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The following sections describe spectrum management implementation using Cisco uBR7200 series software and the Cisco 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:
 | Caution Upstream modulation profiles can be assigned to specific upstream ports based on the Cisco cable modem card used. Only those familiar with DOCSIS who have received the proper training should create upstream modulation profiles. |
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:
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. Figure 1 illustrates sparse versus 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.
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 Upstream Channel Descriptor (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.
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.
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.
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:
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.
With the release of the Cisco MC16S cable modem card, you can perform automatic upstream frequency hopping. You can configure the 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.
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.
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.
This section presents tips, capabilities, and guidelines to keep in mind when configuring the Cisco uBR7200 series for spectrum management.
In general, when defining your spectrum, be sure to take the following into consideration:
Using the Cisco uBR7200 series cable modem cards and Cisco IOS Release 12.0(7)XR2 CMTS images, you can configure the router to:
Following is an example topology for a Cisco uBR7223 with combiner groups designated A through J. Combiner groups C and E have multiple upstream ports. These should be configured in a shared spectrum group. The other upstreams should be configured in a non-shared spectrum group.
In this example, ten combiner groups are served with frequency hop tables from three spectrum groups:
Cable3/0 DS +-----+ Upconverter +----- laser group 1 U0 +----- combiner group A U1 +----- combiner group B U2 +------combiner group C U3 +------combiner group C U4 +----- combiner group D U5 +------combiner group E Cable4/0 DS +-----+ Upconverter +----- laser group 2 U0 +------combiner group E U1 +----- combiner group F U2 +----- combiner group G U3 +----- combiner group H U4 +----- combiner group I U5 +----- combiner group J
The laser group term refers to the set of fiber nodes that share the same downstream signal. An optical splitter is often used to create individual feeds-per-node.
In the downstream direction, two 6 MHz channel slots are assigned. All fiber nodes in combiner groups A-E should have a channel slot containing the downstream signal from Cable3/0. Combiner groups A-E are said to belong to "laser group 1."
All fiber nodes in combiner groups E-J should have a channel slot containing the downstream signal from Cable4/0. Combiner groups E-J are said to belong to "laser group 2."
Because combiner group E belongs to two laser groups, there should be two different downstream channel slots for Cable3/0 and Cable4/0.
Assuming that all combiner groups use the frequency band from 20 to 26 MHz, the following configuration enables spectrum management for all upstream ports:
cable spectrum-group 1 band 20000000 26000000 cable spectrum-group 2 shared cable spectrum-group 2 band 20000000 26000000 cable spectrum-group 3 shared cable spectrum-group 3 band 20000000 26000000 interface Cable3/0 cable spectrum-group 1 cable upstream 2 spectrum-group 2 cable upstream 3 spectrum-group 2 cable upstream 5 spectrum-group 3 interface Cable4/0 cable spectrum-group 1 cable upstream 0 spectrum-group 3
A description of the spectrum groups 1 through 3 follows:
Upstream Port RF Domain Cable3/0 U0 combiner group A Cable3/0 U1 combiner group B Cable3/0 U4 combiner group D Cable4/0 U1 combiner group F Cable4/0 U2 combiner group G Cable4/0 U3 combiner group H Cable4/0 U4 combiner group I Cable4/0 U5 combiner group J
Upstream Port RF Domain Cable3/0 U2 combiner group C Cable3/0 U3 combiner group C
Upstream Port RF Domain Cable3/0 U5 combiner group E Cable4/0 U0 combiner group E
For the 20 to 26 MHz band of each RF domain, the spectrum is channelized according to the channel width settings of each member port. For example, if the ports U2 and U3 of Cable3/0 are set to 3.2 MHz and 1.6 MHz channel widths, respectively, then spectrum group 2 uses the following channelization:
> Channel Width Start Stop Center > (Mhz) (Mhz) (Mhz) (Mhz) > 1 3.2 20.0 23.2 21.6 > 2* 1.6 20.0 21.6 20.8 > 3* 1.6 21.6 23.2 22.4 > 4 1.6 23.2 24.8 24.0
Because the group is shared, ports U2 and U3 will be assigned channels 1 and 4, respectively, to prevent overlap.
