ITU-T J.25 (05 1986)(英) Estimation of transmission

INTERNATIONALTELECOMMUNICATIONUNION)454*EX#-44 TELECOMMUNICATION(05/86)STANDARDIZATIONSECTOROFITU4%,%6)3)/.!.$3/5.$42!.3-)33)/.%34)-!4)/./&42!.3-)33)/.0%2&/2-!.#%/&3/5.$02/'2!--%#)2#5)433(/24%2/2,/.'%24(!.4(%(90/4(%4)#!,2%&%2%.#%#)2#5)4)454Recommendation*(FormerlyRecommendationITU-RCMTT.605)FOREWORDTheITUTelecommunicationStandardizationSector(ITU-T)isapermanentorganoftheInternationalTelecom-municationUnion.TheITU-Tisresponsibleforstudyingtechnical,operatingandtariffquestionsandissuingRecommendationsonthemwithaviewtostandardizingtelecommunicationsonaworldwidebasis.TheWorldTelecommunicationStandardizationConference(WTSC),whichmeetseveryfouryears,establishedthetopicsforstudybytheITU-TStudyGroupswhich,intheirturn,produceRecommendationsonthesetopics.ITU-TRecommendationJ.25(formerlyRecommendationITU-RCMTT.605)waselaboratedbytheformerITU-RStudyGroupCMTT.SeeNote1below.___________________NOTES1AsaconsequenceofareformprocesswithintheInternationalTelecommunicationUnion(ITU),theCCITTceasedtoexistasof28February1993.Initsplace,theITUTelecommunicationStandardizationSector(ITU-T)wascreatedasof1March1993.Similarly,inthisreformprocess,theCCIRandtheIFRBhavebeenreplacedbytheRadiocommunicationSector(ITU-R).ConformingtoajointdecisionbytheWorldTelecommunicationStandardizationConference(Helsinki,March1993)andtheRadiocommunicationAssembly(Geneva,November1993),theITU-RStudyGroupCMTTwastransferredtoITU-TasStudyGroup9,exceptforthesatellitenewsgathering(SNG)studyareawhichwastransferredtoITU-RStudyGroup4.2InthisRecommendation,theexpression“Administration”isusedforconcisenesstoindicatebothatelecommunicationadministrationandarecognizedoperatingagency.ITU1990Allrightsreserved.Nopartofthispublicationmaybereproducedorutilizedinanyformorbyanymeans,electronicormechanical,includingphotocopyingandmicrofilm,withoutpermissioninwritingfromtheITU.RecommendationJ.25(05/86)1RecommendationJ.251)RecommendationJ.25(05/86)ESTIMATIONOFTRANSMISSIONPERFORMANCEOFSOUND-PROGRAMMECIRCUITSSHORTERORLONGERTHANTHEHYPOTHETICALREFERENCECIRCUIT(1982;revised1986)TheCCIRUNANIMOUSLYRECOMMENDSthatfortheestimationoftransmissionperformanceofsound-programmecircuitsshorterorlongerthanthehypotheticalreferencecircuitthefollowingrulesbeapplied:Lawsofaddition1.CommentsontheuseofthelawsofadditionThedefinitionofacircuitintermsofasinglemultipleofthehypotheticalreferencecircuitisimpossibleifthenumberofaudio-to-audiosectionsandthelengthofthecircuitdifferfromthoseofthehypotheticalreferencecircuitbydifferentratios,i.e.ifn/3≠L/lwheren:numberofaudio-to-audiosections,L:lengthofthecircuit,l:2500km.Insuchcasestwodefinitionsofthecircuitintermsofthehypotheticalreferencecircuitshouldbeused,oneforthoseparametersprimarilyafunctionofthecircuitconfiguration,andasecondforthoseparameters(e.g.continuousrandomnoise)primarilyafunctionofthelengthofthecircuit.2.LawpertainingtocircuitconfigurationForthefirstdefinitionofthecircuitintermsofthehypotheticalreferencecircuitusethefollowingequationforallparametersinTableIIexceptfor“continuousrandomnoise”.LetD3:designobjectiveortheparameterderivedtherefromandindicatedinTableII,permittedvalueforthreehomogeneoussectionsofthehypotheticalreferencecircuit,andDn:performance,ortheparametermentionedabove,tobeestimatedfornsections.Thefollowingexpressionsapply:–forabsolutevaluesandlogarithmicdeviations:Dn=D3(n/3)1/h(1)–forabsolutelevels:Dn=D3+20hlog(n/3)(2)–forlogarithmicratios:Dn=D3–20hlog(n/3)(3)_______________1)FormerlyRecommendationITU-RCMTT.605.2RecommendationJ.25(05/86)hhasthevalue1,3/2or2inaccordancewithTableII:h=1giveslinearorarithmeticlawofaddition,h=3/2givesthe“three-halvespower”lawofadditionandh=2givesthequadratic(r.m.s.)lawofaddition.Calculatedvaluesof⎝⎛⎠⎞n31/hand20hlog⎝⎛⎠⎞n3aregiveninTableI.3.LawpertainingtocircuitlengthFortheseconddefinitionofthecircuitintermsofthehypotheticalreferencecircuitusethefollowingequationfor“continuousrandomnoiselevels”only.Whendistanceisconsideredthelawofadditionbecomes:Dn=D3–20hlog(L/l)(4)whereDn,D3,Landlareasdefinedin§1and§2.Ifl280km,setl=280kmin(4).Note–ThevaluescalculatedasperthisRecommendationprovideonlyindicationsoftheprobableperformance.Theyshouldbeusedwithcautionwhenstudyingthedesignofequipment,becausethelawsofadditionarenotpreciselyknownforeverytypeofimpairment.Furtherstudiesarenecessary,especiallytocoverthecaseofmixedanalogue-and-digitalcircuits.TABLEIFormula(1)Formulas(2)and(3)n⎝⎛⎠⎞n31/h20hlog⎝⎛⎠⎞n3h=1h=3/2h=2h=1h=3/2h=21234567891011121314150.330.671.001.331.672.002.332.673.003.333.674.004.334.675.000.480.761.001.211.411.591.761.922.082.232.382.522.662.792.920.580.821.001.151.291.411.531.631.731.831.912.002.082.162.24–9.5dB–3.50.02.54.46.07.48.59.510.511.312.012.713.414.0–6.4dB–2.30.01.73.04.04.95.76.47.07.58.08.58.99.3–4.8dB–1.80.01.22.23.03.74.34.85.25.66.06.46.77.0RecommendationJ.25(05/86)3TABLEIIREFERENCESCCIRDocuments[1978-82]:CMTT/233(Japan).ParameterD3expressedinApplicableformulah(tentativevalue)ParametersInsertiongain(1.0kHz)relevanttomonoandAdjustmenterrordB12stereocir