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Chapter 2
Cisco CMTS Configuration Commands
Table 2-13 Allowable DOCSIS Power Levels
Symbol Rate (Symbols per
second)
2,560,000
5,120,000
1. The 5.12 MSymbols/sec symbol rate and 6.4 MHz channel width are supported only on upstreams that are configured for
You can use inline attenuators to force CMs to transmit at higher power levels and to achieve a higher
Tip
CNR value on the network.
Caution
If you increase the input power level or add inline attenuators before the CMTS, the CMs on your HFC
network increase their transmit power level. Be careful if you adjust this parameter. You might violate
the upstream return laser design parameters or exceed the CM's maximum transmit power level.
Do not adjust your input power level by more than 5 dB in a 30-second interval. If you increase the
Note
power level by more than 5 dB within 30 seconds, you will disrupt CM service on your network. If you
decrease the power level by more than 5 dB within 30 seconds, the CMs on your network will be forced
to re-range.
When setting upstream power levels, Cisco recommends that the adjacent channels of equal bandwidth
Tip
not have a large variation. The recommended maximum input power variance is 5 to 6 dB.
Examples
The following example shows how to set the input power level for upstream port 0 to -5 dBmV:
Router(config)# interface cable 5/1/0
Router(config-if)# cable upstream 0 power-level -5
Router(config-if)#
Related Commands
Command
cable upstream fec
cable upstream frequency
cable upstream power-adjust
cable upstream shutdown
OL-1581-08
Channel Width (Hz)
3,200,000
1
6,400,000
DOCSIS 2.0 A-TDMA-only operation.
Some cable interfaces might allow smaller ranges of either –10 to +10 or –10 to +25 dBmV.
Note
Allowable Power Range (dBmV)
–4 to +26
–1 to +29 (max. valid value for DOCSIS is +26)
Description
Enables the upstream FEC.
Enters a fixed frequency of the upstream RF carrier for an upstream
port.
Controls how the CMTS adjusts the CM power level so that the
CMs reach the target transmit power setting.
Disables the upstream port.
Cisco Broadband Cable Command Reference Guide
cable upstream power-level
2-341
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