Introduction to Wireless Networking and Overview of 802.11 Networks

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Introduction to Wireless Networking and Overview
of 802.11 Networks

• Discussion based on Gasts802.11 Wireless
  Networks (2nd Ed.) Chapters 1 and 2

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Now you know . . .

• 802 is the IEEE LAN project
• 11 is the working group
• g is the task group
• i (lower case) is a task group working on
  802.11-dependent security standards
• F (upper case) is a task group working on
  independent roaming protocols (e.g., that could
  be used in non-WLAN applications as well)

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Know your units . . .

• 10x Abbrev. Symb.
• -18 atto a
• -15 fempto f
• -12 pico p
• -9 nano n
• -6 micro µ
• -3 milli m
• -2 centi c
• -1 deci d

• 10x Abbrev. Symb.
• 1 deca da
• 2 hecto h
• 3 kilo k
• 6 mega M
• 9 giga G
• 12 tera T
• 15 peta P
• 18 exa E

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Important relationships

• c ?f
• C speed of light (meters/second)
• 186,000 miles/second
• 3 108 meters/second
• ? wavelength in meters (meters/cycle)
• f frequency in Hertz (Hz) (cycles/second)
• Q Wavelength corresponding to 2.4 GHz?

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Wireless Advantages

• Mobility and increased reach
• Ease and speed of deployment
• Flexibility and ease of configuration
• Cost savings (sometimes)
• New business opportunities (m-commerce)

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Wireless Challenges

• Scarce total bandwidth available
• Compared to wired, generally
• Slower (partially due to limited analog
  bandwidth)
• Less reliable (dynamic, noisy environments)
• Less secure (lack of physical boundaries)
• Less able to ensure QoS

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Electromagnetic Spectrum
Details at http//www.ntia.doc.gov/osmhome/allochr
t.html
ACPower
Voice
ISM
VHFTVFMRadio
UHFTV
AM Radio
IR, Visible Light, UV
PCS
Hearing
Satellite
AnalogCell Phone
ISM Industrial, Scientific, Medical (allows
unlicensed but not unregulated uses).902-928
MHz, 2.4-2.48 GHz, 5.x GHz
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Table 1-3. standards

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Figure 2-1. The IEEE 802 family and its relation
to the OSI model
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Figure 2-3. Components of 802.11 LANs
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Figure 2-4. Independent and infrastructure BSSs
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Figure 2-5. Extended service set
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Figure 2-6. Distribution system in common 802.11
access point implementations
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Figure 2-7. Overlapping BSSs in an ESS
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Figure 2-8. Overlapping network types
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Figure 2-9. BSS transition
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Figure 2-10. ESS transition
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Table 2-1. Network services