Introduction to WIFI
WIFI is an alternative network to wired network which is commonly used for
connecting devices in wireless mode.
WIFI is stand for Wireless Fidelity is generic term that refers to IEEE802.11
standard for Wireless Local Networks or WLANs.
WIFI connects computers to each other, to the internet and to the wired
network.
WIFI uses radio technology to transmit and receive data at high speed.
i. IEEE 802.11b
ii. IEEE 802.11a
iii. IEEE 802.11g
IEEE 802.11b features
i. Appeared in Late 1999
ii. 2.4Ghz radio spectrum
iii. 11Mbps (theoretical speed) within 30m range
iv. 4-6Mbps (actual speed)
v. 100-150 feet range
vi. Most popular and Less expansive
vii. Interference from mobile phones and Bluetooth devices which can
reduce the transmission speed
IEEE 802.11a Features
i. Introduced in 2001
ii. 5.0Ghz radio spectrum
iii. 54Mbps (theoretical speed)
iv. 15-20Mbps (actual speed)
v. 50-75 feet range
vi. more expensive not compatible with IEEE 802.11b
IEEE 802.11g Features
i. introduced in 2003
ii. combine the feature of both standards (a,b)
iii. 100-150 feet range
iv. 54Mbps speed
v. 2.4Ghz radio spectrum
vi. compatible with b
Elements of WIFI network
i. Access Point (AP) -The AP is a wireless LAN transceiver or “base station”
that can connect one or many wireless devices simultaneously to the
Internet.
ii. Wi-Fi cards -They accept the wireless signal and relay information.
They can be internal and external.
iii. Safeguards - Firewalls and anti-virus software protect networks from
uninvited users and keep information secured.
WIFI Topologies
Peer-to-peer topology (Ad-hoc Mode)
i. AP is not required.
ii. Client devices within a cell can communicate with each other
directly.
iii. It is useful for setting up a wireless network quickly and easily.
AP-based topology (Infrastructure Mode)
i. The client communicates through Access Point.
ii. Any communication has to go through AP.
iii. If a Mobile Station (MS), like a computer, a PDA, or a phone, wants to
communicate with another MS, it needs to send the information to
AP first, then AP sends it to the destination MS.
Hotspots
i. A Hotspot is a geographical area that has a readily accessible
wireless network
ii. Hotspots are equipped with Broad band Internet connection and
one or more Access points that allow users to access the internet
wirelessly
iii. Hotspots can be setup in any public location that can support an
Internet connection. All the locations discussed previously are
examples of Hotspots.
How a Wi-Fi Network Works
i. A Wi-Fi hotspot is created by installing an access point to an internet
connection.
ii. An access point acts as a base station.
iii. When Wi-Fi enabled device encounters a hotspot the device can then
connect to that network wirelessly.
iv. A single access point can support up to 30 users and can function within
a range of 100 – 150 feet indoors and up to 300 feet outdoors.
v. Many access points can be connected to each other via Ethernet cables
to create a single large network.
Advantages
i. Mobility
ii. Ease of Installation
iii. Flexibility
iv. Cost
v. Reliability
vi. Security
vii. Use unlicensed part of the radio spectrum
viii. Roaming
ix. Speed
Limitations
i. Interference
ii. Degradation in performance
iii. High power consumption
iv. Limited range
