The document provides an overview of IEEE 802.11 standards for wireless local area networks. It discusses the creation of 802.11 by IEEE, the physical layer, frame formats, and various 802.11 protocols including 802.11b, 802.11a, 802.11g, 802.11n, and 802.11ac. It also describes the media access control including CSMA/CA and security features like authentication and WEP encryption.

1. PRESENTATION
ON
IEEE 802.11
Prepared By:
Shreejan Acharya
BEX 68114

2. Slides Includes
Introduction
Physical Layer
Architecture
Frame format
Different Protocols
Media Access Control (MAC)

3. Introduction
 Created and maintained by IEEE
 Set of media control(MAC) and physical layer
 Used to implement wireless local area
network(WLAN)
 In the frequency band 2.4,3.6,5 and 60 GHz
 Wi-fi refers to the IEEE 802.11 communication for
WLAN
The Linksys WRT54G contains a router with an
802.11b/g radio and two antennas

4. Introduction cntd.
Adopted in 1997
Family of 802
Origins in a 1985 ruling by the U.S. Federal
Communications commission
Consist of series of half duplex over the air
modulation
Uses same basic protocols
It uses two spread spectrum technology
Frequency Hopping Spread Spectrum (FHSS)
 Direct Sequence Spread Spectrum (DSSS)

5. 802.11 Physical Layer (PHY)
The 802.11 physical layer (PHY) is the interface
between the MAC and the wireless media where
frames are transmitted and received.
 The PHY provides three functions.
 First, the PHY provides an interface to exchange
frames with the upper MAC layer for transmission and
reception of data.
Secondly, the PHY uses signal carrier and spread
spectrum modulation to transmit data frames over
the media.
 Thirdly, the PHY provides a carrier sense indication
back to the MAC to verify activity on the media.

6. Architectures
Station (STA) Architecture:
 It contains IEEE 802.11
conformant MAC and PHY
interface to the wireless
medium, but does not
provide access to a
distribution system
Access-Point Architecture:
 Device that contains
IEEE802.11 conformant
MAC and PHY interface to
the wireless medium, and
provide access to a
distribution system for
associated stations
 Implemented in infra-
structure products that
connect to wired backbones

7. General terminologies
BSS (basic service set):
Group of stations that communicate each other
IBSS(independent basic service set):
It is a BSS without access point
Extended Service Set (ESS):
A set of one or more Basic Service Sets inter
connected by a distribution System (DS)

8. BSS IBSS

9. General terminologies cntd
Service Set Identifier (SSID):
It is network name similar to domain id
One network (ESS or IBSS) has one SSID
Basic Service Set Identifier (BSSID)
It is cell identifier and is 6 octets long
Similar to NW ID in pre-IEEE Wave LAN systems

10. Frame format
Bytes 2 22 6 6
6
66 2 6 0-
2312
4
Frame control Durati
on ID
A1 A2 A3 seq.ctr
l
A4 Frame
body
CRC
802.11 MAC header
Bits :2
2 2 4 1 1 1 1 1 1 1
Protocol
version
type Sub
type
To DS From
DS
More
flag
Retry Pwr
Mgt
More
data
wep rsvd
Frame control Field

11. protocols
802.11 legacy
Release in Jun 1997
Original version of 802.11
Specifies two net bit rate 1or 2 mbits per sec
It has forward error correction code
Three alternatives physical layer
Diffuse infrared
Frequency hopping spread spectrum
Direct sequence spread spectrum

12. 802.11a(ofdm waveform)
Release in sep 1999
Data rates 1.5 to 54 mbit/s
First widely accepted 802 family
Operates at 5GHz frequency band
Less range

13. 802.11b
Release on the market in 2000
Maximum raw data rate of 11mbit/s
High throughput
Low cost
Interference problem

14. 802.11g
Release on june 2003
Operates in the 2.4 GHz band
Uses OFDM based transmission scheme
Operates at the average bit rate of 22 Mbit/s or
maximum 54 Mbit/s
Its hardware are full back compatible with
802.11b hardware

15. 802.11n
Release on October 2009
It is the improvement over previous 802.11
standard
It has MIMO antennas
Operates at the 2.4 GHz or less than 5GHz
bands
Data rates from 54 Mbit/s to 600 Mbit/s

16. 802.11ac
Release in December 2013
It is an amendment to IEEE 802.11
It has wider channels(80 or 160 MHz)
Operates at 5GHz band
It supports multi-user MIMO
Data rates up to 1300 Mbit/s

17. 802.11ad
Release in Dec 2012
It defines new physical layer for 802.11 n/w
Operates in the 60GHz millimeter wave
spectrum
Product implementing this standard are being
brought under the name of wigig brand
Peak transmission rate 7 Gbit/s

18. Other Protocols
802.11 AH
Estimated to release 2016
Bandwidth 900MHz
802.11 AJ
 Estimated to release 2016
Bandwidth 24/60
802.11 AX
Estimated to release 2019
Bandwidth 2.4/5

19. 802.11 Media Access Control
 The 802.11 MAC layer provides functionality to allow reliable data
delivery for the upper layers over the wireless PHY media.
 The data delivery itself is based on an asynchronous, best-effort,
connectionless delivery of MAC layer data.
 There is no guarantee that the frames will be delivered successfully.
 The 802.11 MAC provides a controlled access method to the shared
wireless media called Carrier-Sense Multiple Access with Collision
Avoidance (CSMA/CA).
 CSMA/CA is similar to the collision detection access method
deployed by 802.3 Ethernet LANs.

20. 802.11 Media Access Control cntd
Another function of the 802.11 MAC is to
protect the data being delivered by providing
security and privacy services.
 Security is provided by the authentication
services and by Wireless Equivalent Privacy
(WEP), which is an encryption service for data
delivered on the WLAN.

21. Security
For security 802.11 specifies two
Authentication modes:
OSA(Opens Systems Authentication)
• Device that request to access the network is granted
without any security check
Shared Key Authentication
• Device that request to access the network is granted
with security check
• WEP: wired equivalent privacy
ESSID offers casual separation of traffic

22. THANK YOU