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HITRON CGNV2 USER’S GUIDE
CABLE
When the CGNV2 is not in routing mode, the service provider assigns an IP address
to each computer connected to the CGNV2 directly. The CGNV2 does not perform
any routing operations, and traffic flows between the computers and the service
provider.
Routing mode is not user-configurable; it is specified by the service provider in the
CGNV2’s configuration file.
2.1.8
CONFIGURATION FILES
The CGNV2’s configuration (or config) file is a document that the CGNV2 obtains
automatically over the Internet from the service provider’s server, which specifies the
settings that the CGNV2 should use. It contains a variety of settings that are not
present in the user-configurable Graphical User Interface (GUI) and can be specified
only by the service provider.
2.1.9
DOWNSTREAM AND UPSTREAM TRANSMISSIONS
The terms “downstream” and “upstream” refer to data traffic flows, and indicate the
direction in which the traffic is traveling. “Downstream” refers to traffic from the
service provider to the CGNV2, and “upstream” refers to traffic from the CGNV2 to
the service provider.
2.1.10
CABLE FREQUENCIES
Just like radio transmissions, data transmissions over the cable network must exist
on different frequencies in order to avoid interference between signals.
The data traffic band is separate from the TV band, and each data channel is
separate from other data channels.
2.1.11
MODULATION
Transmissions over the cable network are based on a strong, high frequency periodic
waveform known as the “carrier wave.” This carrier wave is so called because it
“carries” the data signal. The data signal itself is defined by variations in the carrier
wave. The process of varying the carrier wave (in order to carry data signal
information) is known as “modulation.” The data signal is thus known as the
“modulating signal.”
Cable transmissions use a variety of methods to perform modulation (and the
“decoding” of the received signal, or “demodulation”). The modulation methods
defined in DOCSIS 3 are as follows:
QPSK
: Quadrature Phase-Shift Keying
QAM
: Quadrature Amplitude Modulation
QAM TCM
: Trellis modulated Quadrature Amplitude Modulation
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