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Cisco uBR7225VXR Universal Broadband Router Hardware Installation Guide
OL-17309-02
Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation
Provisioning the Cable Headend
Note For a VoIP system using H.323, ensure that the CMTS has been properly provisioned with equipment
such as VoIP gateways and gatekeepers. For SGCP-based VoIP systems, ensure that the CMTS has been
properly provisioned with equipment such as VoIP gateways and call-agents.
Headend Certification
The cable headend plant must pass both analog and digital certification:
• In the United States, the Federal Communications Commission (FCC) mandates minimum technical
performance requirements for cable systems.
• For international requirements, consult with local agencies for certification requirements.
The digital certification process is described in Chapter 4, “Connecting the Cisco uBR7225VXR Router
to the Cable Headend.”
Diplex Filters
For coaxial cabling, diplex filters must be installed in the RF path between the cable interface cards in
the Cisco uBR7225VXR universal broadband router and cable interfaces and STBs. Diplex filters
separate the downstream signals from the upstream signals.
Note For fiber optics, laser transmitters and optical receivers handle the frequency separation of upstream and
downstream. Refer to the “Receivers” section on page 2-11.
High-frequency signals flow in the downstream direction from the Cisco uBR7225VXR router to
cable interfaces and STBs. Low-frequency signals flow in the upstream direction from the
cable interfaces to the Cisco uBR7225VXR router.
A diplex filter has three ports: low, high, and common. The downstream attaches to the high port because
it runs at high frequency. The upstream attaches to the low port because it runs at a low frequency. The
common port attaches to a splitter attached to one or more cable interfaces and STBs.
In two-way cable networks, the diplex filter takes the upstream and downstream and combines them on
one cable for the cable interface. The downstream output signal from the Cisco uBR7225VXR router
runs through the upconverter and then enters the high filter port of the diplex filter. The signal exits the
common port of the filter and is distributed to the cable interfaces. The upstream signal from the cable
modem enters the common port of the diplex filter and flows to the upstream receive ports of the
Cisco uBR7225VXR cable interface line cards through the diplex filters’ low port.
Note Appendix F, “Manufacturers for Headend Provisioning Requirements,” provides a list of diplex filter
manufacturers and websites for more information.
Receivers
If the upstream channels of your cable plant terminate at the headend over fiber-optic lines, ensure that
you have a receiver allocated for each upstream in your network.