Cisco UBR904 - Router - EN Troubleshooting Tips page 3

usable in the upstream direction. Numbers indicate number of code points per symbol. The QAM
rate or the number of points in the QAM constellation can be computed by 2 raised to the power of
<number of bits/symbol>.
QPSK—Quadrature Phase-Shift Keying. A method of modulating digital signals onto a
radio-frequency carrier signal using four phase states to code two digital bits.
Ranging—The process of acquiring the correct timing offset such that the transmissions of a cable
modem are aligned with the correct mini-slot boundary.
SID (Service ID)—A number that defines (at the MAC sublayer) a particular mapping between a
cable modem (CM) and the CMTS. The SID is used for the purpose of upstream bandwidth
allocation and class-of-service management.
Subscriber Unit (SU)—An alternate term for cable modem. See cable modem.
Upstream—The set of frequencies used to send data from a subscriber to the headend.
Platforms
The uBR904 cable modem is a standalone device; it works in conjunction with the Cisco uBR7246
universal broadband router.
Prerequisites
See the companion to this document,
for information regarding prerequisites.
Supported MIBs and RFCs
See the companion to this document,
for information regarding supported MIBs and RFCs.
"Bridging and Routing Features for the Cisco uBR904 Cable Modem"
"Bridging and Routing Features for the Cisco uBR904 Cable Modem"
Troubleshooting Tips for the Cisco uBR904 Cable Modem 3
List of Terms