Cisco uBR-MC16S Spectrum Management
Enhancements
This feature module describes the spectrum management enhancements in the Cisco uBR-MC16S cable
modem card for Cisco uBR7200 series universal broadband routers running
Cisco IOS software Release 12.1(3a)EC1.
This document includes the following sections:
•
Feature Overview, page 1
•
Supported Platforms, page 7
•
Supported Standards, MIBs, and RFCs, page 7
•
Prerequisites, page 8
•
Configuration Tasks, page 8
•
Configuration Examples, page 11
•
Command Reference, page 12,
•
Debug Commands, page 33
Feature Overview
The Cisco uBR-MC16S spectrum management cable modem card helps you reduce the negative effects
of upstream ingress noise by performing a spectrum analysis of available upstream channels, and
selecting an upstream channel with appropriate signal quality. The Cisco uBR-MC16S delivers
hardware-assisted spectrum management, resulting in better service, quality, and reliability.
To use the spectrum management feature, you must install the Cisco uBR-MC16S cable modem card in
the Cisco uBR7246 VXR. For installation information, see the Cisco uBR7200 Series Universal
Broadband Router Hardware Installation Guide, Release 12.1.
The spectrum management card in Cisco uBR-MC16S cable modem scans the upstream spectrum for
clean (usable) channels of the specified width: 3.2 MHz, 1.6 MHz, 800 KHz, 400 KHz, and 200 KHz.
If the card does not find acceptable channels of the specified width, it scans the upstream spectrum for
the next largest available channel width. The spectrum management card enables the
Cisco uBR-MC16S cable modem get live data samples of the upstream frequency spectrum.
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Cisco uBR-MC16S Spectrum Management Enhancements
Feature Overview
When the user-defined threshold percentage of offline modems is met,
Cisco IOS software Release 12.1(3a)EC1 analyzes the collected data, and initiates a frequency hop to
a clean channel in the upstream spectrum. The upstream channel frequency reassignment process is
initiated by the number of lost station management messages exceeding a configured threshold. The
Cisco uBR7200 series moves all cable modems on the upstream port by sending upstream channel
descriptor (UCD) messages that contain the next frequency and input power level defined in the
spectrum management group. The frequency changes occur rapidly without data loss and minimal
latency.
The Cisco uBR-MC16S spectrum management card enhances the frequency agility software feature
already available on Cisco uBR7200 series routers. With the Cisco uBR-MC16S card, service response
time is improved by using an intelligent, hardware-assisted spectrum analyzer.
The following sections describe spectrum management implementation using Cisco uBR7200 series
software and Cisco uBR-MC16S cable modem card.
The Cisco uBR7200 series supports the creation of up to 32 cable spectrum groups, allowing multiple
upstream ports in a single spectrum group, and specifications of configured channel widths for upstream
segments. Upstream frequencies can be assigned as follows:
•
Fixed.
•
Single subband—the CMTS administrator can define a center frequency and symbol rate such that
the boundaries of the upstream carrier stay within the subband. The frequency and symbol rate can
change within the boundary in response to noisy line conditions, based on the defined upstream
parameters.
•
Multiple subbands—the data carrier can remain in a particular subband for a duration of time and
then hop to another subband based on the defined upstream parameters.
The above frequency agility specifications are based on predetermined sets of frequencies which
may or may not have adequate carrier-to-noise (C/N) ratio at any given time.
•
Caution
Dynamically assigned based on a CMTS administrator-specified threshold percentage of
disconnected cable modems that must be met before a frequency hop will occur—the
Cisco uBR7200 series software can initiate a frequency hop to a clean upstream channel based on
upstream spectrum data collected by the Cisco uBR-MC16S’s spectrum management daughter
card.
Upstream modulation profiles can be assigned to specific cable modems based on the
Cisco cable modem card used. Only those familiar with DOCSIS who have received the
proper training should create upstream modulation profiles.
Two-Way Cable
The Cisco uBR7200 series universal broadband routers divide a cable network into downstream and
upstream segments. Each upstream segment typically serves one or more fiber nodes. Upstream
segments can be defined as:
Note
•
Sparse segment—Containing one upstream channel per upstream segment.
•
Dense segment—Containing multiple upstream channels per upstream segment; frequencies must
be different.
A cable modem card supports either sparse or dense segments—not both.
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Feature Overview
Defining sparse segments allows the cable operator to share upstream bandwidth among fiber nodes
with fewer subscribers. Defining dense segments allows the cable operator to provide larger upstream
bandwidth to fiber nodes with lots of subscribers. illustrates sparse versus dense segments.
Sparse Versus Dense Segment
Figure 1
Sparse and Dense Segments
Sparse
Segment
3
Segment
4
DS
US0
US1
US2
US3
US4
US5
1x4 CM card
Optical
receiver
=
attenuator
x
attenuator
Segment
5
Segment
6
27979
DS
US0
US1
US2
US3
US4
US5
1x4 CM card
Cable
modems
Reverse optical
Fiber-optic transmitter
cable
Distribution
network
As shown in Figure 1, the downstream segment can contain multiple upstream segments. Two fiber
nodes can be in one downstream segment, but in different upstream segments.
An upstream frequency has an associated upstream input power level in dBmV. Cable operators must
make noise measurements and determine the cable plant’s spectrum management policy. Different
modulation schemes and symbol rates can be used based on the characteristics of the cable plant and
the cable modem card contained in the chassis. Bits are encoded into a two-dimensional mapping called
a constellation. Good carrier-to-noise ratio is needed to properly decode symbols into bits.
Upstream Signals
The upstream channel is characterized by many cable modems transmitting to the CMTS. These signals
operate in a burst mode of transmission. Time in the upstream channel is slotted. The CMTS provides
time slots and controls the usage for each upstream interval.
The Cisco uBR7200 series equipment periodically broadcasts UCD messages to all cable modems.
These messages define upstream channel characteristics including the upstream frequencies, symbol
rates and modulation schemes, forward error correction (FEC) parameters, and other physical layer
values.
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Feature Overview
Cisco supports all DOCSIS error correction encoding and modulation types and formats. Upstream
signals are demodulated using Quadrature Phase Shift Keying (QPSK) or quadrature amplitude
modulation (QAM). QPSK carries information in the phase of the signal carrier, whereas QAM uses
both phase and amplitude to carry information.
