1、 CEPT T/CS*LO-13*E 1 2326414 0004474 9 M TCS10-13 Page E 1 Recommendation T/CS 10-13 (Innsbruck 1981, revised in Copenhagen 1987) GENERAL MAINTENANCE CONCEPT AND TERMS Recommendation proposed by Working Group T/WG 11 “Signaling, Protocols and Switching” (SPS) Text of the Recommendation adopted by th
2、e “Telecommunications” Commission: “The European Conference of Postal and Telecommunications Administrations, considering : - that the provision of telecommunication services is dependent to a large degree on complex technical systems - that the service perceived by the user is thus the result of th
3、e functioning of a great many component parts, - that degradation of and failures in the fiinctioning of certain component parts may be expected, but that the collective influence of such improper functioning on the service can be controlled by adequate maintenance measures applied to the component
4、parts, - that Administrations have the responsibility for these maintenance measures during the whole time the equipment concerned is in service and have to take into account all the factors which contribute to the efforts the maintenance may require, including such factors as availability performan
5、ce characteristics, design or choice of systems, standards, acquisition of documentation, training of personnel and the assurance of delivery of spare parts, etc., - that although in some cases the same personnel are in charge of maintenance and operation, it may be desirable to distinguish between
6、operation and maintenance, making up the network and the terminal equipment connected to it, recommends: the following general maintenance concept dealing with maintenance activities and the principal causes of them, the related overview classifications and the standardisation of terms and definitio
7、ns to be used in telecommunication systems maintenance.” Edition of February 29, 1988 I CEPT T/CS*LO-L3*E 3 W 2326434 0004475 O T/CS 10-13 E Page 2 TABLE OF CONTENTS O . BASIC CONCEPTS . 0.1 . Item 0.2. Repaired item 0.3. Non-repaired item . 0.4. Service . 0.5. Required function . 0.6. Instant of ti
8、me 0.7. Period of time 0.8. Time interval . 0.9, Accumulated time . 0.10. Operation 0.1 1 . Expectation/mean of a random variable . 1. RELATIONSHIP BETWEEN MAINTENANCE AND QUALITY ASPECTS OF PROVIDING TELECOMMUNICATION SERVICE . 1.1, Definitions 1.2, Call approach and failure approach . 2 . MAINTENA
9、NCE CONCEPTS 2.1. Definitions 2.2. Classifications 3 . FAILURE CONCEPT 3.1. Definitions 3.2 . Classifications of failures 4 . INTERRUPTION CONCEPT . 4.1. Interruption . 5 . TIMECONCEPT 5.1. Times in relation to whether the item is required or not . 5.2. Times in relation to whether the item is opera
10、ting or not 5.3. Times in relation to the state of the item 5.4. Breakdown of internal down time 5.5. Breakdown of maintenance time . 5.6. Reliability performance related measures . 5.7. Time period with respect to failure occurrence of a maintained item . 5.8. Time diagram 6 . DESIGN CONCEPTS .I .
11、6.1. Redundancy . 6.2. Activeredundancy 6.3. Standby redundancy 6.4. Pail safe . 7 . EXPLANATORY TEXT . 7.2. Failure terms . REFERENCE . . 7.1. Arrangement principles 3 3 3 3 3 3 3 3 3 3 3 3 4 4 5 5 5 5 8 8 9 11 11 11 11 11 12 12 12 14 14 15 17 17 17 17 17 17 17 17 17 Edition of February 29. 1988 O.
