1、CEPT T/CS*54-04*E 232b4L4 0005LbO 12 TfCS54-Q4E Page 1 Recommendation T/CS 54-04 (Innsbruck 1981, modified in Vienna 1982) AUTOMATIC TRANSMISSION SUPERVISION AND MEASURING BETWEEN DIGITAL EXCHANGES Recommendation proposed by Working Group T/WG 11 ?Switching and Signalling? (CS) Text of the Recommend
2、ation adopted by the ?Telecommunications? Commission : ?The European Conference of Postal and Telecommunications Administrations, considering - that the national telephone networks in all European countries are now integrally automatic or close to being so; - that automatic measuring in accordance w
3、ith the CCITT ATME No. 2 method i is widely used on international links, and that automatic transmission measuring in the national networks is a desirable reform several Adminis- trations are striving for; - that digital switching systems are now being planned or introduced for the telephone network
4、s either analogue or digital; - that automatic transmission supervision and measuring is an essential feature of such systems, and that standard- isation will facilitate the harmonisation of systems and equipment, recommends to the members of the CEPT, automatic transmission supervision and measurin
5、g of transmission links between digital exchanges as specified in the following.? 1. 1.1. 1.2. 1.3. 2. 2.1. 2.1.1. 2.1.2. GENERAL This harmonisation project applies to digital local and transit exchanges whether these exchanges are located in a fully digital network (switching and transmission) or i
6、n a mixed analogue/digital network. Note: Application of ATME No. 2 to international connections is covered by CCITT Recommendation 0.22 I. The digital exchanges are defined in Recommendations T/CS 68-01 to 68-04 and 62-01 to 62-04 2, 31, and in CCITT Recommendations Q.501 to 4.507 4. The supervisio
7、n and measuring detailed in this Recommendation applies only to transmission links and circuits between two opposite exchanges. Measures on a per call basis are not described here. The measures performed may be divided into two parts, namely: - transmission supervision in order to determine whether
8、the transmission performance of a channel is - transmission performance measurements which are mainly maintenance oriented. satisfactory enough; TRANSMISSION SUPERVISION General Functional requirements A digital exchange should be able to supervise the transmission links in a digital network and the
9、 circuits in a mixed analogue/digital network. The supervision is based on automatic routine procedures. Furthermore, some facilities for maintenance actions may also be offered to the staff. The transmission supervision should be different according to the type of network. In an analogue or a mixed
10、 network, the circuits will be tested periodically. For the digital transmission links, the exchange has to perform an error rate monitoring. These tests might also be applied to the digital links. Alarm detection mechanism Failures which cannot be detected by the exchange terminals, but which are d
11、etected by digital or analogue transmission equipment, should be transferred to the exchange by service alarm indicators (such as group-pilot failure indication and loss-of-frame alignment indication) so that appropriate actions can be undertaken. The means by which the alarm indications are transmi
12、tted through the transmission switching interface have to be determined, especially in the case of common channel signalling. c CEPT T/CS*SY-O4*E 2326414 0005161 4 TICS 54-04 E 1 Page 2 2.1.3. 2.1.4. 2.2. 2.2.1. 2.2.2. EQUIPMENT DI RECTI NG A solution is preferred where the alarm indications corresp
13、onding to equipment connected digitally to the exchange (interfaces A and B) are conveyed within the 2 or 8 Mbit/s bit stream. For more details, also see Recommendation T/CS 68-04 2, Section 6 Service quality assurance function. Continuity check The continuity check, in conjunction with common chann
14、el signalling systems, has also been recognised as an additional method for assuring transmission performance. Information output The results of supervision will be presented on a man-machine terminal. The information to be edited will include: i) The list of the analogue circuits, mixed circuits an
15、d digital transmission links declared faulty. For each of these, the circuit or transmission link identity and the indication of the failure detected shall be provided. ii) The list of the analogue or mixed circuits which could not be checked due to occupancy or blocking. Supervision of analogue and
16、 mixed circuits The supervision of analogue and mixed circuits should be performed periodically by an automatic test called automatic circuit test. Equipment for the automatic circuit test The exchange shall be equipped within itself or with auxiliary equipment to perform these tests. The equipment
17、consists of two parts: directing equipment at the outgoing end; responding equipment at the incoming end. Method of access The directing equipment may be connected to the circuit to be tested via the switching network of the outgoing exchange as shown in Figure 1 (T/CS 54-04) or directly by other me
