DOCSIS 3.1 Upstream Profile Selection

DOCSIS 3.1 introduces the concept of upstream profiles for OFDMA channels. This document describes how to configure the DOCSIS 3.1 Upstream Profile Selection on the Cisco cBR Series Converged Broadband Router.

Your software release may not support all the features that are documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. The Feature Information Table at the end of this document provides information about the documented features and lists the releases in which each feature is supported.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://tools.cisco.com/ITDIT/CFN/. An account on http://www.cisco.com/ is not required.

Hardware Compatibility Matrix for the Cisco cBR Series Routers


Note
The hardware components that are introduced in a given Cisco IOS-XE Release are supported in all subsequent releases unless otherwise specified.
Table 1. Hardware Compatibility Matrix for the Cisco cBR Series Routers

Cisco CMTS Platform

Processor Engine

Interface Cards

Cisco cBR-8 Converged Broadband Router

Cisco IOS-XE Release 16.5.1 and Later Releases

Cisco cBR-8 Supervisor:

  • PID—CBR-SUP-250G

  • PID—CBR-CCAP-SUP-160G

Cisco IOS-XE Release 16.5.1 and Later Releases

Cisco cBR-8 CCAP Line Cards:

  • PID—CBR-LC-8D30-16U30

  • PID—CBR-LC-8D31-16U30

  • PID—CBR-RF-PIC

  • PID—CBR-RF-PROT-PIC

  • PID—CBR-CCAP-LC-40G

  • PID—CBR-CCAP-LC-40G-R

  • PID—CBR-CCAP-LC-G2-R

  • PID—CBR-SUP-8X10G-PIC

  • PID—CBR-2X100G-PIC

Digital PICs:

  • PID—CBR-DPIC-8X10G

  • PID—CBR-DPIC-2X100G

Cisco cBR-8 Downstream PHY Module:

  • PID—CBR-D31-DS-MOD

Cisco cBR-8 Upstream PHY Modules:

  • PID—CBR-D31-US-MOD

Note

Do not use DPICs (8X10G and 2x100G) to forward IP traffic, as it may cause buffer exhaustion, leading to line card reload.

The only allowed traffic on a DPIC interface is DEPI, UEPI, and GCP traffic from the Cisco cBR-8 router to Remote PHY devices. Other traffic such as DHCP, SSH, and UTSC should flow via another router, since DPICs cannot be used for normal routing.

Information about Upstream Profiles

A modulation profile is a list of interval usage codes (IUCs) that are defined for an OFDMA channel. Each IUC will have a modulation order and pilot pattern. Multiple IUCs within a modulation profile allow for different modulation orders on the same OFDMA channel. The CMTS can define multiple profiles for use in an OFDMA channel, where the profiles differ in the modulation orders assigned to each minislot.

You can use the following commands to view the profiles:

  • To display the profiles associated with the cable modems (CMs), use the show cable modem [ip-address| mac-address| cable| {slot | subslot | cable-interface-index}] phy ofdm-profile upstream command.

  • To display detailed profile management data associated with specific cable modem, use the show cable modem [ip-address| mac-address] prof-mgmt upstream verbose command.

The CMTS can assign different data IUCs for different groups of CMs.

A DOCSIS 3.1 CM can only have two active OFDMA Upstream Data Profile IUCs on a given channel.

Default Data IUC

Data IUC 13 is intended to be the most robust IUC and able to be used by all cable modems.

Recommended Interval Usage Code (IUC)

Based on the receive modulation error ratio (RxMER) values collected periodically during upstream probing, the CMTS finds among the existing IUCs up to two that provide the highest speed while having sufficient signal to noise ratio (SNR) margin for the CMTS to receive code words with acceptable error rates. The show cable modem phy ofdm-profile upstream command displays the one or two recommended IUCs for each CM.

In Cisco IOS XE Everest 16.6.1 release, data IUC 13 will be one of the IUCs assigned to the CM.

