1、CCITT RECMN*O*Lb2 92 I 4862593 0579232 382 I INTERNATIONAL TELECOMMUNICATION UNION CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COMMITTEE 0.1 62 (1 0/92) SPECIFICATIONS OF MEASURING EQUIPMENT EQUIPMENT TO PERFORM ON 2048, 8448, 34368 AND 139 264 kbit/s SIGNALS IN-SERVICE MONITORING R
2、ecommendation 0.1 62 CCITT RECMN*O.362 92 4862593 0579233 219 FOREWORD The CCITT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of the International Telecommunication Union (ITU). CCITT is responsible for studying technical, operating and tariff questions and
3、 issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The Plenary Assembly of CCIT which meets every four years, establishes the topics for study and approves Recommendations prepared by its Study Groups. The approval of Recommendations by the members
4、 of CCITT between Plenary Assemblies is covered by the procedure laid down in CCIT Resolution No. 2 (Melbourne, 1988). Recommendation 0.162 was revised by Study Group IV and was approved under the Resolution No. 2 procedure on the 5th of October 1992. CCIT NOTE In this Recommendation, the expression
5、 “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized private operating agency. O 1T 1993 Ail rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopy
6、ing and microfilm, without permission in writing from the ITU. CCITT RECMN*O=Lb2 92 4862591 0579234 155 9 Recommendation 0.162 EQUIPMENT TO PERFORM IN-SERVICE MONITORING ON 2048, 8448, 34 368 AM) 139 264 kbis SIGNALS (Published in 1980; revised 1988 and 1992) Abstract Defines the requirements for an
7、 equipment to perform in-service monitoring of digital signals at bit rates of 2,8,34 and 140 Mbit/s using the frame alignment signai. Keywords - frame alignment signal monitoring; - frameanalyser; - in-service monitoring; - measurement; - tester. PREAMBLE Section 1 applies to ali four bit rates (20
8、48,8448,34 368 and 139 264 kbids). Section 2 provides additional information applicable to 2048 kbit/s signals only. 1 General 1.1 Application This specification describes equipment for performing in-service error tests on digital signals having frame structures that are in accordance with 0 2.3 and
9、 2.4 of Recommendation G.704 i, and Recommendation G.751 2. The equipment is required to monitor signals at the first, second, third and fourth hierarchical levels, as defined in Recommendation G.702 3. 1.2 Events to be monitored The following events shall be monitored: 1.2.1 Alarm conditions, frame
10、 alignment signal errors The equipment is required to display any inherent alarm conditions in the signal and to be capable of counting errors in the Frame Alignment Signal (FAS). 1.2.2 Code violations The equipment may also, if so desired, count and display violations of the relevant code as a sepa
11、rate operation. 1.2.3 Cyclic redundancy check The equipment is required to monitor any Cyclic Redundancy Check (CRC) procedure signals, in accordance with Recommendations G.704 i and G.706 4. Recommendation 0.162 (10/92) 1 CCITT RECMN*O.LbZ 92 9862.571 0579235 091 E 1.2.4 Access to time slots As an
12、option, the equipment may provide access to the information bits conveyed in any selected time slot. 1.3 . Decoding strategy When necessary, the received digital signal shall be decoded by the equipment in an appropriate manner. 1.3.1 HDB3 decoding strategy When necessary, the received digital signa
13、l shall be decoded by the equipment in a manner such that, when sampling the signal, on recognition of 2 consecutive zeros (spaces) followed by a bipolar violation, the decoder shall substitute 4 consecutive zeros in place of the bipolar violation and the 3 preceding digits. 1.3.2 CMI decoding strat
14、egy Under study. 1.4 Functionality, demultiplexing The functionality required for more than one bit rate may be provided in a single piece of equipment. As an option, the functionality for more than one bit rate may be combined with a demultiplexing capability to allow tributaries at bigher order ra
15、tes to be monitored. 1.5 Digital signal input 1.5.1 Interfaces The equipment is required to operate at the following interfaces and under the following input conditions: 1.5.1.1 Recommendation G. 703 Input impedances and levels in accordance with Recommendation G.703 5. 1.5.1.2 Recommendation G.772
16、Input impedances and levels in accordance with the specifications for protected monitoring points of Recommendation G.772 6. 1.5.1.3 Return loss The return loss at the digital signal input to the measuring equipment shall comply with Table U0.162. The limits defined in Table V0.162 shall be met when
17、 measured against a non-reactive resistance equal to the nominal impedance. 1.5.2 Signal input gating The equipment shall incorporate a timing recovery circuit, operated from the incoming digital signal, such that the monitored bit stream is sampled during a short gating period at the mid-point of e
