docsPnmCmDsOfdmSymCapTable
DOCS-PNM-MIB ·
.1.3.6.1.4.1.4491.2.1.27.1.2.2
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 from the CM's perspective.
At the CM, the received I and Q time-domain samples of one full OFDM
symbol before the FFT, not including the guard interval, are captured
and made available for analysis. This capture will result in a number
of data points equal to the FFT length in use, time aligned for receiver
FFT processing. The number of captured samples can be reduced for
narrower channels if the sampling rate, which is implementation dependent,
is reduced. The capture includes a bit indicating if receiver windowing
effects are present in the data. The time domain samples are expressed
as 16 bit two's complement numbers using s3.12 format. The CM samples are
scaled such that the average power of the samples is approximately 1, in
order to avoid excessive clipping and quantization noise.
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
'docsPnmCmDsOfdmSymTrigEnable' object. The status of the capture is
obtained by reading the value of the 'docsPnmCmDsOfdmSymMeasStatus'
object.
This table will have a row for each ifIndex for the modem.
Context
- MIB
- DOCS-PNM-MIB
- OID
.1.3.6.1.4.1.4491.2.1.27.1.2.2- Type
- table
- Status
- current
- Parent
- docsPnmCmObjects
- Siblings
- 9
- Children
- 1
Syntax
No syntax metadata recorded.
Values & Constraints
No enumerated values or constraints recorded.
Related Objects
Sibling Objects
| Object | Type | Syntax | OID |
|---|---|---|---|
| docsPnmCmControlObjects | node | - | .1.3.6.1.4.1.4491.2.1.27.1.2.1 |
| docsPnmCmUsPreEqTable This object provides access to CM upstream pre-equalizer coefficients.
The CM pre-equalizer coefficients and the CMTS upstream adaptive
equalizer coefficient update values, when t… | table | - | .1.3.6.1.4.1.4491.2.1.27.1.2.10 |
| docsPnmCmOfdmChanEstCoefTable The purpose of this table is for the CM to report its estimate of the
downstream channel response. The reciprocals of the channel response
coefficients are typically used by the C… | table | - | .1.3.6.1.4.1.4491.2.1.27.1.2.3 |
| docsPnmCmDsConstDispMeasTable The downstream constellation display provides received QAM
constellation points for display. Equalized soft decisions (I and Q)
at the slicer input are collected over time, possib… | table | - | .1.3.6.1.4.1.4491.2.1.27.1.2.4 |
| docsPnmCmDsOfdmRxMerTable This item provides measurements of the receive modulation error ratio
(RxMER) for each subcarrier. Each subcarrier RxMER value consists of one
byte which represents the RxMER valu… | table | - | .1.3.6.1.4.1.4491.2.1.27.1.2.5 |
| docsPnmCmDsOfdmMerMarTable The purpose of this item is to provide an estimate of the MER margin
available on the downstream data channel with respect to a candidate
modulation profile. This is similar to th… | table | - | .1.3.6.1.4.1.4491.2.1.27.1.2.6 |
| docsPnmCmDsOfdmFecTable The purpose of the table is to provide a series of codword error rate
measurements on a per profle basis over a set period of time.
This table will have a row for each … | table | - | .1.3.6.1.4.1.4491.2.1.27.1.2.7 |
| docsPnmCmDsOfdmReqMERObjects | node | - | .1.3.6.1.4.1.4491.2.1.27.1.2.8 |
| docsPnmCmDsHistTable The purpose of the downstream histogram is to provide a measurement of
nonlinear effects in the channel such as amplifier compression and laser
clipping. For example, laser clippi… | table | - | .1.3.6.1.4.1.4491.2.1.27.1.2.9 |
Child Objects
| Object | Type | Syntax | OID |
|---|---|---|---|
| docsPnmCmDsOfdmSymCapEntry The conceptual row of the docsPnmCmDsOfdmSymCapTable. An instance
is dynamically created and exists for an associated ifIndex of the
physical downstream channel upon which the tes… | row | - | .1.3.6.1.4.1.4491.2.1.27.1.2.2.1 |