1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU TELEGRAPHY TELEGRAPH TRANSMISSION R.102 (03/93) 4800 bit/ CODE AND SPEED DEPENDENT AND HYBRID TDM SYSTEMS FOR ANISOCHRONOUS TELEGRAPH AND DATA TRANSMISSION USING BIT INTERLEAVING ITU-T Recommendation R.102 (P
2、reviously “CCITT Recommendation”) ITU-T RECMN*R-IJU 93 4862573 0593220 TI3 W 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 issu
3、ing 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 on t
4、hese topics. ITU-T Recommendation R.102 was revised 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
5、. 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 Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector.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 made in
6、the text to references containing the acronyms “CCITT, CCIR or IFRl3” 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 recogni
7、zed 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 microfi
8、lm, without permission in writing from the ITU. ITU-T RECMM*R=lO2 73 4862573 0533223 95“ CONTENTS 1 System capacity 2 Start-stop channel inputs 3 Start-stop channel outputs 4 Multiplexing details 5 Frame structure . 6 Synchronizing 7 Telex signalling . 8 Aggregate signais and interface . . . 9 Syste
9、m clock arrangements i O System maintenance, control and alarms . 11 Link performance and availability indicators . References . Recommendation R.102 (03193) Page 1 2 3 4 4 5 10 10 10 10 11 11 1 ITLI-T RECMN*R*LO? 93 111 4862591 0573222 89b Recommendation R.102 4800 bith CODE AND SPEED DEPENDENT AND
10、 HYBRID TDM SYSTEMS FOR ANISOCHRONOUS TELEGRAPH AND DATA TRANSMISSION USING BIT INTERLEAVING (Malaga-Torremolinos, 1984; modified at Melbourne, 1988 and at Helsinki, 1993) The CCITT, considering (a) telegraph and data transmission using an aggregate bit rate of 4800 bits; that there is a demand for
11、a bit-interleaved code and speed dependent TDM system for anisochronous (b) that an increase of the economical transmission of large numbers of anisochronous telegraph and data signals, especially those of higher modulation rates, e.g. 300 bauds, can be achieved by doubling the system capacity norma
12、lly carried over a code and speed dependent TDM using an aggregate bit rate of 2400 bids; (c) that the doubling of system capacity should be based on the already well defined multiplexing (TDM) technique used for the multiplexing system according to Recommendation R. 10 frame structure of alternativ
13、e B; time division retaining the (4 that unit modularity, operation and maintenance should best be rationalized for b th the basic Recommendation R.lO1 (alternative B) TDM and the expanded multiplexing system with the higher aggregate bit rate; (e) that the expanded multiplexing system should permit
14、 the accommodation of code-dependent and code-independent (transparent) channels using the TDM hybrid technique according to Recommendation R. 1 12; ( f future, that the expanded multiplexing system should permit the accommodation of new facilities emerging in the unanimously declares the view that,
15、 where bit-interleaved code and speed dependent TDM systems with the provision for a limited use of code-independent (transparent) channels are used for anisochronous telegraph and data transmission with an aggregate bit rate of 4800 bits carried either by an analogue telephone-type circuit or by a
16、higher order TDM, the equipment shall be constructed as an expanded multiplexing system to the basic Recommendation R.lO1 (alternative B) TDM to comply with the following standard: 1 System capacity 1.1 The capacity of the system shall be 92 channels at 50 bauds (7.5 units including a stop element o
17、f 1.5 units). 1.2 For other modulation rates see Table 1. 1.2.1 indicated for homogeneous configurations. The modulation rates and character structures shown in Table 1 shall be accommodated with the capacities Recommendation R.102 (03/93) 1 ITU-T RE.CMN*R.LQE 93 4862511 0533223 722 W TABLE 1R.102 S
18、ystem capacity NOTE - The system capacity for code-independent channels using the TDM hybrid technique according to Recommenda- tion R. 1 12 is not covered by this table. 1.2.2 The TDM system shall be capable of multiplexing the eight modulation rates shown in Table 1 simultaneously. 1.2.3 The TDM s
19、ystem shall provide for a limited use of transparent channels. In using the TDM hybrid technique, the system capacity and the overall characteristics of the code-independent channel from the channel input to the channel output shall be in accordance with Recommendation R. 1 12. NOTE - The overall ch
20、aracteristics of code- and speed-dependent channels are the subject of this Recommendation and are specified in the following clauses. 2 Start-stop channel inputs 2.1 signals with a stop element of 1.4 units shall be at least k 1.4%. The modulation rate tolerance that shall be accepted on continuous
21、 incoming 50- and 75-baud start-stop 2.2 When receiving characters at 50 or 75 bauds having nominally 1.5-unit stop elements, the system shall be capable of transmitting without error, isolated incoming characters that have a one-unit stop element, occuring at a maximum rate of one per second. 2.3 T
