1、INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU v.91 (05199) SERIES V: DATA COMMUNICATION OVER THE TELEPHONE NETWORK Simultaneous transmission of data and other signals A digital modem operating at data signalling rates of up to 64 O00 bis for use on a 4-w
2、ire circuit switched connection and on leased point-to-point 4-wire digital circuits ITU-T Recommendation V.91 (Previously CCITT Recommendation) STD*ITU-T RECMN V-91-ENGL 1999 4862591 ObbbOb7 O19 ITU-T V-SERIES RECOMMENDATIONS DATA COMMUNICATION OVER THE TELEPHONE NETWORK 1- General Interfaces and v
3、oiceband modems Wideband modems Error control v.1-v.9 v. 1 0-v. 34 v.35-v.39 v.40-v.49 II Transmission quality and maintenance v.50-v.59 I V.60-11.9 11 Interworking with other networks v. 1 0o-v. I 99 Interface layer specifications for data communication Control procedures Modems on digital circuits
4、 V.200-V.249 v.250-v.299 V.300-V.399 For further details, please rejr to iTU-T List of Recommendations. ITU-T RECOMMENDATION V.91 A DIGITAL MODEM OPERATING AT DATA SIGNALLING RATES OF UP TO 64 O00 bit/s FOR USE ON A 4-WIRE CIRCUIT SWITCHED CONNECTION AND ON LEASED POINT-TO-POINT 4-WIRE DIGITAL CIRCU
5、ITS Summary This Recommendation specifies the operation of a duplex digital modem for use on a 4-wire circuit switched connection and on leased point-to-point 4-wire digital circuits at data signalling rates of up to 64 O00 bith. The modem is specified in terms of coding, start-up sequences, operati
6、ng procedures and DTE-DCE interface functionalities. The modem includes an optional control channel and support for transparent mode on unrestricted 64 O00 bit/s channels. The network interface of the modem and the signalling rate that is used to connect the modem locally to a 4-wire connection are
7、considered to be national matters and are hence not specified. Source ITU-T Recommendation V.91 was prepared by ITU-T Study Group 16 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on 27 May 1999. Recommendation V.91 (0999) 1 - - . STD-ITU-T RECMN VeSL-ENGL 1999 48b2591 ObbbOb
8、S 991 m FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff qu
9、estions and issuing Recommendations 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 Reco
10、mmendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WSC Resolution No. 1. In some areas of information technology which fall within ITU-Ts purview,.the necessary standards are prepared on a collaborative basis with IS0 and
11、 IEC. NOTE In this Recommendation the term recognized operating agency (ROA) includes any individual, company, corporation or governmental organization that operates a public correspondence service. The terms Administration, ROA and public correspondence are defined in the Constitution of the ITU (G
12、eneva, 1992). INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intel
13、lectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, the ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation.
14、 However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. O ITU 2000 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical
15、, including photocopying and microfilm, without permission in writing from the ITU. 11 Recommendation V.91 (0999) STD-ITU-T RECMN V-91-ENGL 1999 = 48b2591r 0bbb070 603 m 2 3 4 5 5.1 5.2 6 6.1 6.2 6.3 6.4 6.5 7 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 7.10 7.1 1 CONTENTS Page Scope References Definitions
16、Abbreviations . Interchange circuits List of interchange circuits . Asynchronous character-mode interfacing . Line signals . Data signalling rates . Symbol rate . Encoder for non-transparent mode . 6.3.1 6.3.2 6.3.3 6.3.4 6.3.5 6.3.6 6.3.7 6.3.8 6.3.9 Scrambler Mapping parameters Input bit parsing M
17、odulus encoder . Mapper Differential encoding Sign assignment Control channel bit assignment . Mux . Control channel Encoder for transparent mode Start-up sequences B1 . CP . DIL . E. E. E. E, . INFO . J PHIL . SCR Recommendation V.91 (05199) 1 1 2 2 5 5 6 6 6 8 9 9 9 9 9 10 10 10 . 111 8 8.1 8.2 8.
18、3 8.4 8.5 8.6 8.7 8.8 9 10 STD-ITU-T RECMN Vm91-ENCL 1999 m 4862593 0bbb071 Operating procedures v.91 start-up . 8.2.1 Call and answer modem Escape to V.34 8.3.1 Call modem . 8.3.2 Answer modem . Retrains . 8.4.1 Initiating retrain i 8.4.2 Responding to retrain . . : Loss of frame synchronization .
