Cisco Cisco IOS Software Release 12.1(7)CX

Improves frequency agility to help eliminate dropped packets and thereby maintain full upstream 
data rates. 

Supports frequency agility in dense-mode combining environments across a shared spectrum. 

Restricts frequency hopping to a set of discrete frequencies or to a range of frequencies, as desired. 

Allows frequency hop conditions to be customized for specific plant environments and 
requirements. 

Optionally schedules frequency hops to take advantage of known usage patterns or plant conditions. 

Optionally dynamically reduces channel width to allow cable modems to remain online, even in 
noisy upstream conditions. 

The Cisco uBR-MC16S line card can be installed in existing deployments of the 
Cisco uBR7223, uBR7246, and uBR7246 VXR universal broadband routers. 

As is the case with the other cable interface line cards, the Cisco uBR-MC16S line card supports 
Online Insertion and Removal (OIR), allowing for hotswappable upgrades and maintenance. 

The Advanced Spectrum Management Features for the Cisco uBR-MC16S cable interface line card, 
available in Cisco IOS Release 12.1(7)CX1, are a software-only upgrade that provides the following 
additional features:

Supports proactive channel management, so as to avoid the impacts of ingress and keep subscribers 
online and connected. 

Offers flexible configuration choices, allowing users to determine the priority of the actions to be 
taken when ingress noise on the upstream exceeds the allowable thresholds. The configurable 
actions are frequency hopping, switching the modulation profile, and reducing the channel width. 

Performs CNR calculations using DSP algorithms in real-time on a per-interface and a per-modem 
basis. 

Intelligently determines when to modify the frequency, channel width, or modulation profile, based 
on CNR calculations in the active channel, the number of missed station maintenance polls, and the 
number of correctable or uncorrectable Forward Error Correction (FEC) errors. Previously, channel 
hopping occurred when the number of missed station maintenance polls exceeded a user-defined 
threshold or the SNR reported by the Broadcom chip exceeded the DOCSIS thresholds. 

Enhances the Dynamic Upstream Modulation feature for the Cisco uBR-MC16S line card. This 
feature supports dynamic modulation using two upstream profiles. The primary profile (typically 
using 16-QAM or a mixed modulation profile) remains in effect at low noise conditions, but if 
upstream conditions worsen, the cable modems switch to the secondary profile (typically using 
QPSK modulation) to avoid going offline. When the noise conditions improve, the modems are 
moved back to the primary profile. 

The Dynamic Upstream Modulation feature was introduced in Cisco IOS 
Release 12.1(3a)EC1. The above enhancements to this feature currently exist only in 
12.1(7)CX1; they do not exist in any 12.1 EC release. 

When using a Cisco uBR-MC16S line card on a Cisco uBR7200 series router running Cisco IOS 
Release 12.1(7)CX1, the spectrum management hardware uses the real-time CNR readings from the 
DSPs onboard the Cisco uBR-MC16S line card instead of the signal-to-noise ratio (SNR) values 
from the Broadcom 3137 chip to determine the signal quality of the upstream channel. The CNR 
value is a more accurate description of noise conditions on the upstream.