Specifications

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Cisco Cable Modem Termination System Feature Guide
0L-1467-02
Chapter 3 Spectrum Management for the Cisco Cable Modem Termination System
Configuration Examples
Step 2 To display modulation profile group information, use the show cable modulation-profile command in
privileged EXEC mode:
Router# show cable modulation-profile [ profile ] [ iuc-code ]
profile—(Optional) Profile number. Valid values are from 1 to 8.
iuc-code—(Optional) Internal usage code.
Valid options are:
– initial—Initial ranging burst
– long—Long grant burst
– request—Request burst
– short—Short grant burst
– station—Station ranging burst
Modulation Profiles Example
In Cisco IOS Release 12.1(3a)EC1 and later, the Cisco CMTS has one preconfigured modulation profile
resident in memory, which defines a typical profile for QPSK modulation. To use the
Dynamic Upstream Modulation feature, a second profile must be created that is unique from the first
profile, and typically provides a higher, more robust modulation scheme.
The following example is a modulation profile for QAM-16, in which the initial, request, and station
maintenance messages are sent as QPSK, and the short and long data packets are sent as QAM-16. The
QAM-16 modulation is more bandwidth-efficient than QPSK, but QPSK is more robust than QAM-16.
Note The upstream request and station maintenance messages use less time on the cable network when
configured in QPSK for symbol rates of 640, 1280, and 2560K symbols/sec. Thus, these messages are
actually more efficient when used in QPSK mode and they ensure a more reliable modem connection.
The upstream initial maintenance message takes exactly the same amount of time on the cable network,
no matter how it is configured. Modems connect more quickly and experience fewer cycles of power
adjustment during initial maintenance if the system is set for QPSK.
Router# configure terminal
Router(config)# cable modulation-profile 2 request 0 16 1 8 qpsk scrambler
152 no-diff 64 fixed uw16
Router(config)# cable modulation-profile 2 initial 5 34 0 48 qpsk scrambler
152 no-diff 128 fixed uw16
Router(config)# cable modulation-profile 2 station 5 34 0 48 qpsk scrambler
152 no-diff 128 fixed uw16
Router(config)# cable modulation-profile 2 short 6 75 6 8 16qam scrambler 152
no-diff 72 fixed uw16
Router(config)# cable modulation-profile 2 long 8 220 0 8 16qam scrambler 152
no-diff 160 fixed uw16
In the following example, all message types are carried with QAM-16 modulation. Although QAM-16
modulation offers a consistent modulation scheme for all five types of messages, the added length of the
QAM-16 preamble offsets the increased bandwidth efficiency of the MAC data message for the station
maintenance messages and bandwidth request messages.
Router# configure terminal
Router(config)# cable modulation-profile 2 request 0 16 1 8 16qam scrambler
152 no-diff 128 fixed uw16