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7.Proposed additions and revisions to Recommendation M.1020
CHARACTERISTICS OF SPECIAL QUALITY LEASED CIRCUITS
WITH SPECIAL BANDWIDTH CONDITION
2.1 Reword 2.8 as follows:
"2.8 Total distortion (including quantizing distortion)
On a mixed analogue/digital circuit the signal will be accompanied by
quantizing distortion. An end-to-end distortion measurement made using an
instrument conforming to Recommendation O.132 [5] will include contributions from
random circuit noise, single tone interference and harmonic distortion. The
level of random noise power at the renter's premises depends upon the length of
frequency division multiplex carrier systems in the circuit. The level of
quantizing distortion power depends on the number of unintegrated digital processes in
the circuit.
The signal to total distortion ratio should be better than 28 dB using
a sine-wave signal at -10 dBmO (see also Annex A to this Recommendation)."
2.2 Change the title of 2.11 to:
"2.11 Harmonic and intermodulation distortion"
Add a second alinea to 2.11 as follows:
"The limit of second and third order intermodulation products measured
using an instrument complying with Recommendation O.42 is
for further study."
2.3 Amend the annex to Recommendation M.1020 as follows:
Renumber the title to read:
"A.1 Random circuit noise"
Amend the first sentence as follows:
"Figure A-1/M.1020 displays random noise versus length of FDM carrier
systems and is presented as a guide to the random noise
performance which may be found on an international leased
circuit."
The axis of the graph in Figure A-1/M.1020 which is labelled "circuit
length" should be changed to "Length of FDM carrier systems".
The note to the figure should be amended to read:
"Note - At the present time the section of the circuit provided by a satellite
(between earth stations) employing FDM techniques contributes approximately
10 000 pWOp (-50 dBmOp) of noise. Therefore, for the purpose of determining
maintenance limits for noise measurements on leased circuits, the length of this
section may be considered to be equivalent to 1,000 km in Figure A-1/M.1020."
The contribution to noise of a circuit section provided by a satellite
employing TDM techniques remains as a subject for further study.
Add new section A.2 as follows:
"A.2 Total distortion
Table A-1/M.1020 is a guide to the signal-to-total distortion ratio
which may be found on circuits with different analogue section lengths and numbers
of quantizing distortion units (QDU). When interpreting this table,
particularly for circuits with long analogue sections, it should be noted that it may be
possible to increase the number of QDUs in a circuit provided the analogue
sections contribute less noise than might be expected from
Figure A-1/M.1020."
Add the following new Table A-1/M.1020 to the annex of
Recommendation M.1020:
TABLE A-1/M.1020
Signal to total distortion ratio using a sinusoidal signal at -10 dBmO
┌────────────────────────────────────────────┬─────────────────────────────────────────────────────────────┐
│ │ Distance in analogue transmission │
├────────────────────┬────────────────┬──────┼────────┬────────┬────────┬───────┬────────┬────────┬────────┤
│ │ │ │ │ 321 │ 641 │ 1,601 │ 2,501 │ 5,001 │ 10,001 │
│ │ Number of QDUs │ │ < 320 │ to │ to │ to │ to │ to │ to │
│ Type of circuit │ (Note 1) │ Unit │ km │ 640 │ 1,600 │ 2,500 │ 5,000 │ 10,000 │ 20,000 │
│ │ │ │ │ km │ km │ km │ km │ km │ km │
├────────────────────┼────────────────┼──────┼────────┼────────┼────────┼───────┼────────┼────────┼────────┤
│ Analogue │ 0 │ dB │ 43 │ 41 │ 38 │ 36 │ 33 │ 30 │ 28 │
├────────────────────┼────────────────┼──────┼────────┼────────┼────────┼───────┼────────┼────────┼────────┤
│ │ 1 │ dB │ 34 │ 34 │ 33 │ 32 │ 31 │ 29 │ 28 │
│ ├────────────────┼──────┼────────┼────────┼────────┼───────┼────────┼────────┼────────┤
│ │ 2 │ dB │ 32 │ 31 │ 31 │ 31 │ 29 │ 28 │ 28 │
│ ├────────────────┼──────┼────────┼────────┼────────┼───────┼────────┼────────┼────────┤
│ Composite circuit │ 3 │ dB │ 30 │ 30 │ 30 │ 9 │ 28 │ 28 │ 28 │
│ ├────────────────┼──────┼────────┼────────┼────────┼───────┼────────┼────────┼────────┤
│ │ 4 │ dB │ 29 │ 29 │ 28 │ 8 │ 28 │ 28 │ 28 │
│ ├────────────────┼──────┼────────┼────────┼────────┼───────┼────────┼────────┼────────┤
│ │ 5 │ dB │ 28 │ 28 │ 28 │ 8 │ 28 │ 28 │ 28 │
└────────────────────┴────────────────┴──────┴────────┴────────┴────────┴───────┴────────┴────────┴────────┘
Note 1 - The number of QDUs contributed by various digital processes are given in Table 1 of
Recommendation G.113 [7].