DOCS-PNM-MIB Table View

This table provides the objects needed for the device to upload
a bulk data file to the Server. This object is a table with a row for
each file that is available in the device for upload. The parameters
used for the upload are provided under the 'docsPnmBulkCtl' object.

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.

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 CM as its frequency-domain
downstream equalizer coefficients. The channel estimate consists of a
single complex valued coefficient per subcarrier. The channel response
coefficients are expressed as 16 bit two's complement numbers using s2.13
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.
Summary metrics (tilt, ripple, and group delay) are defined in order to
avoid having to send all coefficients on every query. The summary metrics
are calculated when the corresponding MIB is queried. A Coefficient
filename and trigger are provided to obtain the channel coefficients.
This table will have a row for each ifIndex for the modem.

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, possibly subsampling to
reduce complexity, and made available for analysis. This measurement is
intended for data subcarriers only. Up to 8192 samples are provided for
each query; additional queries can be made to further fill in the plot.
The complex Constellation Display values are expressed as 16 bit two's
complement numbers using s2.13 format. The CM samples are scaled such
that the average power of the QAM constellation is approximately 1, in
order to avoid excessive clipping and quantization noise.
          
The object controls the CM capturing and reporting of received
soft-decision samples, for a single selected constellation
from the set of profiles it is receiving, within a single OFDM
downstream channel.
          
This table will have a row for each ifIndex for the modem.

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 value with range 0 to 63.5 dB in 0.25 dB
steps. If some subcarriers (such as exclusion bands) cannot be measured
by the CM, the CM indicates that condition by reporting a value of 0xFF
for the RxMER for those subcarriers. Any measured RxMER value below 0 dB
is clipped to 0 dB (0x00), and any measured value above 63.5 dB is clipped
to 63.5 dB (0xFE).
          
Mathematical notation for the calculation of RxMER is provided in [PHYv3.1]:
'Downstream Receive Modulation Error Ratio (RxMER) Per Subcarrier'.
          
This table will have a row for each ifIndex for the modem.

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 the MER Margin reported in the
OPT-RSP Message [MULPIv3.1].
          
The CM calculates the Required Average MER based on the bit loading for
the profile and the Required MER per Modulation Order provided in the
RequiredDsOfdmQamMer Table. The CM then measures the RxMER per
subcarrier and calculates the Average MER for the Active Subcarriers
used in the Profile and stores the value as MeasuredAvgMer.
          
The CM also counts the number of MER per Subcarrier values that are
below the threshold determined by the Required MER for the Modulation
Order and the ThrshldOffset. The CM reports that value as
NumSubcarriersBelowThrshld.
          
This table will have a row for each ifIndex for the modem.

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 ifIndex for the modem.

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 clipping causes one tail of the histogram
to be truncated and replaced with a spike. The CM captures the histogram
of time domain samples at the wideband front end of the receiver (full
downstream band). The histogram is two-sided; that is, it encompasses
values from far-negative to far-positive values of the samples. The
histogram has either 256 or 255 equally spaced bins. These bins typically
correspond to the 8 MSBs of the wideband analog-to-digital converter (ADC).
The histogram dwell count, a 32-bit unsigned integer, is the number of
samples observed while counting hits for a given bin, and may have the
same value for all bins. The histogram hit count, a 32-bit unsigned
integer, is the number of samples falling in a given bin. The CM
reports the dwell count per bin and the hit count per bin. When
enabled, the CM computes a histogram with a dwell of at least 10
million samples at each bin in 30 seconds or less. The CM continues
accumulating histogram samples until it is restarted, disabled or times
out. If the highest dwell count approaches its 32-bit overflow value,
the CM stops counting and sets the docsPnmCmDsHistMeasStatus attribute to
'sampleReady'. The CM reports the start and end time of the histogram
measurement using bits 21-52 of the extended timestamp, which provides
a 32-bit timestamp value with resolution of 0.4 ms and range of 20 days.
          
This table will have a row for each ifIndex for the modem.

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 taken together describe the
linear response of the upstream cable plant for a given CM. During the
ranging process, the CMTS computes adaptive equalizer coefficients based
on upstream probes; these coefficients describe the residual channel
remaining after any pre-equalization. The CMTS sends these equalizer
coefficients to the CM as a set of Transmit Equalization Adjust
coefficients as part of the ranging process.
          