To disable the automatic profile downgrade, use no cable upstream ofdma-prof-mgmt prof-upgrade-auto command in global configuration mode.

How to Configure Upstream Profiles

Configuring RxMER to Bit Loading Mapping

There are many ways to map the Receive Modulation Error Ratio (RxMER) values to bit loading values. We use the following mapping recommended in DOCSIS 3.1 OSSI, as our baseline mapping:

RxMER (in ¼ DB)

QAM

Bit Loading

60

16

4

84

64

6

96

128

7

108

256

8

122

512

9

136

1024

10

148

2048

11

164

4096

12

184

8192

13

208

16384

14

  • To configure a margin to adjust the RxMER to bit loading mapping, use the following command: 
    Router(config)# cable upstream ofdma-prof-mgmt mer-margin-qdb interval-in-minutes
    This configured value (quarter-DB) is added to the RxMER values collected by CMTS before using the above mapping table, thus giving a user more control in selecting the recommended profiles.
  • To specify the percentage of minislot average RxMER that can be ignored in the recommended profile calculation, use the following command: 
    Router(config)# cable upstream ofdma-prof-mgmt exempt-mslot-pct percent
    This provides a way to specify the extent that the outliers can be ignored.
  • To configure the RxMER poll interval, use the following command: 
    Router(config)# cable upstream ofdma-prof-mgmt rxmer-poll-interval interval-in-minutes
    The CMTS uses upstream probing to collect RxMER data per CM. This occurs during registration and periodically thereafter. The collected RxMER data is averaged per minislot and used to compute the recommended IUCs for each CM.

    The no cable upstream ofdma-prof-mgmt rxmer-poll-interval command sets the rxmer-poll-interval to 1440, which is the value to disable the feature. The rxmer data is also not displayed after disabling the feature.

Configuring Codeword Error Threshold

Starting from Cisco IOS XE Gibraltar 16.12.1x release, user can configure a codeword error threshold above which the profile will be downgraded, that is, switch to a lower order QAM.

Compared with the existing profile management scheme, in which the RxMER is read at configured interval, and data IUC is upgraded or downgraded based on RxMER data and configurable criteria, using customized codeword error threshold has several benefits, including:

  • React to noise within minimal time window to maintain service quality

  • If IUC selected by RxMER causes errors, it can be downgraded quickly

  • Downgrade interval is much shorter than RxMER interval

To configure the codeword error threshold, enable this feature first:

Router(config)# cable upstream ofdma-prof-mgmt downgrade enable

Then configure the minimum number of codewords required within downgrade interval to consider for downgrade:

Router(config)# cable upstream ofdma-prof-mgmt downgrade min-cws value

Use show cable modem prof-mgmt upstream to check whether this feature is enabled: 

Router#show cable modem 4800.33ef.3dd2 prof-mgmt upstream
Upstream Profile Management Data:
MAC Address            : 4800.33ef.3dd2
Number of US Chan      : 1
 
Ucid                    : 6
RxMer Exempt Percent    : 0
RxMer Margin qDB        : 0
RxMer Threshold Percent : 2
Start Sc                : 148
End Sc                  : 1907
Num RxMER Measurement   : 1908
Tx Time                 : 0h:04m:50s ago
Rx Time                 : 0h:04m:50s ago
MER Poll Period   (min) : 5
Auto Profile Upgrade    : Yes
Upgrd Dly Cnt (cur/cfg) : 0/1
Upgrd Dly rcmd IUC      : none
Recommended IUC         : 5
Current IUC             : 5
Downgrade IUC           : 6
RxMER send/recv count   : 1/1
DBC                     : 1/1/0/0/0
                         (send/succeed/err/reject/timeout)
State                   : Ready
Profile Downgrade       : Enabled
Profile Downgrade count : 0
Interval good/cor/uncor : 294/93/0
Downgrade Check Time    : 0h:00m:14s ago

After a downgrade, Profile Downgrade count is updated in the command output:

Router#show cable modem 4800.33ef.3dd2 prof-mgmt upstream
Upstream Profile Management Data:
MAC Address            : 4800.33ef.3dd2
Number of US Chan      : 1
 
Ucid                    : 6
RxMer Exempt Percent    : 0
RxMer Margin qDB        : 0
RxMer Threshold Percent : 2
Start Sc                : 148
End Sc                  : 1907
Num RxMER Measurement   : 1908
Tx Time                 : 0h:00m:01s ago
Rx Time                 : 0h:00m:01s ago
MER Poll Period   (min) : 5
Auto Profile Upgrade    : Yes
Upgrd Dly Cnt (cur/cfg) : 0/1
Upgrd Dly rcmd IUC      : none
Recommended IUC         : 6
Current IUC             : 6
Downgrade IUC           : 9
RxMER send/recv count   : 3/3
DBC                     : 2/1/0/0/0
                         (send/succeed/err/reject/timeout)
State                   : MER Received
Profile Downgrade       : Enabled
Profile Downgrade count : 1
Interval good/cor/uncor : 222/0/119
Downgrade Check Time    : 0h:00m:03s ago
Holddown Time           : 0h:00m:03s ago

The Holddown Time will not be displayed in the command output anymore after the configured holddown time is expired. In the following example, after two downgrades, the holddown time was expired, an RxMER was read and checked, and the profile was upgraded back to 5. 

Router#show cable modem 4800.33ef.3dd2 prof-mgmt upstream
Upstream Profile Management Data:
MAC Address            : 4800.33ef.3dd2
Number of US Chan      : 1
 
Ucid                    : 6
RxMer Exempt Percent    : 0
RxMer Margin qDB        : 0
RxMer Threshold Percent : 2
Start Sc                : 148
End Sc                  : 1907
Num RxMER Measurement   : 1908
Tx Time                 : 0h:03m:07s ago
Rx Time                 : 0h:03m:07s ago
MER Poll Period   (min) : 5
Auto Profile Upgrade    : Yes
Upgrd Dly Cnt (cur/cfg) : 0/1
Upgrd Dly rcmd IUC      : none
Recommended IUC         : 5
Current IUC             : 5
Downgrade IUC           : 6
RxMER send/recv count   : 6/6
DBC                     : 4/4/0/0/0
                         (send/succeed/err/reject/timeout)
State                   : Ready
Profile Downgrade       : Enabled
Profile Downgrade count : 2
Interval good/cor/uncor : 269/72/0
Downgrade Check Time    : 0h:00m:03s ago

Downgrading to Partial Mode

Starting from Cisco IOS XE Gibraltar 16.12.1y release, user can configure a codeword error threshold above which the profile will be downgraded to partial mode, that is disable some of the OFDMA channels when the CM is currently using IUC13 due to MER or downgrade.

To configure the codeword error threshold, enable this feature first:

Router(config)# cable upstream ofdma-prof-mgmt downgrade enable

Then configure the threshold to consider for downgrading to partial mode:

Router(config)# cable upstream ofdma-prof-mgmt downgrade partial-threshold value

Use show cable modem partial-mode to check the reason for downgrading to partial mode: 

Router#show cable modem 4800.33ef.3dd2 partial-mode
MAC Address    IP Address  I/F       MAC      Prim  RCC  UP-reason/    
                                     State    Sid   ID   Failed-tcsf
81d.0f01.1e10  9.2.0.46    C1/0/0/p  w-online 1     1    0x10 / 0x20

Note: 0x01 = Ranging
      0x10 = CWErr Partial Mode
      0x11 = Both

Configuring RxMER Downgrade

Comparing to the existing upstream profile managements mechanism, RxMER downgrade has the following benefits:

  • Ability to downgrade to partial mode based only on RxMER data

  • Configurable desired lowest acceptable IUC

  • This allows IUC 13 modulation to be robust for registration and DBC

  • Allow certain percentage of subcarriers under threshold

  • Re-evaluate RxMER data at next poll interval

  • Channel leaves partial-mode and uses recommended IUC when RxMER data is above threshold