12、 0.1. 1 CEPT T/CS*LO-L3*E 83 2326434 O004476 2 BASIC CONCEPTS Item 0.2. 0.3. 0.4. 0.5. 0.6. 0.7. 0.8. 0.9. 0.10. 0.11. TICS 10-13 E Page 3 Any part, device, subsystem, functional unit, equipment or system that can be individually considered. Note. An item may consist of hardware, software or both, a
13、nd may also include people, e.g. operators in a telephone operator system. Repaired item A repairable item which is in fact repaired after a failure. Non-repaired item An item which is not repaired after a failure. Note. A non-repaired item may be repairable r not. Service A set of functions offered
14、 to a user by an organization. Required function A function or a combination of functions of an item which is considered necessary for the provisioning of a given service. Instant of time A single point on a time scale. Note. The time scale may be continuous as calendar time, or discrete e.g. number
15、 of use cycles. Period of time All instants of time between two given instants of time. Time interval The difference between the end points of a period of time, Accumulated time The sum of time intervals characterized by given conditions over a given period of time. Operation Combination of all tech
16、nical and corresponding administrative actions intended so that an item can perform a required fiinction recognizing necessary adaptation to changes in external conditions. Note. By external conditions are understood for example service demand and environmental conditions. Expectationlmean of a rand
17、om variable a) For a discrete random variable X taking the values xi with the probabilities pi E (X) = Cpixi the sum being extended for allthe values xi which can be taken by X. E (X) = Jx f(x) dx the integral being extended for all values of the interval of variation of X. b) For a continuous rando
18、m variable X having the density f(x): Edition of February 29, 1988 “I CEPT T/CS*LO-L3*E 1 = 2326414 0004477 4 T/CS 10-1 3 E Page 4 1. 1.1, 1.1.1. 1.1.2. 1.1.3. 1.1.4. 1.1.5. 1.1.6. RELATIONSHIP BETWEEN MAINTENANCE AND QUALITY ASPECTS OF PROVIDING TELECOMMUNICATION SERVICE CCIT Recommendation G. 106
19、I provides a framework for availability and reliability studies and the terins and definitions given therein apply generally to this present Recommendation. Figure 1 (T/CS 10-13) is derived from Recommendation G.106 and depicts the relationship between maintenance and performance aspects for providi
20、ng telecommunications services. Definitions The foilowing definitions apply. Network tecknical pe-formance The ability of a telecommunication network, under combined aspects of its traffic (ability), availability and transmission performances, to perform or to be in a state to perform a required ser
21、vice for a stated condition of time. Note. A stated condition of time refers to a stated instant of time or to a stated interval of time. NETWORK SERVICE PERFORMANCE TRAFFIC (ABILITY) PERFORMANCE PERFORMANCE PERFORMANCE r3LY-l MAINTAINABILITY MAINTENANCE SUPPORT * Implies that the relation is not hi
22、erarchical but characterises the subscribers experiences. PERFORMANCE PERFORMANCE PERFORMANCE Figure 1 (T/CS 10-13). Concept of service quality from a maintenance point of view Network service performance (provisional term) The ability of a telecommunication network, under combined aspects of its tr
23、affic (ability), availability and transmission performances as seen by the subscriber, to perform or to be in a state to perform a required service for a stated condition of time. Availability performance The ability of an item, under combined aspects of its reliability performance, maintainability
24、performance and of the maintenance support performance, to perform or to be in a state to perform a required function for a stated condition of time. Reliability performance The ability of an item to perform a required function, under stated conditions, for a stated period of time. Note. The term re
25、liability is used as a measure of the functional reliability performance. Maintainability performance The ability of an item, under stated conditions of use, to be retained in, or restored to a state in which it can perform a required function, when maintenance is performed under stated conditions a
26、nd using stated procedures and resources. Note. The maintainability is used as a measure of the functional maintainability performance, denoting the probability that the active maintenance is carried out within a given period of time. Maintenance support performance The ability of a maintenance orga
27、nisation, under stated conditions, to provide upon demand the resources required to maintain an item. Note I. Maintenance organisation includes physical resources expected to act under a given maintenance policy. Note 2. The stated conditions are related to the item itself and to the conditions unde
28、r which the item is used and maintained. Edition of February 29, 1988 -CEPT T/CS*LO-L3*E 81 2326414 0004478 b _ 1.1.7. 1.1.8. 1.2. 2. 2.1. 2.1.1. 2.1.2. 2.1.3. 2.1.4. 2.1.5. 2.1.6. 2.1.7. a 2.2. 2.2.1. TICS 10-13 E Page 5 TrafJic(abi1ity) performance) The ability of a telecommunication system to han
29、dle the offered traffic under specified conditions. I The term trafic performance is preferred by CCITI Study Group II. Note. Specified conditions refer to any combination of failed and not-failed parts of the system. Transmission peiformance The ability of an item to have the relevant transmission
30、characteristics in the allowable range. Call approach and failure approach There exists a direct relationship between the network technical performance and the use of the telecommu- nication system. The imperfect behavior of the system can be considered in two ways as shown in Figure 2 (T/CS 10-13):
