The first wireless LAN technologies defined by the 802.11 standard were low-speed proprietary offerings of 1 to 2 Mbps. Despite these shortcomings, the freedom and flexibility of wireless allowed these early products to find a place in technology markets. Mobile workers used hand-held devices for inventory management and data collection in retail and warehousing. Later, hospitals applied wireless technology to gather and deliver patient information. As computers made their way into the classrooms, schools and universities began installing wireless networks to avoid cabling costs, while enabling shared Internet access. Realizing the need for an Ethernet-like standard, wireless vendors joined together in 1991 and formed the wireless Ethernet Compatibility Alliance (WECA). WECA proposed and built a standard based on contributed technologies. WECA later changed its name to Wi-Fi. 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. Specified media include the following:
-Infrared light
-Three types of radio transmission within the unlicensed 2.4-GHz frequency bands:
Frequency hopping spread spectrum (FHSS)
Direct sequence spread spectrum (DSSS)
Orthogonal frequency-division multiplexing (OFDM) 802.11g
-One type of radio transmission within the unlicensed 5-GHz frequency bands:
Orthogonal frequency-division multiplexing (OFDM) 802.11a
Spread spectrum is a modulation technique that was developed in the 1940s. It spreads a transmission signal over a broad range of radio frequencies. This technique is ideal for data communications because it is less susceptible to radio noise and creates little interference.