1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 - TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU-!).4%.!.#% ).4%2.!4)/.!,G0G04%,%0(/.%G0G0#)2#5)43,).).G0G050G0G0!.$G0G0-!).4!).).).4%2.!4)/.!,G0G0$%-!.$!33).-%.4G0G0#)2#5)43G0G0 30!$%G9)45G134G0G0RecommendationG0G0- (Extract from the “LUEG0“OOK)NOTES1 ITU
2、-T Recommendation M.675 was published in Fascicle IV.1 of the Blue Book. This file is an extract fromthe Blue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are identical to the Blue Book version and copyright condi
3、tions remain unchanged (see below).2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of this publication may be reproduced or utilized in a
4、ny form or by any means, electronic ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle IV.1 - Rec. M.675 1Recommendation M.675Fascicle IV.1 - Rec. M.675LINING UP AND MAINTAINING INTERNATIONALDEMAND ASSIGNMENT CIRCUITS (SPADE)GeneralSection 3.3 ref
5、ers to Figure 1/M.675 and describes the features of demand assignment (DA) circuits1)established by means of single channel per carrier, PCM, multiple access demand assignment, equipment (SPADE)located in satellite earth stations.Circuits thus provided are established between two international excha
6、nges (CTs) on demand, with theconstituent transmission paths making up the circuit being connected only for the duration of each demand. Atransmission link is established between earth stations as required by the outgoing CT. The international DA circuit isformed via the distant earth station and it
7、s connection to the incoming CT by the terrestrial demand assignment section.Upon release of this demand the transmission link establishing the demand assignment section is returned to acommon pool allowing its reuse when required by other international exchanges operating in the demand assignmentsa
8、tellite network. Recommendation Q.48 1 outlines the signalling system incorporated between demand assignmentequipments located in satellite earth stations.In general the Series M Recommendations concerned with preassigned international circuits apply equally tothe sections of DA circuits. However, b
9、ecause of the variable nature concerning the establishment of circuits on demand,special consideration in provisioning, maintenance and fault finding is required. The following sections will providedetails concerning these requirements.1 Initial line-up and maintenance of demand assignment circuits
10、and their constituent parts1.1 The demand assignment circuit may be seen as being divided into three parts for setting-up, lining-up andmaintenance: the outgoing terrestrial demand assignment section, the satellite demand assignment section and theincoming terrestrial demand assignment section. It i
11、s considered that the overall limits in Recommendation M.580 willbe met by the application of the line-up limits given in Table 1/M.675 for the individual DA sections. However,sectional requirements prevail if the limits of Recommendation M.580 are not met on overall measurements.1.2 The maintenance
12、 schedule, Table 2/M.675, should be utilized in the development of an initial demandassignment capability with a given CT (for example, commissioning of a new SPADE terminal) and establishing theappropriate periodic tests.1.3 When terrestrial DA sections are added or a new corresponding terminal com
13、es into service, tests should beconducted in accordance with Table 2/M.675.2 Demand assignment circuit control responsibilities and fault location procedures2.1 In the assignment of maintenance responsibilities, recognition is given to the constitution of a DA circuit asoutlined in 1.1 above. Sectio
14、n control and sub-control stations will be nominated for each terrestrial DA section. Theinitiation of fault localization procedures for a faulty DA circuit will be the responsibility of the fault report point(circuit) receiving the report. Upon being notified, the control station initiates tests to
15、 determine the location of the fault.If the fault condition is located beyond the satellite DA section, the fault report point (circuit) associated with the distantterrestrial DA section will be notified of the condition and will assume control responsibility for further localization andclearance of
16、 the fault.2.2 Faults should be investigated in a systematic manner, section by section. After verifying the report, e.g., byperformance records or test calls, a recommended procedure for fault location is as follows:2.2.1 Establish a CT to ones own CT satellite loop circuit, utilizing the suspected
17、 outgoing terrestrial DA section._1)This type circuit may be considered to be equivalent to an international telephone circuit (preassigned) from a transmission pointof view and is under study by Study Group XII.2 Fascicle IV.1 - Rec. M.6752.2.2 Determine if this configuration is faulty. If this is
18、not the case then the associated earth station should, assub-control, be instructed to check the satellite DA section to the particular distant earth station involved. If this sectionis found to be performing satisfactorily then the fault report is passed to the fault report point (circuit) at the d
19、istant CT.The distant CT then assumes responsibility for fault localization and the originating fault report point (circuit) advises itsassociated network analysis point of the action taken.2.2.3 If the satellite loop of 2.2.1 above was found faulty, action should be taken by the control station and
20、 itsassociated DA terminal to localize the fault to the outgoing terrestrial DA section.2.3 Full use should be made of the operational status indications available to the DA satellite section sub-controlstation to determine fault situations on the outgoing terrestrial DA section and on the incoming
21、and outgoing satellite DAsections. The DA section sub-control station should advise the fault report point (circuit) or fault report point (network),as appropriate, at its associated CT, of any observations indicating fault situations and ensure that the control station isaware of the situation.2.4
22、Administrations establishing international circuits utilizing satellite demand assignment links should be able toobtain statistical information concerning the outgoing call processing of their respective countries from the demandassignment system operating authority. The information is required by t
23、he network analysis points, in their continuinganalysis of the quality of the international network.d01-scFascicle IV.1 - Rec. M.675 3FIGURE 1/M.675D01d02-scFIGURE 2/.675D024 Fascicle IV.1 - Rec. M.675TABLE 1/M.675Target objectives for setting up and lining up a demand assignment (SPADE)internationa
24、l public telephone circuit and its sectionsDemand assignmentcircuitDemand assignmentsectionTransmissionparametersZCT to CTbetween circuitaccess pointsYBetween SPADEterminals,demand assignmentXCT to SPADEterminal,terrestrial1. Loss/frequencya)relative to the loss at referencefrequency (in dB)(Series
25、MRecommendations)300- 400 Hz +3.5 to 1.0 + 0.5 to 0.5 +1.7 to 0.5400- 600 Hz +2.0 to 1.0 + 0.5 to 0.5 + 0.9 to 0.5600-2400 Hz +1.0 to 1.0 + 0.5 to 0.5 + 0.5 to 0.52400-3000 Hz +2.0 to 1.0 + 0.9 to 0.5 + 0.9 to 0.53000-3400 Hz +3.5 to 1.0 +1.8 to 0.5 +1.7 to 0.52. Overall loss at referencefrequency.
