User`s guide

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HITRON CGN USER’S GUIDE

3.1.7 CONFIGURATION FILES

The CGN’s configuration (or config) file is a document that the CGN obtains

automatically over the Internet from the service provider’s server, which specifies the

settings that the CGN 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.

3.1.8 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 CGN, and “upstream” refers to traffic from the CGN to the

service provider.

3.1.9 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.

3.1.10 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