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.810 Ф ФPAGE1У Уб cмˆ4 PŽТ б ЮееЃ† а HH аааб cмˆ4 PŽТ бPAGE2У Уб cмˆ4 PŽТ б Fascicle II.3 Р-Р Rec. E.810 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.810 Ср(<Сб cмˆ4 PŽТ бMODEL FOR THE SERVEABILITY PERFORMANCE ON A BASIC CALL Ср(JСIN THE TELEPHONE NETWORKб cмˆ4 PŽТ бФ ФУУ1жXЯ а HH ааа1)ФФб cмˆ4 PŽТ бAlthough this Recommendation deals with the telephone service, in principle the model and the decomposition of serveability performance can also be applied to other telecommunication services. The elaboration of this principle is left for further study. Xж)б cмˆ4 PŽТ бУ УФФ б cмˆ4 PŽТ бТа ТIntroductionЦЦ а H аС СThis Recommendationб cмˆ4 PŽТ бУУ2жђIа H ааа2)ФФб cмˆ4 PŽТ бSome of the terms in this Recommendation, for example the noun Р"РmeasureР"Р, are used in the sense of their definition given in Recommendation E.800. ђж) ФФб cмˆ4 PŽТ бis one of a set of closely related Recommendations concerned with the accessibility and retainability of telephone services, as listed below. Та ТThe CCITT,ЦЦ УУconsidering а H аФФС С(a)СpСthat there is a desire to establish overall objectives for the quality of service as perceived by the users; С С(b)СpСthat such objectives can then be used as a basis for the design, planning, operation and maintenance of telecommunication networks and their component parts; С С(c)СpСthat Recommendation E.800 contains terms and definitions for the quality of service, the reliability and availability performances and related characteristics of services and networks, УУrecommends а H аФФС Сthat the telephone call model given in this Recommendation shall be used by Administrations to design, plan, operate and maintain their networks taking into account the objectives given in Recommendations: а H аТа ТТ№ ТТhpТС€СС€ СE.830Си СModels for the allocation of international telephone connection retainability, accessibility and integrity;ЦЦ а H аТа ТТ№ ТС€ СE.845Си СConnection accessibility objective for the international telephone service;ЦЦ а H аТа ТТ№ ТС€ СE.850Си СConnection retainability objective for the international telephone service.ЦЦ а H аС СУУNoteФФ Р-Р Refer also to the draft Recommendation on interruption objectives which is being studied under Question 39/II. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС‚У У1С  Сб cмˆ4 PŽТ бModel of a basic telephone call and its serveability performanceЦЦ а H аб cмˆ4 PŽТ бФ ФС  СThe following simplified model illustrates the principal phases of a basic аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаtelephone callй@ basic telephone callб cмˆ4 PŽТ б@й. It also interrelates these phases to the serviceР-Рrelated performance concepts and their principal measures as well as to the main causes of failure in the establishment and retention of such a call and its subsequent billing. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС СThe model also indicates where, in this series of phases, user actions or mistakes may influence the call. ‚У У2ТX ТComments to the model and its applicationsФ ФЦЦ 2.1Тh  ТУУMathematical modellingЦЦ а H аФФС СIn a simple case of statistical independence, the probabilities may be combined into the following mathematical models: аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHp8А"(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ Ьа‚УУС СС pССШ8СPƒФФ = (УУPФФУУ11ФФ .УУ PФФУУ12ФФ) .УУ PФФУУ2ФФ . (УУPФФУУ31ФФ .УУ PФФУУ32ФФ) .УУ PФФУУ4ФФ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаto express the probability of a correctly billed revenueР-Рmaking call and, аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHp8А"(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ Ьа‚УУС СС pССШ8СPƒФФ = (УУPФФУУ11ФФ .УУ PФФУУ12ФФ) .УУ PФФУУ2ФФ . (УУPФФУУ31ФФ .УУ PФФУУ32ФФ) аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаto express the probability of a successfully completed call. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС2.2С   Сб cмˆ4 PŽТ бУУContributions to causes of call failureЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СIt is generally recognized that the various parts of a national or international network may be of different importance to the successful completion of the various phases of a call. For example, the network accessibility is mainly determined by the telephone set, the subscriber line and the local exchange; the connection accessibility by the exchanges, transmission network and signalling network used; the billing integrity is dependent on the charging facilities used by the network parts that constitute the connection and the equipment for processing the billing information, etc. In some Administrations, the telephone set is not considered as a part of the network and in that case it is not included in the concept of network performance. 2.3Тh  ТУУTime aspects of measuresЦЦ а H аФФС СDepending on the intended application of the measures indicated in Figure 1/E.810, it may be appropriate to express these measures as instantaneous values related to a given instant of time or as a mean over a given time interval. а H аС СAdvice on which variant to use should be given in each specific relevant Recommendation. 2.4Тh  ТУУSpace aspects of averagesЦЦ ФФС СThe measures as indicated in Figure 1/E.810 could be applied to calls between particular destinations as traffic weighted averages over a number of destinations, etc. а H аС СEach relevant Recommendation should clearly specify which alternative(s) to use. ‚Ср KСб cмˆ4 PŽТ бFIGURE 1/E.810 Љ T0200373Љ88 б cмˆ4 PŽТ б 