Guided Frequency Hop

Chapter 4 Troubleshooting the System

Managing Cable Modems on the HFC Network

•Using time scheduled spectrum management, the upstream channel frequency reassignment process is initiated at a configured time of day or week.

With combined blind and time scheduled strategies, blind hop tables are given time-variant configurability. The frequency or subband list can change with time. Blind frequency hop is performed within the spectrum specified to be currently available. An example follows:

uBR(config)# cable spectrum-group 2 time Mon 09:00:00 frequency 10000000 uBR(config)# cable spectrum-group 2 time Tue 09:05:00 delete frequency 10000000 uBR(config)# cable spectrum-group 2 time Tue 09:00:00 frequency 5000000 uBR(config)# cable spectrum-group 4 time Fri 09:00:00 band 15000000 25000000 uBR(config)# cable spectrum-group 4 time Sat 09:00:00 delete band 15000000 25000000

Using guided frequency hop, the upstream channel frequency is reassigned if a threshold number or percentage of cable modems suddenly go offline. You can adjust the thresholds and assign explicit frequencies or frequency subbands and associated input power levels in the unified spectrum group table. The Cisco uBR7200 series locates the defined channel or a suitable channel and moves all cable modems on the upstream port.

The example below shows the Cisco uBR7200 series’ ability to force the CTMS to change the upstream to another frequency before the CMTS sends a message to increase output power levels. You can configure the frequency hop table so that the next entry has the same frequency, but a different power level:

uBR(config)# cable spectrum-group 2 frequency 20000000 uBR(config)# cable spectrum-group 2 frequency 20000000 2 uBR(config)# cable spectrum-group 2 frequency 20000000 -2 uBR(config)# cable spectrum-group 2 frequency 22000000 uBR(config)# cable spectrum-group 2 frequency 22000000 2 uBR(config)# cable spectrum-group 2 frequency 22000000 3

The order of the configuration commands defines the order which frequency or power level is changed. There is always a single allocation set per-spectrum group, listing the currently available bands. In the case of a shared spectrum group, there is also a single free set and “in-use” set since there is a single RF domain. Otherwise, there are free and in-use sets for each upstream port since each upstream port has its own RF domain.

Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

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