1、INTERNATIONAL TELECOMMUNICATION UNION)45 4 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU$)4!, 3%#4)/.3 !.$ $)4!, ,).% 3934%-3$)4!, ,).% 3934%-3 02/6)$%$“9 further amended)The CCITT,considering(a) that there is an urgent need to provide long-haul facilities mainly for nontelephony services (e.g. data
2、,facsimile, visual telephony) for national use and for international interworking, and these non-telephony services needdigital transmission at a low and medium bit rate (e.g. primary and secondary hierarchical levels);(b) that long-haul digital links begin to be available, but that nevertheless the
3、 implementation of thesefacilities on a general basis will take some time;(c) that it is possible to use analogue FDM links specified in Recommendation G.211 1, or the frequencieswithin or over the bandwidth used by analogue FDM line systems specified in Section 3 of the SeriesG Recommendations to c
4、arry a digital stream, and that some realizations are already available,recommendsthat the digital line systems provided by FDM transmission bearers should comply with the followingrequirements:1 General characteristicsTwo basic methods can be used for the transmission of digital signals on FDM tran
5、smission bearers:- the first method consists of using either a part or the whole of the band normally employed for FDMsystems Data-in-Voice (DIV),- the second method consists of using a band outside the one normally employed for FDM systemsData-over-Voice (DOV).The international interconnection shou
6、ld be performed at digital hierarchical levels using the interfaces specified inRecommendation G.703.Since these digital line systems on FDM transmission bearers could form part of a digital path, theirperformance standards in terms of error rate, jitter and availability should be in accordance with
7、 the relevantRecommendations in Section 9 of the Series G Recommendations concerning digital line sections at the correspondingbit rates.The systems should be designed in such a way that the quality requirements given in the relevantRecommendations for the analogue circuit are still met.Administrati
8、ons intending to use digital line systems provided by FDM bearers in their networks should ensurethat compatible designs of equipment are used at each end of a link. For international links the systems to be used shouldbe by the agreement of the Administrations concerned.The application of digital l
9、ine systems provided by FDM transmission bearers for the interconnection of digitaland analogue networks is covered in Supplement No. 28.2 Data-in-Voice systems2.1 Characteristics of DIV systems providing digital transmission at hierarchical bit rates on analogue carrier-transmission systems specifi
10、ed in Recommendation G.211 1.Note - Examples of hierarchical DIV digital line systems are given in Annex A. Examples of DIV digital linesystems at non-hierarchical levels either in the analogue or in the digital interfaces are given in Annex B.2.1.1 Digital interfaceThe DIV system digital interface
11、should conform to the appropriate sections of the Recommendation G.703.2 Fascicle III.5 - Rec. G.9412.1.2 Analogue interface2.1.2.1 Frequency bandThe DIV signal frequency band should be displaced into the frequency band specified inRecommendation G.211, 1.2.1.2.2 Power levelThe relative power level
12、at the distribution frame should conform to the appropriate of theRecommendation G.233.The mean power level of the wideband signal over the frequency band specified in 2.1.2.1 should not exceed-15 + 10 log10n dBm0, n being the total number of telephone channels in the analogue system which are repla
13、ced by thedata channels.In order to limit cross modulation effects, the power level of any individual spectral component in thefrequency band specified in 2.1.2.1 should not exceed -10 dBm0.2.1.3 Disturbances of the analogue signal by the DIV signalThe total distributed noise produced by the DIV sig
