1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU%.%2!,G0G0!30%#43G0G0/ amended at Geneva, 1980)The CCITT,considering(a) that various third- and higher-order multiplex equipments exist due to the differing characteristics ofnetworks and signal sources in thos
2、e networks;(b) that, although studies will continue with the aim of reducing the differences between various systems, theexisting situation cannot be changed in the near future;recommends the following(1) when countries using 1544 kbit/s primary multiplex equipments, such as the PCM multiplex equipm
3、entaccording to Recommendation G.733 and second-order multiplex using 6312 kbit/s according to RecommendationsG.743 and G.746, are planning digital paths requiring interconnection at higher bit rates they should, when practical,utilize third-order bit rates of either 32 064 kbit/s or 44 736 kbit/s.
4、When countries using 32 064 kbit/s third-ordermultiplex equipments are planning digital paths requiring interconnection at higher bit rates, they should, when practical,utilize the fourth-order bit rate of 97 728 kbit/s.For Figure 1/G.752 refer to Figure 1/G.702 for the basic multiplex arrangements
5、recommended forAdministrations using 1544 kbit/s primary multiplex equipment. The bit rates of terrestrial systems should accommodatemultiples of 1544 kbit/s. Whenever practical, the bit rate should also accommodate a multiple of 6312 kbit/s, either32 064 or 44 736 kbit/s, and 97 728 kbit/s;(2) the
6、characteristics of the third-order multiplex equipments using positive justification is given in 1,below;(3) the characteristics of the fourth-order multiplex equipments using positive justification is given in 2below.1 Third-order digital multiplex equipment based on second-order bit rate of 6312 k
7、bit/s and using positivejustification1.1 GeneralThe third-order digital multiplex equipment using positive justification described below, is intended for use ondigital paths and between countries using 1544 kbit/s and 6312 kbit/s primary and secondary multiplex equipments.A bit rate of either 32 064
8、 kbit/s or 44 736 kbit/s is recommended to allow for the efficient and economicalcoding of wideband signals in the networks of Administrations using primary systems according to RecommendationsG.733 and G.743. For instance for a 300 voice-circuit mastergroup (Recommendation G.233 1) 32 064 kbit/s is
9、appropriate, while for a 600 voice-circuit mastergroup 44 736 kbit/s coding is appropriate.1.2 Third-order digital multiplex equipment operating at 32 064 kbit/s1.2.1 Bit rateThe nominal bit rate should be 32 064 kbit/s. The tolerance on that rate should be 10 parts per million (ppm).2 Fascicle III.
10、4 - Rec. G.7521.2.2 Frame structureTable 1/G.752 gives:- the tributary bit rate and the number of tributaries;- the number of bits per frame;- the bit numbering scheme;- the bit assignment;- the frame alignment signal.TABLE 1/G.75232 064 kbit/s multiplexing frame structureTributary bit rate (kbit/s)
11、 6312Number of tributaries 5Frame structure Bit numberBits for frame alignment signal (see Note 1)Bits from tributariesCj1(j = 1 to 5) for justification control signal (see Note 2)Bits from tributariesCj2(j = 1 to 5) for justification control signal (see Note 2)Bits from tributariesBits for frame al
12、ignment (see Note 2)Bits from tributariesCj3(j = 1 to 5) for justification control signal (see Note 2)Bits from tributariesAuxiliary bits Hn(n = 1, 2, 3, 4, 5) (see Note 4)Bits from tributariesSet I1 to 56 to 320Set II1 to 56 to 320Set III1 to 56 to 320Set IV1 to 56 to 320Set V1 to 56 to 320Set VI1
13、to 56 to 320Frame lengthBits per tributary (including justification)Maximum justification rate per tributaryNominal justification ratio1 920 bits378 bits16 700 bits0.036Note 1 - The frame alignment signal is a 11010 pattern.Note 2 - Cjnindicates the nth justification control bit of the jth tributary
14、 (j = 1 to 5).Note 3 - The frame alignment signal is a 00101 pattern.Note 4 - H5is used for transmitting failure information from the receive end to the transmit end.Note 5 - The bit available for the justification of each tributary is the first slot of the tributary in set VI.Fascicle III.4 - Rec.
