џWPCL ћџ2BJ|xа АH аа АА X агга ХА6p&А6p&Х аеЮ† а Hр аааУ Уб cмˆ4 PŽТ б Fascicle II.3 Р-Р Rec. E.855 Ф ФPAGE1У Уб cмˆ4 PŽТ б ЮееЃ† а HH аааб cмˆ4 PŽТ бPAGE4У Уб cмˆ4 PŽТ б Fascicle II.3 Р-Р Rec. E.855 Ѓеа H№ ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаа X  аб cмˆ4 PŽТ бAll drawings appearing in this Recommendation have been done in Autocad. ‚У УRecommendation E.855 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр(?Сб cмˆ4 PŽТ бCONNECTION INTEGRITY OBJECTIVE FOR INTERNATIONAL Ср(OСTELEPHONE SERVICE аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бТа ТIntroductionФ ФЦЦ а H аС СThis Recommendation is one of a set of closely related Recommendations comprising Recommendations E.810, E.830, E.845, E.850 and E.855 concerned with the accessibility, retainability and integrity of telecommunication services, specially telephone services. Та ТThe CCITT,ЦЦ УУconsidering а H аФФС С(a)СpСthat users of the telephone service can perceive the speech loss due to transmission interruptions with durations shorter than 10 seconds; а H аС СУУNoteФФ Р-Р Transmission interruptions with durations longer than or equal to 10 seconds in a conversation phase are not tolerable by telephone users (Annex A). Such transmission interruptions are considered as a premature release of the connection as defined in Recommendation E.850. а H аС С(b)СpСthat speech loss causing transmission interruptions are caused by a change beyond given limits for a given period of time in one or more parameters, e.g. power level, noise level, signalР-РtoР-Рnoise ratio, bit error ratio, etc.; а H аС С(c)СpСthat the objective should take into account the expectations of the users for quality of voice communications as well as the capabilities of current technologies; а H аС С(d)СpСthat the objective should take into account the concerns of network planners and system planners, provide useful guidance to each and that it can be used by Administrations in a consistent way to measure transmission interruptions; а H аС С(e)СpСthat the objective should be in conformity with other Recommendations; С С(f)СpСthe definition ofУУ interruptionФФ as given in Recommendation E.800, УУrecommends ‚У УФФ1ТX ТDefinitionsФ ФЦЦ 1.1Тh  ТУ Уconnection integrity for telephone serviceФ ФЦЦ а H аС СThe degree to which an established telephone connection is offered without excessive transmission interruptions. 1.2Тh  ТУ Уmean time between interruptions (MTBI)Ф ФЦЦ С СThe expectation of the time between interruptions. The time between interruptions is the time duration between the end of one interruption and the beginning of the next. 1.3Тh  ТУ Уmean interruption duration (MID)Ф ФЦЦ С СThe expectation of interruption duration. 1.4Тh  ТУ Уtransmission interruptionФ ФЦЦ а H аС СTemporary inability of the userР-РtoР-Рuser transmission path to be provided persisting for less than 10 seconds (maximum duration) and more than а H аanother given time duration (or minimum duration) characterized by a reduction below a certain threshold in received signal power level. The minimum duration of transmission interruption and the а H аminimum power threshold are for further study. Transmission interruptions caused by changes beyond certain thresholds of other parameters essential to connection integrity e.g. noise level, signalР-РtoР-Рdistortion ratio, are for further study. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС‚У У2С  СA measure to quantifyб cмˆ4 PŽТ б telephone connection integrity performanceЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ ФС СThe measure to be used shall be the complement of connection integrity, namely the probability of speech loss,УУ PУУiФФФФ, which is tolerable to telephone users due to transmission interruptions with durations shorter than 10 s. The estimator of the speech loss probability,УУ PУУieФФФФ, is the ratio of accumulated transmission interruption duration to the total observation period of time. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHp8А"(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ Ьа‚С СС pССШ8Сeq PƒУУieФФ = \i\su(i=1,N, ) TDУУiФФ/T аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаwhereУУ TФФ is the observation time andУУ TDУУiФФФФ is the time duration of theУУ iФФ th transmission interruption ofУУ NФФ transmission interruptions measured duringУУ TФФ (see Annex B). С СУУNoteФФ Р-Р There are two major parameters: time between interruptions (or frequency) and duration to specify characteristics of transmission interruptions. Those parameters should be easy to observe from the practical point of view. Actually it seems very difficult to measure very short duration of transmission interruptions in analogue networks and to separate interruptions from burst errors in digital networks. