Setting the Upstream Frequency, MC-544

Configuring Headend Broadband Access Router Features

Configuring the Upstream Cable Interface

•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

Note

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.

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.

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.

If you are using the first version of the MC11 cable modem card, you cannot define an alternative upstream modulation profile.

Cisco IOS Multiservice Applications Configuration Guide