Sending data reliably in the upstream direction is an issue. Because upstream spectrum varies greatly
between cable plants, select upstream parameters based on your cable plant’s return paths. Select or
customize upstream profiles for maximum trade-offs between bandwidth efficiency and upstream
channel robustness. For example, 16 QAM requires approximately 7 dB higher C/N ratio to achieve the
same bit error rate (BER) as QPSK, but it transfers information at twice the rate of QPSK.
Combiner Groups
The return path of several fiber nodes can be combined together at a single point to form a single RF
frequency domain, called a combiner group. The Cisco uBR7200 series universal broadband router
software allows a frequency hop table to be associated with a combiner group, called a spectrum group.
Note
A combiner group refers to an RF topology point. A spectrum group refers to the
frequency hop table associated with a combiner group.
The Cisco uBR7200 series universal broadband routers support up to 32 spectrum groups. Each
spectrum group defines the table of frequencies to be used in a specific frequency plan. Cisco
cable modem cards interface the downstream and upstream ports to the cable plant.
Frequency Allocation Table
The Cisco uBR7200 series universal broadband router software includes Cisco IOS commands that can
be used to define upstream frequency hop tables. In the global and interface configuration modes, these
are grouped under the cable spectrum-group command hierarchy.
The steps to configure a spectrum group are as follows:
•
Determine the upstream ports assigned to a combiner group.
•
Create the frequency hop table under Cisco IOS global configuration.
•
Assign the upstream port to the frequency hop table under Cisco IOS interface configuration.
Frequency Management Policy
Due to the nature of CATV technology, upstream noise management is a significant issue. Cisco
recommends that you follow rigorous North American plant maintenance procedures documented in the
NCTA Supplement on Upstream Transport Issues to adjust return amplifiers and lasers.
Cisco also recommends that system administrators configure upstream frequency hopping as a
countermeasure to long-term, narrowband noise. Cisco IOS Release 12.0(5)T1 or higher CMTS images
support blind, time-scheduled, and guided frequency hopping.
With the release of the Cisco uBR-MC16S cable modem card, you can perform automatic upstream
frequency hopping. You can configure the Cisco uBR-MC16S to scan the upstream spectrum in your
cable network and point to “clean” available upstream channels (of a width you designate) to accept a
frequency hop.
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Feature Overview
Note
The choice of spectrum is usually limited to those bands having sufficient C/N ratio and
carrier-to-ingress power ratio to support transmission of QPSK and QAM data. DOCSIS
sets the minimum value for both of these parameters to 25 dB in the 5-to-42 MHz
frequency range. Bands with known ingress should be avoided.
Higher frequency bands are also preferred because they are least likely to suffer noise interference.
Measurement of noise power levels with a spectrum analyzer is a mandatory part of the setup procedure
to characterize your cable plant.
Upstream port frequency should be set to a fixed value during system installation and testing. This is
chosen from the allocation plan for the RF domain for the RF plant segment connected to the upstream.
Note
Having fixed frequency settings is recommended during early deployment at least until
amplifier cascade adjustments or plant repair becomes infrequent for the nodes connected
to the upstream port. When multiple upstream ports are combined together to provide
increased bandwidth, care should be taken to prevent overlapping frequency bands.
When the system has reached sufficient stability, the RF domain topology can be entered into the
Cisco IOS configuration file to enable RF spectrum management. This management feature—called
spectrum groups described earlier—applies a common frequency management policy to a set of
upstream ports.
Note
When each upstream port has its own RF domain, the group is called a non-shared
spectrum group. When multiple upstream ports share the same RF domain, the group is
called a shared spectrum group.
Dynamic Upstream Modulation
Dynamic Upstream Modulation monitors the signal-to-noise ratio (SNR) and FEC counters in the active
return path of each upstream port, determines whether the upstream channel signal quality can support
the modulation scheme configured, and adjusts to the more robust modulation scheme when necessary.
When Dynamic Upstream Modulation and spectrum groups are configured on the same interface, the
modulation switchover is chosen as the first corrective action, followed by a frequency hop, and finally
a reduction in channel width. For more information on Dynamic Upstream Modulation, see the
document Cisco uBR7200 Series Dynamic Upstream Modulation, Release 12.1.
Benefits
The Spectrum Management Enhancements feature:
•
Gives you the ability to more effectively manage the upstream frequency spectrum due to fewer
cable modems falling offline because of excessive noise in one area of the upstream frequency
spectrum.
•
Scans the upstream spectrum for clean (usable) channels of specified width- improves service
quality in DOCSIS installations offering data, voice, or video services.
•
Improves reliability of the upstream carrier and increase the no. of services and customers the MSO
can support.
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Feature Overview
•
Takes advantage of frequency hopping to a center frequency over a range of different frequencies.
•
Ensures responsive, high-quality subscriber service and eliminates blind frequency hops. It saves
time and effort for Multiple Service Operators (MSOs) when troubleshooting cable plant
impairments.
•
Maximizes the number of online modems with reduced response time to ingress noise impairments.
Frequency agility eliminates dropped packets, maintains full upstream data rates (even with 50
hops per second), and streamlines troubleshooting.
•
Provides the flexibility to assign a specific channel bandwidth (200kHz to 3.2 MHz) at each
upstream channel frequency.
•
Provides an easy way to determine why, how, when, and where frequency hops occur.
•
The Cisco uBR-MC16Scard is not supported in the Cisco IOS Release 12.0SC.
•
The upstream cable modems should be the Cisco uBR7200 series DOCSIS certified cable modems
•
Upstream modulation profiles can be assigned to specific cable modems based on the Cisco cable
modem card used.
•
Only those who have received training and are familiar with DOCSIS should create upstream
modulation profiles.
•
The cable upstream portnum channel-width command applies only to the MC16C card. Varying
widths are available with the Cisco uBR-MC16S card. You cannot configure two widths on the
MC16C card.
•
A cable modem card supports either sparse or dense segment, but not both.
•
The choice of spectrum is limited to bands with sufficient C/N ratio and carrier-to-ingress power
ratio to support transmission of QPSK and QAM data. DOCSIS sets the minimum value for both
of these parameters to 25dB in the 5-42MHz frequency range. Bands with known ingress should be
avoided.
•
When multiple upstream ports are combined together to provide increase bandwidth, care should
be taken to prevent overlapping frequency bands.
