下一代Internet协议——IPv6的服务质量机制探讨

ＩＰｖ６ 与ＩＰｖ４ 在网络服务质量的机制上有明显的不同。本文结合ＩＰｖ６ 头结构具体分析了ＩＰｖ６ 的ＱＯＳ机制,并讨论了它的发展前景。     

QCS──新一代的无线通信系统

本文介绍了由美国ＱＵＡＬＣＯＭＭ通信公司最新推出的无线通信系统ＱＣＳ（ＱＵＡＬＣＯＭＭＣＯｍｍｕｎｉｃａｔｉｏｎＳｙｓｔｃｍ），它采用日益成熟的ＣＤＭＡ技术，并具有独特的开放式网络结构，具有优良的性能和相当大的价格优势，ＱＣＳ支持多种实际应用，可以十分便利地添加新的服务项目。     

采用扩频实现OQAM系统

ＯＱＡＭ系统数字化实现一般采用ＦＦＴ加多相网络，提出了一种相邻载频间隔２ｆ０的ＯＱＡＭ等效复系统，并采用样值为Ｗ＾ｋ２Ｎ＝ｅｘｐｊ２πｋ＾２／Ｎ的扩谱调制器（ＳＳＭ）数字实现，ＳＳＭ取代ＦＦＴ，使系统运算复杂性显下降，计算机模拟结果表明，采用ＳＳＭ实现ＯＱＡＭ，可提高系统抗干扰能力。     

gpsOne设备商用超过百万

近日 ,ＱＵＡＬＣＯＭＭ公司宣布在日本、韩国和美国投入商用的ｇｐｓＯｎｅ技术设备已超百万。随着亚洲和美国大量部署ＣＤ ＭＡ网络 ,ＱＵＡＣＯＭＭ的ｇｐｓＯｎｅ技术成为世界上最为广泛使用的移动电话个人定位技术。ｇｐｓＯｎｅ功能的实现是通过手机端相应的ＱＵＡＬＣＯＭＭＭＳＭ芯片和系统软件 ,以及网络端的ＳｎａｐＳｍａｒｔ定位服务器软件完成的。ｇｐｓＯｎｅ技术是一种混合解决方案 ,它同时使用来自ＧＰＳ卫星和ＣＤＭＡ网络的数据 ,在各种环境下提供高可用性和高精度的定位功能。ｇｐｓＯｎｅ技术是目前具有最高精度的无线…     

QCS CDMA无线通信系统

ＱＣＳＣＤＭＡ系统是美国ＱＵＡＬＣＯＭＭ公司推出的一种采用ＣＤＭＡ技术的无线电通信系统,ＱＣＳ结构的一个重要特点是网络移动能力与呼叫能力完全分开。传统的无线网络经常以专用交换站为中心,由该中心负责移动通信管理和呼叫交换。ＱＣＳ系统则不然,它专门执行网络移动通信功能,而将所有的呼叫交换功能交给电话网络去处理。ＱＣＳ基站控制器通过标准的接口装置(如综合业务数字网ＩＳＤＮ主要数率接口),直接与标准型的4类或5类交换机连接,由于基站控制器和电话网络之间不需要移动交换机,因此需要特殊的移动交换接口协议,ＱＣＳ提供了这…     

QCS——新二代的无线通信系统

本文介绍了由美国ＱＵＡＬＣＯＭＭ通信公司最新推出的无线通信系统ＱＣＳ，它采用日益成熟的ＣＤＭＡＲＦＳＹ，它采用日益成熟的ＣＤＭＡ技术，并具有独特的开放式网络结构，具有优良的性能和相当大的价格优势，ＱＣＳ支持多种实际应用，可以十分狮 地添加新的服务项目。     

HFC网络QoS协议机制及MIB结构

本文概述了在ＨＦＣ网络中电缆设备（ＣＭＴＳ,Ｃ曲于ＤＯＳＣＳＩＳ／ＳＮＭＰ的服务质量（ＱｏＳ）标准规范和相应管理信息库（ＭＩＢ）的定义和扩充。ＨＦＣ网络服务质量的提出,将极大地促进ＨＦＣ业务开展。研究和掌握ＨＦＣ网络服务质量规范和相应的ＭＩＢ对实现ＨＦＣ网络业务和网络系统开发的意义是十分重要的。     

ISO9000与TQM的关系

ＩＳＯ９０００与ＴＱＭ的关系，可表达为ＱＡ，ＱＭ与ＴＱＭ的关系。阐述了ＩＳＯ９０００是ＴＱＭ的组成部分；ＩＳＯ９０００与ＴＱＭ是基石与发展或更高境界的关系，并借助用户需要的质量体系结构图表明了ＱＡ，ＱＭ与ＴＱＭ之间关系。     

因特网实时业务的发展

文章以实时业务ＱＯＳ为中心，综述因特风地通信时的ＱＯＳ技术体及目前产品和实验的ＤＯＳ水平，并指出目前尚存在的问题及今后的发展趋向。     

IDDQ测试技术及其实现方法

ＩＤＤＱ测试是近几年来国外比较流行的ＣＭＳＯ集成电路测试技术。ＩＤＤＱ测试能够２检测出传统的固定值故障电压测试所无法检测的ＣＭＯＳ集成电路内部的缺陷、所以,能够明显提高ＣＭＯＳ集成电路的使用可靠性。本文叙述了ＩＤＤＱ测试的基本原理和ＩＤＤＱ测试在集成电路测试系统上的实现方法及测试实例。     

