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.
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.
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.