Wi-Fi (How it works?)

Wifi

Q.What is Wifi?

The Wi-Fi logo used by the Wi-Fi Alliance

A.According to Wikipedia :-Wifi is a popular technology that allows an electronic device to exchange data wirelessly (using radio waves) over a computer network, including high-speed Internet connections. The Wi-Fi Alliance defines Wi-Fi as any "wireless local area network (WLAN) products that are based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards". However, since most modern WLANs are based on these standards, the term "Wi-Fi" is used in general English as a synonym for "WLAN".A device that can use Wi-Fi (such as a personal computer, video game console, smartphone, tablet, or digital audio player) can connect to a network resource such as the Internet via a wireless network access point. Such an access point (or hotspot) has a range of about 20 meters (65 feet) indoors and a greater range outdoors. Hotspot coverage can comprise an area as small as a single room with walls that block radio waves or as large as many square miles — this is achieved by using multiple overlapping access points.
"Wi-Fi" is a trademark of the Wi-Fi Alliance and the brand name for products using the IEEE 802.11 family of standards. Only Wi-Fi products that complete Wi-Fi Alliance interoperability certification testing successfully may use the "Wi-Fi CERTIFIED" designation and trademark.

How Wifi Works ?

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. The router 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.
3. They transmit at frequencies of 2.4 GHz or 5 GHz. This frequency is considerably higher than the frequencies used for cell phones, walkie-talkies and televisions. The higher frequency allows the signal to carry more data.
4.  WiFi radios can transmit on any of three frequency bands. Or, they can "frequency hop" rapidly between the different bands. Frequency hopping helps reduce interference and lets multiple devices use the same wireless connection simultaneously.
5. They use 802.11 networking standards, which come in several flavors: 802.11a transmits at 5 GHz and can move up to 54 megabits of data per second. It also uses orthogonal frequency-division multiplexing(OFDM), 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 is the slowest and least expensive standard. For a while, its cost made it popular, but now it's becoming less common as faster standards become less expensive. 802.11b transmits in the 2.4 GHz frequency band of the radio spectrum. It can handle up to 11 megabits of data per second, and it uses complementary code keying (CCK) modulation to improve speeds. 802.11g transmits at 2.4 GHz like 802.11b, but it's a lot faster -- it can handle up to 54 megabits of data per second. 802.11g is faster because it uses the same OFDM coding as 802.11a. 802.11n is the newest standard that is widely available. This standard significantly improves speed and range. For instance, although 802.11g theoretically moves 54 megabits of data per second, it only achieves real-world speeds of about 24 megabits of data per second because of network congestion. 802.11n, however, reportedly can achieve speeds as high as 140 megabits per second. The standard is currently in draft form -- the Institute of Electrical and Electronics Engineers (IEEE) plans to formally ratify 802.11n by the end of 2009.

Here are some pictorial representation on How the Wifi works:-

WiFi Hotspots

On simple speaking :- A Wi-Fi hotspot is a wireless access point that provides Internet access to network devices in public locations such as downtown centers, cafes, airports and hotels. Businesses and schools are increasingly using Wi-Fi hotspots for their internal (intranet) networks. Home wireless networks also use similar Wi-Fi technology.

If you want to take advantage of public WiFi hotspots or start a wireless network in your home, the first thing you'll need to do is make sure your computer has the right gear. Most new laptops and many new desktop computers come with built-in wireless transmitters. If your laptop doesn't, you can buy a wireless adapter that plugs into the PC card slot or USB port. Desktop computers can use USB adapters, or you can buy an adapter that plugs into the PCI slot inside the computer's case.

Many of these adapters can use more than one 802.11 standard.

Once you've installed your wireless adapter and the drivers that allow it to operate, your computer should be able to automatically discover existing networks. This means that when you turn your computer on in a WiFi hotspot, the computer will inform you that the network exists and ask whether you want to connect to it. If you have an older computer, you may need to use a software program to detect and connect to a wireless network.

Advantages and Limitations

Advantages

1. Portability is the great benefit of WiFi which enable people to connects there PDA’s, Laptop, Smartphones and with a network without the hassle of wires.

2. It allows cheaper deployment of local area networks (LANs).

3. Manufacturers are building wireless network adapters into most laptops. The price of chipsets for Wi-Fi continues to drop, making it an economical networking option included in even more devices

4. Power saving mechanisms (WMM Power Save) extend battery life.

Limitations

1. A Wi-Fi signal occupies five channels in the 2.4 GHz band. Any two channels numbers that differ by five or more, such as 2 and 7, do not overlap.

2. It provides a connection in limited area. Its radio connectively can’t reach beyond 20 to 25 meters.

When your location is away from 25 meters you can’t get access to internet or local wireless

network.

Different Hardwares Used for connection to Wifi

Wifi Security Softwares

Here are some useful software for the security of your wifi connection(Download from the below links) :-
1.Wifi Guardian.(Free)
2.Who is on my wifi.(Free trial 30 Days or Premium)
3.lucidlink.(Free)

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SOURCE:- The Wikipedia,Howstuffworks,and other websites.