1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU TELEGRAPHY TELEGRAPH TRANSMISSION RI11 (03/93) CODE AND SPEED INDEPENDENT TDM SYSTEM FOR ANISOCHRONOUS TELEGRAPH AND DATA TRANSMISSION ITU-T Recommendation R.111 (Previously “CCITT Recommendation”) FOREWORD T
2、he 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 ariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwi
3、de 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 on these topics. ITU-T Recommendation R.111 was revised by the ITU-T Study Group IX (1988-19
4、93) 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 Telecommunication Standardization Sector (ITU-T) was created as
5、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 Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector.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 containing the acronyms “CCITT, CCIR or IFRB”, or their associate
6、d 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 this Recommendation, the expression “Administration” is used fo
7、r 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 microfilm, without permission in writing from the ITU. ITU-T RECMN*R.111 73 E 4862571 0593243 5
8、10 CONTENTS 1 64 kbit/s aggregate . 1.1 General 1.2 Aggregate bearer channel . 1.3 Frame structure . 1.5 Allocation of information bits . 1.6 1.8 1.9 Bearer interface . 1.4 Type of multiplexing Telegraph and data channels . 1.7 Frame alignment . Loss of telegraph input . 1.10 Telegraph interface . A
9、ggregate bearer rates lower than 64 kbit/s . 2 2.1 2.2 2.3 2.4 2.5 2.6 2.1 2.8 2.9 2.10 General., Aggregate bearer channels Frame structure . Type of multiplexing Allocation of information bits . Telegraph and data channels . Frame alignment . Loss of telegraph input . Bearer interface . Telegraph i
10、nterface . 3 Compatibility Annex A - Transition coding process . References . Recommendation R.lll (03/93) Page 1 1 2 2 2 2 2 3 3 3 4 4 4 4 4 5 5 5 5 6 6 6 6 8 9 ITU-T RECNN*R.LLL 93 4862573 0573244 457 m Recommendation R.lll CODE AND SPEED INDEPENDENT TDM SYSTEM FOR ANISOCHRONOUS TELEGRAPH AND DATA
11、 TRANSMISSION (Geneva, 1976; amended at Geneva, 1980, Malaga-Torremolinos, I984 and at Helsinki, 1993) The CCITT, considering (a) that the use of voice-frequency telegraph (VFT) equipment on voice channels provided by frequency division multiplexing of a primary group or by time slots in a pulse cod
12、e modulation (PCM) transmission system may not always be the optimum solution for telegraph and low-speed data transmission, if aspects of transmission quality, equipment complexity, technological progress, miniaturization, power consumption and overall cost are globally considered; (b) speed-indepe
13、ndent channels may be achieved by using time division techniques; that the economic transmission of telegraph and low-speed anisochronous data signals requiring code- and (c) might be preferred in some (e.g. short-haul) applications; that a relatively simple TDM (time division multiplex) system, eve
14、n if less efficient in bandwidth utilization, (4 when replacing them by TDM systems; that Administrations might be interested in conserving code and speed independence inherent in VFT systems (e) (anisochronous. isochronous, telegraph, data, signalling for switching purposes); that code and speed in
15、dependent transmission systems are capable of transmitting any type of digital signal (0 network, depending on the number of circuits connected in tandem; that a code and speed independent TDM system can adapt its inherent telegraph distortion to the needs of a (g) being defined by its maximum modul
16、ation rate and inherent distortion); that a code and speed independent TDM system can adapt to a number of different types of channels (each (h) that a basic 64 kbi/s telegraph multiplexer may provide interfaces for remote submultiplexers if required. The submultiplexers may be associated in some ap
17、plications with Recommendations X.50 i and X.5 1 2 data multiplexers and with telephone channel modems andlor baseband modems, unanimously deciares the following views 1 64 kbis aggregate 1.1 General 1.1.1 Where code and speed independent TDM systems for transmission of telegraph and low-speed aniso
18、chronous data signals utilize the whole 64 kbit/s capacity (e.g. provided by a PCM time slot or a primary group), the equipment shall be manufactured to comply with the following standards. Recommendation R.111 (03/93) 1 ITU-T RECMN*R-LLL 93 m 48b259L 0593245 393 m 1.2 Aggregate bearer channel 1.2.1
19、 The aggregate bearer channel may be a 64 kbids PCM time slot or a 64 kbids synchronous data modem in accordance with the Recommendation cited in 3. The nominal data signalling rate is 64 o00 bids with a tolerance off 3 bids. However, it should be noted that if a synchronous data modem in accordance