18、ans. Incoming access will be gained via the normal exchange switching network. RESPONDING -_ c.- QU I PMENT -i SWITCHING NETWORK TRANSMISSION 2.2.3. 2.2.3.1. 2.2.3.2. SW ITCH1 NG NETWORK OUTGO1 NG INCOMING EXCHANGE EXCHANGE Figure 1 (T/CS 54-04). Test principle and data for the automatic circuit tes
19、t Basic principle The automatic circuit test consists of testing the level of a tone of defined frequency in both transmission directions. The received tone level has to be contained in determined limits. Sending requirements The nominal frequency value of the test tone will be 820 Hz. The accuracy
20、of the frequency will be f 10 Hz on a provisional basis. The definition of the frequency is aligned with the results reached in CCITT Recommendations 0.1 1, 0.95, 0.132 and 0.141 5, 6, 7, 81. The nominal sending level is between - 5 dBmO and - 12 dBmO (tolerance O. I dB). For the time being, each Ad
21、ministration will define the levels of the receiving and sending tones in directing and responding equipment according to the national transmission plan. These levels will be reconsidered following the CCITT Study Group XVI studies on harmonisation of national transmission plans. Edition of May 15,
22、1986 CEPT T/CS*54-04*E m 2326414 0005162 b m TICS 54-04 E Page 3 2.2.3.3. Receiving requirements (a) Operating conditions: - test tone frequency: inside the frequency band 820 Hz f 15 Hz; test tone level range: the absolute power level M of the received test tone shall be within the following limits
23、: (N - y + n) 5 M 5 (N + x + n) dBm, where N is the nominal level expected, n is the relative level at the receiver input, x and y are separately adjustable between O and 5 dB in steps of 0.5 dB; - the recognition time of the 820 Hz test tone should be 100 ms f 20 ms; - maximum permissible interrupt
24、ion of the tone after recognition should be 25 ms or less. (b) Non-operating conditions: - test tone frequency: outside the frequency band 820 Hz f 80 Hz; test tone level (M): M 2 (N + x + n + A)dBm M I (N - y + n - A)dBm where A is the tolerance (0.5 dB maximum), see Figure 2 (T/CS 54-04); - interr
25、uption of the tone after recognition greater than 25 ms. Note: For each circuit to be tested, the level of the sending or receiving tones may be adapted so that the tone at the receiving equipment is at the nominal receiving level. HZ i 2.2.4. 900 835 820 805 760 dB N+n-y N+n N+n*r N+ n - y -.A N+n+
26、x*A Figure 2 (T/CS 54-04). Operation non-operation requirements. Details of testing procedure and signals io be transmitted between directing and responding equipment The connection between the directing and the responding equipment will be Set-up after the circuit seizure, the access to the respond
27、ing equipment having been performed through an appropriate access code. After the answer signal has been received, the directing equipment sends the test tone in the forward direction for a given time. If the responding equipment receives a tone outside the level limits already stated, or does not r
28、eceive the tone within the given lapse of time, then the responding equipment initiates a release process if possible. If the test tone is received correctly by the responding equipment, then the responding equipment sends an identical tone to the directing equipment for a given time. The directing
29、equipment also checks whether the test tone is received within the limits stated and, after this check, releases the circuit. The responding equipment also disconnects itself upon failure of the directing equipment to release the circuit. For internationally recommended signalling systems, interwork
30、ing with digital exchanges conforming to CEPT Recommendations, the transmission times and holding times can be defined. For other national signalling systems, Administrations should define these different times in the best way. Edition of May 15, 1986 CEPT T/CS*54-04*E 9 232b4L4 0005Lb3 8 9 TICS 54-
31、04 E Page 4 2.2.5. 2.2.6. 2.2.7. 2.2.8. 2.3. 2.3.1. 2.3.1.1. 2.3. 2.3. 2.3. .2. .3. .4. 2.3.2. 2.3.3. In case of malfunctioning in the procedure, e.g. answer signal not received, test tone not received, reception of the test tone outside the limits stated (see 9 2.2.3.3.), inappropriate backward sig
32、nal (clear-back signal) received, the directing equipment states the circuit is faulty and releases it. Annex 1 presents this testing procedure using the CCITT SDL 9. The specified timing requirements (Tdl, Td2, Tri, T,) are provisionally defined as follows: Tdl = Tr2 = 5 6 1 seconds Td2 = TrI = 100
33、0 & 250 milliseconds Automatic control arrangements The circuit tests will be started automatically at a predetermined time. The directing equipment will test each circuit in turn. It will be possible to test all the circuits of the exchange or the circuits on a selected trunk route or trunk routes.
