bandwidth

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bandwidth

1. The range of frequencies over which an instrument, such as a radio telescope, is sensitive. A wide bandwidth gives good sensitivity to sources that emit over a wide range of frequencies (e.g. by synchrotron emission), whereas a narrow bandwidth gives good sensitivity to spectral lines.
2. (coherence bandwidth) The range of frequencies over which electromagnetic or other emissions from a source maintain coherence.

bandwidth

[′band‚width]
(communications)
The difference between the frequency limits of a band containing the useful frequency components of a signal.
A measure of the amount of data that can travel a communications path in a given time, usually expressed as thousands of bits per second (kbps) or millions of bits per second (Mbps).

bandwidth

(communications)
The difference between the highest and lowest frequencies of a transmission channel (the width of its allocated band of frequencies).

The term is often used erroneously to mean data rate or capacity - the amount of data that is, or can be, sent through a given communications circuit per second.

bandwidth

(1) Computer people may use the term for capability and time. For example, "not enough bandwidth to get the job done" means not enough staff or time to do it. Its true meaning follows.

(2) The transmission capacity of an electronic pathway such as a communications line, computer bus or computer channel. Digital bandwidth is the number of pulses per second measured in bits per second (bps). For example, Ethernet transmits at different speeds, including 10 Mbps, 100 Mbps and 1000 Mbps (see Mbps and baseband).

When transmitting alternating frequencies, as with all wired analog, many wired digital and most wireless communications, the bandwidth is the difference between the highest and lowest frequencies, measured in cycles per second, or Hertz (Hz). For example, 802.11n Wi-Fi transmits in 20 MHz and 40 MHz channels within the 2.4 GHz and 5 GHz bands. The 20 and 40 MHz channel frequencies are the bandwidths, and each channel is divided into subchannels.

From Hertz to Bits - A Complicated Process
When using alternating frequencies for digital transmission, the frequencies are modified (modulated) by the digital input. Using the 802.11n Wi-Fi example, the resulting bit rate can range from 6.5 Mbps to 600 Mbps. This extremely wide range is determined by the signal strength and interference in the environment at any given moment. Any one of more than 30 combinations of channel bandwidth (20, 40 MHz), modulation scheme, error correction rate, channel spacing and number of antennas may be selected, on a packet-by-packet basis. See modulation, video bandwidth, space/time and bandwidth junkie.


Bandwidth in Hertz to Bandwidth in Bits
This quadrature PSK (QPSK) example is one of the simplest modulation schemes. Each set of two input bits modifies the carrier into four phase angles. The amplitude remains constant, unlike QAM modulation, in which the amplitude is varied (see QAM).











References in periodicals archive ?
Last year nearly two million people logged on to a 25 minute Victoria's Secret fashion show Webcast during business hours, using a bandwith capacity equivalent to nearly 200 million TI lines.
Tenders are invited for Providing 2 Mbps Bandwith (1To1) Internet Leased Line(Ill) Facility At Area Office/ Gm Unit Of Rajhara Area On Rental Basis.
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Mediaserv, a subsidiary of Loret Telecom, is a multiservice telecom operator with telephone, internet, and TV offerings in Guadeloupe, Saint Martin, Saint Barthelemy, Martinique, Guyance and Reunion for consumers, professionals and large accounts: access to high bandwith Internet and low bandwith Internet, pre-selection, interconnection network of sites, Internet site hosting and servers, management and domain names buying, email management, mediaserv box.
Tenders are invited for Providing 2 mbps bandwith (1 to1) internet leased line(ill) facility one at gm office akashdeep,dakra and second at project office ,tandwa of magadh amrapali area on rental basis.
Cook also asked him if their solution is "just enough" bandwith or "more than enough" to serve the growing trend of automated, "algo" trading and what the 7ticks strategy for 2009 looks like to bring high-performance market access to the rest of the world.
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Ronald Hickling, Chief Technology Officer of TechnoConcepts, stated in the article, that with True Software Radio(R) "it will be possible to realize the ultimate communication terminal, able to freely select RF signal frequency and bandwith.