An overview of emerging CCITT Recommendations for the synchronousdigital hierarchy: multiplexers, line systems, management, and networkaspects

The scope of CCITT (International Consultive Committee for Telephone and Telegraphy) Recommendations on which significant progress has been made is reviewed. These consist of Recommendations G.781, 782, and 783, dealing with synchronous multiplexers; Recommendation G.784, dealing with synchronous digital hierarchy (SDH) management; Recommendation G.958, concerning digital line systems based on the SDH for use on optical fiber cables; Recommendation G.957, dealing with optical interfaces; and Recommendations G.sna1 and 2, concerning network aspects of SDH     

光传送网分层结构及网络节点接口特征信息

标准人的网络节点接口信息结构是将来网络互通的基础。同时也为各设备生产商提供了标准的规范和设计依据。文章介绍了光传送网的分层结构和节点特征信息。     

International standardization?interface with the future

International standardization has always been important to the smooth flow of world trade but today, with the breakup of empire and the rapid birth of new nations, the more affluent countries must re-examine their standardization policies. The first step toward international standards came in 1906 with the creation of the IEC, and in 1946 the ISO was founded. However, U.S. business has been notoriously apathetic in its attitude, with the result that many sales have been lost because of the incompatibility of American and foreign standards. With the predicted merger of IEC and ISO into what is hoped will be an imaginative, dynamic organization, the U.S. should find an incentive for more vigorous participation.     

A synchronous digital hierarchy network management system

The critical issues in multivendor environments and operation systems of telecommunication networks essential to speeding up the handling of service orders and service restoration after failures are discussed. To overcome these problems as the software backlog grows, the authors propose the application of a telecommunications management network (TMN) architecture together with an object-oriented network resource (ONR) model. The second phase of the synchronous digital hierarchy (SDH) network management system, which is based on the TMN architecture and ONR model, is examined     

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.     

异构认知网络环境下的动态分级资源管理方法

针对异构认知网络中的资源管理问题,提出了基于认知的动态分级资源管理方法(DHRM)。根据不同时间尺度,引入小波神经网络、基于维纳过程的预测方法和增强学习算法获得业务分布变化、切换呼叫资源需求量以及用户喜好等信息,从而动态调配异构多网络各级可用资源。在资源合理分配基础上,根据各网络实时状态以及用户喜好,通过多属性决策算法动态地将业务流分配到最佳接入网络中。仿真结果表明,DHRM相对于网间静态资源管理方法系统容量提高了约20%。     

The ATM Forum's private network/network interface

The ATM Forum completed the first version of its private network/network interface (PNNI) in March 1996 and many ATM switch manufacturers are now offering early implementations. PNNI offers a different type of internetwork or internodal interface from the traditional Signalling System No 7 based approach favoured to date by 'public' network operators, such as BT. In spite of its name, however, PNNI may find its place in network service provider networks as well as in 'private' or customer networks. Some of the perceived limitations of the current specification for such an environment are currently being addressed in version 2, tentatively due for completion in the second half of 1998.The PNNI really consists of two parts, a signalling protocol based around the ATM Forum's UNI signalling specification, and a dynamic source routeing protocol. This paper aims to provide an overview of the functionality and mechanics of PNNI, and to compare and contrast with the functionality offered by ITU-T's B-ISUP.     

Intelligent network feature transaction interface

The feature transaction interface and associated software structures required to support an intelligent network are addressed. A layer service logic execution environment is used to describe the operation of the feature transaction interface for provisioning intelligent network services. Included in the discussion are: the need for service creation; unbundled service logic for functional flexibility; remote operation using the SS7 network; and reduced service-provisioning intervals. Service examples using the feature transaction interface are given     

智能光网络体系结构与服务功能的探讨

大容量、智能化、综合业务处理将成为传送网络未来的基本发展方向，本文着重对智能光网络的网络体系与结构、智能光网络拄制平面相关技术“硬智能光网络的网络服务功能进行探讨。     

A standardization plan for broadband access network transport

ITU-T has designated Study Group 15 as the Lead Study Group on access network transport, with the mandate to define and maintain the overall framework for standards, in collaboration with other Study Groups and standards bodies, to coordinate, assign, and prioritize studies done by the Study Groups, and to ensure the development of consistent, complete, and timely Recommendations. This article gives an overview of existing and ongoing standardization activities within ITU-T in the area of access network transport, focusing on broadband access systems such as xDSL and optical access networks     