•
When using the Dynamic Upstream Modulation feature with the Cisco uBR-MC16S cards, and/or
when setting variable upstream channel widths for the Cisco uBR-MC16S card in HFC
environments where Voice Over IP (VoIP) services are required, frequent changes to upstream
modulation or channel width could briefly impact the quality of voice calls. Future software
enhancements will provide commands to set the SNR and FEC thresholds broad enough to avoid
frequent upstream modulation or channel width changes.
Restrictions
Related Documents
•
Cisco IOS Release 12.1 Multiservice Applications Configuration Guide
•
Cisco IOS Release 12.1 Multiservice Applications Command Reference
•
Cisco uBR7200 Series Dynamic Upstream Modulation, Release 12.1
•
Cisco uBR7200 Series Configuration Notes, Release 12.1
•
Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide, Release 12.1
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Supported Platforms
•
Cisco uBR7200 Series Universal Broadband Router Hardware Installation Guide, Release 12.1
•
Cisco uBR7200 Series Software Release Notes and Features, Release 12.1
•
Regulatory Compliance and Safety Information for the Cisco uBR7200 Series Universal Broadband
Router, Release 12.1
Supported Platforms
•
Cisco uBR7223 with Cisco uBR-MC16S cable modem card
•
Cisco uBR7246 with Cisco uBR-MC16S cable modem card
•
Cisco uBR7246 VXR with Cisco uBR-MC16S cable modem card
Supported Standards, MIBs, and RFCs
Standard
No new or modified standards are supported by this feature.
MIBs
Note
•
CISCO-CABLE-SPECTRUM-MIB.my
•
CISCO-CABLE-SPECTRUM-MIB-V1SMI.my
•
CISCO-DOCS-EXT-MIB
In Cisco IOS Release 12.0(7)XR2, a new table entitled “cdxIfUpstreamChannelExtTable”
was added to CISCO-DOCS-EXT-MIB supporting the use of a second channel width
designation for hierarchical spectrum analysis, as in the cable upstream interface number
channel-width width1 width2 command.
To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules,
go to the Cisco MIB web site on Cisco Connection Online (CCO) at
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.
RFCs
No new or modified RFCs are supported by this feature.
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Prerequisites
Prerequisites
•
Verify that you are using the Cisco IOS software release that supports the Cisco uBR-MC1xC or
Cisco uBR-MC16S cable modem card.
•
Ensure your network is designed to support reliable broadband data transmission.
At minimum, your network must include:
– Computer on the WAN side of your Cisco uBR7200 series configured as a Dynamic Host
Configuration Protocol (DHCP) server to assign IP addresses to cable modems or set-top boxes
on the hybrid fiber coaxial (HFC) network.
– Cisco uBR7200 series-compatible IF-to-RF upconverter installed in the downstream data path
at your headend site. The upconverter is installed between the Cisco uBR7200 series and the
combiner.
The combiner refers to all cables, amplifiers, and taps at the headend or cable distribution
center that connect the Cisco uBR7200 series to the HFC network.
– Diplex filters installed in the downstream RF path between the cable modems and the cable
modem cards in the Cisco uBR7200 series. RG-59 headend coaxial cable with the maximum
braid available (60 percent + 40 percent braid), double foil, and the correct connector for this
cable.
•
Complete a basic configuration of the Cisco uBR7200 series as described in the Cisco uBR7200
Series Universal Broadband Router Software Configuration Guide.
•
Avoid frequencies with known ingress problems such as amateur radio bands or short-wave bands
•
Avoid hostile spectrum below 20 MHz
•
Allow extra bands for frequency hopping
•
Place upstream ports in the same combiner group in a shared spectrum group
•
Use the receive power level setting to perform slight equalization adjustments
•
Due to the nature of CATV technology, upstream noise management is a significant issue. Cisco
recommends that you follow rigorous North American plant maintenance procedures documented
in the NCTA Supplement on Upstream Transport Issues to adjust return amplifiers and lasers.
Configuration Tasks
•
Configuring Spectrum Groups, page 9
•
Configuring Frequency Hopping, page 10
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Configuration Tasks
Configuring Spectrum Groups
Command
Purpose
Step 1
Router(config)# configure terminal
Enters configuration mode.
Step 2
Router(config)# cable spectrum-group
group-number [time hh:mm:ss] frequency
up-freq-hz [power-level-dbmv]
Creates a frequency hop table by configuring
spectrum management characteristics (upstream
frequencies and power levels) for the given spectrum
group.
group-number = Spectrum group number. Valid
range is 1 to 32. Configuring a spectrum group with
multiple entries of this type, defines a list of
frequencies which are available for use as upstream
frequencies.
time hh:mm:ss = (Optional) For scheduled spectrum
groups, specifies the time of day that the frequency
and input power level should change.
frequency up-freq-hz = Upstream frequency. Valid
range is 5,000,000 to 42,000,000 Hz.
power-level-dbmv = (Optional) Nominal input
power level. Valid range is -10 to +10 decibels per
millivolt (dBmV). Some cable plants might want to
change only the input power level and not frequency
on a daily time schedule.
Step 3
Router(config)# interface type slot/port
Step 4
Router(config-if)# cable
Step 5
Router(config-if)# cable upstream port
spectrum group y
Assigns upstream ports individually. Valid only for
Cisco uBR-MC16S card.
Step 6
Router(config-if)# exit
Exits configuration mode and force the system to
hop.
Configures the interface where:
- type = cable
- slot = slot number in chassis (slot numbers begin
with a 0)
- port = port number on cable modem slot (port
numbers begin with a 0)
n spectrum-group y Enters interface configuration mode, and assigns the
upstream port to the frequency hop table.
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Configuration Tasks
Configuring Frequency Hopping
Command
Purpose
Step 1
Router(config)# configure terminal
Enters configuration mode.
Step 2
Router(config)# cable spectrum-group
group-number [time hh:mm:ss] frequency
up-freq-hz [power-level-dbmv]
Creates a frequency hop table. Configures spectrum
management characteristics (upstream frequencies
and power levels) for the given spectrum group.
group-number = Spectrum group number. Valid
range is 1 to 32. Configuring a spectrum group with
multiple entries of this type, defines a list of
frequencies which are available for use as upstream
frequencies.
time hh:mm:ss = (Optional) For scheduled spectrum
groups, specifies the time of day that the frequency
and input power level should change.
frequency up-freq-hz = Upstream frequency. Valid
range is 5,000,000 to 42,000,000 Hz.
power-level-dbmv = (Optional) Nominal input
power level. Valid range is -10 to +10 decibels per
millivolt (dBmV). Some cable plants might want to
change only the input power level and not frequency
on a daily time schedule.
