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is usually mounted high but may be mounted essentially anywhere that is practical as
long as the desired radio coverage is obtained.
End users access the WLAN through wireless LAN adapters, which are implemented as
PC cards in notebook computers, or use PCI adapters in desktop computers. WLAN
adapters provide an interface between the client network operating system (NOS) and
the airwaves (via an antenna). The nature of the wireless connection is transparent to
the NOS.
1.2
Wireless LAN Standard and Structure
¦
Wireless LAN Standard – IEEE802.11b
The widespread acceptance of WLANs depends on industry standardization to ensure
product compatibility and reliability among the various manufacturers. The Institute of
Electrical and Electronics Engineers (IEEE) ratified the original 802.11 specifications in
1997 as the standard for wireless LANs. That version of 802.11 provides for 1 Mbps and
2 Mbps data rates and a set of fundamental signaling methods and other services. The
most critical issue affecting WLAN demand has been limited throughput. The data rates
supported by the original 802.11 standard are too slow to support most general business
requirements and have slowed adoption of WLANs. Recognizing the critical need to
support higher data -transmission rates, the IEEE recently ratified the 802.11b standard
(also known as 802.11 High Rate) for transmissions of up to 11 Mbps.
With 802.11b, WLANs will be able to achieve wireless performance and throughput
comparable to wired Ethernet. Outside of the standards bodies, wireless industry leaders
have united to form the Wire -less Ethernet Compatibility Alliance (WECA).
WECA’s mission is to certify cross-vendor interoperability and compatibility of IEEE
802.11b wireless networking products and to promote that standard for the enterprise,
the small business, and the home. Members include WLAN semiconductor
manufacturers, WLAN providers, computer system vendors, and software makers.
¦
Wireless LAN Network Equipment
802.11 defines two pieces of equipment, a wireless
statio
n, which is usually a PC
equipped with a wireless network interface card (NIC), and an
access point (AP
), which
acts as a bridge between the wireless and wired networks. An access point usually
consists of a radio, a wired network interface (e.g., 802.3), and bridging software
conforming to the 802.1d bridging standard. The access point acts as the base station
