WIFI STANDS FOR WIless FIdelity AND ENCOMPASSES A WORLDWIDE (DEFACTO) STANDARD, WHICH ALLOWS HIGH-SPEED WIRELESS INTERNET TRANSMITTED VIA RADIO WAVES WITH SPEEDS OF MBPS, RATHER THAN KBPS.



THE SO-CALLED HOTSPOT OR HUB OR WLAN ACCESS POINT SENDS OUT A WIRELESS SIGNAL TO ALLOWS WIRELESS DEVICES ACCESS WITHIN A CIRCLE OF 100 METER.



Brief History Of Wi-Fi

•In 1990 , the IEEE 802 committee formed a new working group devoted to wireless LANs, with a charter to develop MAC protocol & physical layer specifications.

•WLANs operating in ISM band frequencies.

•IEEE 802.11 working group issued following standard list having different frequencies & data rates i.e.

•802.11 In 1997

•802.11a In 1999

•802.11b In 1999

•802.11g In 2003







Brief History Of Wi-Fi

•For Different vendors compatibility/ interoperability ,Wireless Ethernet Compatibility Alliance (WECA) in 1999 certifies WLAN products i.e. 120 vendors qualified for IEEE 802.11b the term used for certified 802.11b products is now known as Wi-Fi.

•Certification process for 802.11a products called Wi-Fi5 certified.

ØIEEE established the 802.11 Group in 1990 (very first commercial WLAN).

ØInitial speeds were 1 and 2 Mbps.

ØSupporting following data rates & frequencies.



i.Infra Red

ii.2.4 GHz FHSS,

iii.2.4 GHz DSSS.



802.11a



ØFlexible because multiple channels can be combined for faster throughput and more access points can be co-located.

ØShorter range than 11b and 11g.

ØRuns in the 5 GHz range, so less interference from other devices.

ØHas 12 channels,8 non-overlapping, and supports rates from 6 to 54 Mbps, but realistically about 27 Mbps max.

ØUses frequency division multiplexing OFDM technology





802.11b



ØBeen around the longest

ØAnd cost effective ,but runs in the 2.4 GHz range that makes it prone to interference from other devices (microwave ovens, cordless phones, etc) and also has security disadvantages.

ØLimits to the number of access points in range of each other, three.

ØHas 11 channels,with 3 non- overlapping, and supports rates from 1 to 11 Mbps,but realistically about 4- 5 Mbps max.

ØUses DSSS direct-sequence spread-spectrum technology

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