Wifi 802.11x WLAN Basics

WLAN – 802.11x

topics covered:

-wifi types
-standards and ranges
-spread spectrum
-antenna types
-CA vs CD
-SSID and MAC authentication
-WLAN facts:

lilly pad network – free example: hotels have free wifi
hot spots – credentials neeeds example truck stops.
Ad hock – PC to PC wlan connection
AP to pc is infractructure connection
ESS is multiple access point (AP)
BSS is basic 1 Access point only
cells is what is called the coverage area
Example below:



3 Services WLAN:

1. Independent Basic Service Set (IBSS)

– no AP
– AD hoc only

2. Basic Service Set (BSS)

-1 AP only

3. Extended Service Set (ESS)

– multiple AP
– large area coverage
Wireless 802.11x standards
802.11 IEEE

802.11a – 25 MBps – 54 MBps, indoor range 100 feet 5 Ghz 

802.11b – 6.5 MBps – 11 MBps, 100 feet indoor range, 2.4 Ghz

802.11g – 25 MBps – 54 MBps, indoor 100 feet, 2.4 Ghz comapt with  802.11b

802.11n – 200 MBps – 540 MBps indoor 160 feet, 2.4 Ghz or 5 Ghz

wifi issues of inerferrence:

– microave ovens or microaves

– Wirless phones on 2.4 Ghz channel

– Solid objects walls etc…

Talking about Spread Spectrum Types:

FHSS-Frequent Happening Spread Spectrum – sender/reveiver agree on frequency range.

DSSS-Direct Sequence Spread Spectrum-Spread signal over entire range at once (11b, 11g, 11n)

OFDM-Orthogonal Frequency Division Multiplexing- Splits signal and sends the signal fragments over different frequencies at the same time at once.

Why all the talk about Spread Spectrum?

– Increases resistance to noise
– allows sharing of frequency band
– more difficult to intercept
Types of Antennas

Type 1 : Yagi antenna :

– signal in single direction
– must be aligned correctly
– called directional antenna
– p2p direction
Type 2: Omni –
– sends signal all directions hence name OMNI
– omni directional
– Point to multipoint

CSMA/CA  wifi

Carrier Sense Multiple Access with Collission Avoidance!
– Listens first
– if channel idle (random timer)hosts listen again.
– if channel is busy host cannot transmit

Wifi facts:

– no jam signal used
– half-duplex only  – no full-duplex used in wifi

– 32 character max
– case sensitive
– if disable broadcast, must be statically configured
– wifi allow mac addresses only can be set


– WEP 1st came
– WPA evolved from WEP
– WPA2 evolved from WPA

-Wired Equivalent Privacy
– clear text key
– static keys
-one way auth -client doesnt authenticate
-Authentication (open-shared key)
– no friendly to older devices.
-Wifi protection authentication
– 2 way authentication
– TKIP with preshared key
WPA2 – not on exam
-wpa2 complex


3 Responses to “Wifi 802.11x WLAN Basics”

  1. thanks it worked ;)))

    That’s rally nice………..keep it up!

  2. A pal encoraged me to look at this site, great post, fascinating read… keep up the good work!

    • hey thanks man. I am back on the band wagon. I am studying for my ccnp and hope to start posting again my ccnp stuff
      but it is all fun and hope I can improve on my stuff…stuff that you can use to help…
      thanks man cheers!
      ps. if you ever neen anyquestions or configs just email me at robert (at) itdaddy (dot) net and I can send you what I have or point you to some good stuff to learn this cool stuff.

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