Chapter 6 - TV Measuring Range
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6.2.2.2
DOCSIS (downstream)
DOCSIS (Data over Cable Service Interface Specification) is the standard for the transmission of
data in interactive cable networks. DOCSIS includes a downstream and an upstream.
DOCSIS differentiates between US-DOCSIS (transmission in 6 MHz channels) and Euro-DOCSIS
(transmission in 8 MHz channels).
Similarities and differences in the downstream:
US-DOCSIS
EURO-DOCSIS
Modulation type
64QAM, 256QAM
64QAM, 256QAM
Symbol rate
5,057 and 5,361
6,952
FEC
J.83/B
DVB-C
Channel bandwidth
6 MHz
8 MHz
Transmission frequency range
50…862 MHz
112…862 MHz
Differences in the upstream:
US-DOCSIS
EURO-DOCSIS
Transmission frequency range
0…42 MHz
5…65 MHz
As you can see in the comparison, you can use a DVB-C receiver for the reception of a Euro-
DOCSIS downstream signal. It is only necessary to set the symbol rate to 6,952kBd. For US-
DOCSIS, a receiver according to ITU J.83/B is required.
The measuring receiver has a common receiver for both DOCSIS variants.
You can activate the DOCSIS receiver of the measuring instrument via the menu item
MODULATION
->
DOCSIS
.
Figure 6-7 DOCSIS mode
