Có 40+ tài liệu thuộc chủ đề "tín hiệu truyền dẫn"
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Campus and Metropolitan Area Networks (MANs). Metropolitan area networks (MANs) are network technologies similar in nature to local area networks (LANs), but with the capability to extend the reach of the LAN across whole cities or metropolitan areas, rather than being limited to, say, 100-200 metres of cabling. MANS have evolved because of the desire of companies to extend LANs...
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22.1 VIDEOTEXT. The original technology and standards, including special terminals and modem techniques allowing asymmetric transmission (a high bitrate channel for information download to the customer with a low speed control channel for his ordering of different pages of information) have now been overtaken by modern personal computer based technology, but the appearance of the worldwide Internet has stimulated recent...
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The Message Handling System (MHS). The message handling system (MHS) is a concept developed by ITU-T that is intended to lead to the interconnectivity of all different types of message conveying systems, e.g. 23.1 THE NEED FOR MHS. Often a number of technologies provide similar but separate means for conveying identical information, but many users still employ more than one...
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Just as computers and datacommunication are revolutionizing office life, so mobile and radio data networks are enabling corporate computer networks to be extended to every part of the com- pany’s business, including the mobile sales force, the haulage fleet and the travelling executive.. This chapter discusses some of the most recent radio data network technologies, covering the principles of ‘radiopaging’,...
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MULTIMEDIA NETWORKS. Broadband, Multimedia Networks and the B-ZSDN. 25.1 MULTIMEDIA APPLICATIONS: THE DRIVER FOR BROADBAND NETWORKS. and playing a soundtrack (Figure 25.1). Multimedia applications greatly increase the possibilities of the modern computing and entertainment industries, and they are finding their way into all walks of modern life:. 440 BROADBAND, MULTIMEDIA NETWORKS AND THE B-ISDN. Figure 25.1 A modern multimedia computer...
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It will form the basis of the future broadband integrated services digital network (B-ISDN).. 26.1 A FLEXIBLE TRANSMISSION MEDIUM. adjustment in the allocation of the available network capacity between the various users competing for its use. In our discussion, we shall refer frequently to the work of the ATM Forum, an industry-wide common interest group, comprising telecommunications equipment manufacturers, network...
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Telecommunications Management Network ( T M N. The goal of the ‘telecommunications management network’ o r ‘ T M N is to provide for consistent and efficient management of complex telecommunications networks. The T M N model describes the basic operating and management functions which a network operator has to conduct and the standard interfaces to be used between network...
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The control of the routing of calls and connections (so-called ‘traffic’) across telecommunications networks is the most difficult but most important responsibility of a network operator. 27.1 THE NEED FOR A NETWORK ROUTING PLAN. In the example shown in Figure 28.1, a circuit-switched connection (such as a telephone call) is desired from exchange A to exchange B. Unfortunately these circuits...
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Network Numbering and Addressing Plans. The network numbering or addressing plan is an important part of the network routing plan, because the network address is the identification used by a caller to identify the customer or network port to which he wishes to be connected. 0 international public data network numbering scheme according to ITU-T recommendation x.121. 0 international telex...
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30.1 TELECOMMUNICATIONS TRAFFIC. 30.2 TRAFFIC INTENSITY (CIRCUIT-SWITCHED NETWORKS). CCS is a measure of the total call holding time during the network or route busy hour. As an example, the route between exchanges A and B in Figure 30.1 consists of five circuits. The chart in Figure 30.1 also shows the periods of usage of each of these circuits during a...
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31.1 MEASURING NETWORK USAGE. These methods in various ways served to measure, over a predetermined period of time, any of the following parameters. 0 the total number of calls or messages. 0 the total number of data characters (e.g. packets, frames or cells conveyed) We have covered the concept of trafic intensity, which is a measure of the average call...
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32.1 NETWORKS. It is in fact the number of path permutations which determines the robustness of the network to individual link failure and sets the level or grade of service provided (i.e. 32.2 SIZING CIRCUIT-SWITCHED NETWORKS. 0 a forecast of the overall volume of traffic. where E represents the appropriate form of the Erlang formula or function, with inputs A...
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of the service is also important. When designing telephone or other voice transmission networks, the strength of the electrical signal induced by the microphone at the sending end and the final sound volume produced by the receiver is all-important. It varies according to the proximity of the speaker to the microphone and the listener to the ear piece, the total...
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Quality of Service ( Q O S ) and Network Performance ( N P. However, although it is easy enough to test a tangible product to destruction, measure- ment of the quality of a service is more difficult. This chapter reviews some aspects of communica- tions quality and the practices of management, with examples of the commoner quality. Good management...
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Charging and Accounting for Network Use. 35.1 RECOMPENSE FOR NETWORK USE. 648 CHARGING AND ACCOUNTING FOR NETWORK USE. Additionally, accounting between telecommunications operators is becoming more common, as a result of the recent large increase in the interconnection of networks.. 35.1.1 Charging (Also Called Billing). This is the name given to the practice of recovering financial costs from end-users for...
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Maintaining the Network. However, attitudes towards maintenance and the organization behind it vary widely, ranging from the ‘let it fail then fix it’ school of thought right through to ‘prevent faults at any cost’. 36.1 THE OBJECTIVES OF GENERAL MAINTENANCE. 0 the right personnel can be sent to. 36.2 MAINTENANCE PHILOSOPHY. 664 MAINTAINING THE NETWORK proportion of time that the...
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Containing Network Overload. Monitoring and controlling the network to detect and avoid network congestion and the resulting service degradation is a difficult task, but an important one. This chapter discusses these new ‘network management’. 37.1 THE EFFECT OF CONGESTION. Congestion in a telecommunications network manifests itself to customers who are attempting to make calls as a ‘network busy’ tone, or...
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a few of the practical economy measures open to them.. 38.1 COST MINIMIZATION. If a given resource, say a transmission link, is already laid on then there is not much to be gained by applying economy measures which have the sole effect of making some of the available capacity redundant. 38.2 FREQUENCY DIVISION MULTIPLEXING (FDM). Bandwidth for individual telecommunications channels...
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Equally damaging can be the impact of simple mistakes, misinterpreted, or distorted information.. Increased belief in the reliability of systems and the accuracy of information has brought great gains in efficiency, but blind belief suppresses the questions which might have confirmed the need for corrections. This chapter describes the various levels of information protection which may be provided by different...
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Technical Standards for Networks. In the past, telecommunications networks have been evolved in the minds of their designers to meet well defined but changing user demands. These broadly innovative influences are bound to persist and users can look forward to ever more sophisticated telecommunications services in the future. It was only in the mid-1960s that customer-dialled international telephone calls first...