1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU%.%2!,G0G0!30%#43G0G0/ further amended)1 General characteristics1.1 Fundamental characteristicsThe encoding law used is the A-law as specified in Recommendation G.711. The sampling rate, load capacityand the co
2、de are also specified in that Recommendation.The number of quantized values is 256.Note - The inversion of bits 2, 4, 6, and 8 is covered by the encoding law and is applicable only to voice-channel time slots.1.2 Bit rateThe nominal bit rate is 2048 kbit/s. The tolerance on this rate is 50 parts per
3、 million (ppm).1.3 Timing signalIt should be possible to derive the transmitting timing signal of a PCM multiplex equipment from an internalsource, from the incoming digital signal and also from an external source.Note - Further study is required on the effect of jitter of the incoming signal on the
4、 timing signal, and on themeasures to be taken in case of loss of the incoming signal or the external source.2 Frame structureRefer to 3.3.1 and 3.3.2 of Recommendation G.704 for frame structure and use of derived channel time slots.Note - If channel time slot 16 which is assigned to signalling as c
5、overed in 5 below is not needed forsignalling it may be used for purposes other than a voice channel encoded within the PCM multiplex equipment.3 Loss and recovery of frame alignmentThe strategy for the loss and recovery of frame alignment should be according to Recommendation G.706, 4.1.4 Fault con
6、ditions and consequent actions4.1 Fault conditionsThe PCM multiplex equipment should detect the following fault conditions:4.1.1 Failure of power supply.2 Fascicle III.4 - Rec. G.7324.1.2 Failure of codec (except when using single-channel codecs).As a minimum requirement this fault condition should
7、be recognized when, for at least one signal level in therange -21 to -6 dBm0, the signal-to-quantizing noise ratio performance of the local codec is 18 dB or more below thelevel recommended in Recommendation G.712.4.1.3 Loss of incoming signal at the 64 kbit/s input port (time slot 16).Note 1 - The
8、detection of this fault condition is not mandatory when channel associated signalling is used andthe signalling multiplex is situated within a few metres of the PCM multiplex equipment.Note 2 - The detection of this fault condition is not mandatory when contradirectional interfaces are used.4.1.4 Lo
9、ss of the incoming signal at 2048 kbit/s.Note - The detection of this fault condition is required only when it does not result in an indication of loss offrame alignment.4.1.5 Loss of frame alignment.4.1.6 Excessive bit error ratio detected by monitoring the frame alignment signal.4.1.6.1 With a ran
10、dom bit error ratio of 10-4, the probability of activating the indication of fault condition within afew seconds should be less than 10-6.With a random bit error ratio of 10-3, the probability of activating the indication of fault condition within afew seconds should be higher than 0.95.4.1.6.2 With
11、 a random bit error ratio of 10-3, the probability of deactivating the indication of fault condition within afew seconds should be almost 0.With a random bit error ratio of 10-4, the probability of deactivating the indication of fault condition within afew seconds should be higher than 0.95.Note - T
12、he activating and the deactivating period specified as “a few seconds“ is intended to be in the order of 4to 5 seconds.4.1.7 Alarm indication received from the remote PCM multiplex equipment (see 4.2.3 below).4.2 Consequent actionsFurther to the detection of a fault condition, appropriate actions sh
13、ould be taken as specified in Table 1/G.732.The consequent actions are as follows:4.2.1 Service alarm indication generated to signify that the service provided by the PCM multiplex is no longeravailable. This indication should be forwarded at least to the switching and/or signalling multiplex equipm
14、ent dependingupon the arrangements provided. The indication should be given as soon as possible and not later than 2 ms afterdetection of the relevant fault condition.Fascicle III.4 - Rec. G.732 3This specification, taking into account the specification given in 3 above, is equivalent to recommendin
15、g thatthe average time to detect a loss of frame alignment and to give the relevant indication should not be greater than 3 ms.When using common-channel signalling, the indication should be forwarded to the switching equipment bymeans of a separate interface on the PCM multiplex equipment.4.2.2 Prom
16、pt maintenance alarm indication generated to signify that performance is below acceptable standards andmaintenance attention is required locally. When the Alarm Indication Signal (AIS) (see General Notes below to 4.2) isdetected, the prompt maintenance alarm indication associated with loss of frame
17、alignment (see 4.1.5 above) andexcessive error ratio (see 4.1.6 above) should be inhibited, while the rest of the consequent actions are in accordancewith those associated in Table 1/G.732 with the two fault conditions.Note - The location and provision of any visual and/or audible alarm activated by
18、 the alarm indications given in 4.2.1 and 4.2.2 above, is left to the discretion of each Administration.4.2.3 Alarm indication to the remote end, transmitted by changing bit 3 of channel time-slot 0 from the state 0 to thestate 1 in those frames not containing the frame alignment signal. This should
19、 be effected as soon as possible.4.2.4 Transmission suppressed at the analogue outputs.4.2.5 AIS applied to time-slot 16 64 kbit/s output (see General Notes below to 4.2). This action should be taken assoon as possible and not later than 2 ms after the detection of the fault condition.4.2.6 AIS appl
