1、ITU-T RECflN*V-32 93 4862593 0583476 046 = INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU DATA COMMUNICATION OVER THE TELEPHONE NETWORK V.32 (03/93) A FAMILY OF 2-WIRE, DUPLEX MODEMS OPERATING AT DATA SIGNALLING RATES OF UP TO 9600 bit/s FOR USE ON THE GE
2、NERAL SWITCHED TELEPHONE NETWORK AND ON LEASED TE LEP HO N E-TY P E CI RCU ITS ITU-T Recommendation V.32 (Previously “CCIlT Recommendation“) ITU-T RECMN*V.32 93 m 4862591 0581477 T82 = FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom
3、- munication Union. The ITU-T is responsible for studying technical, operating and tariff questions 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, e
4、stablished the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. ITU-T Recommendation V.32 was revised by the ITU-T Study Group XVII (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a reform pro
5、cess within the International Telecommunication Union (ITU), the CCIT ceased to exist as of 28 February 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 Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radi
6、ocommunication 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 ERB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain
7、 the proper terminology related to the new lTU structure. 2 telecommunication administration and a recognized operating agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a O ITU 1993 All rights reserved. No part of this publicatin may be reprodu
8、ced 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*V.32 93 48b2591 0581478 919 CONTENTS Introduction Line signais 2.1 Carrier frequency 2.2 Transmitted spectrum . 2.3 Modulation rate . 2
9、.4 Coding Interchange circuits 3.1 3.2 Transmit da ta 3.3 Receive data 3.4 Timing arrangements 3.5 Data rate control . 3.6 Circuit 106 3.7 Circuit 109 3.8 3.9 Fault condition on interchange circuits . Scrambler and descrambler 4.1 Scrambler/descrambler allocation . Operating procedures . 5.1 Recomme
10、ndation V.25 automatic answering sequence 5.2 Receiver conditioning signal 5.3 Rate signal 5.5 Retrain procedure Testing facilities . Asynchronous to synchronous conversion protocol - Modes of operation . 7.1 Transmitter 7.2 Receiver List of interchange circuits . Electrical characteristics of inter
11、change circuits . 5.4 Start-up procedure Annex A Definitions of Terms Used Interworking of Duplex Modems . A.l A.2 Appendix I - Interworking procedure for echo cancelling modems . Interworking of echo cancelling modems . 1.1 Recommendation V.32 (03/93) Page 1 1 1 2 2 2 3 3 3 4 4 4 5 5 5 6 6 8 9 9 9
12、10 13 15 16 16 16 16 17 17 17 20 20 i ITU-T RECNN*V*3E! 93 m 48b2591 0541479 455 m Recommendation V.32 A FAMILY OF 2-WIRE, DUPLEX MODEMS OPERATING AT DATA SIGNALLING RATES OF UP TO9600 bit/s FOR USE ON THE GENERAL SWITCHED TELEPHONE NETWORK AND ON LEASED TELEPHONE-TYPE CIRCUITS (Malaga-Torremolinos,
13、 1984, amended Melbourne, 1988 and Helsinki, 1993) 1 Introduction This family of modems is intended for use on connections on general switched telephone networks (GSTNs) (see Note 1) and on point-to-point leased telephone-type circuits. The principal characteristics of the modems are as follows: Dup
14、lex mode of operation on GSTN and 2-wire point-to-point leased circuits (see Note 2). Channel separation by echo cancellation techniques. Quadrature amplitude modulation for each channel with synchronous line transmission at 2400 bauds. Any combination of the following data signalling rates may be i
15、mplemented in the modems: 9600 bids synchronous (optional), 4800 bids synchronous (mandatory), 2400 bids synchronous (for further study). At 9600 bids, two alternative modulation schemes, one using 16 carrier states and one using trellis coding with 32 carrier states, are provided for in this Recomm
16、endation. However, modems providing the 9600 bids data signalling rate shall be capable of interworking using the 16-state alternative. Exchange of rate sequences during start-up to establish the data rate, coding and any other special facilities. Optional provision of an asynchronous mode of operat
17、ion in accordance with Recommendations V.14 or V.42. NOTES 1 On international GSTN connections that utilize circuits that are in accord with Recommendation G.235 (l-channel terminai equipments), it may be necessary to employ a greater degree of equalization within the modem than would be required fo
18、r use on most nationai GSTN connections. 2 The transmit and receive rates in each modem shall be the same. The possibility of asymmetric working remains for further study. 2 Line signals 2.1 Carrier frequency The carrier frequency is to be 1800 f 1 Hz. No separate pilot tones are to be provided. The
19、 receiver must be able to operate with received frequency offsets of up to 3 Interchange circuits i o n o-. Ca 1010 IO00 1100 1101 O“ (Re) -2 2 1 ao“ I. ALo- I 1 I I _. I Convoiutionai encoder T1702140-9 Differential encoder a Symbd truth table -b -b 102 FIGURE 2N.32 Trellis coding at 9600 biffs 3.3
20、 Receive data The modems shall pass synchronous data to the DTE on circuit 104 under the control of circuit 115. 3.4 Timing arrangements Clocks shall be included in the modems to provide the DTE with transmitter signal element timing on circuit 114 and receiver signal element timing on circuit 115.
