Glossary
Glossary
broadband—Transmission system that combines multiple independent signals onto one cable. In the cable industry, broadband refers to the frequency-division multiplexing of many signals in a wide bandwidth of RF frequencies using a hybrid fiber-coaxial (HFC) network.
CATV—Originally stood for Community Antenna Television. Now refers to any coaxial or fiber cable-based system that provides television services.
cable modem (CM)—A modulator-demodulator device that is placed at subscriber locations to convey data communications on a cable television system. The Cisco uBR900 series cable access router is also a cable modem.
Cable Modem Termination System (CMTS)—A termination system located at the cable television system headend or distribution hub which provides complementary functionality to the cable modems, enabling data connectivity to a wide-are network.
cable router—A modular chassis-based router optimized for data-over-CATV hybrid fiber-coaxial (HFC) applications.
carrier—A signal on which another, lower-frequency signal is modulated in order to transport the lower-frequency signal to another location.
Carrier-to-Noise—C/N (also CNR). The difference in amplitude between the desired RF carrier and the noise in a portion of the spectrum.
channel—A specific frequency allocation and bandwidth. Downstream channels used for television are 6 MHz wide in the United States; 8 MHz wide in Europe.
CM—cable modem.
CMTS—Cable Modem Termination System.
coaxial cable—The principal physical media over which CATV systems are built.
CPE—Customer Premises Equipment
dB—Decibel. A measure of the relative strength of two signals.
dBm—Decibels with respect to one milliwatt. A unit of RF signal strength used in satellite work and other communications applications.
dBmV—Decibels with respect to one millivolt in a 75-ohm system. The unit of RF power used in CATV work in North America.
DHCP—Dynamic Host Configuration Protocol. This protocol provides a mechanism for allocating IP addresses dynamically so that addresses can be reused when hosts no longer need them.
DOCSIS—Data Over Cable Service Interface Specification. Defines technical specifications for equipment at both subscriber locations and cable operators’ headends.
downstream—The set of frequencies used to send data from a headend to a subscriber.
FDM—Frequency Division Multiplexing. A data transmission method in which a number of transmitters share a transmission medium, each occupying a different frequency.
FEC—Forward Error Correction. In data transmission, a process by which additional data is added that is derived from the payload by an assigned algorithm. It allows the receiver to determine if certain classes of errors have occurred in transmission and, in some cases, allows other classes of errors to be corrected.
