1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU%.%2!,G0G0!30%#43G0G0/- Paragraph 3 contains the interface requirements associated with ports X and Y;- Paragraph 4 contains the requirements which are specific to a 48-channel transcoder equipment realization.
2、2 Characteristics of a 1544 kbit/s signal organized in 32 kbit/s and/or 64 kbit/s time slots (port Z)2.1 Interface ZThe electrical characteristics of the 1544 kbit/s interface are in accordance with 2 of Recommendation G.703.2 Fascicle III.4 - Rec. G.7622.2 Frame structure2.2.1 Frame structure at 15
3、44 kbit/sRefer to 3.2.1 of Recommendation G.704 for the frame structure and use of derived channel time slots.2.2.2 Frame structure at 384 kbit/sRefer to 3.2.3 of Recommendation G.704 for the frame structure at 384 kbit/s.2.3 Loss and recovery of frame and multiframe alignment2.3.1 Loss and recovery
4、 of 1544 kbit/s frame and multiframe alignmentThe criteria for loss and recovery of the frame alignment and multiframe alignment signal for port Z are in accordancewith 2.1 of Recommendation G.706 for the 24-frame multiframe and for the 12-frame multiframe.2.3.2 Loss and recovery of delta channel mu
5、ltiframe alignmentThe criteria for loss and recovery of the signalling grouping channel multiframe alignment signal are in accordancewith 3.2.6 of Recommendation G.704.2.4 SignallingRefer to 3.2.4 of Recommendation G.704 for signalling in the 384 kbit/s stream.3 Characteristics of ports X and Y3.1 I
6、nterfaces X and YThe electrical characteristics of the 1544 kbit/s interface are in accordance with 2 of Recommendation G.703.3.2 Frame structureRefer to 2.1 of Recommendation G.704 for the frame structure and use of derived channel time slots.3.3 Loss and recovery of 1544 kbit/s frame and multifram
7、e alignmentThe criteria for loss and recovery of the frame alignment and multiframe alignment signal for ports X and Y are inaccordance with 2.1 of Recommendation G.706 for the 24-frame alignment and for the 12-frame multiframe.3.4 SignallingRefer to 3.1.3 of Recommendation G.704 and 4.3 below.4 Oth
8、er characteristics of the 48-channel transcoder equipment4.1 48-channel frame structureIn the case where streams X and Y are each carrying 24 voice-frequency signals and no channel-associated signallinginformation is present, stream Z will transmit the full complement of 48 channels. Table 1/G.762 s
9、hows the correspondencebetween the 64 kbit/s PCM channels in streams X and Y and the 32 kbit/s ADPCM channels in stream Z. Time slots 1-12correspond to channels 1-12 from PCM stream X coded with 4 bits. Time slots 13-24 correspond to channels 13-24 from PCMstream X coded with 4 bits. Time slots 25-3
10、6 correspond to channels 1-12 from PCM stream Y coded with 4 bits. Time slots37-48 correspond to channels 13-24 from PCM stream Y coded with 4 bits.Fascicle III.4 - Rec. G.762 3TABLE 1/G.762Organization of the 1544 kbit/s frame for up to 48channels at 32 kbit/s in stream Z4 bit time slot ofstream Z1
11、2345678910112Time slot8 bit channel ofstream X1X 2X 3X 4X 5X 6X 7X 8X 9X 10X 11X 12XorSGCGrouping 14 bit time slot ofstream Z13 14 15 16 17 18 19 20 21 22 23 24Time slot8 bit channel ofstream X13X 14X 15X 16X 17X 18X 19X 20X 21X 22X 23X 24XorSGCGrouping 24 bit time slot ofstream Z25 26 27 28 29 30 3
12、1 32 33 34 35 36Time slot8 bit channel ofstream Y1Y 2Y 3Y 4Y 5Y 6Y 7Y 8Y 9Y 10Y 11Y 12YorSGCGrouping 34 bit time slot ofstream Z37 38 39 40 41 42 43 44 45 46 47 48Time slot8 bit channel ofstream Y13Y 14Y 15Y 16Y 17Y 18Y 19Y 20Y 21Y 22Y 23Y 24YorSGCGrouping 4The signalling grouping channels for time
13、slot groupings 1-4, when present in stream Z, occupy time slots 12, 24, 36and 48 respectively. As shown in Table 2/G.762, the channel capacity for stream X (respectively Y) is reduced by one for eachtime slot grouping associated with stream X (respectively Y) configured with a signalling grouping ch
14、annel. Selection of thetime slot grouping format to include the signalling grouping channel (SGC) is made on a per-time slot grouping basis,independent of the other time slot groupings associated with stream X or Y.4 Fascicle III.4 - Rec. G.762TABLE 2/G.762Unused channels in streams X and Y when the
15、 signallinggrouping channel is present in a time slot groupingSignalling grouping channel present Unused channelTime slot grouping 1Time slot grouping 2Time slot grouping 3Time slot grouping 4Channel 12 in stream XChannel 24 in stream XChannel 12 in stream YChannel 24 in stream Y4.1.1 Unused channel
16、sAs explained in 4.1, the presence of a signalling grouping channel in a time slot grouping causes a given channel instream X or Y to be configured as unused.The unused channels on the receive side of streams X and Y should have their data and signalling bits conditioned ina way that is compatible w
17、ith downstream equipment.The unused channels on the send side of streams X and Y are not processed.4.2 Selection of 1544 kbit/s multiframe formatsSelection of either the 24-frame or 12-frame multiframe format at ports X, Y or Z is independent of the multiframeframe formats selected at the other port