21、The transmitter timing may originate in the DTE and be transferred to the modem via circuit 113. In some applications it may be necessary to slave the transmitter timing to the receiver timing inside the modem. 3.5 Data rate control Data rate selection may be by switch (or similar means) or alternat
22、ively by circuit 111. In cases where three different data signalling rates are implemented in a modem, a manual selector may be provided which determines the two data signalling rates selected by circuit 11 1. The ON condition of circuit 11 1 selects the higher data signalling rate and the OFF condi
23、tion of circuit 11 1 selects the lower data signalling rate. 4 Recommendation V.32 (03/93) ITU-T RECMNrV.32 93 4862593 0581483 286 TABLE 2N.32 Differential encoding for use with trellis coded alternative at 9600 bis Inputs QI, O O O O O O O O 1 1 1 1 1 1 1 1 42, O O O O 1 1 1 1 O O O O 1 1 1 1 Previ
24、ous outputs Y1,- 1 O O 1 1 O O 1 1 O O 1 1 O O 1 1 %-i O 1 O 1 O 1 O 1 O 1 O 1 O 1 O 1 outputs O O 1 1 O O 1 1 1 1 O O 1 1 O O O 1 O 1 1 O 1 O O 1 1 O 1 O O 1 3.6 Circuit 106 Mer the start-up and retrain sequences, circuit 106 must follow the state of circuit 105 within 2 ms. 3.7 circuit 109 OFF to
25、ON and ON to OFF transitions of circuit 109 should occur solely in accordance with the operating sequences defined in 5. Thresholds and response times are inapplicable because a line signal detector cannot be expected to distinguish wanted received signals from unwanted talker echoes. 3.8 Electrical
26、 characteristics of interchange circuits 3.8.1 connector and pin assignment plan specified by IS0 21 10. Use of electrical characteristics conforming to Recommendation V.28 is recommended together with the NOTE - Manufacturers may wish to note that the long-term objective is to replace electrical ch
27、aracteristics specified in Recommendation V.28, and that Study Group XW has agreed that the work shall proceed to develop a more efficient, all-balanced, interface for the V-Series application which minimizes the number of interchange circuits. Recommendation V.32 (03/93) 5 ITU-T RECMN*V.32 93 m 48b
28、2593 0583484 312 m o 10010 o o 00000 o111 180“ )_I -4 11001 -2 00111 OIL o loo00 o o 4; o 11111 11o00 OIOOO LJ 00101 O1010 1 *(D o o 1 o1 o1 1 lok 10100 o0010 01:oi 9 dl1 I - O“ (Re) 4 11110 i 11010 11101 o o 001 00 00110 O1011 -21 o 10111 I 1oO01 10110 O1110 ml J 01:00 o -41 o 11100 11011 270“ T170
29、2150-93/d03 NOTE - The binary numbers denote YO, Y 1, Y2, Q3, Q4,. FIGURE 3N.32 32-point signal structure with trellis coding for 9600 bis and states A B C and D used at 4800 bis and for training 3.9 Fault condition on interchange circuits See 7N.28 for association of the receiver failure detection
30、types. 3.9.1 3.9.2 type 1. 3.9.3 The DTE should interpret a fault condition on circuit 107 as an OFF condition using failure detection type 1. The DCE should interpret a fault condition on circuits 105 and 108 as an OFF condition using failure detection All other circuits not referred to above may u
31、se failure detection types O or 1. 4 Scrambler and descrambler A self-sychronizing scrambler/descrambler shall be included in the modem. Each transmission direction uses a different scrambler. The method of allocating the scramblers/descramblers is described in 4.1. According to the direction of tra
32、nsmission, the generating polynomial is: Call mode modem generating polynomial: (GPC) = 1 + xrI8 + xr23; or Answer mode modem generating polynomial: (GPA) = 1 + x5 + x-23 At the transmitter, the scrambler shall effectively divide the message data sequence by the generating polynomial. The coefficien
33、ts of the quotients of this division, taken in descending order, form the data sequence which shall appear at the output of the scrambler. At the receiver the received data sequence shall be multiplied by the scrambler generating polynomial to recover the message sequence. 6 Recommendation V.32 (03/
34、93) ITU-T RECMN*V=32 93 W 4862591 0581485 059 9 TABLE 3N.32 The two aiternative signai-state mappings for 9600 bids Coded inputs (see Table 1 or Table 2 with Figure 2) Y1 O O O O O O O O 1 1 1 1 1 1 1 1 O O O O O O O O 1 1 1 1 1 1 1 1 Y2 O O O O 1 1 1 1 O O O O 1 1 1 1 O O O O 1 1 1 1 O O O O 1 1 1
35、1 Q3 O O 1 1 O O 1 1 O O 1 1 O O 1 1 O O 1 1 O O 1 1 O O 1 1 O O 1 1 44 O I O 1 O 1 O 1 O 1 O 1 O 1 O I O 1 O 1 O 1 O 1 O 1 O 1 O 1 O 1 Nonredundant coding Re -1 -3 -1 -3 1 1 3 3 -1 -1 -3 -3 1 3 1 3 Im -1 -1 -3 -3 -1 -3 -1 -3 1 3 1 3 1 1 3 3 Trellis coding Re -4 O O 4 4 O O -4 -2 -2 2 2 2 2 -2 -2 -3
