Wi-Fi (or WiFi) (wifi)
a synonym for "WLAN" (Wireless Local Area Network). This technology connects electronic devices to network, mainly using the 2.4 gigahertz (12 cm) UHF and 5 gigahertz (6 cm) SHF ISM radio bands. Many devices can use Wi-Fi, for example, personal computers, video-game consoles, smartphones, digital cameras, tablet computers and digital audio players. They are connected to a network resource such as the Internet via a wireless network access point.
Wi-Fi access point range:
The range covered by a Wi-Fi access point is from 30 to 100 meters indoors while outdoors a single access point can cover about 650 meters.
In the early 2000s, many cities around the world announced plans to construct city-wide Wi-Fi networks. In 2004, Mysore became India's first Wi-Fi-enabled city. In 2005, St. Cloud, Florida and Sunnyvale, California, became the first cities in the United States to offer city-wide free Wi-Fi (from MetroFi). In May 2010, London, UK, is pledged to have London-wide Wi-Fi by 2012. Seoul is granting leases to KT, LG Telecom and SK Telecom this year.
Many universities collaborate in providing Wi-Fi access to students and staff through the eduroam international authentication infrastructure. Carnegie Mellon University built the first campus-wide wireless Internet network.
Worldwide Wi-Fi radio spectrum assignments
United States-802.11b and 802.11g use the 2.4 GHz ISM band
Australia and Europe-2.4 GHz band (1–13)
Wi-Fi connection or speed can be lowered by having other devices in the same area. Many 2.4 GHz 802.11b and 802.11g access-points default to the same channel on initial setup, resulting in congestion on certain channels.
Wi-Fi pollution, or an excessive number of access points in the area,can cause significant additional interference.
Wifi network security
To enable Wi-Fi, one merely needs to be within the range of the Wi-Fi network. Most business networks protect sensitive data and systems by attempting to disallow external access. A common measure to deter unauthorized users involves hiding the access point's name by disabling the SSID broadcast.