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In the wired world,
Ethernet has grown to become the predominant LAN technology. Its
evolution parallels, and indeed foreshadows, the development of the
wireless LAN standard. Defined by the Institute of Electrical and
Electronics Engineers (IEEE) with the 802.3 standard, Ethernet
provides an evolving, high-speed, widely available, and
interoperable networking standard. It has continued to evolve to
keep pace with the data rate and throughput requirements of
contemporary LANs. Originally providing for 10-Mbps transfer rates,
the Ethernet standard evolved to include the 100-Mbps transfer rates
required for network backbones and bandwidth-intensive applications.
The IEEE 802.3 standard is open, decreasing barriers to market entry
and resulting in a wide range of suppliers, products, and price
points from which Ethernet users can choose. Perhaps most
importantly, conformance to the Ethernet standard allows for
interoperability, enabling users to select individual products from
multiple vendors while secure in the knowledge that they will all
work together.
The first wireless LAN technologies
were low-speed (1-2 Mbps) proprietary offerings. Despite these
shortcomings, the freedom and flexibility of wireless allowed these
early products to find a place in vertical markets such as retail
and warehousing where mobile workers use hand-held devices for
inventory management and data collection. Later, hospitals applied
wireless technology to deliver patient information right to the
bedside. And as computers made their way into the classrooms,
schools and universities began installing wireless networks to avoid
cabling costs and to share Internet access. The pioneering wireless
vendors soon realized that for the technology to gain broad market
acceptance, an Ethernet-like standard was needed. The vendors joined
together in 1991, first proposing, and then building, a standard
based on contributed technologies. In June 1997, the IEEE released
the 802.11 standard for wireless local-area networking.
Just as the 802.3 Ethernet standard
allows for data transmission over twisted-pair and coaxial cable,
the 802.11 WLAN standard allows for transmission over different
media. Compliant media include infrared light and two types of radio
transmission within the unlicensed 2.4-GHz frequency band: frequency
hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS).
Spread spectrum is a modulation technique developed in the 1940s
that spreads a transmission signal over a broad band of radio
frequencies. This technique is ideal for data communications because
it is less susceptible to radio noise and creates little
interference. FHSS is limited to a 2-Mbps data transfer rate and is
recommended for only very specific applications; for example,
certain types of watercraft lend themselves to this technology. For all other wireless LAN applications, DSSS
is the better choice. The recently released evolution of the IEEE
standard, 802.11b, provides for a full Ethernet-like data rate of 11
Mbps over DSSS. FHSS does not support data rates greater than 2
Mbps.
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