务的服务质量是一个值得研究的重要课题。本文利用计算机仿真的方法,全面地分析了突发业务环境下,影响CBR业务服务质量的各种因素,指出复接器占有率、缓冲区容量、背景强度、背景流的自相关特征对CBR业务的时延及时延抖动有很大的影响,尤其是背景流具有长时相关性时,CBR业务的服务质量将严重恶化,必须设法加以控制。     

帧中继/ATM PVC业务的网络互通

帧中继/ATM PVC业务的网络互通是目前阶段解决帧中继网向以ATM技术为核心的B-ISDN网过渡的关键技术。本文论述了帧中继网与B-ISDN互通时网络互通功能单元(IWF)完成的功能,它包括帧中继Q.922核心子层和B-ISDN的ATM层及AAL层之间的参数映射。B-ISDN通过IWF来支持帧中继的各种业务。     

基于Matlab的M/M/m排队模型的仿真

在排队论中，排队模型的经典分析方法一般是通过建立Markov链，对其稳态系统进行求解。但是当Markov链状态数较多或排队模型比较复杂时，求解稳态方程将变得比较困难，甚至是无法求解。本文采用基于事件调度(ES)的离散事件的仿真方法，以静态仿真的思想实现动态系统的仿真，利用Matlab语言对M／M／m模型进行了仿真。仿真结果表明，该方法是切实可行的。     

单服务员排队模型及其蒙特卡洛模拟

单服务员的排队模型(M/M/1模型)是排队论中重要的排队系统。介绍排队论的基本概念,讨论和研究单服务员排队模型的过程和基本原理,通过数学计算得出单服务员排队模型中重要的运行指标。针对典型实例,借助于计算机软件包Matlab 6.5进行了蒙特卡洛模拟。     

非均匀业务下反压型输入/输出排队ATM交换机的性能分析

本文分析了一种内部无阻塞反压型输入／输出排队ＡＴＭ交换机，在非均匀负载输入下的信元丢失、信元延时指标，文中采用一一种Ｇｅｏｍ／ＰＨ／Ｉ／Ｋ排队模型分析输入排队系统仲裁系统的分析采用了一种二维Ｍａｒｋｏｖ过程，结论对设计一种反压型输入／输出排队ＡＴＭ交换机有参考意义。     

电信交换技术、交换机与交换系统

N98-05673 9906200电子情报通信学会技术研究报告:交换系统 SSE97-181～192(信学技报,Vol.97,No.617)〔汇,日〕/日本电子情报通信学会.—1998.03.—72P.(LG)本文集收入的12篇文章主要涉及通信业务之间的互作用及其静态探测方法,ATM 公共网上的全球PNNI 互联网,多媒体业务的实时转移,个人通信系统UPT 的信令协议,智能网(IN)业务数据的先进管理方法,自动编码技术,Gb 数量级交换机的多层接线 LSI结构,分组交换网的新调度规程,在有 CBR/VBR 业务时的 ABR 业务特性,ATM 网中周期和突发信息源的相位分配算法,网络业务自相似对服务质量的影响,以及根据业务量变化特性推算高峰率的方法等的研究。     

B—ISDN／ATM网络中的拥塞控制

给出Ｂ－ＩＳＤＮ／ＡＴＭ网络中的业务量类型，描述实时业务量，交互式业务量和成批业务量的拥塞控制，并讨论了用于这种网络的防止性拥塞控制方法。     

基于进化规划的ATM网络优化路由算法

根据ATM网络承载业务的特性，提出了以最小化全网平均信元丢失率为目标函数，以途经交换节点数目为约束的优化路由准则，并应用进化规划方法求解此优化问题。     

Performance of ATM networks under hybrid ARQ/FEC error controlscheme

In ATM networks, fixed-length cells are transmitted. A cell may be discarded during the transmission due to buffer overflow or detection of errors. Cell discarding seriously degrades transmission quality. This paper analyzes a hybrid automatic repeat request/forward error control (ARQ/FEC) cell-loss recovery scheme that is applied to virtual circuits (VCs) of ATM networks. FEC is performed based on a simple single-parity code, while a Go-Back-N ARQ is employed on top of that. Both throughput efficiency and reliability analysis of the hybrid scheme are presented. In the process we investigate the interactive effects of the network parameters (number of transit nodes, traffic intensity, ARQ packet length, …) on the performance. The analysis provides a method for optimizing the FEC code size for a given network specification     