15、G.752 31.2.3 Loss and recovery of frame alignment and consequent actionThe frame alignment recovery time should not exceed 8 ms. The signal to be applied to the tributaries duringthe out-of-frame alignment time should be studied.1.2.4 Multiplexing methodCyclic bit interleaving in the tributary numbe
16、ring order and positive justification is recommended.The justification control signal should be distributed and the Cjn-bits should be used (n = 1, 2, 3, see Table1/G.752).Positive justification should be indicated by the signal 111, no justification by the signal 000. Majority decisionis recommende
17、d.Table 1/G.752 gives the maximum justification rate per tributary and the nominal justification ratio.1.2.5 Jitter1.2.5.1 Specifications at the input portsThe digital signal presented at the input ports shall be as defined in Recommendation G.703 modified by thetransmission characteristic of the in
18、terconnecting cable. The input ports shall be able to tolerate a digital signal withthese electrical characteristics but modified by sinusoidal jitter up to the limits specified by the amplitude frequencyrelationship in Figure 2/G.752. The equivalent binary content of the signal, with jitter modulat
19、ion, applied to the inputsshall be a pseudo-random bit sequence of length 215- 1.Note - The signal with jitter modulation applied to the demultiplexer input shall contain the bits necessary forframing and justification in addition to information bits.Input A1(UI) A2 (UI) f1 (Hz) f2(kHz) f3(kHz) f4 (
20、kHz)6312 kbit/s 1 0.05 60 1.6 32 16032 064 kbit/s(provisional)5 0.05 60 1.6 160 800UI Unit intervalFIGURE 2/G.752Lower limit of maximum tolerable input jitter4 Fascicle III.4 - Rec. G.7521.2.5.2 Multiplex signal output jitterThe jitter at the 32 064 kbit/s output of the multiplexer should not exceed
21、 0.01 UI rms.1.2.5.3 Demultiplexer output jitter with no multiplexer or demultiplexer input jitterThe peak-to-peak jitter at a tributary output of the demultiplexer with no jitter at the inputs should not exceed0.2 UI.1.2.5.4 Demultiplexer jitter transfer characteristicA 6312 kbit/s signal, modulate
22、d by sinusoidal jitter, should be subject to a demultiplexer jitter transfercharacteristic within the gain/frequency limits given in Figure 3/G.752.Note - The frequency f0should be as low as possible taking into account the limitations of measuring equipment.FIGURE 3/G.752Demultiplexer transfer char
23、acteristic1.2.6 Digital interfaceThe digital interfaces at 6312 kbit/s and 32 064 kbit/s should be in accordance with Recommendation G.703.1.2.7 Timing signalIf it is economically feasible, it may be desirable to be able to derive the multiplexer timing signal from anexternal source as well as from
24、an internal source.1.2.8 Service digitsThe service digits are reserved for national use.1.3 Third-order digital multiplex operating at 44 736 kbit/s1.3.1 Bit rateThe nominal bit rate should be 44 736 kbit/s. The tolerance on that rate should be 20 parts per million (ppm).1.3.2 Frame structure (see T
25、able 2/G.752).1.3.3 Loss and recovery of frame and multiframe alignment and consequent actionThe frame alignment recovery time should not exceed 2.5 ms. The signal to be applied to the tributaries duringthe out-of-frame alignment time should be studied. Once frame alignment is established, multifram
26、e alignment should berecovered in less than 250 s.1.3.4 Multiplexing methodCyclic bit interleaving in the tributary numbering order and positive justification is recommended.Fascicle III.4 - Rec. G.752 5The justification control signal should be distributed and the Cjn-bits should be used (n = 1, 2,
27、 3, see Table2/G.752).Positive justification should be indicated by the signal 111, no justification by the signal 000. Majority decisionis recommended.Table 2/G.752 gives the maximum justification rate per tributary and the nominal justification ratio.TABLE 2/G.75244 736-kbit/s multiplexing frame s
28、tructureTributary bit rate (kbit/s) 6312Number of tributaries 7Frame structure (see Note 1) Bit numberBit for multiframe alignment signal (Mj) (see Note 1)Bits from tributaries1st bit for frame alignment signal (F11) (see Note 2)Bits from tributaries1st bit for justification control signal (Cj1)Bits
29、 from tributaries2nd bit for frame alignment signal (F0)Bits from tributaries2nd bit for justification control signal (Cj2)Bits from tributaries3rd bit for frame alignment signal (F0)Bits from tributaries3rd bit for justification control signal (Cj3)Bits from tributaries4th bit frame alignment signa
30、l (F12)Bits from tributaries (see Note 3)Set I12 to 85Set II12 to 85Set III12 to 85Set IV12 to 85Set V12 to 85Set VI12 to 85Set VII12 to 85Set VIII12 to 85Frame lengthMultiframe lengthBits per tribury per multiframe (including justification)Maximum justification rate per tributaryNominal justificati
31、on ratio680 bits4760 bits672 bits9398 bit/s0.390Note 1 - This frame is repeated 7 times to form a multiframe with frames designated j = 1, 2, 3, 4, 5, 6, 7. Themultiframe alignment signal is an XXPP010 pattern where X is a bit assigned to service function, and P isthe parity bit for the preceding mu
32、ltiframe (i.e. from M1to M7). P = 1 if the number of marks in all tributarybits in the preceding multiframe is odd, P = 0 if the number of marks in all tributary bits in the precedingmultiframe is even. Note that the two X bits are identical in any multiframe, as are the two P bits.6 Fascicle III.4
