WiFi - Wireless Fidelity

Wifi, stands for Wireless Fidelity is a type of wireless networking. It's also known as 802.11. The advantages of wifi is easy to setup and inexpensive. With Wifi the information is travel over the air using the radio waves. In fact, communication across a wireless network is a lot like two-way radio communication. Here's what happens:

1. A computer's wireless adapter translates data into a radio signal and transmits it using an antenna.
2. A wireless router receives the signal and decodes it. It sends the information to the Internet using a physical, wired Ethernet connection.

The process also works in reverse, with the router receiving information from the Internet, translating it into a radio signal and sending it to the computer's wireless adapter. The radio waves used in WiFi is higher than the frequencies used for cell phones, walkie-talkies and televisions. The higher frequensi used, more data can carried by the signal. It use 2,4GHz or 5 GHz frequency. There are several versions of 802.11 Standard as belows :

• 802.11a, use 5 GHz frequency, up to 54 Mbps bandwidth. Using OFDM (Orthogonal Frequency Division Multiplexing), a more efficient coding technique that splits that radio signal into several sub-signals before they reach a receiver. This greatly reduces interference.
• 802.11b, use 2,4 GHz frequency, up to 11 Mbps. Using CCK (Complimentary Code Keying).
• 802.11g, use 2,4 GHz frequency, up to to 54 Mbps. Faster than 802.11b, using OFDM.
• 802.11n, use 2,4 GHz frequency, it is reported can achieve speeds as high as 140 megabits per second.

To build wireless network we need wireless router and wireless adapter.

• Wireless Adapter

It is the picture of USB and PCMCIA wireless adapter for WiFi. This adapter can plug into your PC's usb or PCMCIA slot.

• Wireless Access Point

As with wireless adapters, many routers can use more than one 802.11 standard. 802.11b routers are slightly less expensive, but because the standard is older, they're slower than 802.11a, 802.11g and 802.11n routers. Most people select the 802.11g option for its speed and reliability.