NGN和IMS对承载网QOS方面的要求和QOS保障技术

在通信运营商推行的光进铜退和网络演进改造过程中,大量的PSTN用户割接到了NGN或IMS网络;还有大量的企事业单位也在逐步使用企业级的NGN或IMS设备更新换代原有老化的传统的DID交换机设备。现有的PSTN网络以电路交换为特征,在支持语音通信上颇有优势;NGN或IMS网络为保证语音通信的质量,对其承载网在QOS保障方面有明确的指标要求。本文论述了NGN、IMS对承载网QOS方面的指标要求以及QOS的相关保障技术。     

Routing subject to quality of service constraints in integratedcommunication networks

With increasingly diverse QOS requirements, it is impractical to continue to rely on conventional routing paradigms that emphasize the search for an optimal path based on a predetermined metric, or a particular function of multiple metrics. Modern routing strategies must not only be adaptive to network changes but also offer considerable economy of scope. We consider the problem of routing in networks subject to QOS constraints. After providing an overview of prior routing work, we define various QOS constraints. We present a call architecture that may be used for QOS matching and a connection management mechanism for network resource allocation. We discuss fallback routing, and review some existing routing frameworks. We also present a new rule-based, call-by-call source routing strategy for integrated communication networks     

Evolution and service requirements of CBR applications on ATM networks

Broadband integrated networks based on asynchronous transfer mode (ATM) technology are being proposed to provide a single integrated access to a variety of services and applications. Constant bit rate services will form an important part of this unified networking solution. In this paper, we identify and describe the relevant aspects related to the implementation of CBR services on ATM. First, we identify two broad categories of potential CBR services for broadband ATM networks. The ATM infrastructure for the identified services is then developed along with the required functionalities of different network elements. Finally, end-to-end performance objectives for the ATM network are determined and verified empirically based on results of laboratory experiments. These performance objectives help us determine the minimum QOS required by the highest class of service category offered by an ATM network.     

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。     

Priority assignment control of ATM line buffers with multiple QOSclasses

In an asynchronous transfer mode (ATM) network multimedia environment, the bandwidth efficiency can be improved by defining multiple quality of service (QOS) classes and using a traffic control which manages required QOS of each class individually (QOS control). Priority assignment control is presented as a QOS control method in an ATM switching node. To quantitatively evaluate the control performance, the region determined by the offered load of each class where the QOS requirements of all the classes are satisfied is analytically obtained and various combinations of two classes and related control effects are discussed. When required values of cell loss rate and delay time are both different between the classes, the control effect is large; however, when only either of them is different, the effect is relatively small. The control scheme to enlarge the actual admissible offer load region by adaptively changing the priority assignment ratio is presented and its feasibility is confirmed by the simulation     

以太网交换机技术

随着宽带网络技术的发展，以以太网为宽带接入方式逐渐成为主流，以太网交换机成为网络技术中一个重要和热点的领域。本文主要介绍了以太网交换机的基本原理，内部结构，交换方式以及将来的发展趋势。     

IEEE 802.16 WiMax技术概述及在广电数据网中的应用

WiMax技术的产生，为网络传输提供了一种高速、覆盖面广的无线传输方式。而广电宽带数据网经过几年的发展也进入了发展的瓶颈阶段。如何引入WiMax技术，将为广电宽带数据网带来新的发展机遇。     

Loss profiles: A quality of service measure in mobile computing

With rapid technological advances being made in the area of wireless communications it is expected that, in the near future,mobile users will be able to access a wide variety of services that will be made available over future high-speed networks. The quality of these services in the high-speed network domain can be specified in terms of several QOS parameters. In this paper we identify a new QOS parameter for the mobile environment, calledloss profiles, that ensuresgraceful degradation of service (for applications that can tolerate loss) in situations where user demands exceed the network's capacity to satisfy them. A new transport sub-layer is proposed that efficiently implements this new QOS parameter. We also show how this protocol can be easily incorporated into existing proposals for high-speed network transport layer protocols and into the MPEG-2 Transport System.This work was supported by the NSF under grant number NCR-9410357.     

High quality networking of audio-visual information

An overview of low bit rate coding and the interaction between source coding and channel coding is presented. The interaction of coding with networking in a multiuser environment, including algorithms for robust coding which anticipate imperfect network performance, and techniques of decoding a signal that has traversed an imperfect network are described. The performances of such algorithms are illustrated with examples from speech, audio, and video transmission in the presence of packet losses. The challenges in measuring the quality of service (QOS) in the context of new algorithms for coding and networking and the difficulty of measuring QOS in the networking of multimedia information are discussed     

CELL LOSS QUALITY OF SERVICE IN AN INTEGRATED TRAFFIC ATM NETWORK

This paper explores and evaluates several aspects of quality of service (QOS) in an integrated traffic ATM network. Specifically, we consider the relationships between service class definitions, usage parameter control (UPC) or policing of customer traffic, network resource allocation mechanisms, and specific network conditions under which realistic QOS limits on cell loss ratio (CLR) can be met. Traffic consists of a mixture of voice, video, image and data divided into two service classes for UPC and network resource allocation. The block oriented network simulator (BONeS) tool is used for performance evaluations. Limitations associated with evaluating very low CLR values (e.g. 10⁻⁸ and 10⁻⁶) via simulation are overcome by a hybrid simulation and extrapolation technique. It is found that these stringent QOS limits on CLR can be met for most traffic with the techniques used here, reasonable backbone trunk loads (75 per cent) and reasonable buffer sizes (200–250 cell buffers per queue). However, meeting similar limits for extremely bursty traffic (such as our image traffic model) would require extra care in network design and operation, including judicious segregation of traffic.