1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOM M UN I CAT I ON STANDARDIZATION SECTOR OF ITU SERIES Q: SWITCHING AND SIGNALLING Digital exchanges - Transmission characteristics Q.553 (1 1/2001) - Transmission characteristics at 4-wire analogue interfaces of digital exchanges ITU-T Recommendatio
2、n Q.553 ITU-T Q-SERES RECOMMENDATIONS SWITCHING AND SIGNALLING SIGNALLING IN THE INTERNATIONAL MANUAL SERVICE INTERNATIONAL AUTOMATIC AND SEMI-AUTOMATIC WORKING FUNCTIONS AND INFORMATION FLOWS FOR SERVICES IN THE ISDN SPECIFICATIONS OF SIGNALLING SYSTEMS No. 4 AND No. 5 SPECIFICATIONS OF SIGNALLING
3、SYSTEM No. 6 SPECIFICATIONS OF SIGNALLING SYSTEM R1 SPECIFICATIONS OF SIGNALLING SYSTEM R2 DIGITAL EXCHANGES CLAUSES APPLICABLE TO ITU-T STANDARD SYSTEMS Introduction and field of application Exchange interfaces, functions and connections Design objectives and measurement Transmission characteristic
4、s INTERWORKING OF SIGNALLING SYSTEMS SPECIFICATIONS OF SIGNALLING SYSTEM No. 7 Q3 INTERFACE DIGITAL SUBSCRIBER SIGNALLING SYSTEM No. 1 PUBLIC LAND MOBILE NETWORK INTERWORKING WITH SATELLITE MOBILE SYSTEMS INTELLIGENT NETWORK SPECIFICATIONS OF SIGNALLING RELATED TO BEARER INDEPENDENT CALL CONTROL (BI
5、CC) SIGNALLING REQUIREMENTS AND PROTOCOLS FOR IMT-2000 Q. 1-4.3 Q.4Q.59 Q.60-Q.99 Q. 126-4.249 Q.250-Q.309 Q ,400-Q .499 Q.500-Q.599 Q.500-Q.509 Q. 100-Q. 1 19 Q.3 10-Q.399 Q.5 10-4.539 4.540-4.549 4.550-4.599 Q. 60 - input and output connections with 4-wire analogue interfaces; and - half connectio
6、ns with 4-wire analogue interfaces in digital transit and combined local and transit exchanges, in accordance with the definitions given in ITU-T Rec. Q.551, particularly in Figures UQ.551 and 214.551. The characteristics of the input and output connections of a given interface are not necessarily t
7、he same. The characteristics of half connections are not necessarily identical for different types of interfaces. This Recommendation is intended for switched connections that may be part of an international long-distance connection via 4-wire line circuits interconnected by 4-wire exchanges. Since
8、4-wire analogue interfaces of digital exchanges may connect with circuits which are used for both international and national traffic, the same values recommended for international connections may also be used for connections entirely within the national network. 2 Characteristics of interfaces 2.1 C
9、haracteristics common to all 4-wire analogue interfaces 2.1.1 Exchange impedance 2.1.1.1 Nominal value The nominal impedance at the analogue input and output interfaces should be 600 ohms, balanced. 2.1.1.2 Return loss The return loss at the equipment ports, measured against the nominal impedance, s
10、hould not be less than 20 dE3 over the frequency range 300 Hz to 3400 Hz. NOTE - For output measurement, the exchange test point Ti must be driven by a PCM signal corresponding to the decoder output value number O for the plaw or decoder output value number 1 for the A-law. (See 1.2.3.1/Q.551.) 2.1.
