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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
OL-2239-05
Chapter 1 Overview of Cisco uBR7200 Series Software
cops tcp window-size
For additional information about downstream traffic shaping, refer to the following resources:
•
“Setting Downstream Traffic Shaping” section on page 3-10
•
The
“Spectrum Management for the Cisco Cable Modem Termination System”
chapter in the
Cisco Cable Modem Termination System Feature Guide
on Cisco.com:
http://www.cisco.com/en/US/docs/cable/cmts/feature/guide/cmtsfg.html
Dynamic Upstream Modulation
The Dynamic Upstream Modulation feature reduces the risks associated with making transition to
Quadrature Amplitude Modulation (QAM)-16 in the return path, and provides assurance that subscribers
remain online and connected during periods of return-path impairments.
This feature actively monitors the signal-to-noise-ratio (SNR) and forward error correction (FEC)
counters in the active return path of each upstream port. The software tracks whether the current
upstream channel signal quality can adequately support the higher modulation scheme configured, and
adjusts in proactive fashion to the more robust quadrature phase-shift keying (QPSK) modulation
scheme when necessary. When return-path spectrum conditions improve, the software returns the
upstream channel to the higher-modulation QAM scheme. This is done through modulation profiles
supported in Cisco IOS, which can be configured in a variety of ways to support the unique environment
at each user's facility.
You can configure Dynamic Upstream Modulation on interfaces with fixed upstream frequencies or on
interfaces with spectrum groups assigned. Cisco IOS provides one preconfigured modulation profile
resident in memory, which defines a typical profile for QPSK modulation. In order to use the Dynamic
Upstream Modulation feature, a second profile must be created that is unique from the first profile and
typically provides a higher modulation scheme. The upstream port must be assigned this second
modulation profile.
Use the
cable upstream modulation-profile
command in cable interface configuration mode to
configure Dynamic Upstream Modulation:
Router(config)#
cable modulation-profile 2 mix
Use the
cable upstream modulation-profile
command in cable interface configuration mode to assign
the modulation profile to an upstream port:
cable upstream
n
modulation-profile
<
primary profile-number
> <
secondary profile-number
>
For more information, refer to the
Cisco uBR7200 Dynamic Upstream Modulation
feature module on
Cisco.com.
Guided and Scheduled Spectrum Management
Cisco’s initial response to combat upstream ingress was to add frequency agility through software
support on the Cisco uBR-MCxxC DOCSIS line cards. Operators configured spectrum groups to select
the new upstream frequency based on scheduled frequency hopping or based on guided frequency
hopping. Using time scheduled spectrum management, the upstream channel frequency reassignment
process is initiated at a configured time of day or week. Using guided frequency hopping, the number of
missed station management messages from the cable modems or set top boxes on that upstream
exceeding a configured threshold initiates an upstream channel frequency reassignment. All cable
modems on the upstream port migrate to the next frequency, using a round robin scheme to select the
next available frequency band, with an assigned input power level defined in the spectrum management
group. The frequency change occurs rapidly without data loss and minimal latency.
