docsPnmCmtsDsOfdmSymCapTable
DOCS-PNM-MIB ·
.1.3.6.1.4.1.4491.2.1.27.1.3.1
Object
table
The purpose of downstream symbol capture is to provide partial
functionality of a network analyzer to analyze the response of the
cable plant.
At the CMTS, the transmitted frequency-domain modulation values of one
full OFDM symbol before the IFFT are captured and made available for
analysis. The frequency domain samples are expressed as 16-bit two's
complement numbers using s3.12 format. This includes the I and Q
modulation values of all subcarriers in the active bandwidth of the
OFDM channel, including data subcarriers, pilots, PLC preamble symbols
and excluded subcarriers. This capture will result in a number of
samples that depends on the OFDM channel width.
As examples, for 50 kHz subcarrier spacing in a 192 MHz channel with 204.8
MHz sampling rate, 3800 samples will be captured; for 25 kHz subcarrier
spacing in a 192 MHz channel with 204.8 MHz sampling rate, 7600 samples
will be captured; for 50 kHz subcarrier spacing in a 24 MHz channel with
a reduced sampling rate of 25.6 MHz, 475 samples would be captured. Note:
Excluded subcarriers in the guard band on either side of the encompassed
spectrum are not captured.
Capturing the input and output of the cable plant
is equivalent to a wideband sweep of the channel, which permits full
characterization of the linear and nonlinear response of the downstream
plant. The MAC provides signaling via the PLC Trigger Message to ensure
that the same symbol is captured at the CMTS and CM.
The Downstream Symbol Capture is controlled by setting the
'docsPnmCmtsDsOfdmSymTrigEnable' object. The status of the capture is
obtained by reading the value of the 'docsPnmCmDsOfdmSymMeasStatus'
object.
Context
- MIB
- DOCS-PNM-MIB
- OID
.1.3.6.1.4.1.4491.2.1.27.1.3.1- Type
- table
- Status
- current
- Parent
- docsPnmCmtsObjects
- Siblings
- 7
- Children
- 1
Syntax
No syntax metadata recorded.
Values & Constraints
No enumerated values or constraints recorded.
Related Objects
Sibling Objects
| Object | Type | Syntax | OID |
|---|---|---|---|
| docsPnmCmtsDsOfdmNoisePwrRatioTable The purpose of downstream NPR measurement is to view the noise,
interference and intermodulation products underlying a portion of the
OFDM signal. As an out-of-service test, the C… | table | - | .1.3.6.1.4.1.4491.2.1.27.1.3.2 |
| docsPnmCmtsUsOfdmaAQProbeTable The purpose of upstream capture is to measure plant response and view
the underlying noise floor, by capturing at least one OFDMA symbol
during a scheduled active or quiet probe. … | table | - | .1.3.6.1.4.1.4491.2.1.27.1.3.3 |
| docsPnmCmtsUsImpNoiseTable This table provides statistics of burst/impulse noise occurring in a
selected narrow band. A bandpass filter is positioned in an unoccupied
upstream band. A threshold is set, ener… | table | - | .1.3.6.1.4.1.4491.2.1.27.1.3.4 |
| docsPnmCmtsUsHistTable The purpose of the upstream histogram is to provide a measurement of
nonlinear effects in the channel such as amplifier compression and
laser clipping. For example, laser clipping… | table | - | .1.3.6.1.4.1.4491.2.1.27.1.3.5 |
| docsPnmCmtsUsOfdmaRxPwrTable The purpose of the upstream channel power metric is to provide an
estimate of the total received power in a specified OFDMA channel at
the F connector input of the CMTS line card … | table | - | .1.3.6.1.4.1.4491.2.1.27.1.3.6 |
| docsPnmCmtsUsOfdmaRxMerTable This item provides measurements of the upstream receive modulation
error ratio (RxMER) for each subcarrier. The CMTS measures the RxMER
using an upstream probe, which is not subje… | table | - | .1.3.6.1.4.1.4491.2.1.27.1.3.7 |
| docsPnmCmtsUsSpecAnTable The upstream triggered spectrum analysis measurement provides a
wideband spectrum analyzer function in the CMTS which can be triggered
to examine desired upstream transmissions as… | table | - | .1.3.6.1.4.1.4491.2.1.27.1.3.8 |
Child Objects
| Object | Type | Syntax | OID |
|---|---|---|---|
| docsPnmCmtsDsOfdmSymCapEntry The conceptual row of the 'docsPnmCmtsDsOfdmSymCapTable'. An instance
is dynamically created and exists for an associated ifIndex of the
physical downstream channel upon which the… | row | - | .1.3.6.1.4.1.4491.2.1.27.1.3.1.1 |