> Channel Width Start Stop Center > (Mhz) (Mhz) (Mhz) (Mhz) > 1 3.2 20.0 23.2 21.6 > 2 3.2 23.2 26.4 24.8 > 3 1.6 20.0 21.6 20.8 > 4 1.6 21.6 23.2 22.4 > 5 1.6 23.2 24.8 24.0 > 6 1.6 24.8 26.4 25.6 > 7 1.6 26.4 28.0 27.4
Care should be taken to reduce the spectrum allocation when used with small channel widths. Otherwise, there will be a large number of upstream channel slots.
For example, if the allocation is from 20.0 to 28.0 MHz and an upstream port has its channel width set to 0.2 MHz, then there will be 40 possible slots for that channel width. Blind frequency hopping may require quite a long time to find the clean slot since it will try each available slot, one at a time for several seconds each try.
In addition to frequency, the nominal input power level of the upstream receivers can be set at the time of frequency hop. This allows the cable operator to perform minor equalization as a function of frequency.
cable spectrum-group 1 frequency 21600000 cable spectrum-group 1 frequency 24800000 1 cable spectrum-group 1 frequency 28000000 2
In this example, the upstream port nominal receive power at 21.6 MHz is 0 dBmV, at 24.8 MHz is 1 dBmV, and at 28.0 MHz is 2 dBmV. At any time, the power level set in the interface configuration overrides the spectrum group power level.
You can add spectrum on a weekly schedule by including an optional weekday and time:
cable spectrum-group 1 time Mon 08:00:00 frequency 21600000
Deletion is performed using the "delete" keyword:
cable spectrum-group 1 time Mon 18:00:00 delete frequency 21600000
If your cable plant has an upstream noise characteristic on a weekly cycle, use time-scheduled spectrum allocation.
Per DOCSIS RFI specification section 6.3.2.2, RF channel migration occurs by broadcasting a change in the UCD message to all cable modems. The UCD message contains the upstream frequency and transmission parameters associated with an upstream channel.
The speed of channel migration via the UCD message is typically less than 20 ms. During that period of time, upstream transmission is interrupted until the cable modem transmitter adjusts to its new frequency. Data is stored in the cable modem's buffers for this brief period of time and sent when the frequency hop is complete.
Also, per the DOCSIS RFI, station maintenance intervals are used to perform per-modem keepalive polling. The Cisco uBR7200 series routers poll each cable modem at least once every 30 seconds, with the default polling count of once every 25 seconds. When there are fewer than 25 modems per downstream, the default polling rate is every modem per second. The system takes the total number of modems to be polled every 25 seconds, and evenly distributes the number of modems polled per second.
When ingress noise or interference causes loss of keepalive messages from a configurable percentage of all cable modems (resulting in missed polls) connected to an MC16S with Cisco IOS Release 12.0(7)XR2, a new frequency is selected from the allocation table and an UCD update is performed. But, the system must wait until a hop threshold time interval has elapsed before it can act on that hop.
The migration time is 2 msec for any upstream UCD update. Once the UCD is updated, the hop has occurred. The system must wait the hop period until it changes the UCD a second time.
The system will not hop endlessly, because one cable modem is generating 90% of the errors and 90% of the traffic.
If the CMTS does not receive two polls in a row, it will signal a frequency hop. A single modem missing two polls in a row counts as 10% missed polls. The CMTS polls all modems sequentially.
It waits for 20 seconds. If it misses two polls in a row again, it frequency hops again. This pattern is repeated.
The default threshold of 100% can be modified using the following IOS global configuration command:
cable spectrum-group {1|2|3|...|32} frequency hop threshold {1|2|3|...|100}
The percentage threshold method prevents a single failing cable modem from affecting service to other good cable modems. To prevent excessive frequency hop, the minimum period between hops can be changed from the default value of 300 seconds using the following Cisco IOS global configuration command.
cable spectrum-group {1|2|3|...|32} frequency hop period {1|2|3|...|3600}
If the destination channel is expected to be impaired, then the frequency hop period threshold 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.
The current implementation is known as blind frequency hop because there is no "look-ahead" mechanism. In this case, the search time is 0 seconds and the switching time is 20 ms.
The upstream port becomes "up" when it is assigned an upstream frequency and it is configured to be administratively up. Configuring a spectrum group enables frequency agility and disables the fixed upstream frequency setting.
A maximum of 32 spectrum groups can be configured in the system. Configuring a spectrum group allows the upstream frequency and input power level to change whenever noise impairs upstream data traffic.
cable spectrum-group groupnum [ time day hh:mm:ss ] [delete] frequency ctr-freq-hz power-level-dBmV cable spectrum-group groupnum [ time day hh:mm:ss ] [delete] band start-freq-hz end-freq-hz power-level-dBmV groupnum
Specifies the spectrum group number. (The valid range is 1 to 32.)