Step 3
Router(config)# interface type slot/port
Step 4
Router(config-if)# cable
Configures the interface where:
- type = cable
- slot = slot number in chassis (slot numbers begin
with a 0)
- port = port number on cable modem slot (port
numbers begin with a 0)
n spectrum-group y Enters the interface configuration mode, and assigns
the upstream port to the frequency hop table.
Verifying Your Settings
Step 1
Enter the show running-config command at the Router# prompt o check the value of the settings you
have entered.
Router# show running-config
To review changes you make to the configuration, use the EXEC show startup-config command to
display the information stored in NVRAM.
Step 2
Use the show cable modulation-profile privileged EXEC command to display modulation profile
group information.
Router# show cable modulation-profile [profile] [iuc-code]
profile—(Optional) Profile number. Valid values are from 1 to 8.
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Configuration Examples
iuc-code —(Optional) Internal usage code. Valid options are:
•
initial —Initial Ranging Burst
•
long —Long Grant Burst
•
request —Request Burst
•
short —Short Grant Burst
•
station —Station Ranging Burst
Configuration Examples
•
Spectrum Groups Example, page 11
Spectrum Groups Example
Frequency agility is configured and activated using spectrum groups. You can create from 1 to 32
spectrum groups for each cable modem card upstream port. First, upstream channels capable of meeting
the appropriate carrier-to-noise (C/N) values for QPSK (19 dB) and QAM16 (29 dB) within the return
spectrum need to be identified.
Next, spectrum groups can be defined as a set of discrete frequencies, or a continuous frequency band.
To create spectrum groups, specify a list of upstream frequencies and nominal power levels that each
spectrum group can use when an upstream frequency change is necessary. Each spectrum group should
have its own list of upstream frequencies. A spectrum group can also be “scheduled” to occur at a
defined day and time.
Discrete frequency example:
Router(config)# cable spectrum-group 1 frequency 22400000 1
Router(config)# cable spectrum-group 1 frequency 20800000
Router(config)# cable spectrum-group 1 frequency 24000000 2
In the example above, three separate frequencies are defined with their respective nominal power levels.
These frequencies will be chosen in the order entered when frequency hopping occurs with a non
Cisco uBR-MC16S card. The spectrum-group will apply 22.4MHz with 1dB nominal input power when
it is applied to an upstream port.
Should frequency hopping occur, the spectrum group will select 20.8MHz with 0dB input power as its
next choice, then 24MHz with 2dB nominal input power, and then back again to 22.4MHz with 1dv
nominal input power. The Cisco uBR-MC16S card will select the cleanest frequency within the
spectrum group, and utilize its hardware spectrum management capability to choose a clean frequency
on subsequent hops.
Contiguous frequency band example:
Router(config)#cable spectrum-group 1 band 14000000 22000000
Router(config)#cable spectrum-group 1 band 31000000 38000000
The frequencies listed define the edge to edge band range. Services other than DOCSIS upstream data
will be carried in frequencies starting at 22MHz and ending at 31MHz. Check the channel width
specified for the upstream port carefully; if the spectrum group band is narrower than the widest channel
width specified on the upstream port, the uBR7200 will never choose that band and channel width
combination.
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Command Reference
Scheduled frequency band example:
Router(config)#cable spectrum-group 1 time Mon 12:00:00 band 5000000 15000000
Router(config)#cable spectrum-group 1 time Mon 12:00:00 band 27000000
29000000
Router(config)#cable spectrum-group 1 time Mon 16:00:00 delete band 27000000
29000000
This example illustrates a scheduled frequency hop that corresponds to CB radio interference. Local
studies indicate that CB radios are not in use at noon on Monday, but return at 4:00PM that same day.
The scheduled frequency hop to the 27-29MHz band will occur at noon on Monday, and a second
frequency hop will occur at 4:00PM to revert to another frequency defined within the spectrum group.
A second example illustrates a set top box polling application which runs each night from 1:00AM to
3:00AM in the frequency range of 31-33MHz. Using scheduled frequency hopping, cable modems can
use these valuable frequencies when the set top boxes are not being polled. By not specifying a day for
the scheduled frequency hop, it becomes a daily occurrence.
After creating the spectrum group, you must assign it to an upstream port(s).
Router(config)# interface c6/0
Router(config-if)# no cable upstream 0 frequency
Router(config-if)# cable upstream 0 spectrum-group 1
Router(config-if)# no cable upstream 0 shutdown
A discrete frequency assigned to the upstream port will be overridden when a spectrum group is added
to the interface
Command Reference
This section documents commands necessary to configure upstream cable interfaces for spectrum
management. All other commands used with this feature are documented in the Cisco IOS Release 12.1
command reference publications.
•
cable spectrum-group band
•
cable upstream frequency
•
cable upstream hop algorithm
•
cable upstream power-adjust
•
cable upstream shutdown
•
show cable modulation-profile
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cable modulation-profile
cable modulation-profile
To define the modulation profile, use the cable modulation-profile global configuration command. To
remove the specified modulation profile, use the no form of this command.
cable modulation-profile profile iuc fec-tbytes fec-len burst-len guard-t mod scrambler seed diff
pre-len last-cw uw-len
no cable modulation-profile profile iuc fec-tbytes fec-len burst-len guard-t mod scrambler seed
diff pre-len last-cw uw-len
Syntax Description
profile
Modulation profile number.
iuc
Interval usage code. Valid entries are: initial, long, request, short, or station.
fec-tbytes
The number of bytes that can be corrected per FEC code word. Valid values
are from 0 to 10, where 0 means no FEC.
fec-len
FEC code word length. Valid values are from 16 to 253.
burst-len
Maximum burst length in minislots. Valid values are from 0 to 255, where
0 means no limit.
guard-t
Guard time in symbols. The time between successive bursts.
mod
Modulation. Valid entries are 16qam and qpsk.
scrambler
Enable or disable scrambler. Valid entries are scrambler and no-scrambler.
seed
Scrambler seed in hexidecimal format. Valid values are from 0x0000 to
0x7FFF.
diff
Enable or disable differential encoding. Valid entries are diff and no-diff.
pre-len
Preamble length in bits. Valid values are from 2 to 128.
last-cw
Handling of FEC for last code word. Valid entries are fixed for fixed code
word length and shortened for shortened last code word.
uw-len
Upstream unique word length. Enter uw8 for 8-bit unique words or uw16
for 16-bit unique code words.
