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.

Finding Feature Information

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.

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

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.

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

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 2. 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.