27-01-2012, 11:33 AM
Wi-Fi, or Wireless Fidelity, is freedom
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. INTRODUCTION
Wi-Fi, or Wireless Fidelity, is freedom: it allows you to connect to the Internet from your couch at home, a bed in a hotel room or at a conference room at work without wires. How? Wi-Fi is a wireless technology like a cell phone. Wi-Fi enabled computers send and receives data indoors and out: anywhere within the range of a base station. And the best thing of all, it’s fast. In fact, it’s several times faster than the fastest cable modem connection.
However, you only have true freedom to be connected anywhere if your computer is configured with a Wi-Fi CERTIFIED radio (a PC Card or similar device). Wi-Fi certification means that you will be able to connect anywhere there are other Wi-Fi CERTIFIED products-whether you are at home, the office or corporate campus, or in airports, hotels, coffee shops and other public areas equipped with a Wi-Fi access available
2.The ABCs of IEEE 802.11
At the beginning the IEEE802.11 was an extension technology for conventional or wired LANs. Now a days it has grown in to something much more capable, complex and confusing. With growth, new issues have arisen such as security, roaming among multiple access points, and even quality of services. These issues are dealt by extensions to the standard identified by the letters of the alphabet derived from the 802.11 task groups that created them:
802.11a
The 802.11a supplement to 802.11 was published in 2001. It uses Orthogonal Frequency Division Multiplexing (OFDM) to provide data rates to 54 Mbps in the 5 GHz U-NII licensed National Information Infrastructure)
3. WIRELESS NETWORKING COMPONENTS
Wi-Fi is a generic term for IEEE 802.11b Ethernet standard. It operates in the unlicensed frequency band of 2.4 Ghz with a maximum data rate of 11 Mbps.
IEEE 802.11b wireless networking consists of the following components:
• Stations
A station (STA) is a network node that is equipped with a wireless network device. A personal computer with a wireless network adapter is known as a wireless client. Wireless clients can communicate directly with each other or through a wireless access point (AP). Wireless clients are mobile.
4. OPERATION MODES
IEEE 802.11 defines two operating modes: Ad hoc mode and Infrastructure mode.
AD HOC MODE: In ad hoc mode, also known as peer-to-peer mode, wireless clients communicate directly with each other (without the use of a wireless AP). Two or more wireless clients who communicate using ad hoc mode form an Independent Basic Service Set (IBSS). Ad hoc mode is used to connect wireless clients when a wireless AP is not present.
5.RADIO TECHNOLOGY
Wi-Fi network uses radio technology called IEEE 802.11b to provide secure, fast, reliable, wireless connectivity. 11b defines the physical layer and media access control (MAC) sublayer for communications across a shared, wireless local area network (WLAN). At the physical layer, IEEE 802.11b operates at the radio frequency of 2.45 gigahertz (GHz) with a maximum bit rate of 11 Mbps. It uses the direct sequence spread spectrum (DSSS) transmission technique. At the MAC sublayer of the Data Link layer, 802.11b uses the carrier sense multiple access with collision avoidance (CSMA/CA) media access control (MAC) protocol