26、Line-up level limitsrelative to nominal (in dB) 0.3 0.2 0.23. Idle Noise( dBm0p)Table 4/M.580(See Note 3) 60 Table 4/M.5804. Quantizing distortion(signal/total distortion ratioin dB)Not applicableFigure 2/M.675(See Note 1)Not applicable5. Signal crosstalk ratio(Go-return) (in dB)43 60 48a)Reference
27、frequency = 1020 Hz (See Note 2).Note 1 Quantizing distortion should be measured in accordance with the test procedure agreed upon by the satellite systemoperators.Note 2 Test frequencies that are sub-harmonics of the PCM sampling rate should be avoided. (See Rec. O.6 2.)Note 3 Noise measurements sh
28、ould be made with the demand assignment codec voice detector enabled. This can be accomplishedby utilizing a holding tone and notch filter or by conducting tests with the demand assignment equipment, in the pre-assigned mode.Fascicle IV.1 - Rec. M.675 5TABLE 2/M.675Testing and maintenance scheduleTe
29、stsDemandassignmentterminalCT-EarthstationX, X“From CTto own CTlooped viasatellitea)ZEarth station-earth stationYDemandassignmentterminalCT-CTZaccesspointWhen testedaccess pointWhentestedComprehensive signallingand compatibility testQ.163 3 or equivalentA and B(Note 1)Initial systemcommissioning Fun
30、ctional signalling testQ.163 4 or equivalentB(Note 1)Initial line-upand periodicmaintenanceof sectionInitial line-upand periodicmaintenanceof sectionInitial systemcommissioningand new channelline-up(Notes 5 and 8)B(Note 1)(Note 7)Measurement of loss andnoiseRec. M.610(Note 4)Initial line-upand perio
31、dicmaintenanceof sectionInitial line-upand periodicmaintenanceof section(Notes 2 and 3)Initial systemcommissioningand new channelline-up(Notes 5 and 8)A(Note 1)(Notes6 and 3)Loss/frequencycharacteristics and crosstalkratioRec. M.610(Note 4)Initial line-upand periodicmaintenanceof sectionInitial line
32、-upand periodicmaintenanceof section(Notes 2 and 3)Initial systemcommissioningand new channelline-up(Note 8)A(Note 1)(Notes6 and 3)Measurement of quantizingdistortion Initial systemcommissioningand new channelline-up(Note 8)A(Note 1)Spurious signal andchannel intermodulation Initial systemcommission
33、ingand new channelline-up(Note 8)A(Note 1)Subjective testsRec. M.610B(Note 1)Initial line-upand periodicmaintenanceof sectionInitial line-upand periodicmaintenanceof section(Notes 2 and 3)Initial systemcommissioningand new channelline-up(Notes 5 and 8)B(Note 1)(Notes9 and 3)a)Simulated demand assign
34、ment circuit.6 Fascicle IV.1 - Rec. M.675Notes relative to Table 2/M.675:Note 1 A and B refer to the DA terminal testing interface. See Figure 1/M.675 for the location of these interfaces.Note 2 The outgoing CT must be capable of outpulsing its own country code and exchange digits.Note 3 Sectional r
35、equirements supersede if the overall requirements of Recommendation M.580 are not met.Note 4 A and/or B for line-up and A or B for periodic tests. (Reference measurements at initial line-up should includemeasurements made at the access point decided upon for periodic tests).Note 5 Demand assignment
36、system is assumed to operate internal diagnostics to check functional capability andcontinuity.Note 6 Loss, noise, loss/frequency and signal/crosstalk ratio tests may be applied on a sample basis when the system isinitially commissioned, and as required for the extension of service.Note 7 Test calls
37、 may be carried out to verify operational capability initially, and as required.Note 8 These are as agreed upon by the satellite system operators.Note 9 Subjective testing CT-CT may be used on a sample basis, as required.References1 CCITT Recommendation Demand assignment signalling systems, Vol. VI, Rec. Q.48.2 CCITT Recommendation 1020 Hz reference test frequency, Vol. IV, Rec. O.6.3 CCITT Recommendation Manual testing, Green Book, Vol. VI-2, Rec. Q.163, 4.3.4, parts 1 and 2, ITU,Geneva, 1973.4 Ibid., 4.3.3.