22、he minimum interval between start elements of undistorted successive continuous characters that may be presented at the channel input when the nominal modulation rate is 50 or 75 bauds shall be 145 5/6 or 97 2/9 ms respectively. 2 Recommendation R.102 (03/93) 2.4 There shall be no festriction on the
23、 continuous transmission of ail characters specified in clause 1 above (e.g. combination No. 32 of International Telegraph Alphabet No. 2) when they are presented at the maximum permitted rate. 2.5 a nominal character length and rate shall be at least 40%. The effective net margin on all channel inp
24、uts when undistorted signals are received from a transmitter having 2.6 duration and shall be accepted if equal to or more than 0.6 units duration. At the nominal signalling rate, an input character start element shall be rejected if equal to or less than 0.4 units 2.7 stream in the case of: Element
25、s corresponding to start polarity (at the distant multiplexer output) shall be inserted in the aggregate a) unequipped channels; b) equipped but unallocated channels; c) open-circuit line condition at the local start-stop channel input. 2.8 The maximum tolerance on modulation rates other than 50 and
26、 75 bauds shall be 1.8%. 3 Start-stop channel outputs 3.1 The maximum degree of gross start-stop distortion shall be 3% for all permitted modulation rates. 3.2 nominal modulation rate shall be 0.2%. The maximum difference possible between the mean modulation rate of the channel output signals and th
27、e 3.3 range of this Recommendation, the minimum stop element duration released at the output shall be 1.25 units. When characters having a nominal 1.5-unit stop element are presented at any input rate within the specified 3.4 When characters having a nominal 1- or 2-unit stop element are presented a
28、t any input rate within the specified range of this Recommendation, the minimum stop element duration released at the output shall be 0.8 or 1.8 units respectively. 3.5 failure conditions: Channel output shall be controlled as specified below in the event of recognition of any of the following a) ca
29、rrier loss signalled by the modem (OFF condition of received line signal detector - circuit CT109, Recommendation V.24 i); b) loss of aggregate signal (defined as a period of 280 ms without a transition on the aggregate); c) loss of synchronization. 3.6 of the affected TDM: Within 4 ms of the recogn
30、ition of the failures described in 3.5, the following shall occur to the channel outputs 3.6.1 Leased channels - Two options shall be possible on a per channel basis: a) b) set to steady start polarity; set to steady stop polarity; 3.6.2 Circuit-switched service - Two options shall be possible on a
31、per channel basis: a) steady start polarity at the channel output: b) loopback of the channel towards the local end for a period of 5 t 1 seconds, after which channel outputs shall revert to steady start polarity. Additionally, the traffic path shall be maintained towards the distant multiplexer ter
32、minal during this loopback interval. Recommendation RJ02 (03193) 3 ITU-T RECMN*R*LO2 93 m 4b2591 0593225 5T5 = NOTE -The actions taken in case 3.6.2 a) shall ensure that, after recognition of failure, no 50-baud channel used for circuit-switched service shall produce an output pulse of stop polarity
33、 of longer than 20 ms or a series of 20-ms pulses of stop polarity. It should be noted that 20-ms pulses can cause difficulty with some switching equipment. The loopback option in 3.6.2 b) is provided in order to avoid clearance of established connections during short breaks and thus avoid excessive
34、 recall attempts. 3.7 The affected terminal shall signal its synchronization status to the distant terminal in accordance with 6.4. The distant terminal shall control its outputs in accordance with 3.6 above with a delay that shall not exceed 600 ms (measured from the instant of failure), ignoring t
35、he propagation time of the bearer circuit. Alternatively, leased channels have the option, at the customers request, of maintaining the traffic path in the unaffected direction. 4 Multiplexing details 4.1 Channel interleaving shall be on a bit basis. 4.2 Both start and stop elements of each input ch
36、aracter shall be transmitted through the aggregate. 4.3 The transfer delay for 50- and 75-baud signals through a pair of terminals connected back-to-back (excluding the modems) shall not exceed 2.5 units. This delay shall be measured from the reception of the start element of a character at an input
37、 channel of one terminal until the corresponding start element is delivered from the output channel of the second terminal. 4.4 3.5 units. The maximum transfer delay for all other permitted channel speeds for back-to-back terminals shall not exceed 4.5 following element numbers 2 and 5 2. 75-baud ch
38、aracters are conveyed on a lO-bit/s bearer channel by transmitting filling bits in each character 4.6 aggregate signal. 1 10-baud characters are conveyed on a lW-bit/s bearer channel by transmitting at least one stop element in the 4.7 stop polarity before the character start elements in the aggrega
39、te signal. 134.5-baud characters are conveyed on a 150-bit/s bearer channel by transmitting the necessary filling bits of 5 Frame structure 5.1 A unique subframe of 47 bits shall be used. 5.2 A 47-bit subframe shall consist of one synchronization bit in the first bit position and 46 traffic bits. 5.