  • Works independently with codeword error downgrade

By default, RxMER downgrade is disabled, use the following command to enablethis feature:

Router(config)# cable upstream ofdma-prof-mgmt downgrade rxmer-enable

Then configure the data IUC below which the OFDMA channel will be downgraded to partial mode, the default number is 13:

Router(config-ofdma-mod-profile)# ofdma-prof-mgmt downgrade rxmer min-iuc value

You can also configure the number of minislots that can be below minimum IUC and not trigger downgrade, the default number is 0: 

Router(config)# cable upstream ofdma-prof-mgmt downgrade rxmer-exempt-mslot-pct value

The following example shows how to configure RxMER downgrade in cBR-8:


Router(config)# cable upstream ofdma-prof-mgmt rxmer-poll-interval 5
Router(config)# cable upstream ofdma-prof-mgmt prof-upgrade-auto
Router(config)# cable upstream ofdma-prof-mgmt downgrade rxmer-enable 
Router(config)# cable mod-profile-ofdma 466
Router(config-ofdma-mod-profile)# subcarrier-spacing 25KHz
Router(config-ofdma-mod-profile)# initial-rng-subcarrier 64
Router(config-ofdma-mod-profile)# fine-rng-subcarrier 256
Router(config-ofdma-mod-profile)# data-iuc 5 modulation 1024-QAM pilot-pattern 8
Router(config-ofdma-mod-profile)# data-iuc 9 modulation 512-QAM pilot-pattern 8
Router(config-ofdma-mod-profile)# data-iuc 10 modulation 256-QAM pilot-pattern 8
Router(config-ofdma-mod-profile)# data-iuc 11 modulation 128-QAM pilot-pattern 8
Router(config-ofdma-mod-profile)# data-iuc 12 modulation 64-QAM pilot-pattern 8
Router(config-ofdma-mod-profile)# data-iuc 13 modulation 16-QAM pilot-pattern 8
Router(config-ofdma-mod-profile)# ofdma-prof-mgmt downgrade rxmer min-iuc 12

To display the count of profile partial downgrade, use the command as shown in the following example:

Router# show cable modem 4800.33ef.3dd2 prof-mgmt upstream 
Upstream Profile Management Data :
MAC Address             : 4800.33ef.3dd2
Ucid                    : 6
Num RxMER Measurement   : 1908
Tx Time                 : 0h:00m:15s ago
Rx Time                 : 0h:00m:15s ago
MER Poll Period   (min) : 5
Auto Profile Upgrade    : Yes
Recommended IUC         : 13
Current IUC             : 13
Downgrade IUC           : 13
RxMER send/recv count   : 10/10
DBC                     : 0/0/0/0/0                         (send/succeed/err/reject/timeout)
State                   : MER Received
Profile Downgrade Partial count : 1
mslot RxMER(in 1/4 dB):
# msMer    0   : B3B7B4B0 B5ADB1B1 A6A9A5A3 89867A66 3A2C4152 53525D59 595F5C5F 5F636366 
# msMer    32 : 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
# msMer    64 : 00000000 00000000 
SC RxMER Distribution (Excluded SCs are ignored):*: 2% 
>44dB: ***** 10.00% 
>42dB: **  4.31% 
>39dB:   0.86% 
>36dB:   1.55% 
>33dB: *  2.41% 
>30dB:   1.29% 
>27dB: **  5.17% 
>24dB: ****  8.27% 
>21dB: *  3.96% 
>18dB:   1.63% 
>15dB:   1.20% 
<15dB: ***************************** 59.31%
        ---------------------------------------------------100
                           Percent of Subcarriers

Manually Configuring OFDMA Modulation Profile Downgrade

Table 2. Feature History

Feature Name

Release Information

Feature Description

Manually Configuring OFDMA Modulation Profile Downgrade

Cisco IOS XE Dublin 17.12.1z

With this release, you can downgrade to the desired interval usage codes (IUC), while configuring the codeword error threshold for a profile.

