Wi-Fi TechnologyWi-Fi TechnologyWi-Fi TechnologyWi-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.