Transcript Skr4800_Wifi Technology

Wi-Fi Technology
Introduction
• WiFi unofficially known as "wireless
fidelity“.
• The term WiFi was created by an
organization called the WiFi Alliance.
• WiFi Alliance Oversees tests that certify
product interoperability.
• A product that passes the alliance tests is
given the label "WiFi certified"
Introduction
• WiFi is a wireless technology that
enables users to network and connect
to other computers without wires.
• WiFi uses radio waves just like
cellular and cordless phones, TV and
radio
Wi-Fi History
• WiFi was invented in 1991 by NCR
Corporation/AT&T (later Lucent & Agere
Systems) in Nieuwegein, the Netherlands.
• Intended for cashier systems
• The first wireless products were brought
on the market under the name WaveLAN
with speeds of 1 Mbit/s to 2 Mbit/s
Wi-Fi History
• Vic Hayes, who was the primary inventor of WiFi
and has been named the 'father of WiFi,‘ was
involved in designing standards such as IEEE
802.11b, 802.11a and 802.11g.
• In 2003, Vic retired from Agere Systems.
• Agere Systems suffered from strong competition
in the market even though their products were
high quality, as many opted for cheaper WiFi
solutions.
• Agere Systems decided to quit the WiFi market
in late 2004.
How Wi-Fi Works
• The typical WiFi setup contains one or more
Access Points (APs) and one or more clients.
• An AP broadcasts its SSID
(Service Set Identifier, Network name) via
packets that are called beacons, which are
broadcasted every 100 ms.
• The beacons are transmitted at 1 Mbit/s, and are
relatively short and therefore are not of
influence on performance.
How Wi-Fi Works
• Since 1 Mbit/s is the lowest rate of WiFi it
assures that the client who receives the beacon
can communicate at at least 1Mbit/s.
• Based on the settings (e.g. the SSID), the client
may decide whether to connect to an AP.
• Say two APs of the same SSID are in range of
the client, the firmware may decide based on
signal strength to which of the two APs it will
connect.
Wi-Fi Specification
• WiFi is based on the IEEE 802.11 specifications.
• There are currently four deployed 802.11
variations: 802.11a, 802.11b, 802.11g, and 802.11n.
• The b standard permits up to 11 Megabits/second,
while both a and g allow up to 54Mbs
• The new n specification will allow even higher
speeds (up to 100Mbs and beyond).
Wi-Fi Specification
• The 802.11a standard works in the 5GHz
frequency band, and the others work in
the 2.4GHz band.
• The most widespread version of WiFi in
the US market today (based in IEEE
802.11b/g) operates in the 2,400 MHz to
2,483.50 MHz. It allows to operate in 11
channels (5 MHz each), as follows:
Wi-Fi Specification
Wi-Fi Application &
Devices
• Common applications for WiFi include Internet
and VoIP phone access, gaming, and network
connectivity for consumer electronics such as
televisions, DVD players, and digital cameras.
• 1) Wireless Access Point (WAP)
– A wireless connects a group of wireless stations to an
adjacent wired (LAN). An is similar to an but instead of
relaying LAN data only to other LAN stations, an can
relay wireless data to all other compatible wireless
devices as well as LAN stations connected by wire.
Wi-Fi Application &
Devices
• 2) Wireless Routers
– A wireless router connects a group of
WiFi enabled devices (i.e. PDAs, laptops,
etc.) to an adjacent wired network . A
wireless router is a wireless combined
with an ethernet hub. A wireless router
forwards IP packets between your
wireless subnet and any other subnet.
Wi-Fi Application &
Devices
• 3) Range Extender
– A wireless range extender can increase the
range of an existing wireless network by being
strategically placed in locations where the
wireless router or access point signal is
degraded or out of range.
• 4)Wireless Ethernet Bridge
– A wireless ethernet bridge connects two
separate
Wi-Fi Advantages
• WiFiallows LANs to be deployed
without cabling for client devices.
• reducing the costs of network
deployment and expansion.
• Spaces where cables cannot be run,
such as outdoor areas and historical
buildings, can host wireless LANs.
Wi-Fi Disadvantages
• WiFi networks have limited range.
• WiFi pollution, or an excessive
number of access points in the area.
• can prevent access and interfere
with the use of other access points
by others, caused by overlapping
channels in the 802.11g/b spectrum.
Conclusion
• WiFi technology is gaining acceptance
as an alternative to a wired LAN.
• Currently, WiFi coverage is all over
the place.