18、s.4.3 Signalling4.3.1 Common-channel signallingA channel being used to convey common-channel signalling information in stream X or Y will not undergo thetranscoding function. The signalling channel will be transmitted transparently in stream Z at the 64 kbit/s rate, as can otherchannels from streams
19、 X and Y in accordance with 4.4.4.3.2 Channel-associated signallingRefer to Table 1/G.762 and Table 7/G.704 for the association of channel associated a-b-c-d signalling bits betweenstreams X and Y and the signalling grouping channels in stream Z.4.4 Direct time slot transferIt should be possible to
20、select and pass through 64 kbit/s channels from streams X and Y transparently into stream Z.Furthermore, it should be possible to pass through at least one 64 kbit/s channel in each time slot grouping stream Z.Fascicle III.4 - Rec. G.762 5The priority for selecting which time slots from streams X an
21、d Y should be directly transferred and their placementinto stream Z is for further study.4.4.1 Channel-associated signalling in 64 kbit/s pass-through time slotsThe transcoder should allow for selection of reinsertion or no reinsertion of channel-associated signalling bits into thereceive side of st
22、reams X and Y for channels which are passed-through transparently at 64 kbit/s.4.4.2 Conditioning of unused channelsWhen 64 kbit/s channels from stream X (respectively Y) are transferred transparently into stream Z, the transmissioncapacity of PCM stream X (respectively Y) is reduced. The unused cha
23、nnels in stream X (respectively Y) should beconditioned as described in 4.1.1.4.5 Signalling grouping channel alarm indicationsWhen signalling grouping channel frame alignment is lost (as per 3.2.6 of Recommendation G.704), updating of thechannel-associated signalling bits on the receive side of str
24、eams X and Y should be inhibited for the affected channels untilframe alignment is regained.A time slot grouping alarm is declared when the signalling grouping channel multiframe alignment signal is lost for 2to 3 seconds.When signalling grouping channel multiframe alignment is declared (as per 3.2.
25、6 of Recommendation G.704),updating of the channel-associated signalling bits on the receive side of streams X and Y will be enabled.The time slot grouping alarm is released when signalling grouping channel multiframe alignment has been reacquiredfor 10 to 20 seconds.On the send side, M1is set to 1
26、to transmit a time slot grouping alarm to the remote end when the near end is in timeslot grouping alarm. On the receive side, a remote time slot grouping alarm is declared when M1has been set for 335 to1000 milliseconds. Remote time slot grouping alarm is released when M1has been reset for 20 to 10
27、00 milliseconds.On the send side, M2is used to indicate a 1544 kbit/s alarm or a 1544 kbit/s AIS has been received on port X (timeslot groupings 1 or 2) or port Y (time slot groupings 3 or 4). On the receive side, a signalling grouping channel AIS alarm isdeclared when M2has been set for 335 to 1000
28、 milliseconds. Signalling grouping channel AIS is released when M2 has beenreset for 20 to 1000 milliseconds.On the send side, M3is used to indicate a remote 1544 kbit/s alarm has been received on port X (time slot groupings1 or 2) or port Y (time slot groupings 3 or 4). On the receive side, a remot
29、e signalling grouping channel AIS alarm is declaredwhen M3has been set for 335 to 1000 milliseconds. Signalling grouping channel remote AIS alarm is released when M3hasbeen reset for 20 to 1000 milliseconds.4.6 Fault conditions and consequent actions4.6.1 1544 kbit/s fault conditions associated with
30、 stream ZA summary of the 1544 kbit/s fault conditions associated with the receive side of stream Z and the consequent actionsare listed in Table 3/G.762.The transcoder shall detect the following 1544 kbit/s fault conditions associated with stream Z:i) loss of incoming signals at 1544 kbit/s;ii) los
31、s of 1544 kbit/s frame alignment;iii) 1544 kbit/s alarm indication signal (AIS) received;iv) 1544 kbit/s alarm indication received from the remote end.6 Fascicle III.4 - Rec. G.7624.6.2 Consequent actions associated with stream ZUpon detection of 1544 kbit/s fault conditions in stream Z, appropriate
32、 actions should be taken which are inaccordance with 3.2 of Recommendation G.733. In addition, the following consequent actions should be taken as indicatedin Table 3/G.762:i) declare a 1544 kbit/s alarm on the receive side of port Z;ii) send a 1544 kbit/s alarm indication to the remote end on the s
33、end side of port Z in accordance with 4.2.4 ofRecommendation G.733;iii) send a 1544 kbit/s alarm indication signal (AIS) on the receive side of streams X and Y. The AIS consists of anall-1s signal in all channels including the framing bit;iv) declare 1544 kbit/s AIS on the receive side of port Z;v)