18、ach unit interval. I S.3 Input jitter tolerance The equipment shall operate correctly with an input signal jitter in accordance with the relevant limits as defined in Recommendation G.823 7. 2 Recommendation 0.162 (10/92) CCITT RECMN*O-L62 92 4862593 0579236 T28 TABLE V0.162 Return loss at the input
19、 1.6 Fault and error indications The equipment shall incorporate fault indications to meet the alarm strategies of equipment in accordance with the requirements of Recommendations G.732 8, G.742 9 and G.751 2. A possible fault indication plan is illustrated in g 1.6.1. All fault indications are norm
20、ally in the quiescent state, for example if indicator lamps are used they will be extinguished. 1.6.1 Fault indication plan 1.6.1.1 Loss of signal A fault indication shall be given if more than n consecutive zeros are detected. The value of x requires further study. 1.6.1.2 Alarm indication signai T
21、he equipment shall recognize a signal containing less than y consecutive zeros as a valid alarm indication signal (AIS) and the appropriate indication shall be given. The strategy for the detection of the presence of an AIS shall be such that the AIS is detectable even in the presence of a code viol
22、ation ratio of 1 in 103. However, a signal with all bits in the ONES state, except the FAS, shall not be mistaken for a valid AIS. The value of y requires further study. 1.6.1.3 Loss and recovery offrame alignment In the event of a loss of frame alignment, as defined in the G.700-Series Recommendati
23、ons, the equipment shall recognize the loss and the appropriate indication shall be given. In the event of recovery of frame alignment, as defined in the G.700-Series Recommendations, an indication shall be given or cancelled, as appropriate. Note - If applicable, the equipment shall be able to sync
24、hronize to frames with or without CRC bits. Recommendation 0.162 (10192) 3 CCITT RECMN*O.LbZ 92 Y862591 0579237 9bY 1.6.1.4 Distant alam The appropriate indication shall be given if the distant alarm condition is detected. 1.6.2 Error indications 1.6.2.1 Frame alignment signal errors The equipment s
25、hall indicate the equivalent binary error ratio of the incoming digital signal based on the number of detected incorrect FAS. It is assumed that the FAS is a satisfactory sample and the error ratio based on FAS is valid for the whole decoded signal. Error ratios from 1 - 10-3 to 1 10-9 (minimum rang
26、e) shall be indicated. 1.6.2.2 Cyclic redundancy check procedure The equipment shail indicate the equivalent binary error ratio detected by means of the CRC procedures. Error ratios from 1 - 10-5 to 1 - 10-7 (minimum range) shall be indicated. 1.6.2.3 Total error count The equipment shall indicate a
27、 count of the total errors monitored. The capacity of the counter shall be at least 99999. An indication shall be given if the maximum count total is exceeded. 1.7 Display 1.7.1 Count control It shall be possible to manually control the duration of an error count sequence by means of “start“ and “st
28、op“ controls. It shall be possible to reset the error counters and associated displays. 1.7.2 Indicator lock, indicator auto-reset A facility shall be provided whereby a fault indication either clears automatically when the fault condition clears or remains until a manual reset is operated. 1.8 Alam
29、 function check A method of introducing fault conditions into the incoming digitai signal, in order to check the correct functioning of the equipment, shall be considered. 1.9 Output to external recording devices (optional) As an option, an interfacehnteraces shall be provided to enable external rec
30、ording (e.g. by means of a printer) of the following data: - alarm indications; - error indications; - status of the digital signal input to the instrumentation. This interface shall be in accordance with Recommendations O and V.28 i i. At the interface, suitably abbreviated, plain text message in A
31、SCIV.50 coded format according to the requirements of Recommendation V.4 12 is preferred. 1.10 Demultiplexing capability (optional) As an option, it shall be possible to select a tributary from a higher order signal for subsequent analysis of the frame alignment signai in accordance with the require
32、ments of 0 1.6 of this Recommendation. Where the tributary signal contains further lower level tributaries, additional demultiplexing to recover and analyse one selected lower order tributary per hierarchical level shall be provided. this Recommendation shall be provided. For each selected tributary
33、 at each hierarchical level all of the fault and error indications defined in 0 1.6 of 4 Recommendation 0.162 (10192) CCITT RECMN*OmLb2 32 m 4862533 0579238 8TO Average binary error ratio in decoded signai 1.1 1 Performance indications (optional) Probability of indication being given or cancelled wi