Defaults
Modulation profile #1
Command Modes
Global configuration
Command History
Release
Modification
11.3 NA
This command was introduced.
12.0(7)XR2
This command was used
12.1(3)EC
This command was used.
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cable modulation-profile
Usage Guidelines
A modulation profile is a collection of six burst profiles that are sent out in an upstream channel
descriptor (UCD) message to configure modem transmit parameters for the upstream message types:
request, initial maintenance, station maintenance, short grant, and long grant.
You can use the no cable modulation-profile command to remove all modulation profiles except
modulation profile 1. In the case of modulation profile 1, the no cable modulation-profile command
sets all the parameters in a burst to default values.
Caution
Changes to modulation profiles causes changes to the physical layer. Because changing
physical layer characteristics affects router performance and function, this task should be
reserved for expert users.
To use the cable modulation-profile command correctly, enter a line with all parameters for each
upstream burst type. An incomplete burst profile causes unreliable operation, or loss of modem
connectivity.
Turning the scrambler off can cause packet loss, and is only used in lab testing environments.
Errors or incompatible configurations in the burst profile(s) cause modems to either drop connectivity,
drop short or long data packets, or fail to connect to the network. It is possible to build a burst profile
set for which no implementation of a DOCSIS receiver is capable of receiving the modem’s
transmission.
The data rates 160 Ksymbol/sec and 2560 Ksymbol/sec are highly sensitive to unique word length,
preamble length, and FEC sizing. Incorrect choices for these values can cause poor or no connectivity
at these symbol rates.
Examples
The following example defines the burst parameters for profile 2:
The request burst is defined to have:
•
0 fec-tbytes
•
16 kbytes fec-len
•
burst-len of 1
•
guard time of 8
•
mod value of qpsk
•
scrambler enabled with a seed value of 152
•
differential encoding disabled
•
preamble length of 64 bits
•
fixed code word length
•
8-bit unique words for upstream unique word length
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cable modulation-profile
The remaining initial, station, short, and long bursts are defined in similar fashion for profile 2.
Router(config)#
fixed uw8
Router(config)#
128 fixed uw16
Router(config)#
128 fixed uw16
Router(config)#
fixed uw8
Router(config)#
fixed uw8
Note
cable modulation-profile 2 request 0 16 1 8 qpsk scrambler 152 no-diff 64
cable modulation-profile 2 initial 5 34 0 48 qpsk scrambler 152 no-diff
cable modulation-profile 2 station 5 34 0 48 qpsk scrambler 152 no-diff
cable modulation-profile 2 short 6 75 6 8 16qam scrambler 152 no-diff 144
cable modulation-profile 2 long 8 220 0 8 16qam scrambler 152 no-diff 160
You must create all of the bursts (request, initial, station, short and long) for this
modulation profile using the modulation profile command.
See the cable modulation-profile command for a description of the output display fields.
Related Commands
Command
Description
cable upstream hop algorithm
Assigns a modulation profile to an interface.
show cable modulation-profile
Displays modulation profile group information.
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cable spectrum-group
cable spectrum-group
To create a spectrum group, use the cable spectrum-group command in global configuration mode. To
disable this spectrum group, use the no form of this command.
cable spectrum-group group-number type {blind | scheduled | daily periodic-sec seconds}
no cable spectrum-group group-number type {blind | scheduled | daily periodic-sec seconds}
Syntax Description
group-number
Spectrum group number. Valid range is from 1 to 32.
blind
Creates a spectrum group that enables the upstream frequency and
input power level to change whenever noise impairs upstream data
traffic.
scheduled daily
Creates a spectrum group that enables the upstream frequency and
power level to change at a set time during the day.
scheduled periodic-sec
Creates a spectrum group that enables the upstream frequency and
power level to change at a specified interval in seconds.
seconds
Rate in seconds when upstream frequency and power level change.
Defaults
No spectrum group is defined.
Command Modes
Global configuration
Command History
Release
Modification
11.3 XA
This command was introduced.
Usage Guidelines
Upstream traffic may be affected by noise or other cable plant impairments. The spectrum manager
monitors the upstream traffic. If station maintenance messages from cable modems are not received for
approximately 2.5 minutes, the spectrum manager reassigns a different upstream frequency to the
upstream channel.
Frequency agility is configured and activated using spectrum groups. A spectrum group is a table of
frequencies that can be used by upstream ports to implement a frequency-hopping policy. There are two
types of policies, blind and scheduled, with two corresponding types of spectrum groups.
•
Blind—The spectrum manager automatically assigns a new upstream channel frequency when
station maintenance (keepalive) messages fail for approximately 2.5 minutes. This represents a
complete impairment of the upstream channel due to noise, plant, or equipment failure.
•
Scheduled—The spectrum manager automatically assigns a new upstream frequency at set times
during the day.
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cable spectrum-group
Note
The cable interface will not operate until you either create and configure a spectrum group
or set a fixed upstream frequency. From the interface configuration prompt, an interface is
assigned membership in a spectrum group. From the interface point of view, the spectrum
group also represents the set of upstreams connected to the same group of fiber nodes. This
allows the spectrum manager to know if the upstream spectrum is shared.
A maximum of 32 spectrum groups can be configured in the system.