20、ied to time slot 16 of the output 2048 kbit/s composite signal (if supervision of the incoming 64 kbit/ssignal is provided).General Notes to 4.2Note 1 - The equivalent binary content of the AIS is a continuous stream of binary 1s. The strategy for detectingthe presence of the AIS should be such that
21、 the AIS is detectable, even in the presence of an error ratio of 1 10-3.However, a signal with all bits except the frame alignment in the 1 state, should not be mistaken as an AIS.Note 2 - All timing requirements quoted apply equally to restoration, subsequent to the fault condition clearing.5 Sign
22、alling5.1 Signalling arrangementRefer to 3.3.3 of Recommendation G.704. Channel time slot 16 may be used to provide an interface at 64kbit/s which shall be suitable for use with either common channel or channel associated signalling.4 Fascicle III.4 - Rec. G.732TABLE 1/G.732Fault conditions and cons
23、equent actions for the PCM multiplex equipmentConsequent actions (see 4.2)EquipmentpartFault conditions(see 4.1)ServicealarmindicationgeneratedPromptmaintenancealarmindicationgeneratedAlarmindication tothe remoteend transmittedTransmissionsuppressed atthe analogueoutputsAIS appliedto 64 kbit/soutput
24、(time slot 16)AIS appliedto time slot16 of the2048 kbit/scompositesignalMultiplexerandFailure of powersupplyYes Yes Yes(if practicable)Yes(if practicable)Yes(if practicable)Yes(if practicable)demulti-plexerFailure of codec Yes Yes Yes YesMultiplexeronlyLoss of incomingsignal at64 kbit/s inputtime sl
25、ot 16 (seeNotes under 4.1.3)Yes YesLoss of incomingsignal at2048 kbit/sYes Yes Yes Yes YesLoss of framealignmentYes Yes Yes Yes YesDemulti-plexer onlyError ratio 10 -3on the framealignment signalYes Yes Yes Yes YesAlarm indicationreceived from theremote end (bit 3of time slot 0)YesNote - A Yes in th
26、e table signifies that an action should be taken as a consequence of the relevant fault condition. An open space in thetable signifies that the relevant action should not be taken as a consequence of the relevant fault condition, if this condition is the onlyone present. If more than one fault condi
27、tion is simultaneously present the relevant action should be taken if, for at least one of theconditions, a Yes is defined in relation to this action.Fascicle III.4 - Rec. G.732 55.2 Loss and recovery of multiframe alignment in case of channel associated signallingMultiframe alignment should be assu
28、med to have been lost when two consecutive multiframe alignment signalshave been received with an error.Multiframe alignment should be assumed to have been recovered as soon as the first correct multiframealignment signal is detected.Note - To avoid a condition of spurious multiframe alignment, the
29、following procedure may be used in additionto the above:- Multiframe alignment should be assumed to have been lost when, for a period of one or two multiframes,all the bits in time slot 16 are in state 0.- Multiframe alignment should be assumed to have been recovered only when at least one bit in st
30、ate 1 ispresent in the time slot 16 preceding the multiframe alignment signal first detected.5.3 Fault conditions and consequent actions in case of channel associated signalling5.3.1 Fault conditionsThe signalling multiplex equipment should detect the following fault conditions:5.3.1.1 Failure of po
31、wer supply.5.3.1.2 Loss of 64 kbit/s incoming signal at the input of the signalling demultiplexer.Note 1 - The detection of this fault condition is not mandatory when the signalling multiplex equipment issituated within a few metres of the PCM multiplex equipment or when this fault condition results
32、 in an indication of lossof multiframe alignment.Note 2 - Where separate circuits are used for the digital signal and the timing signal then loss of either or bothshould constitute loss of the incoming signal.5.3.1.3 Loss of multiframe alignment.5.3.1.4 Alarm indication received from the remote sign
33、alling multiplex equipment (see 5.3.2.3 below).5.3.1.5 Receipt of the service alarm indication from the PCM multiplex equipment (see 4.2.1 above).5.3.2 Consequent actionsFurther to the detection of a fault condition appropriate actions should be taken as specified in Table 2/G.732.The consequent act
34、ions are as follows:5.3.2.1 Service alarm indication to be forwarded to the switching equipment depending upon the switching andsignalling arrangements provided.5.3.2.2 Prompt maintenance alarm indication generated to signify that performance is below acceptable standards andmaintenance attention is
35、 required locally. If provision is made for detecting the AIS, then on the reception of the AIS,the prompt maintenance alarm indication should be inhibited in the case of loss of multiframe (see 5.3.1.3 above).Note - The location and provision of any visual and or audible alarms activated by the ala
36、rm indications givenin 5.3.2.1 and 5.3.2.2 above is left to the discretion of each Administration.5.3.2.3 Alarm indication to the remote signalling multiplex equipment, generated by changing from the state 0 to thestate 1 bit 6 of channel time slot 16 of frame 0 of the multiframe (see Table 7/G.704)
37、; this should be effected as soon aspossible.5.3.2.4 Application of the condition corresponding to state 1 on the line to all receive signalling channels. Thiscondition should be forwarded as soon as possible and not later than 3 ms after the detection of the fault condition.6 Fascicle III.4 - Rec.
