Home Random Page


CATEGORIES:

BiologyChemistryConstructionCultureEcologyEconomyElectronicsFinanceGeographyHistoryInformaticsLawMathematicsMechanicsMedicineOtherPedagogyPhilosophyPhysicsPolicyPsychologySociologySportTourism






PRINCIPE OF OPERATION

Wi-Fi - a trademark of Wi-Fi Alliance for wireless networks based on the standard IEEE 802.11. The acronym Wi-Fi (from the English phrase Wireless Fidelity, which can be literally translated as "the quality of the wireless" or "Wireless Fidelity") is currently developing a whole family of standards for the transmission of digital data radio streams. Any equipment, complying with IEEE 802.11, can be tested in the Wi-Fi Alliance and receive a certificate and the right to put the logo Wi-Fi.

HISTORY

Wi-Fi was created in 1991 by NCR Corporation / AT & T ( later - Lucent Technologies and Agere Systems) in Nivegeyn , Netherlands. Products , intended originally for systems and cash services , were introduced to the market under the name WaveLAN and provides a data rate of 1 to 2 Mbit / s . Created by Wi-Fi - Vic Hayes (Vic Hayes) was in the team that participated in the development of standards such as IEEE 802.11b, IEEE 802.11a and IEEE 802.11g. In 2003, Vic retired from Agere Systems. Agere Systems could not compete on equal terms in difficult market conditions , despite the fact that its products are occupied the niche of cheap Wi-Fi solutions. 802.11abg all-in-one chipset from Agere ( codename : WARP) sold poorly , and Agere Systems decided to leave the Wi-Fi market in late 2004 .

The IEEE 802.11n standard was approved September 11, 2009 . Its application allows to increase the speed of data transmission is almost four times compared to standard devices 802.11g ( maximum speed is 54 Mbit / s) , when used in 802.11n mode with other devices 802.11n. Theoretically, 802.11n can provide data rates up to 600 Mbit / s [ 1] . From 2011 to 2013, developed standard IEEE 802.11ac, the final adoption of the standard is scheduled for early 2014. Data transfer rate using 802.11ac can reach several Gbit / s. Most of the leading equipment manufacturers have already announced devices that support this standard.

July 27, 2011 Institute of Electrical and Electronics Engineers (IEEE) released the official version of the standard IEEE 802.22 [ 2] . Systems and devices that support this standard will allow to transfer data at speeds up to 22 Mbit / s in a radius of 100 km from the nearest transmitter.

ORIGIN OF NAME

The term «Wi-Fi» was originally coined as a pun to attract consumer attention, "hint" at the Hi-Fi (Eng. High Fidelity - precision). Despite the fact that initially, in some press releases WECA figured phrase «Wireless Fidelity» («Wireless accuracy"), at the moment of such a formulation refused, and the term «Wi-Fi» does not stand.

PRINCIPE OF OPERATION

Typically, Wi-Fi scheme network comprises at least one access point and at least one client. It is also possible to connect two clients in point-to- point (Ad-hoc), where the access point is not used , and the clients are connected via network adapters "directly" . AP broadcasts its network identifier (SSID ( English) Russian . ) Using special signaling packets at a speed of 0.1 Mbit / s every 100 ms . Therefore, 0.1 Mbit / s - the lowest data rate for Wi-Fi. Knowing the SSID of the network , the client can determine whether it is possible to connect to this access point. When injected into the zone of action of the two APs with identical SSID receiver can choose between them based on the data of the signal level. Wi-Fi Standard gives the customer complete freedom in choosing the criteria for joining . More detail the principle of operation is described in the official text of the standard .




Date: 2016-01-14; view: 404


<== previous page | next page ==>
Why is climate change a concern? | COMMERCIAL USE OF WI-FI
doclecture.net - lectures - 2014-2018 year. Copyright infringement or personal data (0.001 sec.)