If the time parameter is present, then the frequency setting or band is made available or is deleted at the specified time.
delete (Optional)
Specifies that the frequency setting or band should be removed from use at the specified time.
frequency
Specifies that a center frequency setting should be a unit of allocated spectrum in this spectrum group.
ctr-freq-hz
Upstream center frequency. Valid range is 5,000,000 to 42,000,000 Hz (5 to 42 MHz) depending on the cable modem card used. Half of the upstream carrier energy is distributed below and the other half above this point.
band
Specifies that a continuous band setting should be a unit of allocated spectrum in this spectrum group.
start-free-hz
Specifies the lower boundary of a frequency band.
end-freq-hz
Specifies the upper boundary of a frequency band.
power-level-dBmV
Specifies the nominal input power level. (The valid range is -10 to +25 dBmV.)
no cable spectrum-group groupnum
Specifies that a given spectrum group should be deleted.
[no] cable spectrum-group n shared
"Shared" indicates that upstream ports must share the same spectrum, and, therefore, must never be set for overlapping carriers.
[no] cable spectrum-group n hop period period-sec [no] cable spectrum-group n hop threshold thres-pcnt hop
Indicates that a frequency hop parameter is to be configured for a period.
period-sec
Valid range is 1 to 3600 seconds. This parameter limits the frequency hop rate to a configured period value in seconds. The configured value may be returned to its default of 300 seconds using the no keyword.
thres-pcnt
Valid range is 0 to 100 percent.
Specify upstream channel width in Hz. Valid values are 200000, 400000, 800000, 1600000, and 3200000 based on the cable modem card used. The corresponding symbol rate is 160000, 320000, 640000, 1280000, and 2560000 symbols/sec. A default value of 1600000 Hz (1280000 symbols/sec) is configured by the no keyword.
cable upstream n channel-width width [no] cable upstream n channel-width width
The channel width set by this command determines the amount of spectrum needed during frequency assignment.
[no] cable upstream port shutdown shutdown (Default)
Disables the upstream port. In this mode, downstream UCD and MAP messages for the upstream channel are disabled which inhibits the upstream transmitters on the cable modems.
no...shutdown
Enables the upstream port. The operator must configure this option to enable data traffic.
[no] cable spectrum-group groupnum no...spectrum-group (Default) Disable frequency agility. groupnum
Enable frequency agility and spectrum management of the upstream frequency and power. The global spectrum group specified by groupnum defines a frequency table; otherwise, the upstream port will assume the "down" state.
Upstream parameters must be configured manually. After the setup facility is run, upstream ports have a default state of "shutdown." To configure upstream channel frequencies, you have two choices:
The cable modem card receiver accepts time-division multiplexed burst transmissions from cable modems which are DOCSIS compliant. The upstream port becomes "up" when it is assigned an upstream frequency and is configured to be administratively up.
Upstream burst parameters can be configured by defining individual modulation profiles. A modulation profile consists of a table of physical layer characteristics for the different types of upstream bursts, for example, initial maintenance, long grant, request/data, request, short grant, and station maintenance.
To activate upstream interfaces on the MC16S, follow these steps:
Step 1 After the setup facility has initially configured non-cable interfaces on the Cisco uBR7200 series, get into enable (privileged EXEC) mode by entering the enable command and your password.
For detailed information regarding the Setup Facility on the Cisco uBR7200 series universal broadband router, refer to the "Configuring the Cisco uBR7200 Series" chapter of the Cisco uBR7200 Series Universal Broadband Router Hardware Installation Guide.
Step 2 Enter the configure terminal command to get into global configuration mode.
Step 3 In global configuration mode, configure modulation profiles and/or spectrum groups for your Cisco uBR7200 series using the cable modulation-profile and cable spectrum-group commands.
For detailed information regarding parameters and allowable values for the cable modulation-profile and cable spectrum-group commands, refer to the "cable upstream hopping blind" section and the "Debug Commands" section.
Step 4 To configure individual upstream interfaces on the MC16S, enter the cable upstream interface number command to get into cable interface configuration mode.
Step 5 While in cable interface configuration mode, you can configure various characteristics for the interface in question using the cable upstream commands defined in this feature module in the "Command Reference" section and the Cisco uBR7200 Series Universal Broadband Router Cable Modem Card Installation and Configuration document.