36、 1 -3 1 3 -1 3 -1 1 -3 1 1 -1 3 -1 -1 Im 1 -3 1 1 -1 3 -1 -I 3 -1 3 -I -3 1 -3 1 -2 -2 2 2 2 2 -2 -2 4 O O -4 -4 O O 4 Recommendation V.32 (03/93) 7 1TIJ-T RECMN*V.32 93 = 4862591 058148b T95 = TABLE 4N.32 No. 102 103 104 105 106 107 108/1 or 108/2 109 111 112 113 114 115 125 140 141 142 Interchange
37、 circuit (see Note 1) 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 Data channel received line signal detector Data signalling rate selector (DTE source) Data signalling rate sel
38、ector CE source) Transmitter signal element timing (DE source) Transmitter signal element timing (DCE source) Receiver signal element timing (DCE source) Calling indicator LoopbacWmaintenance test Local loopback Test indicator Notes ,. z 2 NOTES 1 All interchange circuits which are provided shall co
39、mply with the functional and operational requirements of Recommendation V.24. All interchange circuits shall be properly terminated in the data terminal equipment and in the data circuit-terminating equipment in accordance with the appropriate Recommendation for electrical characteristics (see 3.8).
40、 2 This circuit shall be capable of operation as circuit 108/1 or circuit 108/2 depending on its use. Operation of circuits 107 and 108/1 shall be in accordance with 4.4N.24. 3 This circuit is not essential when only one data signalling rate is implemented in the modem. 4 This circuit is for use wit
41、h the general switched telephone network only. 5 When the modem is not operating in a synchronous mode at the interface, any signals on this circuit shall be disregarded. Many DTEs operating in an asynchronous mode do not have a generator connected to this circuit. 6 When the modem is not operating
42、in a synchronous mode at the interface, this circuit shall be clamped to the OFF condition. Many DTEs operating in an asynchronous mode do not terminate this circuit. 4.1 4.1.1 Scrambler/descrambler allocation General switched telephone network (GSTN) On the general switched telephone network, the m
43、odem at the calling data station (call mode) shall use the scrambler with the GPC generating polynomial and the descrambler with,the GPA generating polynomial. The modem at the answering data station (answer mode) shall use the scrambler with the GPA generating polynomial and the descrambler with th
44、e GPC generating polynomial. In some situations, however, such as when calls are established on the GSTN by operators, bilateral agreement on call mode/answer mode allocation will be necessary. 8 Recommendation V.32 (03/93) ITU-T RECMN*V*32 93 m 4862593 0581487 723 m 4.1.2 Point-to-pint Ieaed circui
45、ts Scrambler/descrambler allocation and call mode and answer mode designation on point-to-point leased circuits will be by bilateral agreement between Administrations or users. 5 Operating procedures 5.1 The Recommendation V.25 automatic answering sequence shall be transmitted from the answer mode m
46、odem on international GSTN connections, The transmission of the sequence may be omitted on point-to-point leased circuits or on national connections on the GSTN where permitted by Administrations. In this event, the answer mode modem shall initiate transmission as in the retrain procedure specified
47、in 5.5. Recommendation V.25 automatic answering sequence 5.2 Receiver conditioning Signal The receiver conditioning signal shall be used in the start-up and retrain procedures defined in 5.4 and 5.5. The signal consists of three segments: 5.2.1 Segment 1, denoted by S in Figures 4 and 5, consists of
48、 alternations between states A and B as shown in Figure 1, for a duration of 256 symbol intervals. 5.2.2 in Figures 4 and 5, consists of alternations between states C and D as shown in Figure 1, for a duration of 16 symbol intervals. The transition from segment 1 to segment 2 provides a well-defined
49、 event in the signal that may be used for generating a time reference in the receiver. 5.2.3 Segment 3, denoted by TRN in Figures 4 and 5, is a sequence derived by scrambling binary ones at a data rate of 4800 bids with the scrambler defined in 4. During the transmission of this segment, the differential quadrant encoding shall be disabled. The initial state of the scrambler shall be all zeros, and a binary one applied to the input for the duration of segment 3. Successive dibits are encoded onto transmitted signal states. The first 256 transmitted signal states are dete
