1、INTERNATIONAL TELECOMMUNICATION UN ION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU TELEGRAPHY TELEGRAPH TRANSMISSION R.117 (03/93) END-TO-END ERROR PERFORMANCE FOR TELEGRAPH, TELEX AND GENTEX CONNECTIONS INVOLVING REGENERATIVE EQUIPMENT ITU-T Recommendation R.117 (Previously “CCITT Recomme
2、ndation”) ITU-T RECMN*R-LL7 73 = 4862571 0570338 362 FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommenditions on t
3、hem with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Rqommendations on these topics. IT-T Recomme
4、ndation R.117 was prepared by the ITU-T Study Group IX (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993. In its place, the ITU T
5、elecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommendation, no change has been made in the text to references co
6、ntaining the acronyms “CCITT. CCIR or IFREI” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new ITU structure. 2 telecommunication administration and a recognized operating agency. In
7、this Recommendation, the expression “Administration” is used for conciseness to indicate both a O IT 1994 Ail 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
8、writing fiom the ITU. ITU-T RECUN+R.LL 93 m YB62591 0590339 2T9 = CONTENTS Page 1 Generai . 1 1.1 Error distribution 1 1.2 Correspondence between bit and character errors 1 2 Definitions 1 3 Correspondence between BER, CER and performance . 2 4 Performance objective 3 Recommenation R117 (03/93) i Re
9、commenation R.117 END-TO-END ERROR PERFORMANCE FOR TELEGRAPH, TELEX AND GENTEX CONNECTIONS INVOLVING REGENERATIVE EQUIPMENT (Helsinki, 1993) The CCm, considering (4 that telegraphy essentially involves the transmission of digital information; (b) that errors reflect either losses or invalid informat
10、ion; (cl that signals can be regenerated at several points along the link (inter alia by multiplexers and/or switching exchanges). so that distortion is no longer the main criterion of performance; (d) that Recommendation F. 10 recommends as an objective, for communications in the public telegram, t
11、elex and leased circuit services operated by Ci-unit start-stop equipment with a modulation speed of 50 bauds, a maximum error rate tolerance of 3 in 1O alphabetic telegraph signals transmitted; (e) that transmission equipment is increasingly based on digital systems such as R. 100-Series Recommenda
12、tions mu1 tiplexers; (0 that, since increasing use will be made of digital network, performance criteria should be consistent with those of Recommendation G.82 1. recommends that the definitions and approach adopted in Table 1 and its associated clauses be used. 1 General in digital telegraph multip
13、lexers, the time slots corresponding to the telegraph channels are distributed and this reinforces the distribution and equiprobability of errors between different channels. 1.1 Error distribution Errors resulting from transmission anomalies may arise in the following two ways: 1.1.1 isolated within
14、 each channel. These are generally due to white or impulsive noise. 1.1.2 breaks or AIS (Alarm Indication Signal) effects from higher-order multiplexers. As isolated errors or in small packets (limited to less than about 10 errors), which may therefore be regardecl as As a particular aggregate chann
15、el state, lasting up to a few tens of milliseconds. This is caused by micro- 1.2 In the case of the first type of error degradation described in 1.1.1 above, bit errors may be considered as being sufficiently far apart for each bit error to be matched by at least one character error, since errors oc
16、curring at the start and stop instants may desynchronize the receiver. Correspondence between bit and character errors 2 Definitions Throughout this Recommendation: - A “degraded interval” means a transmission of lower quality than that stipulated in Recommen- dation F.lO, but which remains limited
17、to less than one error per message, as the reference duration being one day. Recommendation R.117 (03/93) 1 - An “errored interval” is one which may contain up to one error every two lines, the reference duration being one minute. A “severely errored interval” is one in-which the number of errors ex
18、ceeds.t&e limit established above. * Taking the minute as the reference duration, such intervls must be short if they are not to become unacceptable. - - An “garbled interval” is one in which the number of errors approaches or exceeds one in ten characters and the message is rendered incomprehensibl
19、e. According to an analysis of telex traffic, it can be assumed that the average message comprises 30 lines of These definitions do not imply that the level in question is acceptable or not. NOTES 1 2 35 characters, corresponding to a call of three and a-half minutes and roughly 1 200 characters tra
20、nsmitted. 3 Correspondence between BER, CER and performance The correspondence among bit error rate, character error rate and performance for a practical assessment of performance objectives induding transmitter and receiver is given in Table 1. TABLE 1m.117 End-bend error rate for telegraphy, telex
21、 and gentex = 3 erradmessage or i emorll minute Errored interval - 3 errodine = 3 errad35 characters Severely errored Garbled interval 3t- CER Character error rate BER Bit error rate 2 Reeomrnendation R.117 (03/93) ITU-T RECMN*R.117 93 W 4862591 O590342 893 W Degraded days Errored minutes 4 Performa
22、nce objective Fewer than 10% of days to have more than 15 errors Fewer than 0.05% of one-minute intervals to have 3 errors or more The end to end error performance objective for telegraphy, telex and gentex networks involving regenerative TDM is defined in Table 2. TABLE uR.117 End-to-end error performance objective for telegraphy, telex and gentex Performance classification I Objective I Recommendation R.117 (03/93) 3
