Wi-Fi

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Wi-Fi

• Jason Orgill
• John Bodily
• Scott Rowberry

2
Background

• Purpose
• Develop MAC and PHY layer for wireless
  connectivity of fixed, portable and moving
  stations within a fixed area
• The higher OSI-layers are the same as in any
  other 802.X standard, this means that at this
  level there is no perceptible difference between
  wired and wireless media.
• When
• 1997 standard first published

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Background cont.

• Wi-Fi Alliance
• Major industry players formed an alliance in 1999
  under the name of Wireless Ethernet Compatibility
  Alliance (WECA) to create interoperability
  standards
• Coined the term Wi-Fi
• Renamed to Wi-Fi Alliance in 2003
• Establish the standards

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802.11 Standards

• 802.11b
• Ratified in December 1999
• Operates at 2.4 GHz
• Maximum throughput of 11 Mbps
• Actual throughput of 6.5 Mbps
• Typical Range of 100 feet
• Uses Complementary Code Keying (CCK)

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802.11 Standards cont.

• 802.11a
• Ratified in January 2000
• Operates at 5 GHz
• Maximum throughput of 54 Mbps
• Actual throughput of 25 Mbps
• Typical range of 100 feet
• Uses Orthogonal Frequency Division Multiplexing
  (OFDM)

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802.11 Standards cont.

• 802.11g
• Ratified in January 2003
• Operates at 2.4 GHz
• Maximum throughput of 54 Mbps
• Actual throughput of 25 Mbps
• Typical range of 100 feet
• Uses Orthogonal Frequency Division Multiplexing
  (OFDM)
• Interoperable with 802.11b

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802.11 Standards cont.

• 802.11n
• Yet to be ratified
• Operates at 2.4 GHz and 5 GHz
• Maximum throughput of 540 Mbps
• Actual throughput of 200 Mbps
• Typical range of 165 feet
• Added Multiple Input Multiple Output (MIMO)

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Connectivity Modes

• Ad-Hoc
• Create Peer-to-peer networks
• Access Point
• Used to create hotspots where wi-fi devices can
  connect to the network
• Must have ethernet cable run to router/switch to
  access the network
• The router and switch will use this link for the
  wireless activity

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Link Layer Architecture MAC

• Medium Access Control links the nodes
• Wi-fi nodes have transmission gears

BPSK (for weakest signals) 6-9 Mbps
QPSK (for weak signals) 12-18 Mbps
QAM-16 (for good signals) 24-36 Mbps
QAM-64 (for strongest signals) 48-54 Mbps
Data Link (MAC) - Frames
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Wi-Fi Security

• WEP Wired Equivalency Privacy
• Easy to break
• WPA WiFi Protected Access
• WPA2
• MAC Media Access Control
• Uses list of MACs to grant access

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• Any Questions?