The Cable Center

This glossary of cable and telecommunications terms is intended to enhance your understanding of this dynamic industry. We are able to present this information with the generous help of CableLabs - consult their website for the most up-to-date information about cable technology.

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B Channel
An ISDN B Bearer channel can be used to carry voice or data connections at speeds of 56 or 64Kbps.

Back Channel
A back channel is a term that applies to asymmetric data connections. It is the slower of the two data paths, or directions, in the connection. Often times, as with ADSL and 56Kbps modems, the back channel is transmitted over the same set of wires or other media as the larger of the two data paths. In other cases, such as with satellite downlinks and some cable modem systems that use a modem and the telephone system to carry the back channel, the data is returned via a different transmission media.

Back Porch
That portion of the composite picture signal which lies between the trailing edge of the horizontal sync pulse and the trailing edge of the corresponding blanking pulse.

Backus Naur Form (BNF)
A formal notation used to define the syntax of a language.

Backbone
Part of a network used as the primary path for transmitting between network segments. Also, high-speed line or series of connections that forms amajor pathway within a network.

Backbone Microwave System
A series of directional microwave paths carrying common information to be relayed between remote points; engineered to allow insertion of signals, dropping off of signals and switching of signals along its length at designated relay points.

Background Noise
In an amplifier or other device that draws current, there is always some noise output in addition to the desired signal.

Bandwidth
(1) Analog Bandwidth: A measure of spectrum (frequency) use or capacity. For instance, an analog voice transmission by telephone requires a bandwidth of about 3000 hertz (3KHz). A TV channel occupies a bandwidth of 6 million hertz (6MHz) of radio frequency (RF) bandwidth. Cable system bandwidth occupies 50 to 300 MHz on the electromagnetic spectrum. (2) Measure of the frequency width of a transmission channel, or the difference between the highest and lowest frequency levels. Information-carrying capacity of a communication channel. The amount of transmission capacity possessed by a system or a specific location in a system. (3) Digital Bandwidth: The data rate of a digital signal carried in a data transmission channel. Digital bandwidth is commonly stated in units of bits-per-second (bps) and bytes-per-second (Bps) where 8 bits equals one byte. For example, DOCSIS 2.0 is capable of an upstream digital bandwidth of 30,720,000 bits-per-second (30.72 Mbps) in an analog channel bandwidth of 6.4 MHz using the 64 quadrature amplitude modulation (64 QAM).

Bandwidth Allocation Map
The DOCSIS MAC Management Message that the CMTS uses to allocate transmission opportunities to CMs.

Baseband
A transmission scheme that does not employ carrier modulation. In digital baseband systems, data is sent by varying the voltage (pulse amplitude modulation – PAM) or the duration (pulse width modulation—PWM) of signal pulses to indicate different values.
Baseline Privacy Interface (BPI) A set of extended services within the DOCSIS MAC sublayer. BPI gives subscribers data privacy across the RF network, encrypting traffic flows between the cable modem termination system (CMTS) and cable modem (CM).

Baseline Privacy Interface+ (BPI+)
BPI+ strengthens service protection by adding digital-certificate-based cable modem (CM) authentication to its key exchange protocol. BPI+ provides a level of data privacy across the shared medium cable network equal to or better than that provided by dedicated line network access services (analog modems or digital subscriber lines).

Base Station
Also called cell station. A radio transceiver (transmitter/receiver) that uses processing hardware/software and an antenna array to control and relay voice and data signals between the central office of a telephone network, or the internet transport provider, and the remote subscriber unit (fixed or mobile) or internet appliance; it connects wireless users to a phone network, or to an internet service provider.

Basic Cable
The basic program services distributed by a cable system for a basic monthly fee. These include one or more local broadcast stations, distant broadcast stations, non-pay networks and local origination programming.

Basic Rate Interface (BRI)
An ISDN BRI is a basic ISDN telephone connection commonly used for small office, home, and ISDN voice telephone service. Each ISDN BRI has two 56 or 64Kbps B Channels and one 16Kbps D Channel.

Baud Rate
The measure of the speed of transmission of a digital code.

Binder
In telecommunications lexicon, a binder is a grouping of wires inside a common sheath. The common two-pair telephone cable you can buy at hardware stores for household wiring jobs (black, yellow, green, and red wires) is a two-pair binder. Binders can hold almost any number of wires. Thick telephone company trunk binders may hold 250 pairs. Neighborhood streets generally have 20, 50 or even 100 pair telephone binders supplying “dialtone” to the neighborhood. Within a house, two-pair binders are very common. Modern office building often fun 4, 6, or 8 pair cables to each desktop to provide telephone and computer network connections.