Examples
The following example creates three types of spectrum groups and sets the periodic rate to 48000
seconds:
cable spectrum-group 1 blind
cable spectrum-group 2 type scheduled daily
cable spectrum-group 3 type scheduled periodic-sec 48000
Related
Commands
Command
Description
cable spectrum-group Configures a continuous frequency band setting for a cable spectrum group.
band
cable spectrum-group Configures a spectrum group to use a center frequency.
frequency
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cable spectrum-group band
cable spectrum-group band
To configure a continuous frequency band setting for a spectrum group, use the cable spectrum-group
band command in global configuration mode. To delete the band settings for a spectrum group, use the
no form of this command.
cable spectrum-group group-number [time day hh:mm:ss] [delete] band start-freq-hz
end-freq-hz [power-level-dbmv]
no cable spectrum-group group-number
Syntax Description
group-number
Spectrum group number. Valid values are from 1 to 32.
time day hh:mm:ss
(Optional) For scheduled spectrum groups, makes the frequency band
setting available on the specified day at the specified time in hours
(hh), minutes (mm), and seconds (ss).
delete
(Optional) Removes the frequency band setting from use at the
specified time.
start-freq-hz
Lower boundary of the frequency band.
end-freq-hz
Upper boundary of the frequency band.
power-level-dbmv
(Optional) Nominal input power level in decibels per millivolt
(dBmV). Valid values are from –10 to +10 dBmV. Some cable plants
might want to change only the input power level and not frequency on
a daily time schedule.
Defaults
No default behavior or values.
Command Modes
Global configuration
Command History
Release
Modification
11.3 XA1
This command was introduced.
Usage Guidelines
This command specifies that a continuous frequency band setting be used as a unit of allocated spectrum
within this spectrum group. Cable plants can choose to set up a daily schedule that changes the input
power level and not the frequency.
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cable spectrum-group band
Examples
The following example specifies that all the upstream ports for spectrum-group 4 share the same
spectrum from 5000004 Hz to 40000000 Hz with a power level of 5 dBmV on Mondays at noon:
cable spectrum-group 4 time Monday 12:00:00 band 5000004 40000000 5
The following example deletes the frequency band created in the previous example:
cable spectrum-group 4 time Monday 12:00:00 delete band 5000004 40000000 5
Related
Commands
Command
Description
cable spectrum-group Creates a spectrum group of a specified type.
cable spectrum-group Configures a spectrum group to use a center frequency.
frequency
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cable spectrum-group frequency
cable spectrum-group frequency
To configure a list of upstream frequencies and nominal power levels that each spectrum group can use
when an upstream frequency change is necessary, use the cable spectrum-group frequency command
in global configuration mode. To delete a spectrum group list, use the no form of this command.
cable spectrum-group group-number [time day hh:mm:ss] [delete] frequency ctr-freq-hz
[power-level-dbmv]
no cable spectrum-group group-number
Syntax Description
group-number
Spectrum group number. Valid range is 1 to 32. Configuring a spectrum
group with multiple entries of this type defines a list of frequencies which
are available for use as upstream frequencies.
time day hh:mm:ss
(Optional) For scheduled spectrum groups, specifies the day and time of
day that the frequency and input power level should change. Valid entries
for the day argument are:
Monday: mon
Tuesday: tue
Wednesday: wed
Thursday: thu
Friday: fri
Saturday: sat
Sunday: sun
Valid entries for the hh: argument are 00 to 23.
Valid entries for the mm: argument are 00 to 59.
Valid entries for the ss: argument are 00 to 59.
delete
(Optional) Removes the frequency setting from use at the specified time.
ctr-freq-hz
Upstream frequency in Hz. Valid range is 5,000,000 to 42,000,000 Hz.
power-level-dbmv
(Optional) Nominal input power level. Valid range is –10 to +10 decibels
per millivolt (dBmV). Some cable plants might want to change only the
input power level and not the frequency on a daily time schedule.
Defaults
Operator must determine a value based on the spectrum allocation plan.
Command Modes
Global configuration
Command History
Release
Modification
11.3 XA
This command was introduced.
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cable spectrum-group frequency
Usage Guidelines
After you create a spectrum group, you need to configure a list of upstream frequencies and nominal
power levels that each spectrum group can use when an upstream frequency change is necessary. Each
spectrum group should have its own list of upstream frequencies. Valid frequencies are 5,000,000 to
42,000,000 Hz; valid power levels are –10 dBmV to 10 dBmV. The power level value should only be
entered if you want to change only the power level as part of spectrum management. The standard power
level is 0 dBmV.
Examples
The following example creates spectrum group frequencies:
cable
cable
cable
cable
cable
Related Commands
spectrum-group
spectrum-group
spectrum-group
spectrum-group
spectrum-group
Command
1
1
2
3
3
frequency 6500000
frequency 7000000
frequency 750000 -5
time 02:00:00 frequency 9000000
time 12:00:00 frequency 9500000 -5
Description
cable spectrum-group Creates a spectrum group of a specified type.
cable spectrum-group Configures a continuous frequency band setting for a cable spectrum group.
band
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cable spectrum-group hop period
cable spectrum-group hop period
To set the minimum frequency-hop interval, use the cable spectrum-group hop period command in
global configuration mode. To delete the frequency hop interval for this spectrum group, use the no
form of this command.
cable spectrum-group groupnum hop period seconds
no cable spectrum-group groupnum hop period
Syntax Description
groupnum
Spectrum group number. Valid values are from 1 to 32.
seconds
Specifies the frequency-hop time period in seconds. Valid values are
from 1 to 3600 seconds. Default value is 300 seconds.
Defaults
300 seconds
Command Modes
Global configuration
Command History
Release
Modification
11.3 NA
This command was introduced.
Usage Guidelines
The Cisco uBR7200 series router polls each cable modem at a default rate of once every 10 seconds.
When ingress noise causes the loss of keepalive messages for a specified period of time, a new
frequency is selected from the allocation table and a UCD update is performed.
If the destination channel is expected to be impaired, the minimum period between frequency hops can be
reduced to a small value such as 10 seconds. This allows the frequency hop to continue more rapidly until a
clear channel is found. If excessive frequency hop is a concern, the minimum period between hops can be
increased.
Examples
The following example reduces the minimum frequency-hop interval to 60 seconds:
cable spectrum-group hop period 60
Related Commands
Command
Description
cable spectrum-group Specifies a hop threshold for a cable spectrum group.
hop threshold
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cable spectrum-group hop threshold
cable spectrum-group hop threshold
To specify a frequency hop threshold for a spectrum group, use the cable spectrum-group hop
threshold command in global configuration mode. To delete the hop threshold for this spectrum group,
use the no form of this command.
cable spectrum-group groupnum hop threshold [percent]
no cable spectrum-group groupnum hop threshold
Syntax Description
groupnum
Spectrum group number. Valid values are from 1 to 32.
percent
(Optional) Specifies the frequency hop threshold as a percentage of
cable modems going offline. Valid range is from 1 to 100 percent.