33、- Rec. G.752Note 2 - The frame alignment signal is F0= 0 and F11= F12= 1.Note 3 - The bit available for the justification of tributary j is the first slot of tributary j following F12in thejth frame.1.3.5 Jitter1.3.5.1 Specifications at the input portsThe digital signal presented at the input ports
34、shall be as defined in Recommendation G.703 modified by thetransmission characteristic of the interconnecting cable. The input ports shall be able to tolerate a digital signalwith these electrical characteristics but modified by sinusoidal jitter up to the limits specified by the amplitudefrequency
35、relationship in Figure 4/G.752. The equivalent binary content of the signal, with jitter modulation,applied to the inputs shall be a pseudo-random bit sequence of length 215- 1.Note - The signal with jitter modulation applied to the demultiplexer input shall contain the bitsnecessary for framing and
36、 justification in addition to information bits.Input A1(UI) A2 (UI) f1 (Hz) f2(kHz) f3(kHz) f4 (kHz)6312 kbit/s 2 0.05 10 0.6 24 12044 736 kbit/s 14 0.05 10 3.2 900 4500UI Unit intervalFIGURE 4/G.752Lower limit of maximum tolerable input jitter1.3.5.2 Multiplex signal output jitterThe jitter at the
37、44 736 kbit/s multiplexer output should not exceed 0.01 UI rms.1.3.5.3 Demultiplexer output jitter with no multiplexer or demultiplexer input jitterWith no jitter at the input to the multiplexer and demultiplexer, the jitter at the demultiplexer output should notexceed 1/5 UI peak-to-peak.Fascicle I
38、II.4 - Rec. G.752 71.3.5.4 Demultiplexer jitter transfer characteristicThe gain of the jitter transfer characteristic should not exceed the limits given in Figure 5/G.752.Note - The frequency f0should be as low as possible taking into account the limitations of measuring equipment.FIGURE 5/G.752Demu
39、ltiplexer transfer characteristic1.3.6 Digital interfacesThe digital interfaces at 6312 kbit/s and 44 736 kbit/s should be in accordance with Recommendation G.703.1.3.7 Timing signalIf it is economically feasible, it may be desirable to be able to derive the multiplexer timing signal from anexternal
40、 source as well as from an internal source.1.3.8 Service digitsThe service digits are reserved for national use.2 Fourth-order multiplex equipment operating at 97 728 kbit/s2.1 Bit rateThe nominal bit rate should be 97 728 kbit/s. The tolerance on that rate should be 10 parts per million (ppm).2.2 F
41、rame structureTable 3/G.752 gives:- the tributary bit rate and the number of tributaries;- the number of bits per frame;- the bit numbering scheme;- the bit assignment;- the frame alignment signal.8 Fascicle III.4 - Rec. G.7522.3 Loss and recovery of frame alignment and consequent actionThe mean fra
42、me alignment recovery time should not exceed 1 ms.The signal to be applied to the tributaries during the out-of-frame alignment time should be all1s pattern.2.4 Multiplexing methodCyclic bit interleaving in the tributary numbering order and positive justification is recommended.The justification con
43、trol signal should be distributed and the Cjn-bits should be used (n = 1, 2, 3, seeTable 3/G.752).Positive justification should be indicated by the signal 111, no justification by the signal 000. Majoritydecision is recommended.Table 3/G.752 gives the maximum justification rate per tributary and the
44、 nominal justification ratio.TABLE 3/G.75297 728 kbit/s multiplexing frame structureTributary bit rate (kbit/s) 32 064Number of tributaries 3Frame structure Bit numberFrame alignment signal (110)Bits from tributariesJustification control bits Cj1(see Note 1)Bits from tributariesFor justification con
45、trol bits Cj2 (see Note 1)Bits from tributariesFrame alignment signal (001)Bits from tributariesJustification control bits Cj3 (see Note 1)Bits from tributariesAuxiliary bits Hn(n = 1, 2, 3) (see Note 2)Bits from tributariesSet I1 to 34 to 192Set II1 to 34 to 192Set III1 to 34 to 192Set IV1 to 34 to
46、 192Set V1 to 34 to 92Set VI1 to 34 to 192Frame lengthBits per tributary per frame (including justification)Maximum justification rate per tributeNominal justification ratio1 152 bits378 bits84 833 bits0.035Note 1 - Cjnindicates the nth justification bit of the jth tributary (j = 1, 2, 3).Fascicle I
47、II.4 - Rec. G.752 9Note 2 - This signal is H1H2H3pattern where H1is the parity bit for the preceding frame, and H2is a bit reserved fornational use, and H3is a bit to transmit the failure information from the receiving end to the transmitting end.Note 3 - The bit available for justification of tribu
48、tary j is the first slot of tributary j following Hn.2.5 Jitter2.5.1 Specifications al the input portsThe digital signal presented at the input ports shall be as defined in Recommendation G.703 modified by thetransmission characteristic of the interconnecting cable. The input ports shall be able to
49、tolerate a digital signal withthese electrical characteristics but modified by sinusoidal jitter up to the limits specified by the amplitude frequencyrelationship in Figure 6/G.752. The equivalent binary content of the signal, with jitter modulation, applied to the inputsshall be a pseudo-random bit sequence of length 215- 1.Note - The signal with jitter modulation applied to the demultiplexer input shall contain the bits necessary forframing and justification in addition to information bits.Input A1(UI) A2 (UI) f1 (Hz) f2(kHz) f3(kHz) f4 (kHz)32 064 kbit/s 2 0.2 10 0.8 8 4009
