802.11 Concrete Bandage Standards
A wireless LAN enables mobile, portable, and anchored accessories to calmly acquaint with each
other aural an action adeptness and throughout a campus environment. For example, retail stores
have been application wireless LANs back the aboriginal 1990s to accredit wireless bar cipher scanning when
performing amount appearance and account applications. Despite the almost aerial amount for wireless
LAN apparatus at that time, the retail food were still able to accomplish cogent allotment on
investment due to the amazing assets in adeptness and accurateness that wireless LANs provided.
As wireless LAN prices fell badly in 2003, abounding enterprises began to arrange wireless
LANs to abutment accepted appointment applications, such as wireless admission to e-mail from conference
rooms and the adeptness to abutment visiting advisers with ease. In addition, companies began
installing accessible wireless LANs at airports, hotels, restaurants, and added hotspots to accredit people
to accept wire-free admission to the Internet while abroad from their offices and homes.
The IEEE 802.11 standard, which is agnate in ambit and functionality to IEEE 802.3 (Ethernet),
is a accepted base for wireless LAN operation. As with 802.3, the 802.11 accepted defines a
common Media Admission Control (MAC) and assorted concrete layers, such as 802.11a, 802.11b,
and 802.11g.
The antecedent 802.11 wireless LAN standard, ratified in 1997, specifies the use of both absolute sequence
spread spectrum
(DSSS) and abundance bent advance spectrum
(FHSS) for carrying 1- and
2-Mbps abstracts ante in the 2.4-GHz abundance band. DSSS and FHSS are altered forms of transmitting
data over a wireless LAN. This is affluence of bandwidth to abutment bar cipher applications, the first
commercial use of wireless LANs. To accommodate college abstracts ante back operating in the 2.4-GHz
band, the 802.11 accumulation ratified the 802.11b concrete bandage in 1999, acceptable the antecedent DSSS
physical bandage to accommodate added 5.5- and 11-Mbps abstracts rates. Also in 1999, the 802.11 group
ratified the 802.11a standard, which offers abstracts ante up to 54 Mbps in the 5-GHz bandage using
orthogonal abundance analysis multiplexing (OFDM). 802.11g, ratified in 2004, is the best recent
802.11 concrete layer, which added enhances 802.11b to accommodate abstracts ante up to 54 Mbps in the
2.4-GHz bandage application OFDM. For added capacity on advance spectrum and OFDM, accredit to the following
sections begin in this chapter: “Spread Spectrum” and “Orthogonal Abundance Analysis Multiplexing.”