34、declare a remote 1544 kbit/s alarm on the receive side of port Z;vi) send a 1544 kbit/s alarm indication to the remote end on the receive side of streams X and Y in accordance with 4.2.4 of Recommendation G.733.TABLE 3/G.7621544 kbit/s fault conditions associated with stream Zand consequent actionsC
35、onsequentactionsFault conditionsDeclare1544 kbit/salarm on ZSend1544 kbit/salarmindication toremote endon ZSend1544 kbit/sAIS onX and YDeclare1544 kbit/sAIS on ZDeclare remote1544 kbit/salarm on ZSend1544 kbit/salarmindication toremote end onX and YLoss of incomingsignal at 1544 kbit/sYes Yes YesLos
36、s of 1544 kbit/sframe alignmentYes Yes Yes1544 kbit/s AISreceivedYes Yes Yes1544 kbit/s alarmindication receivedfrom remote endYes YesFascicle III.4 - Rec. G.762 74.6.3 Fault conditions associated with the signalling grouping channelA summary of the signalling grouping channel fault conditions assoc
37、iated with the receive side of stream Z and theconsequent actions are listed in Table 4/G.762.The transcoder shall detect the following signalling grouping channel fault conditions associated with stream Z:i) loss of signalling grouping channel multiframe alignment on a single time slot grouping ass
38、ociated with port Xor a single time slot grouping associated with port Y;ii) loss of signalling grouping channel multiframe alignment on both time slot groupings associated with port X orboth time slot groupings associated with port Y;iii) remote time slot grouping alarm indication (M1) received fro
39、m the remote end on a single time slot groupingassociated with port X or a single time slot grouping associated with port Y;iv) remote time slot grouping alarm indication (M1) received from the remote end on both time slot groupingsassociated with port X or both time slot groupings associated with p
40、ort Y;v) signalling grouping channel AIS (M2) received from the remote end on a single time slot grouping associatedwith port X or a single time slot grouping associated with port Y;vi) signalling grouping channel AIS (M2) received from the remote end on both time slot groupings associated withport
41、X or both time slot groupings associated with port Y;vii) remote signalling grouping channel AIS (M3) received from the remote end on a single time slot groupingassociated with port X or a single time slot grouping associated with port Y;viii) remote signalling grouping channel AIS (M3) received fro
42、m the remote end on both time slot groupingsassociated with port X or both time slot groupings associated with port Y.4.6.4 Consequent actions associated with the signalling grouping channelUpon detection of signalling grouping channel fault conditions in stream Z, the following consequent actions s
43、hall betaken as indicated in Table 4/G.762:i) declare time slot grouping alarm on the associated time slot grouping;ii) send a time slot grouping alarm indication to the remote end by forcing the M1bit within the affected signallinggrouping channel to 1;iii) condition the data in the affected channe
44、ls on the receive side of streams X or Y to provide a signal that iscompatible with downstream equipment;iv) condition the channel-associated signalling bits in affected channels on the receive side of streams X or Y toprovide a signal that is compatible with downstream equipment. An example for mos
45、t signalling types would beuniversal trunk conditioning where the signalling bits should be forced to the idle state for 2 to 3 seconds, andthen conditioned to simulate the channel seized condition;v) send a 1544 kbit/s AIS on the receive side of stream X (for time slot groupings 1 and 2) or stream
46、Y (for timeslot groupings 3 and 4). The AIS consists of an all 1s signal in all channels including the framing bit;vi) declare a remote time slot grouping alarm condition on the associated time slot grouping to indicate thereception of a remote time slot grouping alarm indication in the M1bit of the
47、 affected signalling groupingchannel;vii) send a 1544 kbit/s alarm indication to the remote end on the receive side of stream X (for time slot groupings1 and 2) and stream Y (for time slot groupings 3 and 4);viii) declare a signalling grouping channel AIS condition on the associated time slot groupi
48、ng to indicate thereception of a signalling grouping channel AIS indication in the M2bit of the affected signalling groupingchannel;ix) declare a remote signalling grouping channel AIS condition on the associated time slot grouping to indicate thereception of a remote signalling grouping channel AIS
49、 indication in the M3bit of the affected signallinggrouping channel.8 Fascicle III.4 - Rec. G.7624.6.5 Fault conditions associated with streams X and YA summary of the fault conditions associated with the frames of streams X and Y and the consequent actions arelisted in Table 5/G.762.The transcoder shall detect the following fault conditions associated with streams X and Y:i) loss of incoming signals at 1544 kbit/s;ii) loss of 1544 kbit/s frame alignment;iii) 1544 kbit/s AIS received from remote end;iv) 1544 kbit/s alarm indication received from the rem
