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Chapter 2
Cisco CMTS Configuration Commands
Usage Guidelines
A modulation profile is a collection of at least six burst profiles that are sent out in an upstream channel
descriptor (UCD) message to configure a modem's transmit parameters.
You can use the no cable modulation-profile command to remove all modulation profiles except the
default modulation profiles (1, 21, 41, 101, 121, 201, 221, and 241, depending on the cable interface line
cards being used). In the case of the default modulation profiles, the no cable modulation-profile
command resets the default profile to its default values.
You cannot delete the default modulation profiles (1, 21, 41, 101, 121, 201, 221, and 241). Using the no
Note
cable modulation-profile command on these particular profiles resets them to their original, default
values.
We recommend that you use the predefined profiles instead of manually specifying the individual bursts
for a modulation profile. The predefined profiles are optimized for the default of 32 symbols per minislot
for each particular modulation scheme. The robust predefined profiles use a longer preamble for better
handling of noise on the upstream, but at the cost of consuming more PHY layer bandwidth than the
other non-robust profiles.
If you want to manually specify the individual bursts, enter a line with all parameters for each upstream
burst type. Then repeat this command for each burst type, which also must be e fully specified. A profile
with incomplete or missing bursts can cause unreliable operation or loss of modem connectivity.
Changes to modulation profiles causes changes to the physical layer. Because changing physical layer
Caution
characteristics affects router performance and function, this task should be reserved for expert users who
have a thorough understanding of DOCSIS systems and how each parameter affects the network.
The reqdata burst type is included as a placeholder for SNMP scripts that might reference it, but it has
Note
no effect. You can use this command (and SNMP commands) to specify the reqdata types, but the
DOCSIS MAC scheduler on the Cisco CMTS does not use this type of burst.
Modulation Profile Ranges
The valid range for modulation profiles depends on the cable interface being used and the type of
modulation profile being created.
modulation type.
Table 2-5
Allowable Ranges for Modulation Profiles
Cable Interface
Cisco uBR7100 series
Cisco uBR-MC16C
Cisco uBR-MC16S
Cisco uBR-MC28C
Cisco uBR-MC5X20S,
Cisco uBR-MC5X20U
Cisco uBR-MC16U/X, Cisco uBR-MC28U/X 41 to 50, default=41
1. Only 8 modulation profiles are supported in Cisco IOS software releases before 12.2(15)BC1, so in these releases the valid range is from 1 to 8.
OL-1581-08
Table 2-5
lists the valid ranges according to cable interface and
DOCSIS 1.X (TDMA)
Mixed DOCSIS 1.X/2.0
1
1 to 10
, default=1
N/A
1 to 10, default=1
N/A
1 to 10, default=1
N/A
1 to 10, default=1
N/A
21 to 30, default=21
121 to 130, default=121 221 to 230, default=221
141 to 150, default=141 241 to 250, default=241
Cisco Broadband Cable Command Reference Guide
cable modulation-profile
DOCSIS 2.0 (A-TDMA)
N/A
N/A
N/A
N/A
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