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Chapter 2
Cisco CMTS Configuration Commands
cable upstream ingress-noise-cancellation
To configure how often a line card should train its noise-cancellation circuitry so as to adjust to noise
levels on the upstream, use the cable upstream ingress-noise-cancellation command in cable interface
configuration mode. To disable the ingress noise cancellation feature, use the no form of this command.
Syntax Description
n
interval
Defaults
200 milliseconds
Command Modes
Interface configuration (cable interface only)
Command History
Release
12.2(15)CX
12.2(15)BC2
Usage Guidelines
Broadband Processing Engine (BPE) cable interface line cards, such as the Cisco uBR-MC28U/X cards,
contain advanced hardware-based noise cancellation circuitry that digitally removes in-channel
impairments such as ingress, common path distortion, and certain types of impulse noise. To configure
how often these line cards should train their noise cancellation circuity, so as to adapt to changes in the
noise types and levels, use the cable upstream ingress-noise-cancellation command.
When you enable ingress noise cancellation on an upstream, the Cisco CMTS periodically schedules a
256-symbol idle slot on the upstream channel. The interval option specified in the cable upstream
ingress-noise-cancellation command determines how often this idle slot is generated.
The default for BPE cards is for the card to train its circuitry every 200 milliseconds. The smaller the
triggering interval, the faster the card can adjust to changes in ingress noise, which makes the upstream
more robust to noise problems, but at the cost of decreasing bandwidth on the upstream channel. To
determine the bandwidth cost, in percentage of raw bandwidth, use the following formula:
OL-1581-08
cable upstream n ingress-noise-cancellation interval
no cable upstream n ingress-noise-cancellation
Specifies the upstream port number. Valid values start with 0 for the first
upstream port on the cable interface line card.
Triggering interval, in milliseconds. The valid range is 10 to 3000
milliseconds, with a default value of 200 milliseconds.
Modification
This command was introduced for the Cisco uBR-MC16U/X and
Cisco uBR-MC28U/X cable interface line cards on the Cisco uBR7246VXR
router.
Support was added for the Cisco uBR-MC5X20U cable interface line card
on the Cisco uBR10012 router.
(256/interval)/channel-symbol-rate
cable upstream ingress-noise-cancellation
Cisco Broadband Cable Command Reference Guide
2-321
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