1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 6 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU$!4!G0G0#/-5.)#!4)/.G0G0/6%2G0G04(%G0G04%,%0(/.%.%47/2+#/-0!2!4)6%G0G04%343G0G0/ amended at Geneva, 1976 and 1980,Malaga-Torremolinos, 1984 and at Melbourne, 1988)To facilitate the work of Administrations in
2、making comparative tests of modems for use over telephone-typecircuits offered by different manufacturers, it is recommended that the tests should be made in the laboratory under thefollowing operating conditions:1 List of test parameters (see Table 1/V.56)TABLE 1/V.56Test parametersRef. No. Paramet
3、er Four-wireTwo-wire switchednetworkpoint-to-pointSerialmodemsParallelmodems12345678910111213Total attenuation or receiving signal levelAttenuation distortionEnvelope or group delay distorsionFrequency shift (or offset)Sudden changes of attenuationInterruptionsPhase hitsPhase jitterHarmonic distorti
4、onListener echo“White“ noiseImplusive noiseSingle tone interferenceXXXXXXXXXXXXXXXXXXXXXXXXX2 Block diagram for standard test measuring set-upIt is proposed that comparative tests be made using either all or parts of the measuring set-up shown inFigure 1 /V.56.2 Fascicle VIII.1 - Rec. V.563 Test par
5、ameters3.1 Parameters of the line characteristics simulator3.1.1 Symmetric line distortionSee Tables 2/V.56 and 3/V.56. The tolerances for all values are 5%.3.1.2 Asymmetric line distortionSee Tables 4/V.56 and 5/V.56. The tolerances for all values are 5%.3.1.3 Ripple distortionThe ripple distortion
6、 is within the tolerance scheme of Recommendation M.1020 1. See Tables 6/V.56 and7/V.56. The tolerances for all values are 5% 0.1 ms.TABLE 2/V.56Frequency(Hz)Attenuation distortion (dB)Mode 1(see Note 1)Mode 2(see Note 2)Mode 3(see Note 5)300500800 16002500280030006310Unspecified361282 a)08Unspecifi
7、ed12K1b)0.35 K1000.2 K10.3 K10.4 K1a)To be clarified.b)K1is a multiplier with values 1, 2, 3, 4, 5, 6 and 7.Fascicle VIII.1 - Rec. V.56 3TABLE 3/V.56Frequency(Hz)Attenuation distortion (dB)Mode 1(see Note 1)Mode 2(see Note 2)Mode 3(see Note 5)5006001000 1800260028002900300031.50.500.53UnspecifiedUns
8、pecified4.531.501.534Unspecified1.20 K1a)1.90 K10.32 K100.12 K10.23 K10.31 K10.40 K1a)K1is a multiplier with values 1, 2, 3, 4, 5, 6 and 7.TABLE 4/V.56Frequency(Hz)Attenuation distortion (dB)Mode 1(see Note 1)Mode 2(see Note 2)Mode 3(see Note 5)800200025002800300000.75Unspecified360Unspecified8Unspe
9、cified120Unspecified8 K2a)Unspecified12 K2a)K2is a multiplier with values 0.4, 0.8, 1.2 and 1.6.TABLE 5/V.56Frequency(Hz)Group-delay distortion (ms)Mode 1(see Note 1)Mode 2(see Note 2)Mode 3(see Note 5)500190026002800290030000Unspecified0.53UnspecifiedUnspecified0Unspecified1.534Unspecified00.075 K3
10、a)Unspecified0.225 K3Unspecified0.30 K3a)K3is a multiplier with values 0.5, 1, 2, 4 and 8. All values of Mode 3 are provisional.4 Fascicle VIII.1 - Rec. V.56TABLE 6/V.56FrequencyGroup-delay distortion(ms)(Hz)Mode 15006001000140018002200260028002.01.30 (see Note 3)0.5 (see Note 4)0 (see Note 3)0.5 (s
11、ee Note 4)0.3 (see Note 3)2.0TABLE 7/V.56FrequencyGroup-delay distortion(ms)(Hz)Mode 250060080010001200140016001800200022002400260028002.00,80.8 (see Note 4)0 (see Note 3)0.5 (see Note 4)0 (see Note 3)0.5 (see Note 4)0 (see Note 3)0.5 (see Note 4)0 (see Note 3)0.5 (see Note 4)0.3 (see Note 3)2.0Note
12、s to Tables 2/V.56 to 7/V.56Note 1 - Mode 1 is in conformity with Recommendation M.1020 1.Note 2 - Mode 2 is in conformity with Recommendation M.1025 2.Note 3 - Ripple valley values (minima).Note 4 - Ripple peak values (maxima).Note 5 - Mode 3 is in conformity with the relevant European specificatio