The operator can configure the data-iuc data-iuc-type modulation modulation pilot-pattern pilot-pattern-id cwerr-downgrade-iuc cwerr-downgrade-iuc keyword under the cable mod-profile-ofdma command to enable this feature.

The benefit of configuring this command is that you can skip the trial of multiple profiles until it reaches the final IUC13 profile and configure the exact downgrade that you need. The time taken to downgrade the profile to IUC13 is reduced is reduced as some profiles are skipped.

In releases before Cisco IOS XE Dublin 17.12.1z, when a cable modem encounter OFDMA FEC issues, the cBR-8 modem downgrades the assigned profile to the next viable profile based on modulation order. This can result in the trial of up to 7 profiles on the way to IUC13 for a serious issue. Each profile is assigned at the 10-second assessment interval. Downgrade IUC selection is calculated based on the next lowest bitload Data IUC, from the list of available IUCs,

Starting with Cisco IOS XE Dublin 17.12.1z, downgrade IUC selection can be performed as per the cwerr-downgrade-iuc configuration.

The process of downgrade IUC selection which calculates the next lower bitload Data IUC from the list of available IUCs, is still applicable if you do not configure cwerr-downgrade-iuc .

Configuring OFDMA Modulation Profile Downgrade

Here is a sample configuration for manually configuring IUC downgrade:

Router# configure terminal
Router(config)# cable mod-profile-ofdma 461
Router(config-ofdma-mod-profile)# subcarrier-spacing 50KHz
Router(config-ofdma-mod-profile)# initial-rng-subcarrier 32
Router(config-ofdma-mod-profile)# fine-rng-subcarrier 100
Router(config-ofdma-mod-profile)# data-iuc 5 modulation 1024-QAM pilot-pattern 1 cwerr-downgrade-iuc 10
Router(config-ofdma-mod-profile)# data-iuc 6 modulation 512-QAM pilot-pattern 1 cwerr-downgrade-iuc 10
Router(config-ofdma-mod-profile)# data-iuc 9 modulation 256-QAM pilot-pattern 2 cwerr-downgrade-iuc 13
Router(config-ofdma-mod-profile)# data-iuc 10 modulation 128-QAM pilot-pattern 2 cwerr-downgrade-iuc 13
Router(config-ofdma-mod-profile)# data-iuc 11 modulation 64-QAM pilot-pattern 3 cwerr-downgrade-iuc 13
Router(config-ofdma-mod-profile)# data-iuc 12 modulation 32-QAM pilot-pattern 3
Router(config-ofdma-mod-profile)# data-iuc 13 modulation 16-QAM pilot-pattern 4
Router(config-ofdma-mod-profile)# end

Use this command to verify the cwerr-downgrade-iuc downgrade configuration for the upstream channel: 

Router# show controllers upstream-Cable 1/0/14 us-channel 12
USPHY OFDMA support: FULL 
 

Controller 1/0/14 upstream 12  AdminState:UP OpState: UP
  ofdma mode enabled
  Channel Freq Range 18.500 MHz to 28.500 MHz
  Channel Subcarrier Index Range Cfg: 74, 273 Op: 74, 273
  Channel SC0 Freq Cfg: 14.800 MHz Op: 14.800 MHz
  #Excl bands: 2
  (   0,   73), ( 274, 2047), 
  #Unused bands: 0
  Cyclic Prefix Size 96,  Rolloff Period Size 0
  Subcarrier Spacing 50KHz,  Symbols Per Frame 18 Subcarrier Per Minislot: 8

  Modulation Profile (ID 461, Subcarrier Spacing 50KHz)
    IUC type   Cfg   Act  Preamble Bit       Pilot     Cwerr Downgrade
               subc  subc Symbols  Loading   Pattern   IUC
    3  (IR)    32    32      4       -         -          -
    4  (FR)    100   100     1       -         -          -
    5  (data)   -     -      -     1024-QAM    1          10
    6  (data)   -     -      -     512-QAM     1          10
    9  (data)   -     -      -     256-QAM     2          13
    10 (data)   -     -      -     128-QAM     2          13
    11 (data)   -     -      -     64-QAM      3          13
    12 (data)   -     -      -     32-QAM      3          -
    13 (data)   -     -      -     16-QAM      4          -
...
...
...

