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Wi-Fi (or WiFi) is a local area wireless computer networking technology that allows electronic devices to connect to the network, mainly using the UHF and SHF ISM radio bands. The Wi-Fi Alliance defines Wi-Fi as any "wireless local area network" (WLAN) product based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards.〔(【引用サイトリンク】title=What is Wi-Fi (IEEE 802.11x)? A Webopedia Definition )〕 However, the term "Wi-Fi" is used in general English as a synonym for "WLAN" since most modern WLANs are based on these standards. "Wi-Fi" is a trademark of the Wi-Fi Alliance. The "Wi-Fi Certified" trademark can only be used by Wi-Fi products that successfully complete Wi-Fi Alliance interoperability certification testing. Many devices can use Wi-Fi, e.g. personal computers, video-game consoles, smartphones, digital cameras, tablet computers and digital audio players. These can connect to a network resource such as the Internet via a wireless network access point. Such an access point (or hotspot) has a range of about indoors and a greater range outdoors. Hotspot coverage can be as small as a single room with walls that block radio waves, or as large as many square kilometres achieved by using multiple overlapping access points. Wi-Fi can be less secure than wired connections, such as Ethernet, precisely because an intruder does not need a physical connection. Web pages that use TLS are secure, but unencrypted internet access can easily be detected by intruders. Because of this, Wi-Fi has adopted various encryption technologies. The early encryption WEP proved easy to break. Higher quality protocols (WPA, WPA2) were added later. An optional feature added in 2007, called Wi-Fi Protected Setup (WPS), had a serious flaw that allowed an attacker to recover the router's password.〔(【引用サイトリンク】title=Brute forcing Wi-Fi Protected Setup )〕 The Wi-Fi Alliance has since updated its test plan and certification program to ensure all newly certified devices resist attacks. == History == (詳細はALOHAnet connected the Hawaiian Islands with a UHF wireless packet network. ALOHAnet and the ALOHA protocol were early forerunners to Ethernet, and later the IEEE 802.11 protocols, respectively. A 1985 ruling by the U.S. Federal Communications Commission released the ISM band for unlicensed use. These frequency bands are the same ones used by equipment such as microwave ovens and are subject to interference. In 1991, NCR Corporation with AT&T Corporation invented the precursor to 802.11, intended for use in cashier systems. The first wireless products were under the name WaveLAN. The Australian radio-astronomer Dr John O'Sullivan with his colleagues Dr Terrence Percival AM, Mr Graham Daniels, Mr Diet Ostry, Mr John Deane developed a key patent used in Wi-Fi as a by-product of a Commonwealth Scientific and Industrial Research Organisation (CSIRO) research project, "a failed experiment to detect exploding mini black holes the size of an atomic particle". In 1992 and 1996, CSIRO obtained patents for a method later used in Wi-Fi to "unsmear" the signal. The first version of the 802.11 protocol was released in 1997, and provided up to 2 Mbit/s link speeds. This was updated in 1999 with 802.11b to permit 11 Mbit/s link speeds, and this proved to be popular. In 1999, the Wi-Fi Alliance formed as a trade association to hold the Wi-Fi trademark under which most products are sold.〔(【引用サイトリンク】work= Official industry association Web site )〕 Wi-Fi uses a large number of patents held by many different organizations.〔(IEEE-SA – IEEE 802.11 and Amendments Patent Letters of Assurance )〕 In April 2009, 14 technology companies agreed to pay CSIRO $250 million for infringements on CSIRO patents. This led to Australians labeling Wi-Fi as an Australian invention,〔(【引用サイトリンク】title=World changing Aussie inventions – Australian Geographic )〕 though this has been the subject of some controversy.〔(【引用サイトリンク】title=How the Aussie government "invented WiFi" and sued its way to $430 million )〕 CSIRO won a further $220 million settlement for Wi-Fi patent-infringements in 2012 with global firms in the United States required to pay the CSIRO licensing rights estimated to be worth an additional $1 billion in royalties.〔〔(【引用サイトリンク】title=Australian scientists cash in on Wi-Fi invention )〕〔(【引用サイトリンク】title=CSIRO wins legal battle over wi-fi patent )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Wi-Fi」の詳細全文を読む スポンサード リンク
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