Wi-Fi (wireless fidelity) is one of the most widely used non-cellular wireless technologies. Wi-Fi is the trade name for products and systems that use the IEEE’s 802.11 standards for wireless local area networks (WLAN). Originally developed as an extension to wired Ethernet LANs in the enterprise, Wi-Fi has morphed into other applications areas as well.
The earliest wireless LAN standard 802.11 was announced by the IEEE standards group in 1997. This standard was never widely adopted or implemented. However, in 1999, the 802.11b standard was adopted and it soon became a popular wireless extension to wired Ethernet LANs. This standard uses the 2.4 to 2.483 GHz unlicensed spectrum in the US and worldwide. The band is divided into 14 22 MHz wide overlapping channels. Using direct sequence spread spectrum (DSSS), complementary code keying (CCK) and DQPSK modulation, it can achieve a data rate of 11 Mb/s at a maximum range of about 100 meters. Over longer distances, in noisy environments, and in indoor applications, the speed drops back to 5.5, 2 or 1 Mb/s to maintain the link.
In 1998, the Wi-Fi Alliance was formed to support the standard and to provide interoperability testing and certification that helped ensure compatibility between products from different manufacturers.
The IEEE later developed two additional and faster versions of the standard. The 802.11g standard uses the 2.4 GHz band and OFDM to boost speeds to 54 Mb/s. The 802.11a standard also uses OFDM to give a data rate of 54 Mb/s but in the 5 GHz band where there is less interference. The most recent standard is 802.11n that uses OFDM and MIMO to boost data rates to 100 to 600 Mb/s at a range to 100 meters. The IEEE is currently working on the next generation of the 802.11 standard (ac/ad) that seeks to provide a data rate of 1 to 6 Gb/s over short distances for application in home consumer systems for wireless video transmission.
The number of applications for Wi-Fi has grown steadily over the years. It is so popular that it is routinely built into virtually PC, laptop and netbook as a standard feature. Its main use continues to be wireless LAN connections in companies where most employees use their laptops for freedom of movement within the organization. A very popular application is Internet access and email through hot spots, those public access points in hotels, convention centers, coffee shops and airports that anyone can access with a laptop or netbook. Even access inside airplanes is now available. Wi-Fi is also popular as a home networking technology to allow multiple PCs to share a common cable TV or DSL line for Internet access.
Other applications include industrial wireless links and networks, telemetry with sensor networks, and security systems. More and more, Wi-Fi is being incorporated into high end smartphones for faster Internet access than often available on the cellular network.