docsIf31CmDsOfdmChanRollOffPeriod
DOCS-IF31-MIB ·
.1.3.6.1.4.1.4491.2.1.28.1.9.1.9
Object
column
number of samples DsOfdmRollOffPeriod
Roll off period maximizes channel capacity by sharpening the edges of the spectrum of the OFDM signal. For windowing purposes another segment at the start of the IDFT output is appended to the end of the IDFT output - the roll-off postfix (RP). There are five possible values for the (RP), and the choice depends on the bandwidth of the channel and the number of exclusion bands within the channel. A larger RP provides sharper edges in the spectrum of the OFDM signal; however, there is a time vs. frequency trade-off. Larger RP values reduce the efficiency of transmission in the time domain, but because the spectral edges are sharper, more useful subcarriers appear in the frequency domain. There is an optimum value for the RP that maximizes capacity for a given bandwidth and/or exclusion band scenario.
Context
- MIB
- DOCS-IF31-MIB
- OID
.1.3.6.1.4.1.4491.2.1.28.1.9.1.9- Type
- column
- Access
- readonly
- Status
- current
- Units
- number of samples
- Parent
- docsIf31CmDsOfdmChanEntry
- Table
- docsIf31CmDsOfdmChanTable
- Siblings
- 15
Syntax
number of samples DsOfdmRollOffPeriod
- Source
- DsOfdmRollOffPeriod
- Base type
Unsigned32
Values & Constraints
Type Constraints
range: 0
range: 64
range: 128
range: 192
range: 256
Related Objects
Sibling Objects
| Object | Type | Syntax | OID |
|---|---|---|---|
| docsIf31CmDsOfdmChanChannelId The Cable Modem Termination System identification of the
OFDM downstream channel within this particular MAC interface.
if the interface is down, the object returns the most
curren… | column | Integer32 | .1.3.6.1.4.1.4491.2.1.28.1.9.1.1 |
| docsIf31CmDsOfdmChanPlcFreq This is the PHY Link Channel (PLC) frequency. It is the center
frequency of the lowest frequency subcarrier of the PLC. The
aim of the PLC is for the CMTS to convey to the CM the
… | column | Hz SNMPv2-SMIUnsigned32 | .1.3.6.1.4.1.4491.2.1.28.1.9.1.10 |
| docsIf31CmDsOfdmChanNumPilots This attribute indicates the number of continuous pilots configured
for the OFDM downstream channel as received in the OCD message. | column | SNMPv2-SMIUnsigned32 | .1.3.6.1.4.1.4491.2.1.28.1.9.1.11 |
| docsIf31CmDsOfdmChanTimeInterleaverDepth The time interleaving used for this downstream channel as
received in the OCD message. | column | symbols TimeInterleaverDepth | .1.3.6.1.4.1.4491.2.1.28.1.9.1.12 |
| docsIf31CmDsOfdmChanPlcTotalCodewords This attribute represents the total number of PLC codewords
received by the CM. | column | SNMPv2-SMICounter64 | .1.3.6.1.4.1.4491.2.1.28.1.9.1.13 |
| docsIf31CmDsOfdmChanPlcUnreliableCodewords This attribute represents the total number of PLC codewords
which failed post-decoding LDPC syndrome check. | column | SNMPv2-SMICounter64 | .1.3.6.1.4.1.4491.2.1.28.1.9.1.14 |
| docsIf31CmDsOfdmChanNcpTotalFields This attribute represents the total number of NCP fields
received by the CM. | column | SNMPv2-SMICounter64 | .1.3.6.1.4.1.4491.2.1.28.1.9.1.15 |
| docsIf31CmDsOfdmChanNcpFieldCrcFailures This attribute represents the total number of NCP fields
received by the CM which failed the CRC check. | column | SNMPv2-SMICounter64 | .1.3.6.1.4.1.4491.2.1.28.1.9.1.16 |
| docsIf31CmDsOfdmChanChanIndicator This attribute is used to identify the OFDM downstream channel
as primary, backup primary or non-primary. A value of
'primary(2)' indicates that OFDM channel is assigned to be the… | column | PrimaryDsIndicatorType | .1.3.6.1.4.1.4491.2.1.28.1.9.1.2 |
| docsIf31CmDsOfdmChanSubcarrierZeroFreq This attribute specifies the center frequency of the
subcarrier 0 of the OFDM transmission. Note that since
subcarrier 0 is always excluded, it will actually be below the
allowed … | column | Hz SNMPv2-SMIUnsigned32 | .1.3.6.1.4.1.4491.2.1.28.1.9.1.3 |
| docsIf31CmDsOfdmChanFirstActiveSubcarrierNum This attribute corresponds to the number of the first
non-excluded subcarrier. The valid range is 148 to 7895 | column | SNMPv2-SMIUnsigned32 | .1.3.6.1.4.1.4491.2.1.28.1.9.1.4 |
| docsIf31CmDsOfdmChanLastActiveSubcarrierNum This attribute corresponds to the number of the last
non-excluded subcarrier. The valid range is 148 to 7895 | column | SNMPv2-SMIUnsigned32 | .1.3.6.1.4.1.4491.2.1.28.1.9.1.5 |
| docsIf31CmDsOfdmChanNumActiveSubcarriers This attribute represents the number of active data
subcarriers within the OFDM downstream channel (i.e. this
exclude subcarriers for continuous pilots and the PLC).
For 4K FFT mo… | column | SNMPv2-SMIUnsigned32 | .1.3.6.1.4.1.4491.2.1.28.1.9.1.6 |
| docsIf31CmDsOfdmChanSubcarrierSpacing This attribute defines the subcarrier spacing associated with
a particular FFT mode configured on the OFDM downstream
channel. If it is 4K mode, then the subcarrier spacing is
50k… | column | kHz SubcarrierSpacingType | .1.3.6.1.4.1.4491.2.1.28.1.9.1.7 |
| docsIf31CmDsOfdmChanCyclicPrefix Cyclic prefix enables the receiver to overcome the effects of
inter-symbol-interference and intercarrier-interference caused
by micro-reflections in the channel. There are five po… | column | number of samples DsOfdmCyclicPrefix | .1.3.6.1.4.1.4491.2.1.28.1.9.1.8 |