ISDN基本速率接入线路指标测试的探讨

介绍了ISDN基本速率接入 (2B +D)的几个常见的线路指标 ,包括环阻、线间电容、线路衰减、近端串音 ,数字传输指标误码率等 ,并介绍了这些指标的作用以及测量方法。最后介绍了在北京地区试验的情况。     

An ISDN Subscriber Loop Transmission System Based on Echo Cancellation Technique

This paper proposes an ISDN subscriber loop transmission system based on an echo cancellation technique which fully supports the CCITT recommended basic interface for ISDN, i.e.,B + B + Dover metallic cables. System design considerations of cable loss, crosstalk, impulsive noise, and system requirements such as power feeding on a caLl-by-call basis are discussed, and a transmission system is proposed. The proposed system is characterized by the use of a new line code, named "modified biphase code." The use of this code with fixed line loss equalization and coherent detection achieves circuit simplification. A special adaptation algorithm is incorporated with the echo canceller that significantly reduces convergence time. Experimental results show satisfactory performance with respect to the residual echo and the bit error rate. Since the system requires only a simple nonadaptive circuit for analog portion, it is suitable for LSI implementation.     

CCITT Recommendations--Network Aspects of the ISDN

This paper presents an outline of the key network standards issues addressed in CCITT as a necessary part of the development and implementation of ISDN. The results achieved in the 1981-1984 Study Period focused on ISDN network functional requirements, ISDN numbering plan, connection types to link ISDN interfaces across the network, and the relationship of the ISDN protocol model with the seven-layer ISO model. The additional network issues which must be resolved in the current (1985-1988) Study Period are identified and briefly discussed. Of particular interest are internetworking between ISDN and existing networks, numbering plan interworking, routing, and maintenance standards. The market success of ISDN depends upon early resolution of these network standards to meet the field trials scheduled for 1986-1988 and the first implementations expected in 1988-1990.     

CATV线路上的ISDN接入方式探讨

信息公路要有接入网配套。综合业务数字网接入有线电视分配集合到户是实现宽带综合接入的便利途径。本文考虑了ＩＳＤＮ／ＣＡＴＶ结合的方法、ＩＳＤＮ主速率时分多址接入方式以及用户－网络接口的物理层。     

ISDN通信终端接入因特网

ＩＳＤＮ通信终端接入因特网具有十分重要的实际应用价值。文中介绍了ＩＳＤＮ通信终端接入因特网的协议体系和实现ＩＳＤＮ终端接入因特网功能的具体方法     

Technology Aspects for System 12 Broadband ISDN

Although the enhancement of System 12, SEL's digital switching system, for ISDN services is virtually complete, further development work is being carried out to allow broadband switching for videophone services, videoconferencing, and the distribution of radio and television programs. This paper describes an appropriate approach to the evolution Of System 12 toward the broadband ISDN (B-ISDN), emphasizing the crosspoint and technology aspects of the broadband switch. Test results on a broadband switch VLSI circuit for 140 Mbit/s in a 2μm CMOS technology are presented.     

ISDN在电视会议和因特网中的应用

本文介绍ISDN的基本概念 ,中国ISDN业务飞速发展的状况。并结合实际 ,着重讨论了ISDN与电视会议系统、ISDN与Internet的接入等当今ISDN应用最广泛的业务。     

用ISDN构建企业级Internet访问路由器

企业级Ｉｎｔｅｒｎｅｔ访问路由器解决了费用、管理、速度等几个问题，为员工使用Ｉｎｔｅｒｎｅｔ带来方便，为多用户使用Ｉｎｔｅｒｎｅｔ降低了费用。但是如何降低企业级Ｉｎｔｅｒｎｅｔ访问路由器本身的造价呢？本文介绍了珠海人民广播电台构建低成本Ｉｎｔｅｒｎｅｔ访问路由器的经验。     

A Channel Access Structure for Wideband ISDN

To be fully integrated, the Integrated Service Digital Network (ISDN) arena is preparing an evolution from its current narrowband structure (at basic and primary access rates) to a futuristic wideband structure where access rates will be capable of supporting services beyond 100 Mbits/s. A wideband channel structure for ISDN, supplementing the narrowband channel standards, is thus needed. This paper presents a channel structure in which the access bandwidth is organized in a hierarchy of channels of increasing speeds. Channels at a given speed level accommodate services with specific bandwidth and holding time requirements. However, to improve performance, the access interface uses a control strategy whereby a service request at a given level can overflow to a lower level for access at lower bit rate. The performance, in terms of access delay and access throughput, of this access scheme is analyzed. Numerical results are provided for the special case of an interface with two levels of channels. These results show that a significant improvement in access performance can be obtained with the overflow mechanism of the access control discipline used.     