38、G.732Note - All timing requirements quoted apply equally to restoration, subsequent to the fault condition clearing.6 InterfacesThe analogue interfaces should be in accordance with Recommendations G.712, G.713, G.714 and G.715. Thedigital interfaces at 2048 kbit/s should be in accordance with Recomm
39、endation G.703. The digital interfaces at 64 kbit/sshould be of either the codirectional or the contradirectional type specified in Recommendation G.703. Thespecifications for 64 kbit/s interfaces are not mandatory for channel associated signalling. The interface for externalsynchronization of the t
40、ransmitting timing signal should be in accordance with Recommendation G.703.TABLE 2/G.732Fault conditions and consequent actions for channel-associatedsignalling multiplex equipmentConsequent actions (see 5.3.2)Equipment part Fault conditions(see 5.3.1)ServicealarmindicationgeneratedPromptmaintenanc
41、ealarmindicationgeneratedAlarmindication tothe remoteend transmittedApplication of state,equivalent to state 1, online to all receivesignalling channelsMultiplexer anddemultiplexerFailure of power supplyYes Yes Yes(if practicable)Yes(if practicable)Loss of incoming signal Yes Yes Yes YesLoss of mult
42、iframealignmentYes Yes Yes YesDemulti-plexer onlyAlarm indication receivedfrom the remote signallingmultiplex equipmentYes YesReceipt of the service alarmindication from PCM muxYes YesNote - A Yes in the table signifies that an action should be taken as a consequence of the relevant fault condition.
43、 An openspace in the table signifies that the relevant action should not be taken as a consequence of the relevant fault condition, ifthis condition is the only one present. If more than one fault condition is simultaneously present the relevant action should betaken if, for at least one of the cond
44、itions, a Yes is defined in relation to this action.7 Jitter7.1 Jitter at 2048 kbit/s outputIn the case where the transmitting timing signal is derived from an internal oscillator, the peak-to-peak jitter atthe 2048 kbit/s output should not exceed 0.05 UI when it is measured within the frequency ran
45、ge from fl= 20 Hz tof4 = 100 kHz.Fascicle III.4 - Rec. G.732 77.2 Jitter at 64 kbit/s output (for interfaces according to Rec. G.703)7.2.1 In the case where the incoming 2048 kbit/s signal has no jitter, the peak-to-peak jitter at the 64 kbit/s outputshould not exceed 0.025 UI when it is measured wi
46、thin the frequency range from fl= 20 Hz to f4 = 10 kHz. Theequivalent binary content of the test signal applied to the 2048 kbit/s input shall be a pseudo-random bit sequence oflength 215- 1 as specified in Recommendation O.151.Note - In order to carry out this measurement without invoking AIS at th
47、e 64 kbit/s output, it will normally benecessary to include a frame alignment signal in the test signal.7.2.2 The jitter transfer function between the 2048 kbit/s input and the 64 kbit/s output should not exceed -29.6 dBwhen measured over the frequency range f0to 10 kHz. The frequency f0should be le
48、ss than 20 Hz and as low aspossible (e.g. 10 Hz), taking into account the limitations of measuring equipment.Note 1 - The 2048 kbit/s test signal shall be modulated by sinusoidal jitter. The equivalent binary content of thetest signal shall be 1000.Note 2 - In order to carry out this measurement without invoking AIS at the 64 kbit/s output, it will normally benecessary to include a frame alignment signal in the test signal.Note 3 - The jitter reduction of 1/32 due to demultiplexing is equivalent to -30.1 dB.