The CM Pre-Equalizer coefficients are expressed as 16 bit two's
complement numbers using s2.13 format. The power averaged over all
coefficients approximately 1, in order to avoid excessive clipping and
quantization noise. The Pre-Equalizer coefficient update values sent to
the CM by the CMTS in the RNG-RSP are expressed as 16 bit two's
complement numbers using s1.14 format.
          
The CM provides the capability to report its upstream pre-equalizer
coefficients (full set or summary) upon request. The CM also provides
the capability to also report the most recent set of Transmit
Equalization Adjust coefficients which were applied to produce the
reported set of upstream pre-equalizer coefficients. The CM indicates
the status of the most recent Transmit Equalization Adjust coefficients
sent to it by the CMTS. If the CM was able to apply the coefficients it
sets the status to success(2). If the CM was unable to fully apply the
adjustments (for example, due to excess tilt or ripple in the channel),
and it was necessary for the CM to clip the coefficients, it sets the
status to clipped(3). If the CM modified the coefficients other than by
simply clipping them, it sets the status to other(1). If for
some reason the CM is unable to apply the adjustments at all, it sets
the status to rejected(4).
          
The 'docsPnmCmUsPreEqFileEnable' object is used to create files. Other
objects are updated as read.
          
This table will have a row for each ifIndex for the modem.

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.

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 CMTS can define an exclusion
band of zero-valued subcarriers which forms a spectral notch in the
downstream OFDM signal for all profiles of a given downstream channel.
The CM provides its normal spectral capture measurements, or symbol
capture, which permit analysis of the notch depth. A possible use case
is to observe LTE interference occurring within an OFDM band; another
is to observe intermodulation products resulting from signal-level
alignment issues. Since the introduction and removal of a notch affects
all profiles, causing possible link downtime, this feature is intended
for infrequent maintenance.

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. An active probe provides the
partial functionality of a network analyzer, since the input is known
and the output is captured. This permits full characterization of the
linear and nonlinear response of the upstream cable plant. A quiet probe
provides an opportunity to view the underlying noise and ingress while
no traffic is being transmitted in the OFDMA band being measured.
          
The PNM server selects an active CM to analyze by specifying its MAC
address, or performs a quiet probe measurement. When enabled to perform
the capture, the CMTS selects a specified transmitting CM, or quiet
period when no CMs are transmitting, for the capture. The CMTS sets up
the capture as described in MULPIv3.1, selecting either an active SID
corresponding to the specified MAC address or the idle SID, and defining
an active or quiet probe. The active probe symbol for this capture
normally includes all non-excluded subcarriers across the upstream OFDMA
channel, with pre-equalization on or off as specified in the MIB. The quiet
probe symbol normally includes all subcarriers, that is, during the quiet
probe time there are no transmissions in the given upstream OFDMA channel.
For the quiet probe, the CMTS captures samples of at least one full OFDMA
symbol including the guard interval. The CMTS begins the capture with the
first symbol of the specified probe. The sample rate is the FFT sample rate
(102.4 Msps).
          
The CMTS reports the list of excluded subcarriers, the cyclic prefix length,
and the transmit window rolloff period in order to fully define the
transmitted waveform. The CMTS also reports the index of the starting sample
used by the receiver for its FFT. For possible comparison with other events,
the CMTS reports the timestamp corresponding to the beginning of the probe.
In the case where the P-MAPs for the OFDMA upstream being analyzed are being
sent in an OFDM downstream, the timestamp reported is the extended timestamp,
while in a case with OFDMA upstream channels but no OFDM downstream channels,
the reported timestamp is the D3.0 timestamp. For an active probe, the CMTS
reports the contents of the Probe Information Element (P-IE) message
describing that probe.

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, energy exceeding the threshold
triggers the measurement of an event, and energy falling below the
threshold ends the event. An optional feature allows the threshold to
be set to zero, in which case the average power in the band will be
measured. The measurement is time-stamped using the D3.0 field of the
64-bit extended timestamp (bits 9-40, where bit 0 is the LSB), which
provides a resolution of 98 ns and a range of 7 minutes.
          