Theoretical analysis of the ADPCM CCITT algorithm

The unfavorable effects of narrowband inputs on the decoder adjustment when the LMS algorithm is used are analyzed. An explanation is given for the behavior of the CCITT algorithm. Suboptimality of prediction is granted to achieve adjustment, resulting in a satisfactory tradeoff between reduction rate and adjustment. The link between adjustment and uniform stability is enhanced     

A Review of CCITT Standardization to Date

This paper describes the key elements of the International Telephone and Telegraph Consultative Committee's (CCITT's) three Recommendations on ISDN services. Telecommunication services which can be offered to customers are the natural starting point for all standardization work on telecommunication networks. The necessary features of telecommunication networks can only be derived from the services' requirements. The early standardization of services has the added advantage that it allows communication across borders to be made available on identical terms. For the reasons given here, the CCITT has, in all its work on ISDN, given a high priority to a uniform definition of the services and to the specification of services to be offered internationally.     

Transfer efficiency of the CCITT error-protection method

In this letter, the transfer efficiency of the CCITT V.41 error-protection method is determined, pointing out that it is better at a high error rate and long transmisson block than had previously been estimated.     

A scalable high-performance active network node

Active networking in environments built to support link rates up to several gigabits per second poses many challenges. One such challenge is that the memory bandwidth and individual processing power of the router's microprocessors limit the total available processing power of a router. In this article we identify and describe three components, which promise a high-performance active network solution. This implements the key features typical to active networking, such as automatic protocol deployment and application specific processing, and it is suitable for a gigabit environment. First, we describe the hardware of the active network node (ANN), a scalable high-performance platform based on off-the-shelf CPUs connected to a gigabit ATM switch backplane. Second, we introduce the ANN's modular, extensible, and highly efficient operating system (NodeOS). Third, we describe an execution environment running on top of the NodeOS, which implements a novel large-scale active networking architecture called distributed code caching     

IMT-2000 core network node systems

The IMT-2000 third-generation network system has been operating in the Japanese market since May 2001. In order to provide value added phone services including CAMEL services, a layered call control architecture has been developed. This architecture could achieve smooth core network migration from 2G to 3G. This system provides MSC/VLR, SGSN, and GGSN functionalities based on ATM technology.     

Error Sensitivity of CCITT Standard Facsimile Coding Techniques

The CCITT has defined Group 3 facsimile apparatus as that which digitally transmits an ISO A4 document over a switched telephone circuit in approximately one minute. Data compression is employed to achieve the reduced transmission time. Study Group XIV of the CCITT has drafted Recommendation T.4 to achieve compatibility between Group 3 facsimile devices. The standard data compression technique specified by T.4 is a one-dimensional coding scheme in which runlengths are encoded using a modified Huffman code (MHC). The recommendation also includes an optional twodimensional compression technique known as the modified READ code (MRC). It is recognized that the switched telephone network is prone to error when transmitting digital data at the standard T.4 data rate of 4800 bits/s. This paper evaluates the error sensitivity of the MHC and MRC when operating over a typical telephone circuit. The error sensitivity analysis is accomplished by means of computer simulation. The error performance of the two coding techniques is analyzed both quantitatively and qualitatively. The quantitative analysis is accomplished using the error sensitivity factor which represents the average number of incorrect pels in the output document caused by a transmission error. The qualitative analysis is based upon viewing actual error-contaminated images generated in the simulation process. Two separate analyses have been performed. First, error sensitivity data for both the MHC and MRC are developed under identical operational conditions, and their relative performance is discussed. In the second part four different techniques for processing the received facsimile signal (MRC), to minimize the subjective effect of transmission errors, are analyzed.     

基于神经网络的无线网络故障节点定位技术

传统无线网络故障节点定位方法无法有效处理节点功率波动以及模糊环境对故障节点定位精度的干扰。提出基于小波神经网络的无线网络故障节点定位方法,分析了小波神经网络在节点故障定位的三种作用形式,融合形式1和3对冗余节点故障进行定位,将小波神经网络当成预测器,将前一采样时刻的正常输出交叉输入n个小波神经网络,获取节点当前时刻的预测输出值,取节点预测输出值和真实输出值的残差,若该残差值高于阈值,则说明该节点是故障节点。实验结果表明,所提故障节点定位方法能够对节点的附加、倍数以及短路故障进行准确定位。     

基于分层的层内无线传感网络数据融合

无线传感网络数据融合能够有效减少传感节点的数据通信量,减少节点的能量消耗,延长了网络的寿命。本文提出了节点分层算法,在层内传感节点加入了具体的数据融合算法,利用拉依达准则对节点收到的数据进行异常数据检测,在上层节点利用主成分分析对剩余数据进行数据融合。通过仿真实验得出该算法数据融合结果准确率好。