broadband

broadband

Term describing the radiation from a source that produces a broad, continuous spectrum of frequencies (contrasted with a laser, which produces a single frequency or very narrow range of frequencies). A typical broadband-light source that can be used for either emission or absorption spectroscopy is a metal filament heated to a high temperature, such as a tungsten lightbulb. Sunlight is also broadband radiation. See also broadband technology.

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broadband

(1) High-speed transmission. The term commonly refers to Internet access via cable and DSL, which is as much as 400 times faster than analog dial-up. The term has always referred to a higher-speed connection, but the speed threshold varies with the times. Widely employed in companies, the 1.5 Mbps T1 line was often considered the starting point for broadband speeds, while the FCC defines broadband as a minimum upload speed of 200 Kbps.

The T1 line is no longer the coveted connection for Web surfing. Home users with cable modems experience download speeds up to four times that of T1 and more (see cable modem). For example, in 2007, Comcast offered home users a premium service of 1 Mbps upload and 16 Mbps download. Fiber-based offerings from telephone companies are even greater.

It's All Perspective
After the turn of the century, South Korea leapfrogged the U.S. in Internet access, offering DSL up to 50 Mbps and calling their 1.5 Mbps service "light." See broadband router, wireless broadband, T1, cable modem and DSL.

(2) Transmitting data by modulating a carrier wave in order to differentiate it from other signals in the air or in a single line. For example, frequency division multiplexing (FDM) is used to carry hundreds of channels of analog and digital TV in a single coaxial cable. In this context, broadband is used in contrast with "baseband," which is data that has not been modulated or multiplexed (see baseband and TDM). In most cases, the term "broadband" is used for high-speed transmission as in definition #1 above.

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(communications)

broadband - A class of communication channel capable of supporting a wide range of frequencies, typically from audio up to video frequencies. A broadband channel can carry multiple signals by dividing the total capacity into multiple, independent bandwidth channels, where each channel operates only on a specific range of frequencies. The term has come to be used for any kind of Internet connection with a download speed of more than 56 kbps, usually some kind of Digital Subscriber Line, e.g. ADSL. A broadband connection is typically always connected, in contrast to a dial-up connection, and a fixed monthly rate is charged, often with a cap on the total amount of data that can be transferred. Domestic broadband connections typically share a telephone line with normal voice calls and the two uses can occur simultaneously without interference. See also baseband, narrowband.