2-341
Cisco Broadband Cable Command Reference Guide
OL-1581-08
Chapter 2 Cisco CMTS Configuration Commands
cable upstream power-level
Note
Some cable interfaces might allow smaller ranges of either –10 to +10 or –10 to +25 dBmV.
Tip
You can use inline attenuators to force CMs to transmit at higher power levels and to achieve a higher
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.
Note
Do not adjust your input power level by more than 5 dB in a 30-second interval. If you
increase
the
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.
Tip
When setting upstream power levels, Cisco recommends that the adjacent channels of equal bandwidth
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
2,560,000
3,200,000
–4 to +26
5,120,000
1
6,400,000
–1 to +29 (max. valid value for DOCSIS is +26)
1.
The 5.12 MSymbols/sec symbol rate and 6.4 MHz channel width are supported only on upstreams that are configured for
DOCSIS 2.0 A-TDMA-only operation.
Table 2-13 Allowable DOCSIS Power Levels
Symbol Rate (Symbols per
second)
Channel Width (Hz)
Allowable Power Range (dBmV)
Command
Description
cable upstream fec
Enables the upstream FEC.
cable upstream frequency
Enters a fixed frequency of the upstream RF carrier for an upstream
port.
cable upstream power-adjust
Controls how the CMTS adjusts the CM power level so that the
CMs reach the target transmit power setting.
cable upstream shutdown
Disables the upstream port.