You can check your settings and review any changes to your configuration using various software commands.
To check the value of the settings you have entered, enter the show running-config command at the Router# prompt:
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.
You can use a variety of show commands to view information specific to the hardware and cable interface configuration on your Cisco uBR7200 series universal
broadband router. Please refer to the configuration notes that accompanied the various components in your Cisco uBR7200 series for detailed information.
The MC16S consists of a motherboard (based on the MC16C cable modem card) and an additional "piggy-back" spectrum management card. The MC16S supports 256 QAM at 40 Mbps downstream and 16 QAM at 5 Mbps upstream default data rates. The MC16S supports all DOCSIS upstream channel widths—3.2 MHz, 1.6 MHz, 800 kHz, 400 kHz, and 200 kHz—and the card output is +42 dBmV +/- 2 dB. In addition, the MC16S features advanced spectrum management capabilities made possible by hardware and software enhancements.
The MC16S spectrum management daughter card is able to sample the 5-to-42 MHz upstream spectrum and identify clean channels acceptable for a dynamic frequency hop. When a user-defined threshold percentage of "offline" cable modems has been reached, the spectrum management card takes a snapshot of the available upstream spectrum and then passes this information to the Cisco IOS software, where it is analyzed for indications of significant ingress and/or impulse noise. From this analysis, the Cisco IOS software draws informed conclusions regarding the "clean" portion(s) of the upstream frequency spectrum and automatically initiates a frequency hop to a clean upstream channel. The user-defined threshold value is specified by a command in the configuration file of the Cisco uBR7200 series router.
The advanced spectrum management capabilities of the MC16S include the ability to hierarchically scan portions of the upstream spectrum for clean channels of varying widths. For more specific information on MC16S capabilities and programming, refer to the "Command Reference" section.
Table 1 lists the Cisco IOS universal broadband router features related to the scope of this feature module.
| Feature | IOS Release |
|---|---|
Upstream Traffic Shaping Feature | 11.3(9)NA |
Blind Frequency Hopping and Time Scheduled Frequency Hopping Support | 12.0(5)T1 |
Guided Frequency Hopping | 12.0(5)T1 |
Enhanced Spectrum Management | 12.0(5)T1 |
Blind Frequency Hopping Support on the MC16S Cable Modem Card | 12.0(7)XR2 |
Signal-to-Noise Ratio Data Support | 12.0(7)XR2 |
Upstream Spectrum Management Capabilities Expanded Using the MC16S Cable Modem Card—MC16S Can Now Scan Upstream Spectrum for Clean Channel Before Initiating Frequency Hop | 12.0(7)XR2 |
The Cisco uBR7200 series universal broadband router is described in Cisco IOS Release 12.1 and in the following online feature modules:
No new or modified standards are supported by this feature.
Table 2 lists the MIBs necessary to support spectrum management functionality on Cisco uBR7200 series universal broadband routers.
| MIB Filename | Description | Release |
|---|---|---|
CISCO-CABLE-SPECTRUM-MIB.my | This module describes the spectrum management flap list attributes. | 12.0(5)T1 |
No new or modified RFCs are supported by this feature.
This section documents commands necessary to configure upstream cable interfaces for spectrum management. Configuring your Cisco uBR7200 series universal broadband router for spectrum management involves setting up the basic (global) attributes of your upstream interfaces as well as specifically configuring spectrum management capability for those upstream interfaces.
To configure spectrum management capabilities for the MC16S cable modem card, you must configure your upstream interface(s) using the following commands:
Define the elements that are used in a cable modulation profile. You can have up to 8 cable modulation profiles. Profile 1 is the default.
 | Caution If you change a modulation profile, you also make changes to the physical layer. Changing physical layer characteristics affects router performance and function; therefore, this task should only be used by an expert user. |
profile number | Specifies the modulation profile for which you are specifying a parameter value or specifies the number of the modulation profile you wish to remove from your router configuration. Valid range is from 1 to 8. |
parameter |
|
value | The value for the parameter you are assigning to a given modulation profile. |
Modulation profile 1
Global configuration
| Release | Modification |
|---|---|
12.0(5)T1 | This command was introduced. |
The following example to specifies a FEC codeword length of 200 to modulation profile 2:
Router(config)# cable modulation-profile 2 fec-len 200
The following example removes modulation profile 2 from your router configuration:
Router(config)# no cable modulation-profile 2
| Command | Description |
|---|---|
Specifies the center frequency for a given upstream cable interface. | |
Specifies the channel width of the given upstream cable interface. | |
Specifies the upstream cable interface receive power level in dBmV. | |
Activates or shuts down a specified upstream cable interface. | |
Configures spectrum management characteristics for the given spectrum group. | |
Disengages the advanced spectrum management features of the MC16S cable modem card by enabling blind frequency hopping behavior. |
Frequency agility is configured and activated using spectrum groups that are controlled by the spectrum manager. You can create from 1 to 32 spectrum groups for each cable modem card upstream port.