34、 An automatic repeat attempt may be made in order to test the circuits found occupied or blocked during the first test. The automatic circuit tests will be stopped when all the circuits have been tested, or at a predetermined time, or on demand of the staff. Periodicity A periodicity of 24 hours is
35、provisionally identified. Whether this value is a maximum or a minimum is left for further study. On-demand circuit tests The staff will be able to order automatic tests on all circuits or on a selected trunk route, or on a selected circuit. When operating on a selected circuit, it should be possibl
36、e to make continuous tests. Other requirements In some particular cases, it would be possible for Administrations which agree with the test principle defined in 9 2.2.3.1., to perform the automatic circuit test by means of more than one frequency. Supervision of digital transmission links The superv
37、ision of digital transmission links should be performed by the procedures described below. Error rate monitoring Automatic routine procedures are provided for monitoring the error performance of the digital transmission links connected to digital exchanges. Basic principle and data The procedures ar
38、e based on the measurement of the line error rate by counting the number of frame alignment signals received wrong in a definite period. In this way, the performance supervision is executed on the digital lines in service. The exchange should be able to identify different ranges of the error rate: i
39、) 5 ii) the definition of the other ranges needs further study. CCITT Recommendation G.821 lo should be The first range (5 is already defined for the exchange terminal in the existing CCITT Recommenda- tions G.734 and G.746 ll, 121. Characteristics of the procedure Time basis for first range: see CC
40、ITT Recommendations G.732, G.734 and G.746 13, 11, 121. Note: The characteristics of the procedure for the other ranges need further study. Confidence levels (conforming to CCITT Recommendation G.732 131 levels). Actions to be taken When error rate exceeds operational objectives, the exchange will t
41、hen take subsequent action to give appropriate trouble indications or alarm, and perform other appropriate actions such as removing circuits from service. Slip rate monitoring When the slip rate exceeds operational objectives (to be defined: also see CCITT Recommendation G.822 14), the exchange will
42、 take similar actions, as defined in Paragraph 2.3.1.4. for the error rate. Automatic circuit tests for digital networks This subject is still under study. A possible solution coud be based upon periodical tests with measurements of error rates on specific time slots (see also CCITT Recommendation 0
43、.151 15. taken into account. Edition of May 1 a 15, 1986 - CEPT T/CS*54-04*E W 2326434 0005364 T m Exchange 1 Digital Analog Digital xxxxxxxxxxx 3. 3.1. 3.2. Exchange 2 3.3. TICS 54-04 E Page 5 MEASUREMENTS OF TRANSMISSION PERFORMANCE General More detailed measurements on the circuits might be neces
44、sary in order to maintain the performance level provided by the transmission paths. These measurements might be complementary to the automatic tests and the error rate monitoring described above. The more detailed measurements of the transmission performance shall be performed mainly in accordance w
45、ith the maintenance philosophy to be developed. Measurements in an analogue or mixed network These measurements shall be performed by a specialised device such as ATME type equipment (see CCITT Recommendation 0.22 7 or equipment providing the automatic circuit test and additional external test facil
46、ities, e.g. tests on several frequencies, measurement of noise level, quantification distortion, variation of gain with input level. For more detailed information on these parameters, see CCITT Recommendation G.712 16. The control of these measurements could be centralised as shown in Figure 3 (T/CS
47、 54-04 ). Measurement U termi na1 Measurement terminal Common control Figure 3 (T/CS 54-04). It should then be possible to connect the exchange to the measuring equipment by using an external junction. The measurements are performed periodically, mainly during the slack hours, and are in accor- danc
48、e with the pertinent CCITT Recommendations. Measurements in a digital network This subject is still under study. The measurement of error rates on specific time slots is one example (see also CCITT Recommenda- tion O. 15 1 151). References CCITT Recommendation 0.22. Specijcation for the automatic tr
49、ansmission measuring and signalling testing equipmen t. Recommendations T/CS 68-01 to 68-04. Digital transit exchanges for international and national application. Recommendations T/CS 62-0 1 to 62-04. Digital local exchanges. CCITT Recommendation 4.501-4.507. Digital transit exchanges for national and international applications. CCITT Recommendation O. 11. Specijcations for manual maintenance access lines. CCITT Recommendation 0.95. Specijcation for an instrument to count phase and amplitude hits. Edition of May 15, 1986 CEPT T/CS*54-04*E 232b4I4