11、2 Impedance unbalance about earth The value for the Longitudinal Conversion Loss (LCL) at the equipment ports as defined in 4.1.3/G.117, with the circuit under test in the normal talking state, should exceed the minimum values of Figure 1, in accordance with ITU-T Rec. K. 1 O. NOTE 1 -A network oper
12、ator may adopt other values and, in some cases, a wider bandwidth, depending upon actual conditions in its telephone network. NOTE 2 - A limit may also be required for the Transverse Conversion Loss (TCL) as defined in 4.1.2/G. 1 17, if the exchange termination is not reciprocal with respect to the
13、transverse and longitudinal connections. A suitable limit would be 40 dB to ensure an adequate near-end crosstalk attenuation between interfaces. ITU-T Rec. 4.553 (11/2001) 1 Figure UQ.553 - Minimum values of LCL measured in the arrangement shown in Figure 2 Test method LCL should be measured in acc
14、ordance with the principles given in 4.V0.9. Figure 2 shows the basic measuring arrangement. Arrangements containing two resistors each of value R/2 may also be used (see clause Y0.9). Measurements of the longitudinal and transverse voltages should be performed by means of a frequency-selective leve
15、l meter. ! Item under test ! i ! ,“.“., Sinusoidal oscillator I i i ! , -i+- ! iTI ill i ii i i i ._._._.-._.-._. -.-.-J T151-94 R = 600 ohms Longitudinal convertion loss (LCL) = 2010g, Figure 2/Q.553 - Arrangement for measuring LCL 2.1.3 Relative levels In assigning the relative levels to the inter
16、faces, the limiting of “difference in transmission loss between the two directions of transmission“ in Annex NG. 12 1 has been taken into account. For the national extension, this is the value “loss (t-b)-loss (a-t)“. (See the text in the cited 2 ITU-T Rec. Q.553 (11/2001) Recommendation for guidanc
17、e.) This difference is limited to +_4 dB. However, to allow for additional asymmetry of loss in the rest of the national network, only part of this difference can be used by the digital exchange. 2.1.3.1 Nominal levels The nominal relative levels at the analogue input and output interfaces of the di
18、gital exchange depend on the type of equipment which is connected to the exchange. (See Figure UQ.55 1 .) In practice, it may be necessary to compensate for the loss between the output interfaces of the digital exchange and the input ports of the connected equipment to fulfil transmission plan condi
19、tions. The definition of adjustable steps for and the location of this compensation (digital exchange or connected equipment) is within national competence. Nominal values of relative levels are given in 2.2.1, 2.3.1 and 2.4.1 for the different types of half connections. 2.1.3.2 Tolerances of relati
20、ve levels The difference between the actual relative level and the nominal relative level should lie within the following ranges: - input relative level: -0.3 to M.7 dE3; - output relative level: -0.7 to M.3 a. These differences may arise, for example, from design tolerances, cabling (between analog
21、ue equipment ports and the DF) and adjustment increments. NOTE - Adjustment of the relative level should be made in accordance with clause 3/G.712. 2.2 Characteristics of interface Cl1 According to Figure lIQ.55 1, the interface Cl1 of a digital exchange is intended to interwork with the channel tra
22、nslating equipment of an FDM system. 2.2.1 Values of nominal levels The nominal values of relative levels at the channel translating equipment are specified in Table 2/G.232 for the two recommended cases. With the pads in the channel translating equipment set to zero, these values are: I I I I 1 1 +
23、4.OdBr I -+7.OdBr - 14.0 dBr - 16.0 dBr The nominal values of relative levels at the digital exchange must be adjusted to compensate for the total loss between the interface of the digital exchange and the channel translating equipment. Therefore: Li = R - AR where: AR is the total loss in the recei
24、ve path, e.g. direction of trammission from channel translating equipment to digital exchange. ITU-T Rec. Q.553 (11/2001) 3 AS is the total loss in the send path, e.g. direction of transmission from digital exchange to channel translating equipment. 2.3 Characteristics of interface C12 According to
25、Figure UQ.551, the interface Ci2 of a digital exchange is intended to intenvork with the incoming and outgoing relay set of an analogue 4-wire exchange. (See Figure UQ.45 bis.) 2.3.1 Values of nominal levels The nominal values of relative levels at the relay set of an analogue exchange are consisten
26、t with Table 2G.232 for the two recommended cases. These values are: l I I I I I R I -14.0dBr I -16.0dBr I S I +4.0dBr I +7.0dBr I The nominal values of relative levels at the digital exchange must be adjusted to compensate for the total loss between the interface of the digital exchange and the rel
27、ay sets of the analogue exchange. Therefore: Li=R-AR Lo =Si- As where: AR AS is the total loss in the receive path, e.g. direction of transmission from relay set to digital exchange. is the total loss in the send path, e.g. direction of transmission from digital exchange to relay set. 2.4 Characteri
28、stics of interface Cl3 According to Figure UQ.551, the interfice Ci3 of a digital exchange is intended to connect to a 4-wire analogue switching stage. (See Figure 1/G. 142, case 5.) 2.4.1 Values of nominal levels The nominal values of relative levels are determined by the relative levels of the ana
29、logue 4-wire switching stages in the national transmission plans. For example, if these relative levels are -3.5 dBr in both directions of transmission, the nominal input and output levels of a Ci3 interface should be: Li Lo 3.5 dBr Different levels at the switching stages and transmission loss betw
30、een interface Ci3 and the switching stages can require adjusting these levels. 4 ITU-T Rec. 4.553 (11/2001) 3 3.1 3.1.1 3.1.1.1 Characteristics of half connections Characteristics common to all 4-wire analogue interfaces Transmission loss Nominal value The nominal transmission loss, according to 1.2