The CMTS provides the capability to capture the following statistics
in a selected band up to 5.12 MHz wide: Timestamp of event, Duration of
event, Average power of event.
The CMTS provides a time history buffer of up to 1024 events. In steady
state operation, a ring buffer provides the measurements of the last 1024
events that occurred while the measurement was enabled.

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 causes one tail of the
histogram to be truncated and replaced with a spike. When the
UpstreamHistogram Enable attribute is set to 'true', the CMTS will begin
capturing the histogram of time domain samples at the wideband front
end of the receiver (full upstream band). The histogram is two-sided;
that is, it encompasses values from far-negative to far-positive values
of the samples. The histogram will have 256 equally spaced bins. These
bins typically correspond to the 8 MSBs of the wideband analog-to-digital
converter (ADC). The histogram dwell count, a 32-bit unsigned integer,
is the number of samples observed while counting hits for a given bin,
and may have the same value for all bins. The histogram hit count, a
32-bit unsigned integer, is the number of samples falling in a given bin.
The CMTS will report the dwell count per bin and the hit count per bin.
When enabled, the CMTS will compute a histogram with a dwell of at least
10 million samples at each bin in 30 seconds or less. The CMTS will
continue accumulating histogram samples until it is restarted, disabled
or times out. If the highest dwell count approaches its 32-bit overflow
value, the CMTS will save the current set of histogram values and reset
the histogram, so that in a steady-state condition a complete measurement
is always available. The CMTS will be capable of reporting the start and
end time of the histogram measurement using bits 21-52 of the extended
timestamp, which provides a 32-bit timestamp value with resolution of
0.4 ms and range of 20 days.

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 for a given user. The
measurement is based on upstream probes, which are typically the same
probes used for pre-equalization adjustment.
          
The CMTS measures the total power of the probe subcarriers received
from the CM.
          
For channels without boosted pilots, the CCAP calculates the average
power per subcarrier (Paverage) and then calculates the power normalized
to 1.6 MHz as a)Paverage + 10 * log10(32) for 50 kHz subcarrier spacing,
or as b)Paverage + 10 *log10(64) for 25 kHz subcarrier spacing.
          
For channels with boosted pilots, the CCAP calculates the average power
per subcarrier (Paverage) and then calculates the power normalized to
1.6 MHz as a)Paverage + 10 * log10(32) + 1 dB for 50 kHz subcarrier
spacing, or as b)Paverage + 10 *log10(64) + 0.5 dB for 25 kHz subcarrier
spacing.
          
NOTE: The CMTS would also use that adjusted value for comparison with the
Target Receive Power for the purposes of transmit power adjustments in the
RNG-RSP.

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 subject to symbol errors as data
subcarriers would be. The probes used for RxMER measurement are typically
distinct from the probes used for pre-equalization adjustment. For the
purposes of this measurement, RxMER is defined as the ratio of the average
power of the ideal QAM constellation to the average error-vector power.
The error vector is the difference between the equalized received probe
value and the known correct probe value. If some subcarriers (such as
exclusion bands) cannot be measured by the CMTS, the CMTS indicates that
condition in the measurement data for those subcarriers.

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 well as underlying
noise/interference during a quiet period.
          
The CMTS provides wideband upstream spectrum analysis capability
covering the full upstream spectrum of the cable plant. The CMTS can
be made to use 100 kHz or better resolution (bin spacing) in the
wideband upstream spectrum measurement.
          
Depending on the particular CMTS implementation, variable
upstream spectrum analysis span is possible.
          
It is also possible that the CMTS will provide the collection of
time-domain input samples as an alternative to the frequency-domain
upstream spectrum results.
          
In pre-DOCSIS-3.1 mode, the CMTS provides the ability to trigger the
spectrum sample capture and perform spectrum analysis using the
following modes:
    - Free running
    - Trigger on minislot count
    - Trigger on SID (service identifier)
    - Trigger during quiet period (idle SID)
          
In DOCSIS 3.1 mode, the CMTS provides the ability to trigger spectrum
sample capture and perform spectrum analysis using the following modes:
    - Free running
    - A specified timestamp value
    - Minislot Number
    - A specified MAC address defining a SID, triggering at the beginning
    of the first minislot granted to that SID
    - The idle SID, triggering at the beginning of the first minislot
    granted to that SID
    - A specified active or quiet probe symbol, triggering at the beginning
    of the probe symbol