I.R.I.S. DC1100 - Manual (Page 29)

Coaxial Networks, Inc. Page 29 of 60
Configuring Upstream RF Settings
DOCSIS protocol utilizes a separate upstream frequency to provide upstream data
communication back from the cable modem. Your cable plant has to be two way ready or return
passing to provide high speed data communication over cable. The North American plan uses up
to a 3.2MHz wide channel in the 5-42MHz frequency range. The European plan uses up to a 3.2
MHz wide channel in the 5-65MHz frequency range. For upstream communications DOCSIS
provide QPSK or 16QAM modulation schemes. QPSK modulation profiles are much tolerant to
noise. 16QAM modulation profiles require very clean cable plants and signal to noise ratios.
Figure 16 Upstream RF Settings
Depending upon the IRIS model you have, the Upstream RF Settings screen will have the number
of channels. For a DC1100 the screen will only have Channel 1, for DC1200 the screen will show
Channel 1 and Channel 2.
In the Frequency section for each channel type in the desired upstream center frequency you wish
to use. From the available modulation profiles select the modulation profile you wish to use.
Various modulation profiles for both 16QAM and QPSK are provided in the system.
If your system has more than one upstream channel make sure that there frequency values are
separated by a sufficient buffer or else they will interfere with each other resulting in loss of cable
modems.
After you have made the right selection, click on “Save” and the changes will apply after the
system is restarted.