Specifications

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Cisco Cable Modem Termination System Feature Guide
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Chapter 3 Spectrum Management for the Cisco Cable Modem Termination System
Benefits
Table 3-4 summarizes the specific benefits of the Advanced spectrum management features that are
supported on Cisco CMTS routers using the Cisco uBR-MC16S cable interface line card.
Table 3-3 Benefits of Guided and Scheduled Spectrum Management Features
Guided andScheduled Spectrum
Management Feature Benefits
Upstream Traffic Shaping
Downstream Traffic Shaping
• The CMTS can buffer the grants for rate-exceeded modems. This grant buffering at
the CMTS avoids TCP-related timeouts and retransmits, resulting in an improved TCP
throughput performance for the rate-exceeded modems. Thus, traffic shaping enables
the CMTS to enforce the peak upstream rate for the modem without degrading overall
TCP performance for the modem.
• Allows users to configure multiple data rates (defined by the value of the IP precedence
bits in the ToS byte) for a given modem. By specifying a maximum data rate for a
particular ToS, users can override the common maximum downstream data rate.
Input Power Levels • Allows the cable plant operator to perform minor power level equalization as a
function of frequency.
Frequency Hopping Capabilities • Proactively countermeasures upstream noise impairments by assigning a new
upstream channel to the cable modem. MSOs can take advantage of this feature
especially when they have less than an optimal carrier-to-noise ratio in the upstream
frequencies or when their cable plants exhibit random bursts of ingress noise that
affect reliability.
Dynamic Upstream Modulation • Reduces the risk associated with transitioning to QAM-16 modulation in the return
path and provides assurance that subscribers remain online and connected during
return path impairments.
• Checks that the active upstream signal quality can support the configured modulation
scheme and proactively adjusts to the more robust modulation scheme when necessary.
• Eliminates the necessity to hop channels for cable modems to stay online by
automatically switching from the primary modulation profile to the secondary
modulation profile.
Table 3-4 Benefits of Advanced Spectrum Management Features (Cisco uBR-MC16S Card)
Advanced Spectrum
Management Feature Benefits
1
Hardware-Assisted Spectrum
Management
• Offloads much of the spectrum management processing from the main system
processor to the Digital Signal Processing (DSP) hardware onboard the
Cisco uBR-MC16S line card, freeing up the main processor for other duties.
Dynamic Channel Width Change • Imrpoves the DOCSIS upstream channel availability by finding the maximum possible
channel width for an upstream when noise conditions make the current channel width
unusable.
• Provides the maximum RF spectrum utilization efficiency for current plant conditions.
• Customizable range of channel widths that can be used to respond to noise problems.