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 ?
The rest of the world currently waits for their computer screens as they struggle with bandwidth speeds not exceeding 2Mbps.
Concentric Network will deploy NorthPoint's network and support systems to enable a broader range of bandwidth speeds for small to medium size business networks in the Bay Area, with the potential to leverage NorthPoint technology on a nationwide basis in the future.
Many applications require a pure IP network and bandwidth speeds that cannot be achieved unless deploying a fiber optic network.
3's relevance continues to grow multi-dimensionally in order to address additional media types, bandwidth speeds and protocols.
Overture Networks, a leading developer of converged packet access platforms, today announced that THUS plc is deploying the ISG product family to help deliver its business-class Ethernet services to customers seeking a wide range of bandwidth speeds.
BusinessOne can also be customized to meet a company's growth requirements by increasing the number of phone lines or bandwidth speeds.
0 platform, delivering the fastest bandwidth speeds - 56Gb/s InfiniBand and 40GbE - that can optimize a data center's ROI.
QTS data centerConnect offers bandwidth speeds in increments of 10Mbps.
In addition, the company upgraded the college's Internet connection and installed the technology to increase bandwidth speeds when needed.
With Qwest's Ethernet solution, state and local government and businesses in Utah have access to additional bandwidth speeds to help satisfy increasing public demand for online services.
This technology will enable higher bandwidth speeds through Wi-Fi more effectively, solve the issue of data packet loss, and make way for efficient wireless data networks.
The significant driver in the market today is to build intelligent switches and be able to cater to higher bandwidth speeds going forward.