40、3 A fundamental frame consisting of two consecutive subframes shall be used. 5.4 One framing arrangement is allowed. The channel numbers used throughout this Recommendation represent the last two digits of a 4digit numbering scheme - the first two digits are shown in Recommendation R.114. This chann
41、el allocation scheme is shown in Tables 2 and 3. Table 4 shows the channel allocation of 50, 100 and 200 baud code independent channels using the TDM hybrid technique according to Recommendation R. 1 12. 5.5 The channel allocation in the fundamental frame is shown in Table 5 in matrix form giving th
42、e relationship between individual low-speed channels and the corresponding traffic bits. The fundamental frame is represented as divided into four groups of 24 positions. The correspondence between positions in the matrix structure and bit numbers within the fundamental frame is shown in the bit num
43、ber columns. The table also shows the distribution of positions within the specific groups for channels of different speeds and the corresponding channel numbering. (See also Tables 2 and 3.) 4 Recommendation R.102 (03/93) NOTES 1 For all speeds other than 50 and 150 bauds, the second subframe in th
44、e fundamental frame is a repetition of the first In each subframe one position within group 1 is skipped. i.e. allocated zero time in the aggregate signal. subframe. 2 5.6 follows: Substitution of higher speed channels into a homogeneous 50-baud system configuration shall be made as 1 x 75- or 100-
45、or 110-baud channel replaces 2 x 50-baud channels 1 x 150- or 134.5-baud channel replaces 3 x 50-baud channels 1 x 200-baud channel 1 x 300-baud channel replaces 4 x 50-baud channels replaces 6 x 50-baud channels 5.7 All bits from groups 3 and 4 shall give inverted polarity. 5.8 fourth and sixth bit
46、s are contained in the second subframe (see 6.4). The first, third and fifth bits of the synchronization pattern are contained in the first subframe. The second, 6 Synchronizing 6.1 part in 103. The system shall not lose synchronism more than once per hour for a randomly distributed error rate of on
47、e 6.2 One synchronizing arrangement is allowed as described in 6.3 through 6.1 1. 6.3 subframes) containing a synchronization word that consists of six equidistantly spaced bits. A sync frame is defined as a sequence of three consecutive fundamental frames (Le. six consecutive 6.4 The normal sync pa
48、ttern transmitted when the TDM terminal receiver is correctly synchronized will be 100010. When the receiver is out of synchronism the transmitted pattern shall be O11101 (see 6.7 below). The changeover shall only occur at the end of a sync frame. 6.5 Loss of synchronism is defined when three consec
49、utive synchronization patterns are received in error. I 6.6 shall be capable of detecting loss of synchronism within 140 ms. When the received aggregate signal is replaced by steady start or steady stop polarity, the receiver terminal 6.7 terminal within 120 ms, by inversion of the normal synchronization pattern. (See 6.4 above.) With two terminals connected back-to-back, loss of synchronism in one terminal shall be indicated at the other 6.8 corresponding to: Receipt of the inverted sync pattern shall cause the terminal to force the aggregate traffic bits to the polarities a)
