Cisco Cisco IOS Software Release 12.1(3)EC

Reduces the risk associated with transitioning to 16QAM 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.

Upstream modulation profiles can be assigned to specific cable modems based on the upstream 
ports associated with the cable modems.

Only those who have received training and are familiar with DOCSIS should create upstream 
modulation profiles.

When using the Dynamic Upstream Modulation feature with the Cisco uBR-MCxxC or 
Cisco uBR-MC16S cards, and/or when setting variable upstream channel widths for the 
Cisco uBR-MC16S card in HFC environments where Voice Over IP (VoIP) services are required, 
frequent changes to upstream modulation or channel width could briefly impact the quality of voice 
calls. Future software enhancements will provide commands to set the SNR and FEC thresholds 
broad enough to avoid frequent upstream modulation or channel width changes.