Wi-FiWi-Fi

Evolution of Wireless LANEvolution of Wireless LAN Early experiences (1970-72): IBM, HP, MotorolaEarly experiences (1970-72): IBM, HP, Motorola

• Abandoned due to limited performance and Abandoned due to limited performance and unavailability of frequency bandsunavailability of frequency bands

Early challenges:Early challenges:• Complexity and costComplexity and cost• BandwidthBandwidth• CoverageCoverage• InterferenceInterference• Frequency administrationFrequency administration

Emergence of unlicensed bandsEmergence of unlicensed bands• Release of Industrial, Scientific and Medical (ISM) bands Release of Industrial, Scientific and Medical (ISM) bands

in 1985in 1985 Applications: military, home and enterprise Applications: military, home and enterprise

networks, mobile networks, teetherless accessnetworks, mobile networks, teetherless access

Wi-Fi is based on 802.11 technologyWi-Fi is based on 802.11 technology It is originally intended to provide wireless It is originally intended to provide wireless

computing for staffs within businesses and computing for staffs within businesses and commercial organizationscommercial organizations

IEEE 802.11IEEE 802.11 Standardization group formed in 1990, first Standardization group formed in 1990, first

standards completed in 1997standards completed in 1997 IEEE 802.11 is the first WLAN standard; only one IEEE 802.11 is the first WLAN standard; only one

to secure a marketto secure a market 802.11a: PHY layer supports 11Mbps using CKK 802.11a: PHY layer supports 11Mbps using CKK

(complementary code keying) technology(complementary code keying) technology 802.11b: PHY layer supports 54 Mbps using OFDM802.11b: PHY layer supports 54 Mbps using OFDM Uses CSMA/CA for contention dataUses CSMA/CA for contention data Supports both infrastructure as well as ad hoc Supports both infrastructure as well as ad hoc

modesmodes

802.11a – higher speeds, smaller 802.11a – higher speeds, smaller coverage, more channelscoverage, more channels

Wi-Fi is also sold to hotspot operators particularly Wi-Fi is also sold to hotspot operators particularly hotel, convention centres, cafes, airportshotel, convention centres, cafes, airports

Hotspots offer higher-speed Internet access than Hotspots offer higher-speed Internet access than most cellular network’s data offering and cost most cellular network’s data offering and cost less to build than cellular base stationless to build than cellular base station

802.11 wireless standards are based on Ethernet 802.11 wireless standards are based on Ethernet protocols protocols

802.11a is the only 802.11 standard that 802.11a is the only 802.11 standard that operates at 5 GHzoperates at 5 GHz

The use of 5 GHz band avoids interference from The use of 5 GHz band avoids interference from microwave ovens, Bluetooth equipments and microwave ovens, Bluetooth equipments and cordless phones that operate at 2.4 GHzcordless phones that operate at 2.4 GHz

Disadvantage is the signal fade fasterDisadvantage is the signal fade faster

802.11b 802.11b When they were first available, 802.11 When they were first available, 802.11

equipments were equipped with only 802.11b equipments were equipped with only 802.11b chipschips

Now most use b and g which are designed to Now most use b and g which are designed to interoperateinteroperate

Because home broadband connections are slower Because home broadband connections are slower than 802.11 networks, no advantage is gained than 802.11 networks, no advantage is gained

802.11g802.11g

Support higher data rates than 802.11bSupport higher data rates than 802.11b Use 2.4 gHz bandsUse 2.4 gHz bands The higher speeds and capacity of g and a The higher speeds and capacity of g and a

are required to support voice over IP on are required to support voice over IP on WLANsWLANs

802.11n802.11n

Backward compatibility with a, b and gBackward compatibility with a, b and g Improve coverage by overcoming a certain Improve coverage by overcoming a certain

amount of interferenceamount of interference Increase speeds and supports more users Increase speeds and supports more users

per access pointper access point

Benefits..Benefits.. Residential customers adopted Wi-Fi faster than Residential customers adopted Wi-Fi faster than

enterprises because of its simplicity, fewer enterprises because of its simplicity, fewer concerns about security and the benefit of concerns about security and the benefit of avoiding the expenses for cablingavoiding the expenses for cabling

Its advantage is low equipment cost and easier Its advantage is low equipment cost and easier installationinstallation

Benefits were also immediately noticed for Benefits were also immediately noticed for healthcare, education, retailing and warehousinghealthcare, education, retailing and warehousing

Disadvantages..Disadvantages.. Because of the casual nature of Wi-Fi users, most Because of the casual nature of Wi-Fi users, most

of them don’t protect their Wi-Fi networks with of them don’t protect their Wi-Fi networks with strong passwords – This weakness can be strong passwords – This weakness can be exploited by unauthorized persons which exploited by unauthorized persons which (advertently) can gain access to the Wi-Fi and can (advertently) can gain access to the Wi-Fi and can exploit it to satisfy their personal or professional exploit it to satisfy their personal or professional needs.needs.