1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 6 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU$!4!G0G0#/-5.)#!4)/.G0G0/6%2G0G04(%G0G04%,%0(/.%.%47/2+-/$%-3G0G0 amended at Geneva, 1980,Malaga-Torremolinos, 1984 and Melbourne, 1988)On leased circuits, considering that there exist and will come into bein
2、g other modems with features designedto meet the requirements of the Administrations and users, this Recommendation in no way restricts the use of anyother modems.The only group reference pilot frequency which can be used in conjunction with this modem is 104.08 kHz.1 ScopeThe family of modems cover
3、ed by this Recommendation should be applicable to the following uses:a) transmission of data between customers on leased circuits;b) transmission of a multiplex aggregate bit stream for public data networks;c) extension of a PCM channel at 64 kbit/s over analogue facilities;d) transmission of a comm
4、on channel signalling system for telephony and/or public data networks;e) extension of Single-Channel-Per-Carrier (SCPC) circuit from a satellite earth station;f) transmission of a multiplex aggregate bit stream for telegraph and data signals.Principal recommended characteristics to be used for simu
5、ltaneous both-way synchronous operation are thefollowing:2 Data signalling rates2.1 Application a)The recommended data signalling rate (equals the customer signalling rate) for international use issynchronous at 48 kbit/s. For certain national applications or with bilateral agreement between Adminis
6、trations, thefollowing data signalling rates are applicable: 56, 64 and 72 kbit/s.2.2 Applications b), c) and d)For these applications, the recommended data signalling rate is synchronous at 64 kbit/s.For those synchronous networks requiring the end-to-end transmission of both the 8 kHz and 64 kHz t
7、imingtogether with the data at 64 kbit/s, a data signalling rate of 72 kbit/s on the line is suggested.The corresponding data format should be obtained by inserting one extra bit E just before the first bit of eachoctet of the 64 kbit/s data stream. The bits E convey alignment and housekeeping infor
8、mation, according to the patternshown in Figure 1/V.36.2 Fascicle VIII.1 - Rec. V.36The use of the housekeeping bits H is determined with bilateral agreement between Administrations. Whennot used, these bits should be assigned the value 1. A framing strategy is not specified in this Recommendation.W
9、hen the transmission of the 8 kHz timing is not required, the data signalling rate on the line may be64 kbit/s.2.3 Application e)The recommended data signalling rate (equals the customer signalling rate) for international use issynchronous at 48 kbit/s. For certain national applications or with bila
10、teral agreement between Administrations the datasignalling rate of 56 kbit/s is applicable.2.4 Application f)The recommended data signalling rate is synchronous at 64 kbit/s.2.5 The permitted tolerance for all the data signalling rates mentioned above is 5 10-5bit/s.Note - There are equipments in se
11、rvice which will only work successfully with a maximum tolerance of thedata signalling rate of 1 bit/s.3 Scrambler/descramblerIn order to be bit sequence independent and to avoid high amplitude spectral components on the line, the datashould be scrambled and descrambled by means of the logical arran
12、gements described in Appendix I.4 Baseband signalThe equivalent baseband signal shaping process is based upon the binary coded partial response pulse, oftenreferred to as class IV, whose time and spectral function are defined by:andrespectively, where 1/T denotes the data signalling rate.This shapin
13、g process should be effected in such a way that the decoding can be achieved by full waverectification of the demodulated line signal.The reference to equivalent baseband signals recognizes that the modem implementation may be such that thebinary signal at the input and output of the modem is conver
14、ted to and from the line signal without appearing as anactual baseband signal.5 Line signal in 60-108 kHz band (at the line output of the modem)5.1 In the 60-108 kHz band the line signal should correspond to a single sideband signal with its carrierfrequency at 100 kHz 2 Hz.Fascicle VIII.1 - Rec. V.