14、nal measured in any 3.1 kHz bandwidth corresponding to atelephone channel outside the frequency band specified in the Recommendation G.211, 1 should be less than-73 dBm0p.The single tone interference should be less than -73 dBm0.2.1.4 DIV system performanceThe performance relating to error rate, jit
15、ter and availability should conform to the appropriateRecommendations of the G.900 series.2.2 Characteristics of the analogue link to carry the DIV signalThe analogue link used to carry the DIV signal should include no more than three through connections. Itcould be necessary to avoid certain positi
16、ons of the DIV signal band in the analogue carrier transmission system.Note - Reference to H series Recommendations could be made concerning characteristics such as attenuationdistortion, phase jitter and group-delay distortion.3 Data-over-Voice systems3.1 Characteristics of DOV systems providing 20
17、48-kbit/s digital transmission on analogue FDM line systemsdefined by Recommendations G.332 2, G.334 3, G.344 4, G.345 5 and G.346 63.1.1 Digital interfaceThe digital interface of the DOV system should be as specified in Recommendation G.703, 6.3.1.2 Disturbances of the analogue signal by the DOV si
18、gnalThe increase to the total distributed noise due to the DOV signal measured in any 4 kHz bandwidth should beless than 750 pW0p for a reference length of 2500 km (less than 0.3 pW0p/km).Note - The total distributed noise of the line when analogue and DOV signals are present should be below7500 pW0
19、p for a reference length of 2500 km (less than 3 pW0p/km).The level of single tone interference should be less than -70 dBm0.3.1.3 DOV system performanceThe performance relating to error rate, jitter and availability should be in accordance withRecommendation G.921.3.2 Characteristics of the FDM lin
20、e systems used to carry the DOV signalTo allow the through-connection of DOV signals on FDM line systems, spurious analogue signals within thefrequency band of the DOV signal should be suppressed before the coupling point up to a power level of -60 dBm0within 4 kHz bandwidth.Fascicle III.5 - Rec. G.
21、941 3ANNEX A(to Recommendation G.941)Examples of hierarchical DIV systemsAdministration Digital interface Analogue interface DIV system performanceNTT1544 kbit/sRec. G.703, 2Mastergroup(812-2044 kHz) Rec. G.911FRG2048 kbit/sRec. G.703, 6Mastergroup(812-2044 kHz) Rec. G.921NTT6312 kbit/sRec. G.703, 3
22、Mastergroup(812-2044 kHz) Rec. G.912FRG8448 kbit/sRec. G.703, 7Supermastergroup(8516-12 388 kHz) Rec. G.921Italy8448 kbit/sRec. G.703, 715 supergroup assem.(312-4028 kHz) Rec. G.921ANNEX B(to Recommendation G.941)Examples of systems other than those recommendedin Recommendation G.941(see Note 1)Admi
23、nistration Bit rate (kbit/s) Analogue interfaceDesign bit error ratio forregeneration sectionFrance(see Note 2)704Supergroup(312-552 kHz)10-8Netherlands 2048 2 supergroups 10-8Note 1 - Modems for the transmission of digital signals at 48-72 kbit/s or twice these bit rates are covered inRecommendatio
24、ns V.36 and V.37.Note 2 - The digital interface of this DIV equipment is at 2048 kbit/s according to Recommendation G.703 6, and witha frame structure according to Recommendation G.704 3.3.1. Only 11 (including TS0) among the 32 time slots areeffectively used: the useful bit rate is then equal to 10
25、 times 64 kbit/s. The other characteristics of the DIV system satisfyto 2 of this Recommendation.4 Fascicle III.5 - Rec. G.941References1 CCITT Recommendation Make-up of a carrier link, Vol. III, Rec. G.211.2 CCITT Recommendation 12-MHz systems on standardized 2.6/9.5-mm coaxial cable pairs, Vol. II
26、I,Rec. G.332.3 CCITT Recommendation 18-MHz systems on standardized 2.6/9.5-mm coaxial pairs, Vol. III, Rec. G.334.4 CCITT Recommendation 6-MHz systems on standardized 1.2/4.4-mm coaxial cable pairs, Vol. III,Rec. G.344.5 CCITT Recommendation 12-MHz systems on standardized 1.2/4.4-mm coaxial cable pairs, Vol. III,Rec. G.345.6 CCITT Recommendation 18-MHz systems on standardized 1.2/4.4-mm coaxial cable pairs, Vol. III,Rec. G.346.