20、 with 3 is used, a tolerance of I 1 bids may be necessary. 1.2.2 with the requirement of mutual aggregate bearer synchronization indicated in Recommendation R. 1 OO. The possibility of external signalling rate synchronization of the bearer channel should be provided to comply 1.3 Frame structure 1.3
21、.1 The frame consists of 240 bits for information plus 16 symmetrically distributed service bits for framing and other purposes. The 16th bit of the frame is the first service bit. The frame synchronization pattern comprises the first 12 service bits in the sequence 101001010101. 1.3.2 bearer failur
22、e; O = bearer failure. A minimum of three consecutive O conditions is the criterion for an alarm indication. The 13th service bit is used to inform the opposite multiplexer terminal of bearer failure as follows: 1 = no 1.3.3 The 14th service bit is used to inform the opposite multiplexer terminal of
23、 frame alignment loss as follows: 1 = no loss of frame alignment; O = frame alignment loss (this may be accompanied by bearer failure). A minimum of three consecutive O conditions is the criterion for an alarm indication. 1.3.4 is for further study. The time delay between detection of a bearer failu
24、re or frame alignment loss and the sending of the O condition 1.3.5 The 15th service bit is provisionally fixed to 1 and its use is left for further study. 1.3.6 justification strategy, if used, must be agreed bilaterally. The 16th service bit (last bit of the frame) may be used for possible justifi
25、cation and is fixed to 1. However, the 1.3.7 The channel numbering scheme is specified in Recommendation R. 114. 1.4 Type of multiplexing 1.4.1 Channel interleaving shall be on a bit basis. 1.4.2 The coding method shall be the transition coding process in accordance with Annex A. 1.5 Allocation of i
26、nformation bits 1.5.1 4000 bids corresponding to one, two, four, eight or sixteen bits per frame (symmetrically distributed) respectively. The data signalling rate on the bearer for each multiplexed channel should be 250, 500, 1000, 2000 or 1.5.2 purposes. The 64 kbit/s aggregate stream is divided i
27、nto 60 kbit/s for information and 4 kbit/s for framing and other 1.5.3 by bilateral agreement, into twenty bit streams of 3 kbit/s. The 60 kbids information bit stream may be subdivided into five bit streams of 12 kbit/s or, for national use or 1.6 Telegraph and data channels 1.6.1 possible. The nom
28、inal modulation rates are 50, 100, 200, 300, 600 and 1200 bauds. A mixture of these rates should be 1.6.2 The maximum degree of inherent isochronous distortion due to the sampling process is 2.5, 5 or 7.5% according to the application as shown in Table 1, which gives the channel characteristics and
29、full system capacity for various telegraph channel rates and for aggregate signalling rates of 64 kbit/s and below (see clause 2). 2 Recommendation R.lll (03/93) 1.6.3 Where applicable, spurious elements with duration of 1.6 ms (= 8%) or less shall be rejected and elements longer than 2 ms shall be
30、accepted at the 50 baud channel input. The element lengths to be rejected or accepted at higher channel modulation rates is for further study. 1.7 Frame alignment 1.7.1 Frame realignment is ensured within three correct consecutive frame synchronization patterns, i.e. within 12 to 16 ms. In the absen
31、ce of frame realignment, the telegraph channel outputs of the demultiplexer should be locked in their start polarity state for switched applications. NOTE - Stop polarity might be required by some Administrations on a per channel basis for leased applications. TABLE 1R.111 Channel characteristics an
32、d system capacities Nominal modulation rate (bauds) 50 100 200 300 600“) 1200“) Maximum degree of isochronous distortion due to sampling (%I 5 2.5 5 2.5 5 7.5 7.5 7.5 Theoretical maximum modulation rate (bauds) 83 167 167 333 333 333 666 1333 Data signalling rate on the bearer per channel Shortest i
33、solated element (bitk) I (ms) I 250 500 500 lo00 lo00 Io00 2000 4000 4 2 2 1 1 1 0.5 0.25 Maximum number of channels for an integrated system of 64 kbit/s 240 120 120 60 60 60 30 15 9.6 kbi/s 32 16 16 8 8 8 4 2 4.8 kbit/s 16 8 8 4 4 4 2 - 2.4 kbit/s a) The number of channels indicated for modulation
34、 rates of 600 and 1200 bauds is for information only (homogeneous aggregates at these rates are not contemplated). 1.7.2 frame alignment. Three consecutive erroneous frame synchronization patterns should be regarded as the criterion for loss of 1.8 Loss of telegraph input 1.8.1 at the corresponding
