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BW

(ordnance)

butt joint

welded butt joint
butt joint formed by two boards
1. A plain, square joint between two members, where the contact surfaces are cut at right angles to the faces of the pieces; the two pieces are fitted squarely against each other rather than lapped; Also see oblique butt joint.
2.

bw

(networking)
The country code for Botswana.

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 ?
In reestimating the model with the B-W data, the approach taken in this study is to present two different estimates: the first based on the series thought to have been used by B-W themselves (and described in Macunovich, 1990a, 1990b); the second based on a "corrected" and updated version of those original series, incorporating revisions in published data and the new CPI-XI.(3) (These updated versions of the B-W series are only available through 1983, because some of the data used by B-W to estimate their series have not been published since that date.
Table 1 presents the results of estimating the B-W model in these several variants, for women aged 20-24 and 25-34.
The implication of these results is that the years 1947-1954 were driving the estimates presented by B-W: these were years when the fertility rate was still rising for these age groups, and there was little, if any, trend in the female wage and labor force participation.
B-W presented predictions for the period 1957-75 in their 1979 report, with the following description (1979, pp.
While such predictions might owe more to luck than to econometrics (because of the dubious nature of regression results based on only seven observations with only three degrees of freedom), we are now in a position to prepare forecasts with the B-W model using a much longer time series as a base.