This sample shows a partial output of the command. The last column displays the configured cwerr-downgrade-iuc value.

Use this command to display the IUC for a specific modem:

Router# show cable modem XXXX.XXXX.XXXX prof-mgmt upstream 
MAC Address            : XXXX.XXXX.XXXX
Number of US Chan      : 1
Ucid                    : 13
MD US Chan              : Cable0/0/14/U12
Ctlr US Chan            : UC0/0/14:U12 
...
...
...
Recommended IUC         : 5  (1024-QAM)
Current IUC             : 5  (1024-QAM)
Downgrade IUC           : 10  (128-QAM)  
RxMER Recommended IUC   : 5  (1024-QAM)
RxMER send/recv count   : 20/20
RxMER retries curr/total: 0/0
Int  tot/good/cor/uncor : 1003/1002/1/0  (18/0)
Downgrade Check Time    : 0h:00m:57s ago

This sample shows a partial output of the command. The line highlighted in bold (Downgrade IUC           : 10  (128-QAM) displays the configured cwerr-downgrade-iuc value.

Display the Cable Modem Count per Profile

Feature History

Table 3. Feature History

Feature Name

Release Information

Feature Description

Display CM counts per US IUC and DS profile

Cisco IOS XE Bengaluru 17.6.1x

This feature introduces new commands show cable modem phy ofdm downstream prof-count and show cable modem phy ofdm upstream iuc-count , it helps tracking and reporting number of Cable Modems being in use per Upstream IUC and Downstream Profile on each controller separately. These counters are indicative of health of the RF plant.

To display the CM count per upstream port and IUC, use the show cable modem phy ofdm upstream iuc-count command as shown in the example below: 

Router#show cable modem phy ofdm upstream iuc-count
                      |<----------- CM Count per profile ----------->|
I/F           IF-INDX  IUC-5  IUC-6  IUC-9 IUC-10 IUC-11 IUC-12 IUC-13
-----------   ------- ------ ------ ------ ------ ------ ------ ------
C1/0/0/U6     488046       3      0      0      0      0      0      3
C1/0/0/U7     488047       3      0      0      0      0      0      3
C9/0/0/U6     501870       1      0      0      0      0      0      1
C9/0/0/U7     501871       1      0      0      0      0      0      1
C9/0/1/U6     501918       1      0      0      0      0      0      2
C9/0/1/U7     501919       1      0      0      0      0      0      2

Feature Information for Upstream Profile Selection

Use Cisco Feature Navigator to find information about the platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to the https://cfnng.cisco.com/ link. An account on the Cisco.com page is not required.


Note

The following table lists the software release in which a given feature is introduced. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Table 4. Feature Information for Upstream Profile Selection

Feature Name

Releases

Feature Information

DOCSIS3.1 US Profile Selection

Cisco IOS XE Fuji 16.7.1

This feature was integrated into Cisco IOS XE Fuji 16.7.1 on the Cisco cBR Series Converged Broadband Routers.

Codeword Errors Monitoring

Cisco IOS XE Gibraltar 16.12.1x

This feature was integrated into Cisco IOS XE Gibraltar 16.12.1x on the Cisco cBR Series Converged Broadband Routers.

Downgrading to Partial Mode

Cisco IOS XE Gibraltar 16.12.1y

This feature was integrated into Cisco IOS XE Gibraltar 16.12.1y on the Cisco cBR Series Converged Broadband Routers.

RxMER Downgrade

Cisco IOS XE Gibraltar 16.12.1z

This feature was integrated into Cisco IOS XE Gibraltar 16.12.1z on the Cisco cBR Series Converged Broadband Routers.