Cisco Systems UBR10012 Setting the Upstream Frequency

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Cisco uBR10012 Universal Broadband Router Software Configuration Guide

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Chapter3 Configuring Cable Interface Features for the CiscouBR10012Router

Configuring the Upstream Cable Interface

To verify the current value of the upstream channel width, enter the show controllers cable command

for the upstream port you just configured. A sample follows below:

Router# show controllers cable5/0/0 u0

Cable5/0/0 Upstream 0 is up

Frequency 24.016 MHz, Channel Width 0.800 MHz, QPSK Symbol Rate 0.640 Msps

Spectrum Group is overridden

SNR 33.2560 dB

Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288

Ranging Backoff automatic (Start 0, End 3)

Ranging Insertion Interval automatic (60 ms)

Tx Backoff Start 0, Tx Backoff End 4

Modulation Profile Group 1

Perform these steps if you are having difficulty with verification:

Step1 Use a valid combination of modulation format (QPSK and QAM-16), minislot size, frequency, and the

noshutdown command.

Step2 Use a recommended or previously tested modulation profile. It is not uncommon to create a modulation

profile that does not allow cableinterface-to-headend communication. Because each message type is

individually specified, some messages might not work.

Step3 Verify using IP ping packets of varying lengths (64 to 1500 bytes). Ping from the headend to the

cableinterface.

Step4 Verify with your cableinterface vendor that your CM software is fully certified or compatible with

DOCSIS1.0 and extensions, as appropriate.

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 interface line card. To configure upstream channel frequencies, perform

one of the following tasks:

•Configure a fixed frequency from 5 to 42MHz for NTSC operations, then enable the upstream port.

•Create a global spectrum group, assign the interface to it, and enable the upstream port.

Note You can also select a default that does not set a specific fixed value.

Note The upstream port is frequency agile. If you define spectrum groups, the frequency can change while the

interface is up and carrying traffic.

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 does not operate until you either set a fixed upstream frequency or

create and configure a spectrum group.

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 on the cable plant.