Survey of traffic control schemes and protocols in ATM networks

The authors survey a number of important research topics in ATM (asynchronous transfer mode) networks. The topics covered include mathematical modeling of various types of traffic sources, congestion-control and error-control schemes for ATM networks, and priority schemes to support multiple classes of traffic. Standard activity for ATM networks and future research problems in ATM are also presented. It is shown that the cell-arrival process for data sources can be modeled by a simple Poisson process. However, voice sources or video sources require more complex processes because of the correlation among cell arrivals. Due to the effects of high-speed channels, preventive control is more effective in ATM networks than reactive control. Due to the use of optical fibers in ATM networks, the channel error rate is very small. The effects of propagation delay and processing time become significant in such high-speed networks. These fundamental changes trigger the necessity to reexamine the error-control schemes used in existing networks. Due to the diversity of service and performance requirements, the notion of multiple traffic classes is required, and separate control mechanisms should be used according to the traffic classes. The priority scheme is shown to be an effective method to support multiple classes of traffic     

Traffic management for TCP/IP over satellite ATM networks

Several Ka-band satellite systems have been proposed that will use ATM technology to seamlessly transport Internet traffic. The ATM UBR, GFR, and ABR service categories have been designed for data. However, several studies have reported poor TCP performance over satellite ATM networks. We describe techniques to improve TCP performance over satellite ATM networks. We first discuss the various design options available for TCP end systems, IP-ATM edge devices, as well as ATM switches for long-latency connections. We discuss buffer management policies, guaranteed rate services, and the virtual source/virtual destination option in ATM. We present a comparison of ATM service categories for TCP transport over satellite links. The main goal of this article is to discuss design and performance issues for the transport of TCP over UBR, GFR, and ABR services for satellite ATM networks     

Broadband satellite networks-the global IT bridge

Next-generation broadband satellite networks are being developed to carry bursty Internet and multimedia traffic in addition to the traditional circuit-switched traffic (mainly voice) on a global basis. These satellites provide direct network access for personal applications as well as interconnectivity to the terrestrial remote network segments. The main requirement in success of these networks is that they should be able to transmit high data rate traffic with prescribed quality of service (QoS). Thus, the broadband satellite network has no choice other than the rise of ATM technology and to be optimized for Internet-based traffic. ATM is the promising technology for supporting high-speed data transfer potentially suitable for all varieties of private and public telecommunications networks. IP, on the other hand is the fast-growing Internet layer protocol that is applicable over any data link layer Internet-based applications are the emerging source of traffic in the future wireless networks and broadband satellite networks should consider Internet as the primary service. In this paper, we discuss the traditional ATM and wireless ATM networks and explain the characteristics of the wireless IP networks. The paper then uses those concepts in defining the criteria for the broadband satellite networks such as the QoS and traffic management. Application of the broadband satellite networks is also proposed     

A new ATM adaptation layer for TCP/IP over wireless ATM networks

This paper describes the design and performance of a new ATM adaptation layer protocol (AAL‐T) for improving TCP performance over wireless ATM networks. The wireless links are characterized by higher error rates and burstier error patterns in comparison with the fiber links for which ATM was introduced in the beginning. Since the low performance of TCP over wireless ATM networks is mainly due to the fact that TCP always responds to all packet losses by congestion control, the key idea in the design is to push the error control portion of TCP to the AAL layer so that TCP is only responsible for congestion control. The AAL‐T is based on a novel and reliable ARQ mechanism to support quality‐critical TCP traffic over wireless ATM networks. The proposed AAL protocol has been validated using the OPNET tool with the simulated wireless ATM network. The simulation results show that the AAL‐T provides higher throughput for TCP over wireless ATM networks compared to the existing approach of TCP with AAL 5. This revised version was published online in July 2006 with corrections to the Cover Date.     

A local fairness algorithm for gigabit LAN's/MAN's with spatialreuse

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     

Congestion control for multimedia services

The problem of congestion control in high-speed networks for multimedia traffic, such as voice and video, is considered. It is shown that the performance requirements of high-speed networks involve delay, delay-jitter, and packet loss. A framing congestion control strategy based on a packet admission policy at the edges of the network and on a service discipline called stop-and-go queuing at the switching nodes is described. This strategy provides bounded end-to-end delay and a small and controllable delay-jitter. The strategy is applicable to packet switching networks in general, including fixed cell length asynchronous transfer mode (ATM), as well as networks with variable-size packets     

Applying ATM/AAL2 as a switching technology in third-generationmobile access networks

In this article we focus on the transport and switching part of third-generation mobile access networks and outline some important aspects of applying ATM in these networks. In particular, we argue that in order for the mobile access network to support low-bit-rate delay-sensitive traffic consisting of short packets, the standardization of a new ATM adaptation layer, AAL2, and associated signaling protocol has been necessary. The AAL2 protocol has been designed to support low-bit-rate delay-sensitive services (typically compressed voice) where other adaptation layers fail to deliver the required QoS and maintain efficient resource utilization at the same time. Furthermore, in order to provide mobility and soft handover support in W-CDMA-based mobile networks such as UMTS or IMT-2000, there is also a strong demand for fast connection establishment and release. Therefore, when designing ATM-based cellular access networks some specific architectural and traffic management issues need to be addressed