34、thin the periods stated below As an option, the equipment shall be capable of providing performance information in accordance with Recommendation G.821 13. 50% within 0.3 s 5% within 0.3 s - 1.12 Operating conditions 5% within 0.3 s 95% within 0.3 s - The electrical performance requirements of this
35、Recommendation shall be met when the equipment is operated within the environmental conditions defined in Recommendation 0.3 141. 1.10-4 1 -10-5 1 .io-s 5.104 1.106 5.10-5 2 Requirements for equipment operating at 2048 kbiUs 50% within 3 s 5% within 3 s - 5% within 3 s - 95% within 30 s 5% within 30
36、 s - 95% within 30 s 50% within 30 s 5% within 30 s - 2.1 Events to be monitored 2.1.1 Loss and recovery offiame alignment in the event of a loss of frame alignment, as defined in 4 3 of Recommendation G.706 4, the equipment shall recognize the loss and the appropriate indication shall be given. In
37、the event of recovery of frame alignment, as defined in 0 3 of Recommendation G.706 4, an indication shall be given or cancelled, as appropriate. 2.1.2 Errors in the frame alignment signal The indication of binary error ratios occurring in the received decoded signal shall comply with the limits giv
38、en in Table 2/0.162. The binary error ratios are calculated from detected incorrect FAS. It is assumed that the FAS is a satisfactory sample and the error ratio calculated is valid for the whole of the counters measurement period. TABLE 20.162 Probability of occurrence of binary error ratio indicati
39、ons (from FAS) Binary error ratio indication i .10-5 I Indication given I Indication cancelled i. 10-3 5.10-4 1.10-4 2.1.3 Loss and recovery of rnultiframe alignment In the event of a loss of multiframe alignment, as defined in $5.2 of Recommendation G.732 8, the equipment shall recognize the loss a
40、nd an appropriate indication shall be given. In the event of recovery of multiframe alignment, as defined in 0 5.2 of Recommendation G.732 81, an indication shall be given or cancelled, as appropriate. Recommendation 0.162 (10192) 5 CCITT RECMNtO-Lb2 72 M Li862571 0579239 737 H l.l 5.1137 i. 1137 1.
41、1137 5.10-8 1.10-8 Note - If time slot 16 is used for common channel signalling, the multiframe alignment signal is not present in a nominal input signal to the equipment. In this case it shall be possible to inhibit the loss of multiframe indicator in order to prevent false alarm indications. 50% w
42、ithin 10 s 5% within 10 s - 50% within 100 s 5% within 100 s - 2.1.4 Distant alarm The equipment shall recognize the distant alarm condition as defined in RecommendationG.732 8, as conveyed by the state of bit 3 of time slot O in frames alternate to those containing the FAS. The distant alarm condit
43、ion shall be considered to be active, and the appropriate indication given, when bit 3 is set to state ONE in four or more consecutive occurrences, and shall be considered to be inactive, and the appropriate indication not given, when bit 3 is set at state ONE in less than two consecutive occasions.
44、 2.1.5 Distant multiframe alarm The equipment shall recognize the distant multiframe alarm condition as defined in Recommenda- tion G.732 8, as conveyed by the state of bit 6 of time slot 16 of frame O. The distant multiframe alarm condition shall be considered to be active, and the appropriate indi
45、cation given, when bit 6 is set at state ONE in three consecutive occurrences, and shall be considered to be inactive, and the appropriate indication not given, when bit 6 is set at state ONE in less than two consecutive occasions. Nute - The text above is only applicable if time slot 16 is not carr
46、ying a payload e.g. common channel signalling. If time slot 16 is used for common channel signalling, bit 6 will be continuously in state ONE. In this case, it shall be possible to inhibit the distant multiframe alarm in order to prevent false alarm indications. 2.1.6 Cyclic redundancy check procedu
47、re Where a CRC procedure in accordance with Recommendation G.704 2048 kbit/s signal, the equipment shall provide the features detailed in this sub-section. is implemented within the The equipment shall indicate the presence of CRC framing bits. The indications of binary error ratios occurring in the
48、 received decoded signal (detected by means of the CRC procedure) shall comply with the limits given in Table 3/0.162. The indication shall be provided accordingly. TABLE 310.162 Probability of occurrence of binary error ratio indications (from CRC) Binary error ratio indication 1.1135 1. lod i .10-
49、7 Probability of indication be the periods Indication given Average binary error ratio in decoded signai 50% within 1 s 5% within 1 s - ig given or cancelled within :tated below Indication cancelled 5% within 1 s 95% within 1 s - 5% within 10s 95% within 10s - 5% within 100 s 95% within 100 s - 6 Recommendation 0.162 (10/92) CCITT RECMN*O-LbZ 92 D 4862593 0579240 459 2.1.7 Code violation detection 2.1.7.1 Definition of an HDB3 code vialation Two consecutive bipolar violations of the same polarity constitute a code violation. This
