1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 2 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%2!0(94%,%2!0(G0G042!.3-)33)/.%,%-%.4G0G0%22/2G0G02!4%)45G134G0G02ECOMMENDATIONG0G02 (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation R.2 was published in Fascicle VII.1 of the Blue Book. This file
2、 is an extract from theBlue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are identical to the Blue Book version and copyright conditions remain unchanged (see below).2 In this Recommendation, the expression “Admin
3、istration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic ormechanical, including photocopying and micro
4、film, without permission in writing from the ITU.Fascicle VII.1 - Rec. R.2 1Recommendation R.2Fascicle VII.1 - Rec. R.2ELEMENT ERROR RATE(Geneva, 1964)The CCITT,considering(a) that in practice, the error rate on transitions is not used and, with the development of data transmission, it isthe notion
5、of element error rate that has come into use,(b) that in general, the expression element error rate is used with the meaning of error rate on unit elements.Although this equivalence of meaning is acceptable for isochronous signal trains, this is not so for start-stop signaltrains. In fact, there may
6、 be elements in start-stop signal trains whose duration is different from that of the unitelements (for example, the stop element of a start-stop signal in accordance with International Telegraph Alphabet No.2),unanimously declares the view(1) that the following definitions be adopted:element error
7、rate: the ratio of the number of incorrectly received elements to the number of emitted elements.unit element error rate for isochronous modulation: the ratio of the number of incorrectly received elementsto the number of emitted elements.(2) that, for start-stop signal trains, the notion of charact
8、er error rate be used;(3) that, when error rates are measured to assess the quality of a communication, the original message acting asa reference for the calculation of the error rate shall be considered as being free of error;(4) that measurement of the element error rate assumes that it has been p
9、ossible to record the elements receivedin such a way that they can be recognized as being correctly or incorrectly recorded. As the result of an error ratemeasurement thus depends on the recording system at the end of the connection, this system must be specified whenthe results of the element error rate are given. Whenever possible the element error rate should be measured at theoutput of the regenerating device which normally precedes the translation device; the signals should be translated forchecking purposes.