15、36 35.2 The relationship between the binary signals at the real or hypothetical output of the scrambler and thetransmitted line signal states shall be in accordance with the amplitude modulation case of Recommendation V.1, i.e.,tone ON for binary 1 and tone OFF for binary 0.In a practical case this
16、means that the voltage or no voltage conditions which will result from the full waverectification of the demodulated line signal will correspond with the binary 1 and binary 0 signals respectively at theoutput of the scrambler.5.3 The amplitude of the theoretical line signal spectrum, corresponding
17、to binary symbol 1 appearing at theoutput of the scrambler, is to be sinusoidal, with zeros and maxima at the frequencies listed below:Data signalling rate(kbit/s)Zeros at(kHz)Maxima at(kHz)6448567268 and 10076 and 10072 and 10064 and 100848886825.4 In the 60-108 kHz band, amplitude distortion of th
18、e real spectrum relative to the theoretical spectrum asdefined under 5.3 above is not to exceed 1 dB; the group delay distortion is not to exceed 8 microseconds. Thesetwo requirements are to be met for each frequency band centred on one of the maxima mentioned in 5.3 and whosewidth is equal to 80% o
19、f the frequency band used.5.5 The nominal level of the line data signal should be -6 dBm0. The actual level should be within 1 dB of thenominal level.5.6 A pilot carrier at the same frequency as the modulated carrier at the transmitter and with a level of-9 0.5 dB relative to the actual level mentio
20、ned under 5.5 above, should be added to the line signal. The relativephase between the modulated carrier and the pilot carrier at the transmitter should be time invariant.6 Group reference pilot6.1 Provision should be made for facilitating the injection of a group reference pilot of 104.08 kHz from
21、a sourceexternal to the modem.6.2 The protection of the group reference pilot should conform to Recommendation H.52 1.7 Voice channel7.1 The service speech channel is an integral part of the applications a) and e) of this system and is used on anoptional basis. The channel corresponds to channel 1 o
22、f a 12-channel SSB-AM system in the 104-108 kHz band(virtual carrier at 108 kHz). It can transmit continuous voice at a mean level of maximum -15 dBm0 or pulsedsignalling tones according to the individual specifications.To avoid overloading of the system by peak signals a limiter shall be used with
23、cut-off levels above +3 dBm0.To avoid stability problems the channel shall be connected to 4-wire equipment only.For operator-to-operator signalling Recommendation Q.1 2 shall be followed, but instead of 500/20 Hz anon-interrupted tone of 2280 Hz at a level of -10 dBm0 shall be used.4 Fascicle VIII.
24、1 - Rec. V.36For other signalling purposes application e) the R1 or R2 inband signalling, described inRecommendations Q.322 3, Q.323 4 and Q.454 5, Q.455 6 respectively, is preferred.The transmit filter shall be such that any frequency applied to the transmit input terminals at a level of-15 dBm0 wi
25、ll not cause a level exceeding:a) -73 dBm0p in the adjacent group,b) -61 dBm0 in the vicinity ( 25 Hz) of the pilot 104.08 kHz,c) -55 dBm0 in the data band between 64 and 101 kHz,d) the values specified in Recommendation Q.414 7 to protect the nearest low level signalling path.The voice band is suff
26、iciently protected if the same filter is used in the receive direction of the channel. Theattenuation/frequency characteristic, measured between the voice-frequency input and the group band output or thegroup band input and the voice-frequency output, with respect to the value at 800 Hz is limited b
27、y:-1 dB over the 300-3400 Hz band,+2 dB between 540 and 2280 Hz.7.2 The voice channel is inapplicable to applications b), c), d) and f). It is used on an optional basis forapplications a) and e).Note - When the modem is installed at the repeater station, the voice channel should be extended to the r
28、enterspremises.8 Adjacent channel interferenceIn the bands 36-60 kHz and 108-132 kHz, the adjacent channel interference should conform toRecommendation H.52 1.9 Line characteristicsThe modem is intended to operate satisfactorily over group links according to reference 8 at data signallingrates of 48
29、 up to 64 kbit/s.For group links, comprising more than three group sections, or where a data signalling rate of 72 kbit/s isrequired, the characteristics given in reference 8 are not adequate.Furthermore, compliance of a group link with reference 8 does not necessarily guarantee proper operation oft
30、he modem, nor does noncompliance imply improper operation.In Annex A a method is presented to calculate the suitability of a group link for data transmission using amodem according to this Recommendation.When an automatic adaptive equalizer is included in the modem, proper operation over a circuit o
31、f similarconstruction as the hypothetical reference circuit as specified in reference 9 will be possible at data signalling rates upto 64 kbits.Note 1 - Reference 9 specifies a maximum number of 8 through-group filters, but this figure is subject tofurther study and possible amendment.Note 2 - The m
32、odem may allow operation at 72 kbit/s over a circuit having a maximum of 5 through groupfilters. This value is left for further study.10 Interface10.1 Interface for applications a), e) and f) indicated in 110.1.1 List of interchange circuits (See Table 1/V.36)Fascicle VIII.1 - Rec. V.36 5TABLE 1/V.3
