ABSTRACT

Definition: A digital data transmission technique used by television broadcasting stations in the United States, Canada, and several other countries. Using this technique, eight discrete amplitude levels of information are transmitted over the so-called vestigial sidebands (VSBs) of the main television carrier signal. VSB is an analog modulation technique developed to reduce the amount of spectrum needed to transmit information through cable TV or terrestrial broadcasting. (See also Vestigial Sideband.)

802.11x Level: 2 Definition: Refers to a family of wireless networking protocols that were first approved in 1997. 802.11: Managing the communication between a wireless device and a base station (or between two wireless devices), the original 802.11 allowed for transfer rates of 1 to 2 megabits per second (Mbps) in the 2.4-Ghz band using either frequency-hopping spread spectrum (FHSS) or direct sequence spread spectrum (DSSS). 802.11a: Emerged in 1999, making transfer rates of up to 54 Mbps possible using orthogonal frequency division multiplexing (OFDM). 802.11b: Also known as “Wi-Fi,” emerged at the same time as 802.11a. Because it is significantly less expensive to deploy, it has been the most widely adopted wireless networking technology in homes and businesses all around the world (even though it is much slower than 802.11a). 802.11b transmits in the 2.4-Ghz frequency range. This range is unregulated, meaning that radio transmitters built into other products may use the same frequency and interfere with the 802.11b network. These products include some cordless telephones, microwave ovens, garage door openers, and baby monitors. 802.11g: Allows for transfer rates of up to 54 Mbps, with compatible products appearing in the market in 2002. 802.11g is backward compatible with 802.11b, meaning that 802.11g access points will work with 802.11b wireless network adapters, and vice versa.