Considerations on Customer Access to the ISDN

A concept for a digital customer access to an integrated services digital network (ISDN) is proposed. It is based on a passive bus which conveys information by means of two circuit switched B channels and aDchannel to support associated signaling (outslot channel) dynamically multiplexed with slow speed packetized data and telemetry. The customer access can support multiple terminal arrangements with simultaneously active users. Information to be conveyed by theDchannel is transferred in the form of messages, each associated with a logical link which has to coexist with other logical links on the common physicalDchannel. Access to that channel is regulated by level 1 arbitration with collision avoidance. It is possible to connect one X.25 DTE with minimum adaptation to the customer installation.     

VSAN光纤综合业务接入系统

介绍一款VSAN光纤综合业务接入系统产品结构特点。     

用户环路接入网

介绍了用户环路接入网的概念、结构及接口的演变等。对Ｖ５接口和采用Ｖ５接口及光纤接入网的方式作了具体的论述和介绍。     

基于V5的用户接入系统ISDN接入模块的设计与实现

介绍Ｖ５接入网用户接入系统的ＩＳＤＮ接入模块硬件和软件设计方案。这个方案具有系统配置灵活的特点。另外,此方案主要采用西门子公司的芯片组。     

利用MAX 4060为因特网开放ISDN接入

介绍了4000系列接入服务器中的一种产品——MAX4060接入服务器和典型的ISDN接入方式,并从硬件改造、软件改造和改造后的接入服务器连接关系等方面介绍了MAX4060ISDN接口改造实施方案及实施此方案中几种常见的故障现象和解决方法。最后介绍了荆门市电信分公司采取这种方案后所取得的实际效果。     

矿井综合业务数字网络视频传输QoS研究术

设计了一种基于图像抽帧算法的视频传输QoS控制系统.通过解析RTCP报文中的数据包丢失率,估计当前网络传输质量,发送端根据接收到的反馈信息,利用图像抽帧算法动态改变并重组视频编码序列,依据QoS策略调整发送重组序列,使其适应网络质量的变化,实现视频传输的QoS控制,从而达到网络质量变化情况下的最佳视频传输效果.     

ISDN多址静止图像传送系统

本系统是采用ＪＰＥＧ（ＪｏｉｎｔＰｈｏｔｏｇｒａｐｈｉｃＥｘｐｅｒｔｓＧｒｏｕｐ）算法，经数字网进行静止图像通信的日本国标系统。它可同步完成多点广播，拓宽了静止图像的应用范围。其另一优点是可为符合ＴＴＣ标准的其它类型的终端提供图像传输。     

An LSI Implementation of an ISDN Echo Canceller: Design and Network Aspects

This paper describes a single/chip VLSI implementation of aU-interface system component called transceiver with echo cancelling (TEC). The transceiver is implemented with the adaptive echo cancelling method and is combined with a decision feedback equalizer. The algorithms are based on the sign algorithm, but have been considerably improved by using an adaptive reference level. Besides the transceiver functions, functions for activation/deactivation, maintenance, and test are also included in the chip.     

用户环路和接入网中的SDH（上）

介绍ＳＤＨ在用户环路和接入网中的应用，比较了ＰＤＨ和ＳＤＨ的优缺点，叙述了采用ＳＤＨ的接入网和用户环路的网络结构和设备的应用。文中还分析、介绍了接入网和用户环路向ＳＤＨ的过渡策略与方法，包括网管的演进。最后给出了一些ＳＤＨ在接入网和用户环路中应用的实例。     

VDSL数字用户环路接入及其关键技术

本文首先介绍了VDSL的体系结构,然后就实现VDSL接入的关键技术如线路编码技术,以及复用技术和回波抵消技术等相关技术进行了分析,最后指出了VDSL的发展现状和前景。