33、6Interchange circuit (see Note 1) Remark102102 a102 bSignal ground or common returnDTE common returnDCE common returnSee Note 2See Note 3See Note 3103104Transmitted dataReceived data105106107109Request to sendReady for sendingData set readyData channel received line signal detector113114115Trasmitte
34、r signal element timing (DTE source)Trasmitter signal element timing (DCE source)Receiver signal element timing (DCE source)140141142Loopback/Maintenance testLocal loopbackTest indicatorSee Note 2See Note 2See Note 2Note 1 - When the modem is installed at the repeater station, this interface should
35、appear at the customers premises withoutrestrictions regarding the data signalling rate and the provision of the voice channel. The method to achieve this is subject to nationalregulations.Note 2 - Equipment may be in service that does not implement these circuits.Note 3 - Interchange circuits 102a
36、and 102b are required where the electrical characteristics defined in Recommendation V.10 areused.10.1.2 Electrical characteristicsUse of electrical characteristics conforming to Recommendation V.10 and/or V.11 is recommended togetherwith the use of the connector and pin assignment plan specified by
37、 ISO 4902.i) Concerning circuits 103, 104, 113, 114 and 115, both the generators and the receivers shall be inaccordance with Recommendation V.11.ii) In the case of circuits 105, 106, 107 and 109, generators shall comply with Recommendation V.10 oralternatively Recommendation V.11. The receivers sha
38、ll comply with Recommendation V.10, category 1or V.11 without termination.iii) In the case of all other circuits, Recommendation V.10 applies with receivers configured as specified byRecommendation V.10 for category 2.Note - For an interim period the connector and contact-assignment plan specified i
39、n ISO 2593 and commonlyreferred to as the “V.35 interface“ may optionally be used. In this case electrical characteristics may be either V.11 forcircuits 103, 104, 113, 114 and 115 together with V.10 (receivers configured as specified in category 2) for all othercircuits, or V.35 Appendix II togethe
40、r with V.28 respectively.10.2 Interface for applications b), c) and d) indicated in 1For applications b), c) and d) the interface may comply with the functional requirements given in reference6 Fascicle VIII.1 - Rec. V.3610 for the 64 kbit/s interface. In these cases, the electrical characteristics
41、may comply with reference 11.If an end-to-end transmission of the 8 kHz timing signal is not used, an 8 kHz timing signal across theinterface will not be supplied nor utilized by the modem.Alternatively the interface according to 10.1 may be used for these applications.11 Threshold and response time
42、 of circuit 10911.1 ThresholdFor a data line signal level greater than -13 dBm0, circuit 109 is ON. For data line signal level less than-18 dBm0, circuit 109 is OFF.Note - The corresponding levels for the pilot carrier are -22 dBm0 and -27 dBm0 respectively.The condition of circuit 109 for levels be
43、tween the above levels is not specified, except that the signal detectorshall exhibit a hysteresis action such that the level at which the OFF to ON transition occurs is at least 2 dB greaterthan that for the ON to OFF transition. To measure the thresholds of the detector, a modulated data signal wi
44、th its pilotcarrier at the level specified in 5.6 should be used.11.2 Response timeFrom OFF to ON: 15 ms to 150 ms,From ON to OFF: 5 ms to 15 ms.The response times of circuit 109 are the time intervals between the appearance or disappearance of the linesignal at the reception input terminal of the m
45、odem and the occurrence of the corresponding ON or OFF condition oncircuit 109.The line signal level should be within the range from 3 dB above the actual threshold of the line signaldetector at reception and the maximum permissible level of the signal at reception.12 Error performance12.1 For a hyp
46、othetical reference circuit, 2500 km in length, with characteristics in accordance withRecommendation H.14 8, and with not more than two through-group connection equipments, the performanceobjective in terms of error rate should be not worse than 1 error per 107bits transmitted. This is based on an
47、assumedGaussian noise power of 4 pW per km/per 4 kHz band psophometrically weighted (this figure corresponds to4 pW0p/km).13 Additional information for the designer13.1 Input level variationThe step-change in the input level is, under normal conditions, smaller than 0.1 dB. The gradual input levelch
48、ange is smaller than 6 dB and includes the tolerance of the transmitter output level.13.2 Interference from adjacent group bandsA sinusoidal signal of +10 dBm0 in the frequency bands of 36-60 kHz and 108-132 kHz can appear togetherwith the data line signal at the input of the receiver.Fascicle VIII.
49、1 - Rec. V.36 7ANNEX A(to Recommendation V.36)Line characteristicsFor proper operation of the modem, the line characteristic of a group link shall comply with:whereAPPENDIX I(to Recommendation V.36)Scrambling processI.1 DefinitionsI.1.1 applied data bitThe data bit which has been applied to the scrambler but has not affected the transmission at the time ofconsideration.I.1.2 next transmitted bitThe bit which will be transmitted as a result of scrambling the applied data bit.I.1.3 earlier transmitted bitsThose bits which hav
