user manual

Configuring Headend Broadband Access Router Features
Configuring the Upstream Cable Interface
MC-544
Cisco IOS Multiservice Applications Configuration Guide
• Activating Upstream Differential Encoding
• Activating Upstream Rate Limiting
• Activating Upstream Frequency Adjustment
• Activating Upstream Power Adjustment
• Activating Upstream Timing Adjustment
• Activating the Upstream Ports
• Setting Upstream Backoff Values
Setting the Upstream Frequency
The upstream channel frequency of your RF output must be set to comply with the expected input
frequency of your Cisco cable modem card. To configure upstream channel frequencies, you may
configure a fixed frequency of 5 to 42 MHz and enable the upstream port, or create a global spectrum
group, assign the interface to it, and enable the upstream port.
You can also select a default that does not set a specific fixed value.
Note Some cable systems cannot reliably transport frequencies near the edges of the 5 to 42 MHz
band. The wider the upstream channel (in MHz), the more difficulty you could have. Enter
a center frequency of 20 to 38 MHz if you are having difficulty.
The cable modem card receiver accepts time-division multiplexed burst transmissions from
cable modems that are DOCSIS compliant. The upstream port becomes “up” when it is assigned an
upstream frequency and is configured to be administratively up.
The upstream port is frequency-agile. The frequency can change while the interface is up and carrying
traffic, if you define spectrum groups. See the “Configuring and Activating Frequency Agility” section
later in this chapter for details.
Upstream burst parameters can be configured by defining individual modulation profiles. A modulation
profile consists of a table of physical layer characteristics for the different types of upstream bursts; for
example, initial maintenance, long grant, request/data, request, short grant, and station maintenance.
Note The upstream cable interface will not operate until you either set a fixed upstream
frequency or create and configure a spectrum group. See the “Configuring and Activating
Frequency Agility” later in this chapter for details.
If you are setting a fixed upstream frequency, make sure that the frequency selected does
not interfere with the frequencies used for any other upstream applications running in the
cable plant.
Note If you are using the first version of the MC11 cable modem card, you cannot define an
alternative upstream modulation profile.