SAGEM 3P@C
Factors Affecting the ADSL transmission quality
Subscriber line attenuation
The attenuation of the ADSL subscriber line is an important factor to affect the ADSL commissioning, relevant to the length of lines. In the condition of the 0.4mm twisted pairs, the test data for the subscriber line attenuation is shown in the table below:
Table
Line |
| Twisted pair |
| Adding 30m house parallel | |
attenuation |
| Downstream | Upstream | Downstream | Upstream |
Length | of | attenuation | attenuation | attenuation | attenuation |
lines |
| (dB) | (dB) | (dB) | (dB) |
1km |
| 22.0 | 16.0 | 24.0 | 16.5 |
2km |
| 40.0 | 28.5 | 44.5 | 30.0 |
3km |
| 56.5 | 40.0 | 58.5 | 41.5 |
4km |
| 63.5 | 51.0 | 65.5 | 51.5 |
The greater the degree of attenuation of the subscriber line is, the lower the connection rate of subscriber line becomes. The subscriber line will exceed the limit for commissioning the ADSL service when it exceeds a certain length and its attenuation becomes extremely high.
The above is the attenuation pair standard determined by the line length. In the same way, the Ministry of Posts and Telecommunications definitely provides the requirements on line attenuation (per kilometer) within different frequency bands, and different core diameters lead to different degrees of attenuation, for details, see the table below:
Table
f0 |
|
|
|
|
|
|
|
(kHz) | 40 | 60 | 80 | 120 | 150 | 300 | 1,024 |
Core diameter | |||||||
attenuation |
|
|
|
|
|
|
|
(dB) |
|
|
|
|
|
|
|
0.32mm | 11.40 | 13.01 | 14.38 | 15.12 | 16.80 | 18.13 | 33.50 |
0.4mm | 8.29 | 9.34 | 10.05 | 10.87 | 12.10 | 14.78 | 27.30 |
0.5mm | 5.99 | 6.85 | 7.06 | 7.77 | 9.00 | 12.18 | 22.50 |
Crosstalk interference
When there are multiple ADSL subscribers in the same cable, or there are HDSL subscribers, ISDN subscribers or the data transmission subscribers in other modes, the crosstalk interface would occur, and the characteristics of the channel will vary along with the number of such subscribers, enabling/disabling status and the changes of transmission rate. Based on the analysis on ADSL, HDSL and ISDN by means of transmission spectrum, the ISDN service can basically ignore the crosstalk interference from the ADSL service due to its low frequency band, and the ADSL equipment using the FDM technology can minimize the affects of crosstalk only against the ADSL line due to its separation of upstream/downstream frequency bands. The
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3P@C Installation Manual
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