31、 the call approach and the failure approach. MAINTENANCE CONCEPTS Definitions Main tenance The combination of all technical and corresponding administrative actions intended to retain an item in, or restore it to, a state in which it can perform its required function. Maintenance philosophy A system
32、 of underlying principles for the organization and execution of the maintenance (T/CS 50-01). Maintenance policy A description of the interrelationship between the indenture level, line of maintenance and the levels of maintenance to be applied for the maintenance of an item. Level of maintenance Th
33、e maintenance action to be carried out at a specified indenture level. Note. Examples are replacing a component, a printed circuit board, a subsystem, etc. Line of maintenance The position in an organization where specified levels of maintenance are to be carried out on an item. Note I. Examples of
34、maintenance echelons are: field, repair shop, manufacturer. Note 2. The maintenance echelon is characterized by the skill of the personnel, the facilities available, the location, etc. Indenture level A level of subdivision of an item from the point of view of a maintenance action. Note I. Examples
35、of indenture levels could be a subsystem, a circuit board, a component. Note 2. The indenture level depends on the complexity of the items construction, the accessibility to subitems, skill level of maintenance personnel, test equipment facilities, safety considerations, etc. Maintenance phases The
36、activities carried out for a given purpose. Note. Examples are failure detection, failure localization, failure correction or combinations thereof. Classifications ClassiJication of maintenance in relation to its intention Maintenance I Preventive maintenance I Corrective maintenance 1 Controlled ma
37、intenance Edition of February 29, 1988 CEPT T/CS*LO-L3*E 3 2326434 0004479 M T/CS 10-13 E Page 6 I- I v) a L =J I- *I- 5 (c O c, a 3 U v) I- - lu u c v) O A ll- va a3 %U cc .I- 5v) wul- as5 L.7 u 3 I-cn .I- s 5 IA* *I- I- v) w cf 3 -1 4 LL H - c C r I l i ! i l c v) O O - 4- t) h (t) = lim E N(t + A
38、t) - N(t) At+O+ At Z(t) = where N(t) is the number of failures in the period of time (O, t) and E the abbreviation of expectation. Early failure period That possible early period in the life of an item, beginning at a given instant of time (e.g. from the time of installation or power on) and during
39、which the failure intensity for a repaired item or the failure rate for a non-repaired item decreases rapidly. Note. In any particular case, it is necessary to explain what is meant by “decreases rapidly”. Constant failure intensity period That possible period in the life of a repaired item during w
40、hich the failure intensity is approximately constant. Note. In any particular case it is necessary to explain what is meant by “approximately constant”. Constant failure rate period That possible period in the life of a non-repaired item during which the failure rate is approximately constant. Note.
41、 In any particular case it is necessary to explain what is meant by “approximately constant”. Wear-out failure period That possible later period in the life of a repaired item during which the failure intensity for a repaired item or the failure rate for a non-repaired item increases rapidly. Note.
42、In any particular case it is necessary to explain what is meant by “increases rapidly”. Edition of February 29, 1988 CEPT T/CS*LO-L3*E 83 I 2326434 0004488 7 E, 1 Early I I Wear-out failure i Constant failure I failure period I period I intensity period I I I i I. i c TICS 10-13 E Page 15 Figure 3 (
43、T/CS 10-13). Time periods with respect to fahre occurrence during the lifetime of a repaired item. 5.1.1. Mean time to Jirst failure; MTTFF (abbreviation) The expectation of the time to first failure. Mean time to failure; MTTF (abbreviation) The expectation of the time to failure. Mean time between
44、 failures; MTBF (abbreviation) The expectation of the time between failures, Mean ip time; MUT (abbreviation) The expectation of the up time. Mean down time; MDT (abbreviation) The expectation of the down time. Mean accumulated down time; MADT (abbreviation) The expectation of the accumulated down t
45、ime. Mean time to repair; MTTR (abbreviation) The expectation of the time to repair. 5.1.8. 5.1.9. 5.7.10. 5.1.1 1. 5.1.12. 5.1.13. 5.8. Time diagram The subdivision of total time can be made from different points of view. A diagram showing all these pasts at the same time is thus difficult or impos
46、sible to draw. The following time diagram in Figure 4 (T/CS 10-13) is an example and shows the relationship between the various phases in the total time of a maintained item and some of the elements which make up these phases, No significance is to be given to the lengths of the boxes containing the
47、 time phase names, the space being determined by the space needed. The diagram incorporates the facility to show overlapping times. The diagram represents the case of a typical piece of equipment in order to show the general relationship which means that some simplifications have been adopted, e.g.
48、to avoid repetitions. In specific cases of equipment and conditions, the drawing of a more complex or a more simplified diagram may be appropriate os necessary. This may also be needed when times are to be shown in strict time order. It is advisable in practical applications to draw a separate diagr
49、am which includes those time concepts relevant to that study, 0 Edition of February 29, 1988 CEPT T/CS*LO-L3*E 1 E 2326434 0004489 O E I up time T/CS 10-13 E Page 16 Disabled ti me External Down time disabled time Undetected fault time Maintenance time Figure 4 (T/CS 10-13). Time diagram. Administrative delay Edition of February 29, i988 9 Preventive maintenance Repair time time Active repair time Logistic delay Fault Fault time time localization delay correction Check- out time CEPT T/CS*LO-L3*E 3 2326434 0004470 7 =-,: - _ 6. 6.1. 6.2. 6.3. 6.4. 7. O 7.
