Cisco Cisco Digital Service Access Node (DSAN) 8211 Installation Guide
Chapter 1 Startup Guide
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Bypass Output Port (Port 2)
For optional downstream use, this port replicates the input signal at Port 1. The
signal level is -9 dB relative to the signal level at the Input port. This value is not
internally adjustable.
signal level is -9 dB relative to the signal level at the Input port. This value is not
internally adjustable.
To Check and Adjust eCM Signal Levels
The final step in DSAN RF setup is to adjust plant levels in the reverse signal path so
that the upstream signal transmitted by the DSAN eCM is received at the correct
level by the CMTS in the headend.
that the upstream signal transmitted by the DSAN eCM is received at the correct
level by the CMTS in the headend.
Notes:
The downstream DOCSIS channel level is set up properly when the DSAN RF
input levels are configured as described in the preceding sections.
input levels are configured as described in the preceding sections.
You can monitor upstream eCM power levels on CLI diag page 4.1 as described
in the CLI Diagnostics (on page 63) section in this document. The power levels
reported in CLI differ from those which you might otherwise try to measure at
Port 1.
Specifically, the upstream power level reported in CLI is 13.7 dB higher than the
level at Port 1 because it is measured internally before attenuation. For example,
a CLI reported power level of 49 dBmV would imply a power level of (49 - 13.7
=) 35.3 dBmV measurable at Port 1.
in the CLI Diagnostics (on page 63) section in this document. The power levels
reported in CLI differ from those which you might otherwise try to measure at
Port 1.
Specifically, the upstream power level reported in CLI is 13.7 dB higher than the
level at Port 1 because it is measured internally before attenuation. For example,
a CLI reported power level of 49 dBmV would imply a power level of (49 - 13.7
=) 35.3 dBmV measurable at Port 1.
The maximum upstream transmit level of the DSAN eCM is +54 dBmV. This level is
attenuated by 13.7 dB internally, resulting in a maximum launch power of +40.3
dBmV as measured at Port 1. The actual eCM operating output power is set
automatically by the DSAN eCM power ranging process in communication with the
CMTS.
attenuated by 13.7 dB internally, resulting in a maximum launch power of +40.3
dBmV as measured at Port 1. The actual eCM operating output power is set
automatically by the DSAN eCM power ranging process in communication with the
CMTS.
As with any eCM, the best signal-to-noise performance is achieved by having the
DSAN eCM transmit upstream at the highest possible level while holding enough
launch power in reserve to allow for worst-case plant fluctuations. To do this, you
apply a back-off from the maximum launch power to find a target value for DSAN
eCM transmit level under nominal plant conditions. You then adjust nominal
reverse path plant levels between the DSAN and CMTS so that the eCM transmits at
this target value.
DSAN eCM transmit upstream at the highest possible level while holding enough
launch power in reserve to allow for worst-case plant fluctuations. To do this, you
apply a back-off from the maximum launch power to find a target value for DSAN
eCM transmit level under nominal plant conditions. You then adjust nominal
reverse path plant levels between the DSAN and CMTS so that the eCM transmits at
this target value.
The back-off that you apply to find the target eCM transmit level will vary with
plant characteristics and with the location of the DSAN within the plant, making it
difficult to provide a general figure. If your company has a back-off rule that eCM
installers currently use on the plant, then apply the same rule when adjusting plant
levels to achieve the desired DSAN upstream transmit level at Port 1.
plant characteristics and with the location of the DSAN within the plant, making it
difficult to provide a general figure. If your company has a back-off rule that eCM
installers currently use on the plant, then apply the same rule when adjusting plant
levels to achieve the desired DSAN upstream transmit level at Port 1.