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cable modulation-profile
You cannot delete the default modulation profiles (1, 21, 41, 101, 121, 201, 221, and 241).
Note
DOCSIS 1.0 and DOCSIS 1.1 Support
For DOCSIS 1.0 and 1.1 cable modems, the following burst types are required: request, request data,
initial maintenance, station maintenance, short grant, and long grant. You must issue this command six
times for each individual burst type to correctly create a new modulation profile.
The three default profiles can be used to quickly create modulation profiles, without having to specify
the parameters for each individual burst: mix, qpsk, and qam-16. The burst parameters for the request,
initial, station maintenance, short, and long bursts are set to their default values for each burst type. (The
reqdata burst type is not created when using the default modulation profiles because it is not used by
the MAC scheduler.)
The default profiles allow basic profiles to be implemented for initial network connectivity. As the
characteristics of a cable plant become better known, the profiles can then be adjusted accordingly.
Note
Do not use the qam-16 mode unless you have verified that your cable plant can support that modulation
profile. Most cable plants should instead use the qpsk or mix modulation profile for the primary profile.
Turning the scrambler off can cause packet loss and is used only in lab testing environments.
Caution
Errors or incompatible configurations in the burst profiles cause CMs to drop connectivity, to drop short
or long data packets, or to fail to connect to the network. It is possible to build a burst profile set for
which no implementation of a DOCSIS receiver is capable of receiving the modem's transmission.
Data rates of 160 Ksymbol/sec and 2560 Ksymbol/sec are highly sensitive to unique word length,
preamble length, and FEC sizing. Incorrect choices for these values can cause poor, or no, connectivity
at these symbol rates.
DOCSIS 2.0 Support
Cisco IOS Release 12.2(11)CY, 12.2(15)BC1, and later releases support 10 modulation profiles for each
of the three DOCSIS modes (DOCSIS 1.X, DOCSIS 2.0, and mixed mode), for a total maximum of 30
modulation profiles. In addition, the router also creates several default modulation profiles (1, 21, 41,
101, 121, 141, 201, 221, and 241, depending on the cable interface line cards that are installed).
The default profiles (1, 21, 41, 101, 121, 141, 201, 221, and 241) cannot be deleted. Using the no cable
Note
modulation-profile command on these particular profiles resets them to their original, default values.
Examples
The following example shows how to create a mixed modulation profile, using 16-QAM for the short
and long grant bursts and QPSK for the request, initial ranging, and station maintenance bursts. The burst
parameters are set to their default values for each burst type.
Router(config)# cable modulation-profile 8 mix
Router(config)# exit
Router# show cable modulation-profile 8
Mod IUC
Cisco Broadband Cable Command Reference Guide
2-172
Type Preamb Diff FEC
length enco T
Chapter 2
FEC
Scrambl Max
Guard Last Scrambl Preamb
CW
seed
B
time
Cisco CMTS Configuration Commands
CW
offset
OL-1581-08
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