Bit
(1) An abbreviation of binary digit. A bit can be one of the two binary characters, either a 1 or 0. (2) A unit of information. One bit of information is sufficient to specify one of two equally likely possibilities.

Bit Error Rate (BER)
The fraction of bits transmitted that are received incorrectly.

Bit Rate
The rate of a binary-coded transmission which is the number of bits per second.

Bits per Second (b/s)
Digital information rate expressed in the number of binary information units transmitted per second. Typically, a data channel is described as having a stated bit rate and a stated expected error rate.

Blanking (Picture)
The portion of the composite video signal whose instantaneous amplitude makes the vertical and horizontal retrace invisible.

Block Tilt
A method of setting the output levels of all low-band channels at a given number of dB lower than high-band channels.

Bonding
Telecommunications shorthand for Bandwidth on Demand Interoperability Group. A method for combining two ISDN B Channels into a single logical 128Kbps connections. Used most often for video conferencing and emulating a standard analog modem connection.

Bookmarks
A specific marked point in a Web document that allows quick access for returning to that point. When you want to easily return to a Web page, create a bookmark for it. This term is usually used by Netscape; Microsoft Internet Explorer calls these favorites.

Boot loader
The boot loader is a software component, provided with the host device, which is responsible for loading the entire software stack from the cable operator.

Bound application
Bound applications are those applications which are bound to, or associated with, a particular service made available by the cable operator.

Bridge Protocol Data Unit (BPDU)
Spanning tree protocol “hello packet” sent out at intervals to exchange information among bridges in the network.

Bridged Tap
Wires that are connected to a network, in which one end of the wire is unconnected to proper termination equipment. (ex: A consumer or technician removes devices without completely disconnecting the old device.)

Bridger Amplifier
Trunk amplifiers serve not only to boost the signal and pass it along, but also to provide branching lines, called feeders, for distribution of the signals to subscribers. The bridger amplifier is housed in the same case as the trunk amplifier. It taps the trunk at about +20 dBmV and splits the signal into 2 to 4 feeder lines.

Broadband
A transmission medium that allows transmission of voice, data, and video simultaneously at rates of 1.544Mbps or higher. Broadband transmission media generally can carry multiple channels—each at a different frequency or specific time slot.

Broadband Communications System
Frequently used as a synonym for cable television. It can describe any system capable of delivering wide-band channels and services.

Broadband Modulation
The transfer of information by a radio signal requires a certain minimum amount of spectrum space. This minimum depends on the rate at which this information is conveyed. Sometimes called wideband modulation.

Broadband Network Bridge
More commonly known as a Cable Modem, a broadband network bridge is a device that “bridges” radio-wave-like signals sent over cable TV wiring to standard Ethernet LAN connections, which you can plug into a computer’s Ethernet network card.

Broadcaster’s Service Area
Geographical area encompassed by a station’s signal.

Broadcasting
The dissemination of any form of radio electric communications by means of Hertzian waves intended to be received by the public. Transmission of over-the-air signals for public use.

Broadcast
A broadcast is a service that is delivered to all customers. Each customer may select a particular broadcast channel out of many.

Broadcast Addresses
A predefined destination address that denotes the set of all service access points.

Broadcast Application
A broadcast application is an application running on a set-top converter that is loaded through in-band information, inserted either at the headend or by a content provider further upstream.

Broadcast Control Channel
The channel, broadcast continually from the base station, that contains telemetry, identification and configuration data.

Broadcast File System (BFS)
A broadcast file system is a data carousel system by which application data can be stored on an application server and transmitted frequently to the set-top converters for application use.

Brouter
A device that routes specific protocols, such as TCP/IP and IPX, and bridges other protocols, thereby combining the functions of both routers and bridges.

Browser
A program used to graphically display HTML documents from the World Wide Web or other sources. Newer versions of most browsers can also display video clips and animations, play sound and interactive games. The two most popular browsers are Microsoft Internet Explorer and Netscape Communicator.

Burst Error Second
Any errored second containing at least 100 errors.

Bus
A local area network (LAN) topology in which all the nodes are connected to a single cable. All nodes are considered equal and receive all transmissions on the medium.

Business-to-Business (B-to-B)
Used to describe an e-commerce site used to facilitate business between two separate businesses.

Business-to-Consumer (B-to-C)
Used to describe an e-commerce site used to facilitate business between a business and a consumer.

Byte
A unit of data measurement made up of eight bits, short for binary term. One byte can represent a character such as a letter, number, or punctuation mark. Large groups of bytes (megabytes and gigabytes) are typical units of measurement for things such as RAM and hard drive size.