Defaults
100 percent
Command Modes
Global configuration
Command History
Release
Modification
11.3 NA
This command was introduced.
Usage Guidelines
The Cisco uBR7200 series router polls each cable modem at a default rate of once every 10 seconds.
When ingress noise causes loss of keepalive messages from a configurable percentage of all
cable modems, resulting in those cable modems going offline, a new frequency is selected from the
allocation table and a UCD update is performed.
Use this command to prevent a single failing cable modem from affecting service to other good
cable modems.
Examples
The following example sets the threshold that triggers frequency hop to 20 percent of all cable modems
for spectrum-group 4:
cable spectrum-group 4 hop threshold 20
Related Commands
Command
Description
cable spectrum-group Sets the minimum frequency-hop interval for a cable spectrum group.
hop period
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cable spectrum-group shared
cable spectrum-group shared
To specify that the upstream ports in a spectrum group share the same upstream frequency, use the cable
spectrum-group shared command in global configuration mode. To delete this specification, use the
no form of this command.
cable spectrum-group groupnum shared
no cable spectrum-group groupnum shared
Syntax Description
groupnum
Defaults
Upstream port frequency the same for all ports in the spectrum group.
Command Modes
Global configuration
Command History
Release
Modification
11.3 NA
This command was introduced.
Spectrum group number. Valid values are from 1 to 32.
Usage Guidelines
Because this command forces upstream ports to use the same spectrum, do not use this command for
overlapping carriers.
Examples
The following example specifies that all the upstream ports for spectrum-group 4 share the same
upstream frequency:
cable spectrum-group 4 shared
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cable upstream channel-width
cable upstream channel-width
To specify an upstream channel width for an upstream port, use the cable upstream channel-width
command in cable interface configuration mode. To set the channel width back to the default setting of
1600000 Hz, use the no form of this command.
cable upstream usport channel-width first-choice-width [last-choice-width]
no cable upstream usport channel-width
Syntax Description
usport
Specifies the port number.
first-choice-width
Specifies upstream channel width in hertz (Hz). Valid values are:
200000 (160000 symbols/sec), 400000 (320000 symbols/sec),
800000 (640000 symbols/sec), 1600000 (1280000 symbols/sec), and
3200000 (2560000 symbols/sec).
last-choice-width
(Optional) The upstream channel width in hertz. The valid values are
the same as those for the first-choice-width parameter. Use this
parameter with the Cisco uBR-MC16S cable modem card to enable
symbol rate management algorithms. The symbol rate automatically
steps up from the first-choice-width value to the highest value until a
stable channel is established.
Defaults
1600000 Hz
Command Modes
Cable interface configuration
Command History
Release
Modification
11.3(5)NA
This command was introduced.
12.0(4)XI
The last-choice-width argument was added.
Usage Guidelines
The last-choice-width parameter is only supported by the Cisco uBR-MC16S cable modem line card.
When the Cisco uBR-MC16S card is installed, the system attempts to increase the channel width from
the first-choice-width value to the last-choice-width value one step at a time.
Examples
The following example configures upstream port 2 with a channel width of 200,000 Hz (which is
equivalent to a symbol rate of 160 kilosymbols/second):
interface cable 6/0
cable upstream 2 channel-width 200000
The following example configures upstream port 3 to step from a channel width of 1600000 Hz to a
channel width of 3200000 Hz in increments of 200000 Hz:
interface cable 6/0
cable upstream 3 channel-width 1600000 3200000
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cable upstream channel-width
Related Commands
Command
Description
cable upstream
fec-strength
Overrides the FEC setting specified in the modulation profile for an
upstream channel.
cable upstream hop
algorithm
Configures the frequency hop algorithm for the upstream port of a cable
router.
cable upstream
modulation
Overrides modulation types specified in the modulation profile for the
specified upstream channel.
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cable upstream frequency
cable upstream frequency
To enter a fixed frequency of the upstream radio frequency (RF) carrier for an upstream port, use the
cable upstream frequency command in cable interface configuration mode. To restore the default
value for this command, use the no form of this command.
cable upstream usport frequency up-freq-hz
no cable upstream usport frequency up-freq-hz
Syntax Description
usport
Specifies the upstream port number. Valid range is from 0 to 5
if you are using a Cisco uBR-MC16S cable modem card.
up-freq-hz
The upstream center frequency is configured to a fixed value.
The valid range is from 5,000,000 to 42,000,000 Hz.
Defaults
Upstream center frequency is not configured to a fixed value.
Command Modes
Cable interface configuration
Command History
Release
Modification
11.3 NA
This command was introduced.
Usage Guidelines
The upstream channel frequency of your RF output must be set to comply with the expected input
frequency of your Cisco cable modem line card. To configure an upstream channel frequency, you may:
•
Configure a fixed frequency between 5 to 42 MHz and enable the upstream port, or
•
Create a global spectrum group, assign the interface to it, and enable the upstream port.
To configure the default upstream frequency (which is no fixed frequency), enter the cable upstream
usport frequency command without specifying a center frequency.
Examples
The following example configures the upstream center frequency for port 0 (located in slot 6) to
5700000 Hz:
interface cable 6/0
cable upstream 0 frequency 5700000
Related Commands
Command
Description
cable spectrum-group band
Specifies the channel width of the given upstream cable interface.
cable upstream power-adjust
Specifies the upstream cable interface receive power level in dBmV.
cable upstream shutdown
Activates or shuts down a specified upstream cable interface.
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cable upstream hop algorithm
cable upstream hop algorithm
To configure the frequency hop algorithm for the upstream port, use the cable upstream hop algorithm
command in cable interface configuration mode. To configure the optimum algorithm, use the no form
of this command.
cable upstream usport hop algorithm {blind | optimum}
no cable upstream usport hop algorithm
Syntax Description
usport
Specifies the upstream port number. Valid range is from 0 to 5 if you
are using a Cisco MC16 cable modem card.
blind
Selects the blind frequency hop algorithm.
optimum
Selects the optimum hop algorithm.
Defaults
Optimum
Command Modes
Cable interface configuration
Command History
Release
Modification
12.0(4)XI
This command was introduced.
Usage Guidelines
This command is only supported on the Cisco uBR-MC16S cable modem card.
