Broadband

This article is about telecommunications signalling methods. For high-speed Internet access, see Broadband Internet access.

The term broadband refers to a telecommunications signal of greater bandwidth, in some sense, than another standard or usual signal. Different criteria for "broad" have been applied in different contexts and at different times.

In telecommunication

Broadband in telecommunications refers to a signaling method that includes or handles a relatively wide range (or band) of frequencies, which may be divided into channels or frequency bins. Broadband is always a relative term, understood according to its context. The wider (or broader) the bandwidth of a channel, the greater the information-carrying capacity. In radio, for example, a very narrow-band signal will carry Morse code; a broader band will carry speech; a still broader band is required to carry music without losing the high audio frequencies required for realistic sound reproduction. A television antenna described as "broadband" may be capable of receiving a wide range of channels; while a single-frequency or Lo-VHF antenna is "narrowband" since it only receives 1 to 5 channels. In data communications a digital modem will transmit a datarate of 56 kilobits per seconds (kbit/s) over a 4 kilohertz wide telephone line (narrowband or voiceband). However when that same line is converted to an non-loaded twisted-pair wire (no telephone filters), it becomes hundreds of kilohertz wide (broadband) and can carry several megabits per second (ADSL).

In data communications

Broadband in data can refer to broadband networks or broadband Internet and may have the same meaning as above, so that data transmission over a fiber optic cable would be referred to as broadband as compared to a telephone modem operating at 56,000 bits per second. However, a worldwide standard for what level of bandwidth and network speeds actually constitute Broadband have not been determined.

However, broadband in data communications is frequently used in a more technical sense to refer to data transmission where multiple pieces of data are sent simultaneously to increase the effective rate of transmission, regardless of data signaling rate. In network engineering this term is used for methods where two or more signals share a medium. Broadband Internet access, often shortened to just broadband, is a high data rate Internet access—typically contrasted with dial-up access using a 56k modem.

Dial-up modems are limited to a bitrate of less than 56 kbit/s (kilobits per second) and require the full use of a telephone line—whereas broadband technologies supply more than double this rate and generally without disrupting telephone use.

In DSL

The various forms of digital subscriber line (DSL) services are broadband in the sense that digital information is sent over a high-bandwidth channel (located above the baseband voice channel on a single pair of wires).

In Ethernet

A baseband transmission sends one type of signal using a medium's full bandwidth, as in 100BASE-T Ethernet. Ethernet, however, is the common interface to broadband modems such as DSL data links, and has a high data rate itself, so is sometimes referred to as broadband. Ethernet provided over cable modem is a common alternative to DSL.

In power-line communication

Power lines have also been used for various types of data communication. Although some systems for remote control are based on narrowband signaling, modern high-speed systems use broadband signaling to achieve very high data rates. One example is the ITU-T G.hn standard, which provides a way to create a high-speed (up to 1 Gigabit/s) Local area network using existing home wiring (including power lines, but also phone lines and coaxial cables).

In video

Broadband in analog video distribution is traditionally used to refer to systems such as cable television, where the individual channels are modulated on carriers at fixed frequencies. In this context, baseband is the term's antonym, referring to a single channel of analog video, typically in composite form with an audio subcarrier. The act of demodulating converts broadband video to baseband video.

However, broadband video in the context of streaming Internet video has come to mean video files that have bitrates high enough to require broadband Internet access in order to view them.

Broadband video is also sometimes used to describe IPTV Video on demand.

See also

• Narrowband
• Wideband
• Mobile broadband
• Ultra-wideband
• Full service broadband
• National broadband plans from around the world

External links

• Broadband gap
• European broadband portal
• DSL Broadband information