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What is Wi-Fi? Wi-fi is a wireless technology that uses
radio frequency to transmit data through
the air. Vic-Hayes has been called the "father of Wi-Fi". The first wireless products were under the name
WaveLAN was introduced in1991. Wi-Fi allows you to use your computer or other
device to connect to the internet from anywhere there is a Wi-Fi access point (often known as a hot Spot.
WiFi 2
WiFi WiFi is the wireless way to handle
networking. It is also known as 802.11 networking. The big advantage of WiFi is its simplicity. You can connect computers anywhere in
your home or office without the need for wires. The computers connect to the network using radio signals, and computers can be up to 100 feet or so apart.
WiFi 3
4
What is the goal of 802.11 standard ?
To develop a Medium Access Control (MAC) and Physical Layer (PHY) specification for wireless connectivity for fixed, portable and moving stations within a local area.
Wi-Fi Standards…
Standard Speed Freq band Notes
802.11 2 Mbps 2.4 GHz (1997) 802.11a 54 Mbps 5 GHz (1999) 802.11b 11 Mbps 2.4 GHz 802.11g 54 Mbps 2.4 GHz
WiFi 5
Range and Performance
Performance decreases as distance increases
802.11a Indoor 40-300 feet
Outdoor – 100 to 1000 feet 802.11b Indoor 100-300 feet
Outdoor 400 – 1500 feetWiFi 6
Wi-Fi network services
Distribution and integration Association, re-association, and
disassociation Authentication and deauthentication Providing privacy.
WiFi 7
WiFi 8
Do I need any license to use 802.11 device ?
No , 2.4 GHz and 5.0 GHz are public available frequency !!!
WiFi Security
WiFi hotspots can be open or secure.
If a hotspot is open, then anyone with a WiFi card can access the hotspot.
If it is secure, then the user needs to know a WEP key to connect.
WEP stands for Wired Equivalent Privacy.
WiFi 9
WiFi Security (Conti…)
WEP is an encryption system for the data that 802.11 sends through the air.
Encryption system prevents any non-authorized party from reading or changing data.
Specifically, it is the process of encoding bit stream in such a way that only the person (or computer) with the key (a digital sequence) can decode it.
WiFi 10
WiFi 11
Wi-Fi Security(conti…)
WEP ( wired equivalent privacy) 64/128 bits
Using RC4 algorithm, almost permanent key, very week
security, able to crack by collecting statistic
Current security level for 99.9% products on the market. TKIP (temporal key integrity protocol )
Used RC4 algorithm with with a 128-bit "temporal key"
but changes temporal keys every 10,000 packets and key dependes on address and sequence number.
Will be required to obtain WiFi certification from 09/01/03 AES (Advanced Encryption Standard )
New, much more stronger encryption, protect against hacker frames in insertion. Need hardware accelerator. Optional feature.
WiFi 12
Frames types and subtypes
Three types of frames: Control
(ACK,RTS,CTS ,Power Save …) Management
(Beacon,Probe Request ,Probe Response,
Association request , Association response …)
Data
(Data, Null Data, Data_CF_Ack , ….)
WiFi 13
How to connect a wi-fi device…?
• Stations (STA)– any wireless device
• Access Point (AP)– connects BSS to DS– controls access by STA’s
• Basic Service Set (BSS)– a region controlled by an AP– mobility is supported within a
single BSS
• Extended Service Set (ESS)– a set of BSS’s forming a virtual
BSS– mobility is supported between
BSS’s in an ESS
• Distribution Service (DS)– connection between BSS’s
DS
BSS1
BSS2
BSS3STA1
STA2
STA3
ESS1
AP1
AP2
AP3
WiFi 14
Two types of access to air
DCF (distributed coordination function )
means everybody can speak and try
to get air : 100% on the market
PCF (point coordination function)
means ONE point coordinator (BOSS)
who will allowed you to speak
(like in bluetooth)
WiFi 15
Summary of required features and difficulties...
Features High speed operation (PHY only) Fair access (DCF, PCF) Time-bounded access (PCF) Flexible configuration (BSS, IBSS) Security (WEP) Mobility support (ESS) Low power (PS)
Difficulties Hidden terminals (RTS/CTS) Capture (CSMA/CA, ACK) Noise and interference (ACK, frag) Limited spectrum (licencing, PHYs)
Conclusion…
WiFi 21
The IEEE standards group that oversees Wi-Fi technology has just approved a brand new next-gen Wi-Fi 802.22 technology that could allow your home network to span up to 60 miles!