Planet Technology VDSL2 VC-200M - Manual (Page 52)

52
Setting Description
Direction To which direction shall the settings apply?
z
Upstream
z
Downstream
Min Date Rate Minimum Payload Date Rate, by factory default is 64 kbps.
Max Date Rate Maximum Payload Date Rate, by factory default is 15000 kbps.
Max Interleave Delay Maximum Interleave Delay, by factory default is 10ms.
z
Click “CANCEL” to exit from this page without saving the changes.
z
Click “APPLY” at any time during configure to save the information that you
have been entered.
4.1.2 Line Configuration
Signal-to-Noise Ratio, often written S/N or SNR, is a measure of signal strength
relative to background noise. The ratio is usually measured in decibels (dB).
If the incoming signal strength in microvolts is V
s
, and the noise level, also in
microvolts, is V
n
, then the signal-to-noise ratio, S/N, in decibels is given by the
formula
S/N = 20 log
10
(V
s
/V
n
)
If V
s
= V
n
, then S/N = 0. In this situation, the signal borders on unreadable, because
the noise level severely competes with it. In digital communications, this will
probably cause a reduction in data speed because of frequent errors that require the
source (transmitting) computer or terminal to resend some packets of data.
Ideally, V
s
is greater than V
n
, so S/N is positive. As an example, suppose that V
s
=
10.0 microvolts and V
n
= 1.00 microvolt. Then
S/N = 20 log
10
(10.0) = 20.0 dB
This results in the signal being clearly readable. If the signal is much weaker but still
above the noise -- say 1.30 microvolts -- then
S/N = 20 log
10
(1.30) = 2.28 dB