31、.4.UQ.551 is defined for input and output connections of a half connection with 4-wire analogue interface in 3.2.1,3.3.1 and 3.4.1. 3.1.1.2 Tolerances of transmission loss The difference between the actual transmission loss and the nominal transmission loss of an input or output connection of the sa
32、me half connection according to 2.1.3.2 should lie within the following values: - 0.3 to + 0.7 dB These differences may arise for example, from design tolerances, cabling (between analogue equipment ports and the DF) or adjustment increments. 3.1.1.3 When a sine-wave test signal at the reference fre
33、quency of 1020 Hz and at a level of -10 dE3mO (if preferred, the value OdBmO may be used) is applied to an analogue interface of any input connection, or a digitally simulated sine-wave signal of the same characteristics is applied to the exchange test point Ti of any output connection, the level at
34、 the corresponding exchange test point To and the level at the analogue interface of the output connection respectively, should not vary by more than f 0.2 dE3 during any 10-minute interval of typical operation under the steady state condition permitted variations in the power supply voltage and tem
35、perature. 3.1.1.4 With a sine-wave test signal at the reference frequency of 1020 Hz and at a level between -55 dBm0 and + 3 the other component to -(67 + 3) dBmOp = - 70 dBmOp for one 4-wire analogue interface including circuit noise in accordance with clause 3/G.123. This results in the maximum va
36、lues for the overall weighted noise in the talking state at the Ci-interface of a digital exchange: - Equipment with signalling on separate wires: input connection: 457.0 dBmOp; output connection: -70.0 dBmOp. Equipment with signalling on the speech wires: input connection: -65.2 dBmOp; output conne
37、ction: 47.0 dBmOp. - 3.1.3.2 Singie frequency noise The level of any single frequency (in particular the sampling frequency and its multiples), measured selectively at the interface of an output connection should not exceed -50 a low level activating signal. A suitable activating signal is, for exam
38、ple, a sine-wave signal at a level in the range from -33 to -40 dBm0. Care must be taken in the choice of frequency 8 RU-T Rec. 4.553 (11/2001) and the filtering characteristics of the measuring apparatus in order that the activating signal does not significantly affect the accuracy of the crosstalk
39、 measurement. 3.1.4.1 Crosstalk measured with analogue test signal 3.1.4.1.1 Far-end and near-end crosstalk A sine-wave test signal at the reference frequency of 1020 Hz and at a level of O dBm0, applied to an analogue input interface, should not produce a level exceeding -73 dBm0 for Near-End Cross
40、talk (NEXT) or -73 dBm0 for Far-End Crosstalk (FEXT), at the output of any other half connection. (See Figure 6.) Digital ! Analogue ,.-.-.-.-.-.-.-.-.-.- Figure 6/Q.553 - Measurement with analogue test signal between different input connections of half connections 3.1.4.1.2 Go-to-return crosstalk A
41、 sine-wave test signal at any frequency in the range 300 to 3400 Hz and at a level of O dBm0, applied to the analogue interface of an input connection, should not produce a level exceeding -66 dBm0 at the analogue output of the same half connection. See Figure 7. Analogue Digital ! I *-*- r-.-.-.-.-
42、.-. i L 1 Test signal i i i i i i i T151574094 crosstalk i Figure 7/Q.553 - Measurement with analogue test signals between go and return directions of the same half connection ITU-T Rec. 4.553 (11/2001) 9 3.1.4.2 3.1.4.2.1 Far-end and near-end crosstalk A digitally simulated sine-wave test signal at
43、 the reference frequency of 1020 Hz and at a level of O dBmO, applied to an exchange test point Ti, should not produce a level exceeding -70 dBmO for Near-End Crosstalk (NEXT) or -73 dBmO for Far-End Crosstalk (FEXT), at the output of any other half connection. (See Figure 8.) Crosstalk measured wit
44、h digital test signal Analogue Digital I -i- +- - -0 NEXT Figure WQ.553 - Measurement with digital test signal between different output connections of half connections 3.1.4.2.2 Go-to-return crosstalk A digitally simulated sine-wave test signal, at any frequency in the range 300 to 3400 Hz and at a
45、level of O dBm0, applied to an exchange test point Ti of an output connection, should not produce a crosstalk level exceeding 46 dBm0 at the exchange test point To of the same half connection (See Figure 9.) i i - I .- y i Go-to-rem crosstalk i i i( i i i Figure 9/Q.553 - Measurement with digital te
46、st signals between go and return directions of the same half connection 3.1.5 With a sine-wave test signal at the reference frequency of 1020 Hz (see ITU-T Rec. 0.132) applied to the analogue interface of an input connection, or with a digitally simulated sine-wave signal of the same characteristic
47、applied to the exchange test point Ti of an output connection, the signal-to-total distortion ratio, measured at the respective outputs of the half connection with a proper noise Total distortion including quantizing distortion 10 ITU-T Rec. 4.553 (11/2001) weighting (see Table 4/G.223) should lie a
48、bove the limits shown in Figure 10 for signalling on separate wires and in Figure 11 for signalling on the speech wires. .e OdB 3 35.0 33.8 2 26.5 21.5 4 3 Q 9 .e B 7d v1 0- 45 4 -30 input level Figure 10/Q.553 - Limits for signal-to-distortion ratio as a function of input level for input or output
49、connection with signalling on separate wires 45 4 -30 -20 -10 O Brno input levei T151578094 Figure 1VQ.553 - Limits for signal-to-total distortion ratio as a function of input level for input or output connection with signalling on the speech wires The values of Figure 1 1 include the limits for the coding process given in Figure 12/G.712 and the allowance for the noise contributed via signalling circuits from the exchange power supply and other analogue sources which is limited to 467 + 3) dBmOp = -7OdBmOp for one 4-wire analogue interface by clause 3/G. 123. 3.
