23-02-2011, 09:31 AM
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Wireless Fidelity
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.
802.11 sub-standards(amendments ) ….
802.11 MAC (Media Access Control) ratified 1999
802.11b PHY 2.4 GHz (max 11 Mbps) ratified 1999
802.11a PHY 5.0 GHz (max 54 Mbps) ratified 1999
802.11g PHY 2.0 GHz (max 54 Mbps) ratified 2003
802.11i Security draft number XXX
802.11e QoS, Multimedia draft number XXX
802.11h European regulations for 5GHz draft number XXX
802.11h Japan regulations for 5GHz draft number XXX
Do I need any license to use 802.11 device ?
No , 2.4 GHz and 5.0 GHz are public available frequency !!!
Context with OSI layers
Logical Link Control Services
Standard 802.11 frame format
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 , ….)
Infrastructure Model includes: (most common)
• 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