Wi-Fi uses radio waves to transmit data through the air according to the IEEE 802.11 standards. It allows computers and other devices to connect to the internet and each other wirelessly. The 802.11 standards include 802.11b, 802.11a, 802.11g, 802.11n, and 802.11ac which provide different speeds and capabilities. Wi-Fi networks use access points, wireless cards, and security protocols like WEP, WPA, and WPA2 to transmit data securely between devices over short ranges.

1. Wi-Fi
the
802.11 Standard
VIPUL KUMAR MAURYA
CSE Department, 3rd Year

2. Introduction
Wi-Fi Stands for Wireless Fidelity
Wireless Fidelity is generic term refers to (The Institute of
Electrical and Electronics Engineers ) IEEE 802.11 standards
for Wireless Local Area Network.
Wi-Fi is a wireless technology that uses radio frequency to
transmit data through the air.
Wi-Fi Network Connects Computer to each other, to the
internet and to the wired network.

3. Wi-Fi Works On IEEE 802.11 Standards
 802.11 is primarily concerned with the
lower layers of the OSI model.
 Data Link Layer
 Logical Link Control (LLC).
 Medium Access Control (MAC).
 Physical Layer
 Physical Layer Convergence Procedure
(PLCP).
 Physical Medium Dependent (PMD).

4. 802.11 Standards
IEEE 802 .11 b
IEEE 802 .11a
IEEE 802 .11g
IEEE 802 .11n
IEEE 802 .11ac
IEEE 802.11 is a set of media access control (MAC) and physical
layer (PHY) specifications for implementing wireless local area
network (WLAN) computer communication in the 2.4, 3.6, 5, and
60 GHz frequency bands

5. 802.11b Standard
 Appears in late 1999
 Operates at 2.44Ghz radio spectrum
 11Mbps (theoretical speed)- within 30 meter Range
 4-6 Mbps Actual Speed
 100-150 feet range
 Limits the number of access points in range of each other
to three
 Most Popular , Least Expensive
 Interference from Mobile Phones and Bluetooth device
which can reduce transmission speed
 Uses direct-sequence spread-spectrum technology

6. 802.11a Standard
 Introduce in 2001
 Operates at 5GHz
 Less popular and Less interfered
 54 Mbps (theoretical Speed)
 15-20 Mbps (Actual Speed)
 50-75 feet range
 More Expensive
 Highly Obstructed
 Not Compatible with 802.11b
 Uses frequency division multiplexing

7. 802.11g Standard
 Introduce in 2003
 Combine features of both a and b
 100-150 feet range
 54 Mbps (theoretical speed)
 20-25 Mbps (actual Speed)
 2.4 GHz radio frequency
 Compatible with b
 Uses frequency division multiplexing

8. 802.11n Standard
 802.11n also known as Wireless N
 802.11n Ratified in 2009
 802.11n builds upon previous 802.11 standards by adding
multiple-input multiple-output (MIMO).
 Operates on Both 2.4Ghz and 5Ghz
 Provide Bandwidth up to 300Mbps
 Backward-compatible with 802.11b/g gear
 Increased Speed and range

9. 802.11ac Standard
 Builds on 802.11n ,Published in 2013
 The addition of Multi-user MIMO (MU-MIMO)
 Utilizes dual band wireless technology
 Support Connection both 2.4 GHz and 5GHz
 Backward compatibility to 802.11b/g/n
 Bandwidth rated up to 1300 Mbps on the 5 GHz
 bandwidth rated up to 450 Mbps on the 2.4 GHz

10. Elements Of Wi-Fi
 Access Point- The AP is wireless LAN radio transceiver or “base
station” that can connect to one or many wireless devices
simultaneously to internet.
 Wi –Fi Card- They accept wireless signal and relay information. They
can be external or internal.
 Safeguards – Firewalls and anti-virus protects from uninvited users
and keep information secure.

11. Wi-Fi Network Topologies
 Peer to Peer Topology (Ad-hoc mode)
 AP – Based Topology (Infrastructure mode)

12. Peer to Peer Topology
 AP is not required
 Client devices can communicate with each other directly
 Useful to create wireless network easily and quickly

13. Infrastructure Network
 The client communicate through Access point
 Any Communication has to go through AP
 If a Mobile station like PDA, Computer has to
communicate with other Mobile station, it need to sends
information to AP first , then AP sends Info to destination
mobile station

14. How Wi-Fi Works?
 A Wi-Fi hotspot is created by installing an access point to an
internet connection.
 An Access Point acts as base station
 When a Wi-Fi enabled device encounters a hotspot the device
can then connect to that network wirelessly.
 A computer’s adapter translate data into radio signals and
transmits it using antenna
 A Wireless router receives the signals and decode it. Router
sends the information
 Many access points can connected to each other via Ethernet
cables to create a single large network.

15. CSMA/CA
 Carrier Sense Multiple Access with Collision Avoidance
 CSMA/CA is used by Data Link Layer.
 MS (mobile station) sends its packets, it checks to see if someone else is
sending information. Only when the medium is free can an MS sends packets.
 If some station is sending or receiving signal, the MS that intends to send will
generate a random waiting time and wait for its turn. If several MSs are all
waiting for their turns, since their waiting times are randomly generated and
thus not equal, they will not start sending simultaneously. Thus collision (two
or more MSs sending signals simultaneously) is avoided.

16. Security
 Wired Equivalency Protocol (WEP)
 Wi-Fi Protected Access (WPA)
 Wi-Fi Protected Access 2 (WPA2)
 Extensible Authentication Protocol (EAP)
 Firewall

17. Advantages
 Freedom – You can work from any location that you can
get a signal.
 Setup Cost – No cabling required.
 Flexibility – Quick and easy to setup in temp or permanent
space.
 Scalable – Can be expanded with growth.
 Mobile Access – Can access the network on the move.

18. Disadvantages
 Speed – Slower than cable.
 Range – Affected by various medium.
 Travels best through open space.
 Reduced by walls, glass, water, etc
 Security – Greater exposure to risks.
 Unauthorized access.
 Compromising data.
 Denial of service.

19. Thank You