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. At 1.6 MHz, the valid range is -10 dBmV to 25 dBmV. The power level value should only be changed if you want to change only the power level as part of spectrum management. The standard power level is 0 dBmV.
After you have created one or more spectrum groups for your cable network, you can add characteristics to them, providing you with more definitive control over frequency usage and frequency hopping.
group number | Specifies the spectrum group for which you are specifying a parameter value or specifies the number of the spectrum group you wish to remove from your router configuration. Valid range is from 1 to 32. |
parameter | The spectrum group values that can be changed or added are:
|
value | The corresponding parameter value for the parameter you are defining for a given spectrum group. |
None.
Global configuration
| Release | Modification |
|---|---|
12.0(5)T1 | This command was introduced. |
12.0(7)XR2 | The band parameter for this command was added to enable frequency range scanning capabilities in the MC16S cable modem card. |
See the following example to configure spectrum group 1 with an upstream frequency of 6,500,000 Hz and a default power level of 0 dBmV:
Router(config)# cable spectrum-group 1 frequency 6500000
See the following example to add the upstream frequency 7,000,000 Hz to the list of valid frequencies with a default power level of 0 dBmV for spectrum group 1:
Router(config)# cable spectrum-group 1 frequency 7000000
See the following example to configure spectrum group 2 with an upstream frequency 7,500,000 Hz and change the power level to 5 dBmV:
Router(config)# cable spectrum-group 2 frequency 7500000 5
See the following example to configure spectrum group 3 with an upstream band of 12,000,000 to 18,000,000 Hz and default power level of 0 dBmV:
Router(config)# cable spectrum-group 3 band 12000000 18000000
See the following example to add the upstream band 20,000,000 to 24,000,000 Hz to the list of valid bands with a change in the power level of 13 dBmV for spectrum group 3:
Router(config)# cable spectrum-group 3 band 20000000 24000000 13
See the following example to configure a continuous band between 5,000,004 and 40,000,000 Hz for scheduled spectrum group 4 with a default power level of 0 dBmV. The spectrum group will be available to the spectrum group starting at 12:00 p.m. local time each Monday:
Router(config)# cable spectrum-group 4 time Monday 12:00:00 band 5000004 40000000
See the following example to add the upstream frequency 9,500,000 Hz to the list of valid frequencies and change the nominal power level to 5 dBmV. The spectrum manager adjusts frequencies and power levels on this group at 2:00 a.m. local time each day:
Router(config)# cable spectrum-group 3 time 02:00:00 frequency 9500000 5
See the following example to configure the minimum period before which a frequency hop can occur in seconds:
Router(config)# cable spectrum-group 3 hop period 800
See the following example to configure the threshold value (expressed as a percentage) of the number of "offline" modems identified before the Cisco uBR7200 series initiates an automatic frequency hop:
Router(config)# cable spectrum-group 3 hop threshold 40
See the following example to configure a particular spectrum group as a shared RF spectrum group. Specifying a given spectrum group as "shared" tells the Cisco uBR7200 series that you want to be sure that upstream frequencies assigned to upstream interfaces are not assigned to additional upstream interfaces:
Router(config)# cable spectrum-group 3 shared
See the following example to remove a specified spectrum group from your configuration:
Router(config)# no cable spectrum-group 3
| Command | Description |
|---|---|
Specifies the center frequency for a given upstream cable interface. | |
Specifies the channel width of the given upstream cable interface. | |
Configures preset modulation profiles that you can apply to one or more upstream cable interfaces when you identify and configure spectrum groups. | |
Specifies the upstream cable interface receive power level in dBmV. | |
Activates or shuts down a specified upstream cable interface. | |
Disengages the advanced spectrum management features of the MC16S cable modem card by enabling blind frequency hopping behavior. |
Enter the channel width in hertz (Hz). Valid values are 200000 Hz (160 kilosymbols per second [ksps]), 400000 Hz (320 ksps), 800000 Hz (640 ksps), 1600000 Hz (1280 ksps), and 3200000 Hz (2560 ksps). The default is 1600000 Hz.