19、Cleardown Transparent mode . Phase 1 . Four-wire leased line operation Testing facilities . Glossary Appendix I . Typical network configuration . 54T Page 10 10 11 11 12 12 12 13 13 13 13 13 13 13 13 14 14 iv Recommendation V.91 (05/99) STD=ITU-T RECMN V-91-ENGL 1999 m 4b2591 Obbb072 Li8b Recommenda
20、tion V.91 A DIGITAL MODEM OPERATING AT DATA SIGNALLING RATES OF UP TO 64 O00 bit/s FOR USE ON A 4-WIRE CIRCUIT SWITCHED CONNECTION (Geneva, 1999) AND ON LEASED POINT-TO-POINT 4-WIRE DIGITAL CIRCUITS 1 Scope This modem is specified herein in terms of coding, start-up signals and sequences, operating
21、procedures and DTE-DCE interface functionalities. The network interface of the modem and the signalling rate that is used to connect the modem locally to a 4-wire connection are considered to be national matters and are hence not specified herein. The principal characteristics of the modem are as fo
22、llows: a) b) cl d) e) f) g) h) i) duplex mode of operation on a 4-wire digital connection; channel separation by 4-wire connection; PCM modulation at a rate of 8000 symbols per second; synchronous channel data signalling rates fiom 28 O00 bit/s to 64 O00 bit/s in increments of 8000/6 bids; an option
23、al control channel that uses 125 bids of the primary channel data signalling rate and allows for a 67.5 bit/s secondary channel data signalling rate; adaptive techniques that enable the modem to achieve close to the maximum data signalling rate that the channel can support on each connection; suppor
24、t of transparent mode on unrestricted 64 O00 bit/s channels; exchange of rate sequences during start-up to establish the data signalling rate; and automoding to devices supporting V.8, and optionally V.8 bis, procedures. 2 References The following ITU-T Recommendations and other references contain p
25、rovisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations are subject to revision; all users of this Recommendation and other references are therefore encouraged to investigate the
26、 possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. - - CCITT Recommendation G.7 1 1 (1 988), Pulse code modulation (PCM) of voicefrequencies. ITU-T Recommendation V.8 (
27、1 998), Procedures for starting sessions of data transmission over the public switched telephone network. ITU-T Recommendation V.8 bis (1998), Procedures for the identijication and selection of common modes of operation between Data Circuit-terminating Equipments (DCEs) and between Data Terminal Equ
28、ipments (DTEs) over the public switched telephone network and on leased point-to-point telephone-type circuits. - ITU-T Recommendation V. 14 (1993), Transmission of start-stop characters over synchronous bearer channels. - Recommendation V.91 (05/99) 1 - ITU-T Recommendation V.24 (1 996), List of de
29、finitions for interchange circuits between data terminal equipment (DTE) and data circuit-terminating equipment (DCE). ITU-T Recommendation V.34 (1998), A modem operating at data signalling rates of up to 33 600 bith for use on the general switched telephone network and on leased point-to-point 2-wi
30、re telephone-type circuits. - ITU-T Recommendation V.42 (1 996), Error-correcting procedures for DCEs using asynchronous-to-synchronous conversion. - - - - ITU-T Recommendation V.43 (1 998), Dataflow control. CCITT Recommendation V.54 (1988), Loop test devices for modems. ITU-T Recommendation V.80 (
31、1996), In-band DCE control and synchronous data modes for asynchronous DTE. ITU-T Recommendation V.90 (1 998), A digital modem and analogue modem pair for use on the public switched telephone network (PSTN) at data signalling rates of up to 56 O00 bith downstream and up to 33 600 bith upstream. - 3
32、Definitions This Recommendation defines the following terms: Nominal transmit power: As defined in clause 3N.90. Uchord: As defined in clause 3N.90. Ucode: As defined in clause 3N.90. 4 Abbreviations This Recommendation uses the following abbreviations: DCE Data Circuit-Terminating Equipment DIL Dig
33、ital Impairment Learning sequence DTE Data Terminal Equipment 5 Interchange circuits 5.1 List of interchange circuits References in this Recommendation to V.24 interchange circuit numbers are intended to refer to the functional equivalent of such circuits and are not intended to imply the physical i
34、mplementation of such circuits. For example, references to circuit 103 should be understood to refer to the functional equivalent of circuit 103 (see Table 1). 2 Recommendation V.91 (0999) Table 1N.91- Interchange circuits No. 102 103 104 105 106 107 10811 or 10812 109 125 133 141 142 I Interchange