35、output. In the absence of any signal at a telegraph channel input, the multiplexer system should reproduce start polarity NOTE - Stop polarity might be required by some Administrations on a per channel basis for leased applications. 1.9 Bearer interface 1.9.1 For the interface between the aggregate
36、bearer and a PCM time slot, either a codirectional or contradirectional 64 kbits interface with the PCM equipment could be accepted. Even for a codirectional interface no stuffing device would be provided in the telegraph multiplexer, which would loop back the 64 kHz clock. Recommendation R.lll (03/
37、93) 3 ITU-T RECMN*R-LLL 93 4862573 0593247 Lbb M 1.9.2 Recommendation cited in 4). For the interface to a 64 kbit/s modem the interchange circuits of Table 2 should be provided (see the 1.10 Telegraph interface 1.10.1 requirements. The interface between the multiplexer and the telegraph circuits sho
38、uld be in accordance with national TABLE UR. 11 1 Circuit number (Recommendation V.24 SI) Function Signai ground or common return DCE common return Transmitted data Received data Data channel received line signal detector Transmitter signal element timing (DTE source) Transmitter signal element timi
39、ng (DCE source) Receiver signal element timing a) b, The provision of this conductor is optional. This conductor is used in conjunction with interchange circuit 109. The electrical characteristics of the interchange circuits marked with should be in accordance with Recommendation X.27 6. The circuit
40、s a not so marked should be in accordance with Recommendation X.26 7. d, Either circuit 113 or 114 is to be used. 2 Aggregate bearer rates lower than 64 kbWs 2.1 General 2.1.1 Where code and speed independent TDM systems for transmission of telegraph and low speed anisochronous data signals make use
41、 of capacities lower than 64 kbit/s, the equipment shall be manufactured to comply with the following standards: 2.2 Aggregate bearer channels 2.2.1 Aggregate rates of 2.4, 4.8 and 9.6 kbitfs shall be used. These rates can be provided either using modems in accordance with the V-Series Recommendatio
42、ns or using data multiplexers in accordance with Recommenda- tions X.50 i or X.51 2. 2.3 Frame structure 2.3.1 The frame structure is independent of the frame structure of the 64 kbit/s data multiplexer or of the 64 kbit/s telegraph multiplexer. However, it must be designed to allow easy insertion o
43、f the carried telegraph channels on to the multiplexer defined in clause 1 above (see also clause 3 below). 4 Recommendation R.lll (0383) 2.3.2 result in effective binary rates of 2,4 or 8 kbit/s with actual aggregate rates of 2.4,4.8 and 9.6 kbit/s respectively. 2.3.3 purposes. The sixth bit of the
44、 frame is the first service bit. 2.3.4 distributed service bits. For that purpose, one bit out of every six bits will carry framing information and other functions, which will The frame consists of 160 information bits plus 32 symmetrically distributed service bits for framing and other This frame i
45、s subdivided into two subframes each consisting of 80 information bits plus 16 symmetrically 1000 2000 2.3.5 2.3.6 at O for the first subframe and at 1 for the second subframe. The subframe synchronization pattern comprises the first 12 service bits in the sequence 101001010101. For the allocation o
46、f the 13th, 14th and 15th service bits, see 1.3.2 to 1.3.5 above. The 16th service bit is set 20 40 80 40 80 - 2.4 Type of multiplexing 2.4.1 See 1.4 above. 2.5 Allocation of information bits 2.5.1 2000 and 4000 bids). The same data signalling rates as defined in 1.5 should be used (250,500 and lo00
47、 bids and, where applicable, 2.5.2 channel. These information bits are symmetrically distributed among the 160 information bits of the frame. Table 3 shows the number of information bits per frame for the different data signalling rates on the bearer TABLE 3R.111 Number of information bits per frame
48、 t I I Number of information per frame for each channel in an aggregate system of Data signalling rate on the bearer per channel I (bit/s) I 9.6 kbit/s I 4.8 kbit/s I 2.4 kbit/s I 250 5 10 20 2.6 Telegraph and data channels 2.6.1 See 1.6 above. 2.7 Frame alignment 2.7.1 Frame realignment time is ens
49、ured within three correct consecutive subframe synchronization patterns. This frame realignment will be ensured within 40, 80 and 160 ms for aggregate rates of 9.6,4.8 and 2.4 kbit/s respectively. In the absence of frame realignment the telegraph channel outputs of the demultiplexer should be locked in their start polarity state for switched applications. NOTE - Stop polarity might be required by some Administrations on a per channel basis for leased applications. 2.7.2 See 1.7.2 above. Recommendation R.lll (03/93) 5 ITU-T RECMNwRmLLL 93 4Ab2591 0593249 T39 W 2.8 Loss