13、ns.3.2 Parameters of the fault simulatora) Phase hits: with external control of timing (e.g. 0.25; 1; 100 Hz) adjustable continuously or in steps up to165 degrees.Fascicle VIII.1 - Rec. V.56 5b) Frequency shifts e.g. 5 Hz, 6 Hz or 10 Hz by means of channel converters.c) Peak-to-peak phase jitter fro
14、m 0.2 degree to 30 degrees continuously from 50 to 300 Hz, sinusoidalwaveform.d) Sudden changes of attenuation: with external control of timing (e.g. 0.1; 0.25; 1; 100 Hz) adjustablecontinuously or in steps up to total attenuation.e) Interruptions: with fixed duration of 1 ms and repetition period o
15、f 1s and/or with single interruptionswith variable duration.3.3 Noise sources (this subject needs further study)a) White noise.b) Impulsive noise: with adjustable level and adjustable pulse duration between 100 s and 1 ms and withrepetition period of 1 second.c) Statistically distributed noise by re
16、cording or by simulation which is information to assist instandardizing a “Random noise simulator“ which would encourage the utilization of block error counts.d) Single tone interference: with adjustable level of an additional signal frequency, variable between 300and 3100 Hz.e) Harmonic distortion:
17、i) using a calibrating signal frequency of 700 Hz with the same r.m.s. level as the data signal and withits adjustable harmonic levels: aH2, aH3and aH4, andii) using a calibrating signal frequency of 700 Hz with the same peak-to-peak level as the data signaland with its adjustable harmonic levels: a
18、H2, aH3, and aH4.3.4 Listener echoListener echo: with the variable echo attenuation between 0 and 20 dB and variable echo time delay Ebetween 0 and 20 ms (worst case relevant).4 Measuring procedure4.1 Measurement of the bit error rate (pS) as a function of the signal-to-noise ratio (S/N) in the case
19、 of whitenoiseThe receiving level at the summation point should be -30 dBm for switched line comparisons and -20 dBm forleased line comparisons.For a comparison, the value of S/N ratio at defined pSvalues can be ascertained (e.g. 3 10-4or 10-5).4.2 Measurement of the number of the bit error per seco
20、nd (F/t) as a function of the different faults and noiseparameters (X)The receiving level at the summation point should be -30 dBm for switched line comparisons and -20 dBm forleased line comparisons.For a comparison, the value of F/t for different defined fault and noise parameters, or the value of
21、 the6 Fascicle VIII.1 - Rec. V.56different parameters at the limit of the error-free region, can be ascertained.Fascicle VIII.1 - Rec. V.56 75 Comparative tests of modems (Table 8/V.56)TABLE 8/V.56Eighteen selected tests according to 1, 2, 3 and 4Test Test parameter accordingto Table 1/V.56Test para
22、metersaccording to Measuring procedureaccording to A 11 3.3a) 4.1B 2, 3, 11 3.1.1 mode 1, 3.3a) 4.1C 2, 3, 11 3.1.1 mode 2, 3.3a) 4.1D 2, 3, 11 3.1.2 mode 1, 3.3a) 4.1E 2, 3, 11 3.1.2 mode 2, 3.3a) 4.1F 2, 3, 4, 11 3.1.1 mode 1, 3.2b) ( 6 Hz),3.3.a)4.1G 2, 3, 4, 11 3.1.1 mode 2, 3.2b) ( 10 Hz),3.3.a
23、)4.1H 2, 3, 7 3.1.1 mode 1, 3.2a) 4.2J 2, 3, 7 3.1.1 mode 1, 3.2a) 4.2K 8 3.2c) 4.2L 2, 3, 5 3.1.1 mode 1, 3.2d) 4.2M 2, 3, 5 3.1.1 mode 2, 3.2d) 4.2N 6 3.2e) 4.2P 12 3.3b) 4.2R 13 3.3d) 4.2S 9 3.3 c) ii) 4.1T 10, 11 3.4, 3.3a) 4.1U Statistic noise 3.3c) 4.1 (for block errors)References1 CCITT Recommendation Characteristics of special quality international leased circuits with specialbandwidth conditioning, Vol. IV, Rec. M.1020.2 CCITT Recommendation Characteristics of special quality international leased circuits with basic bandwidthconditioning, Vol. IV, Rec. M.1025.