The MC16S cable modem card features advanced spectrum management capability that allows you to scan the upstream spectrum for clean channel widths of varying size. By entering an optional second channel width value in the appropriate command line, you can instruct the MC16S to hierarchically search for clean upstream channels of 3.2 MHz, 1.6 MHz, 800 kHz, 400 kHz, and 200 kHz width. The spectrum management card on the MC16S will scan the upstream spectrum for clean (usable) channels of the greatest specified width. If no acceptable channels of the specified width can be found, the spectrum management card automatically begins to scan the upstream spectrum for the next largest available channel width. For example, if the spectrum management card is unable to find a usable 1.6 MHz upstream channel, it will automatically begin searching for usable 800 kHz channels. To ensure that only one specified upstream channel width is ever used in a given upstream segment leading to an MC16S, simply enter the same channel width twice in the appropriate command line.
To specify an upstream channel width, use the cable upstream channel-width interface configuration command. Use the no form of this command to set the channel width to 1600000 for a port number.
cable upstream portnum channel-width width1 width2
portnum | Specifies the port number. |
width1 | 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). |
width2 | Specifies the smallest width in hertz (Hz) for this upstream channel. Valid values are 200000 (160000 symbols/sec), 400000 (320000 symbols/sec), 800000 (640000 symbols/sec), 1600000 (1280000 symbols/sec), and 3200000 (2560000 symbols/sec). |
1600000 (1280 Ksymbols/sec)
Cable interface configuration
| Release | Modification |
|---|---|
11.3 NA | This command was introduced. |
12.0(7)XR2 | The width2 option was added. |
See the following example to configure port 2 with a channel width of 3,200,000 Hz and limit the channel width to be no smaller than 400,000 Hz:
Router(config-if)# cable upstream 2 channel-width 3200000 400000
| Command | Description |
|---|---|
Specifies the center frequency for a given upstream cable interface. | |
Configures preset modulation profiles that you can apply to one or more upstream cable interfaces when you identify and configure spectrum groups. | |
Specifies the upstream cable interface receive power level in dBmV. | |
Activates or shuts down a specified upstream cable interface. | |
Configures spectrum management characteristics for the given spectrum group. | |
Disengages the advanced spectrum management features of the MC16S cable modem card by enabling blind frequency hopping behavior. |
Enter a fixed frequency of the upstream RF carrier for an upstream port. You can also select a default that does not set a specific fixed value. The valid range for a fixed upstream frequency is 5,000,000 Hz to 42,000,000 Hz (5 to 40 MHz). The Cisco uBR7200 series will command the cable modems to use this frequency as the center frequency.
interface number | Specifies the upstream interface on the cable modem card for which you want to assign an upstream frequency. |
frequency | Specifies the center frequency (in Hz) for the given upstream interface. Acceptable values range from 5000000 to 42000000. If you wish to have the Cisco uBR7200 series dynamically specify a center frequency for the given upstream interface, you can elect not to enter any frequency value. |
Dynamic (no fixed frequency)
Cable interface configuration
| Release | Modification |
|---|---|
11.3 NA | This command was introduced. |
See the following example to allow the Cisco uBR7200 series to dynamically specify a center frequency upstream interface 0:
Router(config-if)# cable upstream 0 frequency
See the following example to specify a center frequency of 24.016 MHz on upstream interface port 0:
Router(config-if)# cable upstream 0 frequency 24016000
| Command | Description |
|---|---|
Specifies the channel width of the given upstream cable interface. | |
Configures preset modulation profiles that you can apply to one or more upstream cable interfaces when you identify and configure spectrum groups. | |
Specifies the upstream cable interface receive power level in dBmV. | |
Activates or shuts down a specified upstream cable interface. | |
Configures spectrum management characteristics for the given spectrum group. | |
Disengages the advanced spectrum management features of the MC16S cable modem card by enabling blind frequency hopping behavior. |
To override hop decisions, enter the cable upstream hopping blind interface configuration command. To stop blind hopping, enter the no form of this command.