Examples
The following example configures the optimum hop algorithm:
interface cable 6/0
cable upstream 3 hop algorithm optimum
Related Commands
Command
Description
cable upstream
channel-width
Specifies an upstream channel width for a headend cable router.
cable upstream
fec-strength
Overrides the FEC setting specified in the modulation profile for an
upstream channel.
cable upstream
modulation
Overrides modulation types specified in the modulation profile for the
specified upstream channel.
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cable upstream power-adjust
cable upstream power-adjust
To control power adjustment methods on the Cisco uBR7200 series cable routers, use the cable
upstream power-adjust command in interface configuration mode. To disable power adjustments, use
the no form of this command.
cable upstream n power-adjust [continue] [noise % of power adjustment] [threshold #]
no cable upstream power-adjust
Syntax Description
n
Specifies the upstream port number.
continue
Specifies the regular power adjustment method (minimum power
adjustments).
noise
Specifies that a percentage of power adjustment packets is required to
change the adjustment method from the regular power adjustment
method to the noise power adjustment method.
% of power adjustment
Specifies the percentage of power adjustment packets required to
switch from the regular power adjustment method to the noise power
adjustment method. Valid range is from 10 to 100%.
threshold #
Specifies the power adjustment threshold. The threshold range is
from 0 to 10dB.
Defaults
No default behavior or values.
Command Modes
Interface configuration
Command History
Release
Modification
12.0(7)T
This command was introduced.
Examples
The following example illustrates how to change the power adjustment method when the percentage of
power adjustment packets reaches 50 percent:
cable upstream 0 power-adjust noise 50
Related Commands
Command
Description
cable upstream frequency
Configures a fixed frequency of the upstream RF carrier for an
upstream port.
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cable upstream power-adjust
Command
Description
show cable flap-list
Displays a list of cable modems that have exceeded the threshold
number of power adjustments.
show cable modem
Displays cable modem configuration settings.
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cable upstream shutdown
cable upstream shutdown
To disable the upstream port, use the cable upstream shutdown command in cable interface
configuration mode. To enable the upstream port, use the no form of this command.
cable upstream usport shutdown
no cable upstream usport shutdown
Syntax Description
usport
Defaults
Upstream port enabled
Command Modes
Cable interface configuration
Command History
Release
Modification
11.3 XA
This command was introduced.
Examples
Specifies the upstream port number. Valid range is from 0 to 5 if you are using
a Cisco MC16 cable modem card.
The following example disables the upstream port:
interface cable 6/0
cable upstream 0 shutdown
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show cable modulation-profile
show cable modulation-profile
To display modulation profile group information, use the show cable modulation-profile privileged
EXEC command.
show cable modulation-profile [profile] [iuc-code]
Syntax Description
profile
(Optional) Profile number. Valid values are from 1 to 8.
iuc-code
(Optional) Internal usage code. Valid options are:
initial—Initial ranging burst
long— Long grant burst
request—Request burst
short—Short grant burst
station— Station ranging burst
Defaults
No default behavior or values.
Command Modes
Privileged EXEC
Command History
Release
Modification
11.3 XA
This command was first introduced.
12.(0)7XR2
This command was used.
12.1(3)EC
This command was used.
Usage Guidelines
The show cable modulation-profile command displays modulation profile group information. A
modulation profile is a collection of six burst profiles that are sent out in a UCD message to configure
modem transmit parameters for the following upstream message types: request, initial maintenance,
station maintenance, short grant, and long grant.
The following is sample output from the show cable modulation-profile command:
router# show cable modulation-profile 1
Mo IUC
Type
Preamb Diff FEC
length enco T
1
1
1
1
qpsk
qpsk
qpsk
qpsk
64
128
128
72
request
initial
station
short
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no
no
no
no
FEC
CW
Scrambl
seed
bytes
size
0x0
0x10 0x152
0x5
0x22 0x152
0x5
0x22 0x152
0x5
0x4B 0x152
Max
B
1
0
0
0
Guard
time
size
8
48
48
8
Last
CW
size
no
no
no
no
Scrambl Preamb
offset
short
yes
56
yes
0
yes
0
yes
48
Cisco uBR-MC16S Spectrum Management Enhancements
Debug Commands
The following table describes the fields shown in the show cable modulation-profile display.
Field
Description
Mo
Modulation profile group number. A modulation profile group is the
set of burst profiles that define upstream transmit characteristics for
the various types of upstream transmission classes.
IUC
Internal usage code. Each upstream transmit burst belongs to a class
which is given a number called the IUC. Bandwidth maps messages
by IUC codes used to allocate upstream time slots. The following
types are currently defined:
Request—bandwidth request slot
Initial maintenance—initial link registration contention slot
Station maintenance—link keep-alive slot
Short data grant—short data burst slot
Long data grant—long data burst slot
Related Commands
Type
Modulation type.
Preamb length
Preamble length.
Diff enco
Differential encoding enabled (yes) or not enabled (no).
FEC T bytes
Number of bytes that can be corrected for each FEC code word.
FEC CW size
Size, in bytes, of the FEC codeword.
Scrambl seed
Scrambler seed value in hex format.
Max B size
Maximum burst size.
Guard time size
Time between successive bursts measured in symbols.
Last CW short
Handling of FEC for shortened last code word.
Scrambl
Scrambler enabled (yes) or not enabled (no).
Preamb offset
The bits to be used for the preamble value.
Command
Description
cable modulation-profile
Creates a modulation profile
Debug Commands
This section documents the new debug cable hw-spectrum command. All other commands used with
this feature are documented in the Cisco IOS Release 12.1 T command reference publications.
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debug cable hw-spectrum
debug cable hw-spectrum
To display debug messages for spectrum management information, use the debug cable hw-spectrum
EXEC command. To disable the display of this information, use the no form of this command.
debug cable hw-spectrum
no debug cable hw-spectrum
Syntax Description
This command has no arguments or keywords.
Defaults
No default behavior or values.
Command History
Release
Modification
12.0 T
This command was introduced as the debug cable specmgmt
command.
12.0(5)T1
Command renamed to the debug cable hw-spectrum command.
12.0(5)T1
Command included on mainline release.
12.0(7)XR2
Command included on this special release.
Examples
Lab-CMTS# debug cable hw-spectrum
CMTS spectrum analyzer debugging is on
Related Commands
Command
Description
debug cable freqhop
Displays messages for frequency hopping.
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