Short for Wireless Fidelity. It is an easy to use deploy but difficult to administer (e.g. antennas) technology that has taken over the landscape of MobileInformationDevices. Possibly helped by a proliferation of Intel Centrino chipset equipped laptops.
Often referred to as 802.11 (an IEEE IETF reference) by geeks happy to show off their knowledge, the WiFi has spread like wild fire.
Various performance capabilities exist for the WAP and WiFi equipped devices. If you are shopping for one, make sure you get 802.11g compliant hardware, which is backward compatible to the much slower 802.11b equipment.
Products are already out for twice as fast NextBigThing in WiFi (unratified IEEE 802.11n expected for 2007). See http://www.pcworld.com/news/article/0,aid,118666,00.asp
Allows wireless networking: At home use your laptop or HandHeld in any room without running EtherNet? cable all over and easily share your DSL or Cable connection with many computers. At work also in meetings you can be connected in a co-worker's office or the boardroom or even the kitchen. Newer TabletPcs also have WiFi built in you can get rid of that paper organizer less stuff to carry around.
The 802.11b is a IEEE working group. They have other groups such as 802.11a,e,g,i there is also 802.15 for personal area networks similar to BlueTooth and 802.16 for metropolitan area wireless networks. For WiFi b is 11 Mb while a and g are 54 Mb. g and b use 2.4GHz frequency and are compatible (you can use an older b card with a new g router) however presently one b in the network steps everything doen back to 11Mb but this is being worked on. 2.4GHz is also used in home cordless phones and microwaves and can interfere. a uses 5GHz not as susceptible to interference but has shorter range and some see g superceding it. e defines QoS (QualityOfService?) and i defines security incuding WPA which replaces but is backwards compatible with WEP which uses RC4 encryption. WPA however is dynamic using protocols like TKIP where the old WEP was static and not secure and can be broken into by OpenSource software such as AirSnort?. i also defines RSN which can use stronger encryption methods such as AES.
Many "hotspots" are popping up in cafes, airports, hotels and other public places all over the world as the speeds are much higher even than the ThirdGeneration (3G) networks carriers spent billions of dollars to roll out in the late nineties. However they are complementary as once out of range of hotspots (which are currently scattered) that is the only option. Effectively also in a WiFi hotspot you don't get as high as 11Mb as providers usually only connect through dsl or T1 which is less than 3Mb plus you are sharing bandwidth with others. One should use personal firewall, updated antivirus and VPN software with your laptop or HandHeld at hotspots for improved security.
The "last mile" for WiFi is the power as these are still bulky cables to carry around and finding power outlets in coffee shops is harder than you would think. Also usually not beside the comfy chairs and often have to be competing with other laptop users for this scarce resource. A charge usually lasts for a day of intermittent use but forget to charge overnight and you're in trouble. However wireless power is on the way in the form of mats that you can place laptop, mobile, HandHeld on and charge through induction. However existing equipment is not compatible so you will have to buy all new ones and there are competing standards.
WiMax is much more energy efficient, question is whether it will be a commercial success. See http://www.techworld.com/mobility/features/index.cfm?FeatureID=1629
WiFi is also being put on ferries, passenger trains, aircraft and cruise ships for much less and faster than those phones in the back of the chairs. You could have a near real time IM chat with your buddy on a later flight while both in mid air or to your parents on vacation somewhere in the caribbean. It's not about always having to be connected but having a choice.
Also some limousine services. Assuming you have Wifi at home and work you could get picked up by limousine at home, stop to grab something at work, go to the airport (many of which have WiFi), fly to the Cruise terminal ie Miami, take the cruise, fly home and never be without a connection. Even at base camp for mount everest there was talk of a WiFi service being set up (backhaul by satellite as it is for the aircraft and ships). In rural areas where 2.5/3G signal is scarce also since McDonalds is putting in WiFi (http://www.wirelessdevnet.com/news/2003/225/news4.html) , and you can always find one even in the country assuming those get rolled out too even in those areas connection will be available. The goal should be to have cheap fast ubiquitous wireless available almost as an amenity like lighting or electricity.
During Christmas if you spend a lot of time using WiFi in coffee shops, have an older computer with less energy storage and need to be able to plug into the already scarce power outlets, they are even less available as are being used by the owners for decoration lights. Solution - bring your own power splitter but make sure to ask the proprietor first if you can unplug their lights for a few seconds to insert the splitter (and at the end to remove it). Be careful not to pull down the decorations by accident.
WiFi networks can allow almost untraceable entry into networks.WifiProtectedAccess
WindowsXp SP2 users get a free tool (since May05) for WPA v2 protection at GetItFirstFromHere. Other users may benefit from another free tool from Wireless Security Corporation at http://www.wirelesssecuritycorp.com/wsc/public/WPAAssistant.do
Locating "Hot Spots" around the world at http://www.wi-fizone.org/zoneoverview.asp?TID=7
Feb03 document on Wireless ISP roaming best practice at http://www.weca.net/OpenSection/downloads/WISPr_V1.0.pdf
For technical notes in french : http://guide-wifi.blogspot.com/