cable upstream interface number hopping blind
interface number | Specifies the number of the upstream cable interface for which blind frequency hopping will be activated. |
Disabled
Cable interface configuration
| Release | Modification |
|---|---|
12.0(7)XR2 | This command was introduced. |
Enter this command to override the hardware spectrum manager's decision to optimize hopping.
router(config-if)# cable upstream 0 hopping blind
| Command | Description |
|---|---|
Specifies the center frequency for a given upstream cable interface. | |
Specifies the channel width of the given upstream cable interface. | |
Configures preset modulation profiles that you can apply to one or more upstream cable interfaces when you identify and configure spectrum groups. | |
Specifies the upstream cable interface receive power level in dBmV. | |
Activates or shuts down a specified upstream cable interface. | |
Configures spectrum management characteristics for the given spectrum group. |
Enter the nominal input power level for the upstream RF carrier in decibels per millivolt (dBmV). You can also select the default of 0 dBmV, which is the optimal setting for the upstream power level.
The valid range for the input power level depends on the data rate. At 1.6 MHz, the valid range is -10 dBmV to 25 dBmV. If your power levels operate at greater than the maximum valid level, you must use an inline attenuator to bring the power level to within the valid range.
| Caution
If you increase the input power level, the cable modems on your HFC network increase their transmit power level. This increases the C/N ratio on the network, but also increases distortion products. CSO and CTB/CX0 values worsen by 2 dB for every 1 dB-increased C/N. The return path laser immediately enters a non-linear mode called clipping and all communication is no longer reliable. Many return lasers send "short" bursts well above the clipping thresholds and fail on longer or successive bursts. It is almost impossible to see CSO and CTB/CX0 products on a lightly loaded HFC network. Approximately 70-90% upstream traffic utilization is required if you directly measure these products using a spectrum analyzer. Be careful if you adjust this parameter. |
You should not adjust your input power level by more than 5 dB in a 30-second interval. If you increase the power level by more than 5 dB within 30 seconds, cable modem service on your network will be disrupted. If you decrease the power level by more than 5 dB within 30 seconds, cable modems on your network will be forced offline.
interface number | Specifies the upstream cable interface for which you are assigning the given power level |
power | Specifies the power level for the given upstream interface |
0 dBmV
Cable interface configuration
| Release | Modification |
|---|---|
11.3 NA | This command was introduced. |
The following example configures a power level of 2 dBmV to upstream cable interface 0:
Router(config-if)# cable upstream 0 power-level 2
The following example sets the upstream power level for cable interface 0 to the default setting of 0 dBmV:
Router(config-if)# no cable upstream 0 power-level
| Command | Description |
|---|---|
Specifies the center frequency for a given upstream cable interface. | |
Specifies the channel width of the given upstream cable interface. | |
Configures preset modulation profiles that you can apply to one or more upstream cable interfaces when you identify and configure spectrum groups. | |
Activates or shuts down a specified upstream cable interface. | |
Configures spectrum management characteristics for the given spectrum group. | |
Disengages the advanced spectrum management features of the MC16S cable modem card by enabling blind frequency hopping behavior. |
Activate the RF carrier on the upstream ports. Each upstream port must be activated to enable upstream data from the cable modems on the HFC network to the Cisco uBR7200 series.
interface number | Specifies the number of the upstream cable interface you are activating or deactivating. |
Cable interfaces are deactivated until the no shutdown command has been issued for them.
Cable interface configuration
| Release | Modification |
|---|---|
11.3 NA | This command was introduced. |
The following example deactivates a specified upstream cable interface:
Router(config-if)# cable upstream 0 shutdown
The following example activates a specified upstream cable interface:
Router(config-if)# no cable upstream 0 shutdown
| Command | Description |
|---|---|
Specifies the center frequency for a given upstream cable interface. | |
Specifies the channel width of the given upstream cable interface. | |
Configures preset modulation profiles that you can apply to one or more upstream cable interfaces when you identify and configure spectrum groups. | |
Specifies the upstream cable interface receive power level in dBmV. | |
Configures spectrum management characteristics for the given spectrum group. | |
Disengages the advanced spectrum management features of the MC16S cable modem card by enabling blind frequency hopping behavior. |
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.
[no] debug cable hw-spectrumThis command has no arguments or keywords.
No default behavior or values.
| 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. |
Lab-CMTS# debug cable hw-spectrum CMTS spectrum analyzer debugging is on
| Command | Description |
|---|---|
debug cable freqhop | Displays messages for frequency hopping. |
Posted: Mon Oct 2 16:50:02 PDT 2000
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