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Cisco IOS Software Releases 12.1 Special and Early Deployments

Cisco uBR-MC16S Spectrum Management Enhancements

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Cisco uBR-MC16S Spectrum Management Enhancements

Table Of Contents

Cisco uBR-MC16S Spectrum Management Enhancements

Feature Overview

Two-Way Cable

Sparse Versus Dense Segment

Upstream Signals

Combiner Groups

Frequency Allocation Table

Frequency Management Policy

Dynamic Upstream Modulation

Benefits

Restrictions

Related Documents

Supported Platforms

Supported Standards, MIBs, and RFCs

Prerequisites

Configuration Tasks

Configuring Spectrum Groups

Configuring Frequency Hopping

Verifying Your Settings

Configuration Examples

Spectrum Groups Example

Command Reference

cable modulation-profile

cable spectrum-group

cable spectrum-group band

cable spectrum-group frequency

cable spectrum-group hop period

cable spectrum-group hop threshold

cable spectrum-group shared

cable upstream channel-width

cable upstream frequency

cable upstream hop algorithm

cable upstream power-adjust

cable upstream shutdown

show cable modulation-profile

Debug Commands

debug cable hw-spectrum


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

Supported Platforms

Supported Standards, MIBs, and RFCs

Prerequisites

Configuration Tasks

Configuration Examples

Command Reference,

Debug Commands

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.

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.

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.


Caution 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:

Sparse segment—Containing one upstream channel per upstream segment.

Dense segment—Containing multiple upstream channels per upstream segment; frequencies must be different.


Note A cable modem card supports either sparse or dense segments—not both.


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

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.

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.


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.

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.

Restrictions

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.

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

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

CISCO-CABLE-SPECTRUM-MIB.my

CISCO-CABLE-SPECTRUM-MIB-V1SMI.my

CISCO-DOCS-EXT-MIB


Note 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.

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

Configuring Frequency Hopping

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

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)

Step 4 

Router(config-if)# cable n spectrum-group y

Enters interface configuration mode, and assigns the upstream port to the frequency hop table.

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.

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

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)

Step 4 

Router(config-if)# cable 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.

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

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.

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

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.


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

The remaining initial, station, short, and long bursts are defined in similar fashion for profile 2.

Router(config)# cable modulation-profile 2 request 0 16 1 8 qpsk scrambler 152 no-diff 64 
fixed uw8
Router(config)# cable modulation-profile 2 initial 5 34 0 48 qpsk scrambler 152 no-diff 
128 fixed uw16
Router(config)# cable modulation-profile 2 station 5 34 0 48 qpsk scrambler 152 no-diff 
128 fixed uw16
Router(config)# cable modulation-profile 2 short 6 75 6 8 16qam scrambler 152 no-diff 144 
fixed uw8
Router(config)# cable modulation-profile 2 long 8 220 0 8 16qam scrambler 152 no-diff 160 
fixed uw8

Note 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.


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.


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 band

Configures a continuous frequency band setting for a cable spectrum group.

cable spectrum-group frequency

Configures a spectrum group to use a center frequency.


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.

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 frequency

Configures a spectrum group to use a center 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.


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 spectrum-group 1 frequency 6500000
cable spectrum-group 1 frequency 7000000
cable spectrum-group 2 frequency 750000 -5
cable spectrum-group 3 time 02:00:00 frequency 9000000
cable spectrum-group 3 time 12:00:00 frequency 9500000 -5

Related Commands

Command
Description

cable spectrum-group

Creates a spectrum group of a specified type.

cable spectrum-group band

Configures a continuous frequency band setting for a cable spectrum group.


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 hop threshold

Specifies a hop threshold for a cable spectrum group.


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 hop period

Sets the minimum frequency-hop interval for a cable spectrum group.


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

Spectrum group number. Valid values are from 1 to 32.


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.


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

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

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.


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.


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.


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.

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.


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

Specifies the upstream port number. Valid range is from 0 to 5 if you are using a Cisco MC16 cable modem card.


Defaults

Upstream port enabled

Command Modes

Cable interface configuration

Command History

Release
Modification

11.3 XA

This command was introduced.


Examples

The following example disables the upstream port:

interface cable 6/0 
 cable upstream 0 shutdown

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     FEC   Scrambl Max  Guard Last Scrambl Preamb 
                 length enco T       CW    seed    B    time  CW           offset 
                                bytes    size           size  size  short
1  request qpsk  64     no   0x0     0x10  0x152   1    8     no   yes     56 
1  initial qpsk  128    no   0x5     0x22  0x152   0    48    no   yes     0 
1  station qpsk  128    no   0x5     0x22  0x152   0    48    no   yes     0 
1  short   qpsk  72     no   0x5     0x4B  0x152   0    8     no   yes     48 

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

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.


Related Commands

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.

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 CommandsRelated Commands

Command
Description

debug cable freqhop

Displays messages for frequency hopping.