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС‚У У3С  СOverall objective forб cмˆ4 PŽТ б speech loss probabilityЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ ФС СThe provisional objective forУУ PУУiФФФФ shall be such that the performance is better than the value given below: аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHp8А"(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ Ьа‚УУС СС pССШ8СPƒУУiФФФФ =УУ xФФ (to be defined with further study) а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС СУУNoteФФ Р-Р A percentage of speech loss of less than 0.5% due to transmission interruptions with durations shorter than 10 s (Annex C) in a conversation phase is assumed to be tolerable to telephone users. ‚У У4ТX ТAllocation of the overall objectiveФ ФЦЦ а H аС СFrom a practical point of view, instead ofУУ PУУiФФФФ, the value eq \f(УУ PУУб cмˆ4 PŽТ бiб cмˆ4 PŽТ бФФФФ,1 Р-РУУ PУУб cмˆ4 PŽТ бiб cмˆ4 PŽТ бФФФФ) should be allocated to various network components. С СThe method to allocate this value is for further study. ‚Ср VСб cмˆ4 PŽТ бANNEX A Ср MСб cмˆ4 PŽТ б(to Recommendation E.855) аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр ;Сб cмˆ4 PŽТ бУ УTolerability of telephone user to transmission interruptions Ср JСlasting several seconds or more аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ ФA.1Тh  ТУУMeasureЦЦ а H аФФС СThe time interval between the start of transmission interruption occurring in the middle of a conversation and the abandoning of the disturbed call either by a calling or a called party is used as a measure to assess or evaluate the tolerability of telephone users. A.2Тh  ТУУMeasuring methodЦЦ ФФС СFifty intraР-Рoffice calls were selected at random and deliberately interrupted by callers soon after the calls had been established, and time intervals between the start of transmission interruption and the release of calls by the called party were measured. A.3Тh  ТУУResults of testsЦЦ ФФС СThe distribution of the durations of interruptions which forced the telephone users to give up their established calls is depicted in Figure AР-Р1/E.855. The distribution curve is well approximated by an exponential distribution function with the mean value of 17.26 sec. а H аС СThe figure shows that 50% of users released the established calls when the interruption lasted longer than 11.96 sec. ‚Ср JСб cмˆ4 PŽТ бFigure AР-Р1/E.855 Љ CCITT 58280 б cмˆ4 PŽТ б Ср VСб cмˆ4 PŽТ бANNEX B Ср MСб cмˆ4 PŽТ б(to Recommendation E.855) аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр :Сб cмˆ4 PŽТ бУ УRelationship between speech loss probability and its estimation а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ ФС СThe following relationship exists between the speech loss probability (УУPУУiФФФФ) and its estimator (УУPУУieФФФФ): аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHp8А"(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ Ьа‚С СС pССШ8Сeq \o\ac(lim,\s\do10(ƒУУT ФФЉ> Р8Р)) УУPУУieФФФФ = \o\ac(lim,\s\do10(УУT ФФЉ> Р8Р)) \i\su(УУkФФ=1,УУKФФ, ) \f(TDУУб cмˆ4 PŽТ бkб cмˆ4 PŽТ бФФ,T) =УУ PУУiФФФФ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаif such limit exists and whereУУ TФФ is the observation period of time andУУ TDУУkФФФФ is the duration of theУУ kФФ th transmission interruption ofУУ KФФ transmission interruptions overУУ TФФ. С СIt should be noted that there is also the following relationship: аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHp8А"(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ Ьа‚УУС СС pССШ8СPƒУУiФФФФ = eq \f( r, 1 + r) , r =УУ L iФФ=1 eq \f(УУ MIDУУiФФФФ,УУ MTBIУУiФФФФ) а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаwhere,УУ MIDУУiФФФФ is the mean time duration of transmission interruption caused by theУУ iФФ th component of a telephone connection andУУ MTBIУУiФФФФ is the mean time between interruptions caused by theУУ iФФ th component of the connection, under the assumption that the transmission interruption duration and the time between transmission interruptions are exponentially distributed (see also Figure BР-Р1/E.855). ‚Ср JСб cмˆ4 PŽТ бFigure BР-Р1/E.855 Љ T0201430Љ88 б cмˆ4 PŽТ б Ср VСб cмˆ4 PŽТ бANNEX C Ср MСб cмˆ4 PŽТ б(to Recommendation E.855) аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр AСб cмˆ4 PŽТ бУ УQuality of speech impaired by short interruptions аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ ФC.1Тh  ТУУMeasureЦЦ а H аФФС СThe subjective opinion is used as a measure to assess or evaluate speech quality impaired by short interruptions with durations shorter than 1 s. C.2Тh  ТУУMeasuring methodЦЦ а H аФФС СRecommendation P.77 was applied for this subjective evaluation with five grade opinion scores (Excellent = 4, Good = 3, Satisfactory = 2, Poor = 1 and Unacceptable = 0). The test procedure was comprised of a 40Р-Рsecond text tape recorded in Japanese spoken by a female, which was listened to by 20 test subjects through indoor test circuits with a transmission interruption generator. C.3Тh  ТУУTest resultsЦЦ ФФС СThe relationship between frequency and duration of transmission interruptions for a given Mean Opinion Score (MOS) is depicted in Figure CР-Р1/E.855. а H аС СThe dotted line in this figure shows the locus of Р"Рfrequency РxР duration = 0.5%Р"Р which is considered as a permissible limit of the freeze out rate or the percentage of speech loss for designing Digital Speech Interpolation (DSI) and Time Assignment Speech Interpolation (TASI) equipment. а H аС СУУNoteФФ Р-Р The product of frequency and duration of the short interruption is identical toУУ PФФ [=УУ MIDФФ/(УУMTBIФФ +УУ MIDФФ)] in Annex B. ‚Ср QСб cмˆ4 PŽТ бFigure CР-Р1/E.855 б cмˆ4 PŽТ б 