ITU-T E.432-1992 连接质量 Connection Quality (Study Group II) 8 pp

pdf标准 ITU-T E.432-1992 连接质量 Connection Quality (Study Group II) 8 pp

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INTERNATIONAL TELECOMMUNICATION UNION CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COMMITTEE TELEPHONE NETWORK AND ISDN QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING CONNECTION QUALITY Recommendation E.432 Geneva, 1992 E.432 FOREWORD The CCITT (the International Telegraph and Telephone Consultative Committee) is the permanent organ of the International Telecommunication Union (ITU). CCITT is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The Plenary Assembly of CCITT which meets every four years, establishes the topics for study and approves Recommendations prepared by its Study Groups. The approval of Recommendations by the members of CCITT between Plenary Assemblies is covered by the procedure laid down in CCITT Resolution No. 2 (Melbourne, 1988). Recommendation E.432 was prepared by Study Group II and was approved under the Resolution No. 2 procedure on the 16th of June 1992. ___________________ CCITT NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication Administration and a recognized private operating agency. © ITU 1992 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. Recommendation E.432 Recommendation E.432 CONNECTION QUALITY 1 Introduction This Recommendation suggests parameters, measurements and standards to capture the customer perception of connection quality for all services on the public switched telephone network (PSTN) and the evolving integrated services digital network (ISDN). In principle, when a new service is to be implemented, a market analysis has to be undertaken to gain information on the service quality that has to be offered to the users at a given tariff. Here a problem appears to arise: users show their satisfaction in a non-technical way: they judge connection quality ranging from poor to excellent. The same problem applies to existing services. The intention of the Recommendation is to provide a guideline to obtain end-to-end connection of acceptable quality, that satisfies the end users. 2 Scope In considering “connection quality”, it is important to recognize that the “user” must already have a complete end-to-end connection, i.e. a distant end answer signal has been received before the connection quality can be assessed. “Connection quality” does not include call set-up delays, etc. The “connection quality” has to be considered from the users perspective and will be influenced by the subjective perception of the user, the destination and route chosen, the transmission media used and the total ressources available and applicable to the end-to-end connection. As a result, this Recommendation considers the user perspective first, and then develops the network parameters and objectives. 3 Definitions connection quality The degree to which a connection reproduces the offered signal under stated conditions, as a sum of transmission performance, service integrity, service retainability performance, propagation performance. connection transmission quality The level of reproduction of a signal offered to a telecommunication system, under given conditions, when this system is in an up-state. 4 User perspective 4.1 The user perspective is the key issue in connection quality. User’s opinions are subjective but by appropriate methods, a service can assess user’s satisfaction in a quantitative and reproducible way. During an established call the user(s) may notice degradation of the intelligibility. The cause of this may be increased attenuation, inadmissible distortion, strong noise, etc. Recommendation E.432 1 The speech quality is influenced by ther performance and the user conditions applicable to the complete connection from speaker to listener. In general, speech quality is treated by dividing it into sending quality, transmission quality and receiving quality. Among them, the transmission quality is the main factor which can be controlled by the Administration. The other two factors vary widely with the ability of speakers, listeners and the conditions under which speech is sent and received. Low level pulsive noise, produced in a switching system, and group delay distorsion on a transmission line, do not cause any substantial trouble for the telephony service. These impairments are more likely to impact non-telephony applications, such as data and facsimile. It should be noted that there are many other impairments factors that affect nontelephony applications. For m

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