1、ITU-T RECMN*R*LL2 93 m 48b2591 0593254 3Tb m INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU TELEGRAPHY TELEGRAPH TRANSMISSION R.112 (03193) TDM HYBRID SYSTEM FOR ANISOCHRONOUS TELEGRAPH AND DATA TRANSMISSION USING BIT INTERLEAVING ITU-T Recommendation R.1
2、12 (Previously “CCIlT Recommendation”) ITU-T RECMN*R-LL2 73 4862573 0573255 232 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 i
3、ssuing Recommendations on them 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 Recommendations o
4、n these topics. ITU-T Recommendation R. 1 12 was revised by the ITU-T Study Group IX (1 988- 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 Februa
5、ry 1993. In its place, the ITU Telecommunication 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 Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector.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 m
6、ade in the text to references containing the acronyms “CCITT, CCIR or IFRE3” 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
7、recognized operating agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a O ITU 1994 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
8、microfilm, without permission in writing from the ITU. ITU-T RECMN*R.LLZ 93 = 4b259L 059325b 179 CONTENTS System capacity Channel inputs Multiplexing details Synchronizing Channel outputs Frame structure . Aggregate signals and interface, system clock arrangements and system control and alarms . Cha
9、nnel numbering scheme of code independent channels . Link performance and availability indicators . References . Recommendation R.112 (03/93) Page 1 1 2 i ITU-T RECNN*R-LLZ 73 I 48b2.571 0573257 005 Recommendation R.112 TDM HYBRID SYSTEM FOR ANISOCHRONOUS TELEGRAPH AND DATA TRANSMISSION USING BIT IN
10、TERLEAVING (Malaga-Torremolinos, 1984; amended at Melbourne, 1988 and at Helsinki, 1993) The CCITT, considering (a) Table 1R. 101 which may be achieved by using time-division multiplexing (TDM) techniques; that there is a limited requirement on certain routes to provide for rates and codes not inclu
11、ded in (b) that wherever possible the rates and codes given in Table R.101 should not be expanded in the future; (cl that Administrations may be asked to provide code and speed independent channels for cryptography, for telemetry, for rates outside the Recommendation R. 101 tolerance of f 1.4%, wher
12、e the rate and code may be changed frequently, and for maintenance purposes; (dl independent and code dependent traffic; that the aggregate bit rate may be limited to 2400 bids and TDM equipment may be required to pass code (e) that the bearer may not be suitable for using the backward channel as de
13、fined by clause 5N.26 I, or in the provision of telegraph channels above the Recommendation V.26 aggregate by the technique of subdivision of the frequency band as given in Recommendation H.34 2, unanimously deciares the view that where bit-interleaved TDM systems are used for code dependent and cod
14、e independent anisochronous telegraph and data transmission with an aggregate rate of 2400 bids, carried either by analogue telephone-type circuit or by higher order TDM system, the equipment should be constructed to comply with the following standards: 1 System capacity 1.1 channels to alternative
15、B. The TDM system will be capable of multiplexing the rates shown in Table 1R.101 for code dependent 1.2 Each code and rate independent channel should replace three, six or twelve 50 baud code dependent channels. 1.3 The characteristics of the code independent channels should follow the limits shown
16、 in Table 1. 2 Channel inputs 2.1 51.06, 102.12 or 204.24 bauds. The nominal modulation rate will be 50, 100 or 200 bauds; the theoretical maximum modulation rate shall be 2.2 The transition coding process of telegraph signals is in accordance with Recommendation R.111. 2.3 Each channel provides its
17、 individual coding intervals starting within the allocated time slots: each coding interval is subdivided into four quarters. In that coding interval where the skipping bit occurs in the subframe, the forth quarter is shortened by one time slot length. For a 50 baud channel, transmission of the code
18、 character starts with the next corresponding time slot. For channels with higher modulation rates the transmission of the code characters should be delayed by the number of the allocated time slots in the subframe minus 3. Recommendation R.112 (03/93) 1 TABLE 1R.112 Characteristics of code independ
19、ent channels and system capacity 8.3 8.3 I 8.3 Nominal modulation rate (bauds) 50 100 200 Maximum degree of isochronous distortion due to sampling (%I Theoretical maximum modulation rate (bauds) 51.06 102.12 204.24 Data signalling rate on the bearer per channel (bitis) 153.2 306.4 612.8 Duration of
20、the shortest isolated element 6.5 3.25 1.625 Maximum number of channels for an aggregate rate of 2400 bit/s 15 7 3 2.4 Where applicable, spurious elements with duration of 1.6 ms (= 8%) or less shall be rejected and elements longer than 2 ms shall be accepted at the 50 baud channel input. The elemen
21、t lengths to be rejected or accepted at higher channel modulation rates is for further study. 3 Channel outputs 3.1 The maximum degree of inherent isochronous distortion due to the sampling process shall be 8.3%. NOTE -The long-term system distortion on a tandem connection of transition encoded chan
22、nels of an independent TDM system approximates in the worst case to the arithmetic summation of the individual link distortions. 3.2 output. After a TDM link failure, actions described in 3.5 and 3.6R.101, should be taken on the derived channel 4 Multiplexing details 4.1 The multiplexing details are
23、 in accordance with Recommendation R. 101, alternative B, on a bit basis. 4.2 The maximum transfer delay (excluding the modem) for 50, 100 and 200 baud code and rate independent channels for back-to-back terminals shall not exceed 50 ms for the rate 50 bauds and 35 ms for rates 100 and 200 bauds. Th
24、e values of the delay are subject to further study. 5 Frame structure This is as defined in Recommendation R. 101 alternative B. 6 Synchronizing This is as defined in Recommendation R.lO1, alternative B. 7 Aggregate signals and interface, system clock arrangements and system control and alarms These
25、 are defined in Recommendation R. 101. 2 Recommendation R.112 (03/93) ITU-T RECMN*R=LL2 93 48b2591 0593259 988 8 Channel numbering scheme of code independent channels Channel numbers used in the given Recommendation represent two last digits of the four-digit numbering scheme in respect to the Figur
26、e 1, first two digits are shown in Recommendation R.114. 9 Link performance and availability indicators A system must be provided for monitoring performance and availability in accordance with Recommendation R. 118. TOW 174(194/a) 1 CD Code dependent channel CID Code independent channel Service chan
27、nel FIGURE 1R.112 Channel dacatian for code independent channels of 50,100 and 200 bauds References i circuits, Rec. V.26. CCITT Recommendation 2400 bit per second modem standardized for use on 4-wire leased telephone-type 2 other services, Rec. H.34. CCITT Recommendation Sub-division of the frequency band of a telephone-type circuit between telegraph and Recommendation R.112 (03/93) 3 ITU-T RECMN*RmLL2 93 M 4862593 05932bO bTT Printed in Switzerland Geneva, 1994