35、circuit Notes Description Signal ground or common return Transmitted data Received data Request to send Ready for sending Data set ready Connect data set to line Data terminal ready Calling indicator Local loopback Test indicator Data channel received line signai detector 1 Ready for receiving 2 5.2
36、 Asynchronous character-mode interfacing The modem may include an asynchronous-to-synchronous converter interfacing to the DTE in an asynchronous (or start-stop character) mode. The protocol for the conversion shall be in accordance with Recommendation(s) V.14, V.42 or V.80. Data compression may als
37、o be employed. 6 Line signais 6.1 Data signalling rates Synchronous channel data signalling rates from 28 O00 bit otherwise the modem shall transmit Eu followed by the DIL requested by the peer modem. The modem shall then transmit an optional amount of SCR without transmitting PHIL. 8.2.1.7 The mode
38、m shall transmit E, followed by the DIL requested by the peer modem. After transmitting E, the modem shall turn ON circuit 107. The modem shall then transmit an optional amount of SCR. 8.2.1.8 The modem shall transmit CP sequences within 1.5 seconds of receiving E, or E, and condition its receiver t
39、o receive a CP sequence. 8.2.1.9 After receiving a CP sequence, the modem shall complete sending the current CP sequence and send a CP sequence. 8.2.1.10 The modem shall continue to send CP sequences until it has sent a CP sequence and received a CP sequence or E,. The modem shall then complete the
40、current CP sequence and send a single E,. 8.2.1.11 After sending E, the modem shall send B1. The modem shall then enable circuit 106 to respond to the condition of circuit 105 and begin data transmission. 8.2.1.12 After receiving E, the modem shall condition its receiver to receive B1. After receivi
41、ng B 1, the modem shall unclamp circuit 104, turn on circuit 109, and begin receiving data. 8.3 Escape to V.34 The modem may escape to V.34 at any time during start-up. The modem shall escape to V.34 if it does not receive an INFO sequence within 1.5 seconds of beginning the procedure in 8.2.1.2. Th
42、e modem shall escape to V.34 if it does not receive B1 within 10 seconds of beginning the procedure in 8.2.1.2. The signals and sequences referred to in this subclause are defined in Recommendation V. 3 4. 8.3.1 Call modem To escape to V.34 or if it receives repeated INFOoa sequences, the call modem
43、 shall repeatedly send INFOo,. If the call modem receives INFOo, with bit 28 set to 1, it shall condition its receiver to detect Tone A and the subsequent Tone A phase reversal, complete sending the current INFOo, sequence, and then transmit Tone B. Alternatively, if the call modem detects Tone A an
44、d has received INFOo, it shall condition its receiver to detect a Tone A phase reversal, complete sending the current INFOo, sequence, and transmit Tone B. In both cases, the call modem shall then proceed according to 1 1.2.1.1.3N.34. 8.3.2 Answer modem To escape to V.34 or if it receives repeated I
45、NFOo, sequences, the answer modem shall repeatedly send INFOo,. If the answer modem receives INFOo, with bit 28 set to 1, it shall condition its receiver to detect Tone B, complete the current INFOoa, and then transmit Tone A. Alternatively, if the answer modem detects Tone B and has received INFOo,
46、 it shall complete the current INFOo, and transmit Tone A. In both cases, the answer modem shall then proceed according to 1 1.2.1.2.3N.34. 12 Recommendation V.91 (0999) 8.4 Retrains The modem shall start a 1 O-second timer after clamping circuit 104. The timer shall be disabled upon successfully co
47、mpleting a retrain. On expiry of the timer the modem shall turn OFF circuits 106, 107 and 109 and terminate the connection. 8.4.1 Initiating retrain To initiate a retrain, a modem shall turn OFF circuit 106, clamp circuit 104 to binary one, hold circuits 107 and 109 in the ON condition and continue
48、in accordance with 8.2.1.2. If a modem is transmitting the control channel, then it may warn the peer modem that it is about to initiate a retrain by setting bit 17 of the control channel sequence. In this case, the modem shall initiate the retrain after completing the current control channel sequen
49、ce. 8.4.2 Responding to retrain After detecting the onset of INFO, the modem shall turn OFF circuit 106, clamp circuit 104 to binary one, hold circuits 107 and 109 in the ON condition and continue in accordance with 8.2.1.2. 8.5 Loss of frame synchronization If a loss of frame synchronization is detected, the modem shall clamp circuit 104 and start a 1 O-second timer. The modem may either initiate a retrain according to 8.4.1 or attempt to reacquire fiame synchronization by another means. Upon successful reacquisition of frame synchronization the timer shall be disab
