1、ITU-T RECMN*E-458 96 m 4862591 Ob15176 514 m INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU E.458 (02/96) TELEPHONE NETWORK AND ISDN QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING FIGURE OF MERIT FOR FACSIMILE TRANSMISSION PERFORMANCE ITU-
2、T Recommendation E.458 (Previously ?CCIlT Recommendation?) ITU-T RECNN*E-458 9b D 48b2593 Ob35377 450 FOREWORD The IT-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (). The -T is responsible for studying technical, operating and tariff
3、questions and issuing Recommen- dations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce
4、Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). ITU-T Recommendation E.458 was prepared by IT-T Study Group 2 (1993-1996) and was approved under the WTSC Resoluti
5、on No. 1 procedure on thel9th of February 1996. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. O ITU 1996 All rights reserved. No part of this publication may be reproduced or
6、 utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. ITU-T RECMN*E-458 96 4862593 0635378 397 CONTENTS Page 1 Introduction 1 2 Definitions 1 3 Remarks 2 Recommendation E.458 (02196) 1 ITU-T RECMN*E*458 96 m
7、 4862593 Ob35379 223 m SUMMARY This Recommendation introduces mettics for Figure of Merit (FOM) for end-to-end facsimile transmission performance. The Recommendation is intended to facilitate the exchange of network performance data by Recognized Operating Agencies with the aim of improving service
8、quality. The FOM is defined through seven different transaction types that can result from a facsimile transaction. The transaction types are based on call cut-Offs, transmission speed reduction and image quality. They range from Type I (considered to be “perfect”) to Type VII (not completed). The F
9、OM measurements are based on intrusive measurements (i.e. test calls). FOM metrics for non-intrusive measurements and transactions using ECM are for further study. FOM metrics for transactions not using wired access are also for further study. 11 Recommendation E.458 (02/96) Recommendation E.458 FIG
10、URE OF MERIT FOR FACSIMILE TRANSMISSION PERFORMANCE (Geneva, 1996) 1 Introduction The purpose of this Recommendation is to introduce metncs for Figure of Merit (FOM) for end-to-end facsimile transmission performance. The Recommendation is intended for use by Recognized Operating Agencies (ROAs) to e
11、xchange network performance data for service improvement purposes. In previous Recommendations E.45 1, E.452, E.453 and E.456, facsimile merics such as facsimile call cut-Offs, modem speed reduction and image quality based on scan line errors and test transactions, respectively, were defined. It wou
12、ld be very useful to produce simple metrics for facsimile FOM that combine all three parameters so that performance of networks can be compared easily and corrective action taken to improve performance. End-to-end facsimile performance includes performance impacts both due to the network and the fac
13、simile terminals. However, when a fixed set of test terminals with nominal terminal performances are used, it is possible to treat the terminal performance as a constant factor and compare network performances. The impact of terminal performance on facsimile call cut-Offs, modem speed reduction and
14、image quality are more fully discussed in Recommendations E.451. E.452 and E.453. The FOMs considered so far do not address factors such as network blocking, etc. However, the FOMs can be multiplied by the Phase A Completion Ratio, PACR (see Recommendation E.45l)Io obtain a combined view of call com
15、pletion and facsimile transmission performance. The facsimile Figures of Merit are defined through seven different transaction types. Type I transaction is one that is complete, the speed is maximum possible and the image quality is error-free for all pages. Type I transaction can be considered to b
16、e “PERFECT” from a transmission point of view. Type II transactions are complete, the speed is maximum possible but the transactions contained errored but not severely errored pages. In a similar fashion, another five transaction types have been defined depending on whether the transaction is comple
17、te, the speed is the maximum possible and the image quality is error-free, errored or severely errored. ROAs, depending upon their need, may exchange information on some transaction type or combinations of transaction types for service improvement purposes. For the present, this Recommendation does
18、not address the customer preference weights that could be assigned to different performance parameters such as cut-off, speed and image quality. The main reasons are that customer weights may show considerable variation depending upon the customer base, the type of application, national expectations
19、, etc. A large, complex study would be required to obtain a comprehensive view of customer perception. This subject is left for future study. Facsimile FOM for ECM transmission and non-intrusive measurements are for further study. FOM for services not using wired access, (e.g. mobile) are also for f
20、urther study. 2 Definitions As in Recommendation E.45 1, we begin by considering transactions where the intended receiving facsimile terminal has responded by going off-hook and CED has been received at the originating terminal. Table 1 defines seven transaction types that can be used to define facs
21、imile Figures of Merit. The maximum speed of a facsimile transaction is defined as the speed used for the initial TCF message as discussed in Recommendation E.452. Recommendation E.458 (02196) 1 ITU-T RECMN*E.g58 96 48b2591 Ob15181 981 W TABLE 1E.458 Transactions type for facsimile Figures of Merit
22、2 completed pages. If the transaction is incomplete, it is categorized as Type VI1 irrespective of the speed and image quality of the 3 Remarks a) ROAS, depending upon their need, may exchange information on some transaction types or combinations of transaction types. Some useful transaction types a
23、nd combinations are suggested in the following: 0 Type I transaction are those that complete, have the highest possible speed and are error-free, i.e. these can be considered “PERFECT” from a transmission point of view. A combination of Type I and Type LI transactions are those that complete, have t
24、he highest possible speed and do not have any severely errored pages. For most facsimile applications, the transmissions maintain their utility to the customer, i.e. they can be considered “EFFECTIVE”. 0 0 A combination of Types IV, V and VI represents transactions that have speed fallbacks and resu
25、lt in longer connection times. 0 A combination of Type III, VI and VII represent transactions that are “BADLY” damaged in some form. ROAS may wish to exchange this information with a view to take prompt corrective actions. FOM for a particular network may be strongly impacted by the facsimile modem
26、speed, i.e. the speed set by the first TCF, used by the test terminals. For example, the FOM for test terminals employing V.17 modem modulation may be different from that for test terminals employing V.29 modulation. It is recommended that FOM be evaluated separately depending on the speed of the in
27、itial TCF of the test terminals. b) c) The FOM meuics defined in this Recommendation apply, in general, to any type of transmission media. However, the targets for the FOM metrics that the ROAS set may depend on the media type, the operational (e.g. maintenance) cost for meeting the targets, expecta
28、tions of their customers regarding facsimile quality, etc. For network improvement purposes, it may be necessary to further breakdown transactions that were not of Type I to understand the root causes for the imperfections. Service improvement actions can be taken based on the root causes and priori
29、ties assigned to different types of failure. ROAS can set these priorities based on customer-related factors such as customer complaint rate for various types of failures, the quality of the underlying network, the economics for improving a particular performance merric, etc. d) 2 Recommendation E.458 (0296)
