80211 - 802.11 Wireless LANs Abhishek Karnik Dr Ratan Guha...

Info iconThis preview shows pages 1–13. Sign up to view the full content.

View Full Document Right Arrow Icon
802.11 Wireless LANs Abhishek Karnik, Dr. Ratan Guha University Of Central Florida
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
OVERVIEW Introduction 802.11 Basics 802.11e for QoS WEP
Background image of page 2
In 1997 the IEEE adopted IEEE Std. 802.11-1997 Defines MAC and PHY layers for LAN and wireless connectivity. Facilitate ubiquitous communication and location independent computing 802.11b operates at 11Mbps in the 2.4 GHz ISM Band (‘99) 802.11a operates at 54Mbps in the 5 GHz Band (’99) 802.11g operates at 54Mbps in the 2.4 GHz Band (’02) Increased deployment and popularity lead to introduction of QoS 802.11e for QoS – Draft Supplement – Nov 2002 INTRODUCTION
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Wireless LAN Station The station (STA) is any device that contains the functionality of the 802.11 protocol, that being MAC, PHY, and a connection to the wireless media. Typically the 802.11 functions are implemented in the hardware and software of a network interface card (NIC). Ex : PC , Handheld , AP (Access Point) Basic Service Set (BSS) 802.11 defines the Basic Service Set (BSS) as the basic building block of an 802.11 wireless LAN. The BSS consists of a group of any number of stations. 802.11 BASICS
Background image of page 4
STA STA STA STA IBSS (Independent Basic Service Set – Ad-hoc Mode ) peer-peer connections
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
AP Wired Backbone Infrastructure Basic Service Set
Background image of page 6
AP Wired Backbone AP ESS (Extended Service Set) BSS1 BSS2
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
PCF DCF Super Frame DCF - Distributed Coordinated Function ( Contention Period - Ad-hoc Mode ) PCF - Point Coordinated Function ( Contention Free Period Infrastructure BSS ) Beacon - Management Frame Synchronization of Local timers Delivers protocol related parameters TBTT - Target Beacon Transition Time Beacon TBTT
Background image of page 8
Distributed Coordinated Function (DCF) Also known as the Contention Period STAs form peer-peer connections. No central authority First listen and then speak Uses CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) ACK indicates successful delivery Each node has one output buffer
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Inter-Frame Spacing : DIFS - 34 µsec PIFS - 25 µsec ( Used in PCF ) SIFS - 16 µsec Slot Time - 9 µsec DIFS = SIFS + (2 * Slot Time) SIFS required for turn around of Tx to Rx and vice versa
Background image of page 10
DATA A ACK B ACK DIFS SIFS DIFS CW A Data Transmission from Node A to B CW – Contention Window. Starts only after DIFS. Random number ‘r’ picked form range ( 0-CW ) CW min minimum value of CW CW max maximum value the CW can grow to after collisions ‘r’ can be decremented only in CW CW doubles after every collision
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
DATA A ACK B ACK DIFS SIFS DIFS CW A What if some node C wanted to send data while A was transmitting data to B ?
Background image of page 12
Image of page 13
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 06/09/2011 for the course CDA 4527 taught by Professor Zou,c during the Fall '08 term at University of Central Florida.

Page1 / 50

80211 - 802.11 Wireless LANs Abhishek Karnik Dr Ratan Guha...

This preview shows document pages 1 - 13. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online