What is Wi-Fi 10000 знаков

What is WiFi, and where is it used?

The world of modern telecommunication technology is awash with acronyms, long numbers and other weird bits of code that few people understand. The term WiFi should be relatively easy because it’s a play on the words 'high-fidelity' or 'hi-fi', which means sound reproduction that is very similar to the original. But 'WiFi' doesn't really stand for wireless fidelity. It’s simply a catchy term for equipment using a particular wireless communication standard, or protocol, known as IEEE 802.11 (more about this bit of code later). Using this standard, computers and other devices can link in a wireless local area network (WLAN), which is a number of computers or computer-like devices that can talk to each other using high-frequency radio waves instead of connecting cables. The WLAN can in turn be hooked into the internet, usually with the aid of a cable.

Basically, then, WiFi is a generic name for the main method by which a WLAN is set up. But the term WiFi, as well as the technology itself, has evolved quite a bit since it was first coined in about 2000 and is now used more broadly, particularly by the general public, to mean a wide range of wireless communication technologies.

WiFi uses

Perhaps the most visible manifestation of WiFi is the coffee-shop laptop tuned cordlessly into a WLAN and hence into the worldwide web, but some phone users might also be doing it by WiFi. VoIP ('voice over the internet protocol') phones enable users to speak to others via the internet. The increasing availability of WiFi means that people with VoIP phones can use them more and more like mobile phones, talking with friends and colleagues over the internet from the same coffee-shop in which they connect their laptops to the worldwide web.

WiFi is used in many other applications as well. Some televisions are going WiFi, allowing viewers to wander about their houses with their own portable screens. One company recently offered a camera that connects to the internet via WiFi, allowing people to email photos to friends and colleagues directly from their cameras. A more mundane but widespread use of WiFi is in communication between computers and peripheral devices such as printers and projectors.

The great advantage of WiFi over wired networks is that it does not require wires to connect it to a network. Potentially, WiFi and other wireless technologies could be made available everywhere to everyone, not only helping a business person on the move but also remote communities that might otherwise wait years for cables to reach them.

How does it work?

WiFi equipment works by radio waves, which have a very wide and increasingly sought-after range of frequencies. If the world of communication technology is awash with acronyms, the radio wave spectrum is increasingly jammed with signals as different kinds of devices try to communicate with each other. Extremely low frequencies of 3–30 hertz (or cycles per second) are used for radio communications with submarines; the wavelengths can be thousands of kilometres in length.

In contrast, WiFi equipment uses radio waves in the frequency ranges 2.4–2.5 and 4.9–5.8 gigahertz (GHz), with wavelengths of 60 and 120 millimetres. The ranges are classified by the International Telecommunication Union as 'super high frequency' and is much higher than the frequency used for AM radio (300–3000 kilohertz), short-wave radio (3–30 megahertz – MHz), and FM radio and television broadcasting (both 30–300 MHz). It is also generally a little higher than the frequency used for mobile phones and two-way radios (300 MHz to 3 GHz). Telstra's new Next G system, which allows high-speed wireless internet connections, operates at 850 MHz.

Other devices that use radio waves in the super high frequency range include microwaves, automatic roller-doors and cordless phones. Bluetooth, a form of wireless technology normally used for very short-range communication between devices such as a laptop and a personal digital assistant (PDA), operates at about 2.4 GHz.

At the epicentre of a common WiFi set-up involving personal or laptop computers is a wireless access point, connected by hardwire to the internet. A router converts digital information in the form of 1s and 0s into radio waves, and transmits these via an antenna. It can also receive radio waves and convert these to digital data, which it can then send to the internet via its hardwire connection. Laptop computers or other devices within range using the same WiFi protocol can communicate with the access point and, through it, connect to the internet.

The protocol is important. If the laptop and router are to communicate, it is important that they speak the same language. Compatibility between electronic devices is one of the industry's great challenges, and it has been achieved in the current generation of WiFi devices through the adoption of a standard developed by the Institute of Electrical and Electronics Engineers (IEEE) to define the way WiFi equipment operates. This standard, IEEE 802.11, provides the basic parameters within which a WiFi device will operate; for example, it gives the operating frequency and the rate of data transfer. Each area in which WiFi is available is called a 'hotspot' (Box 1: Hotspots and meshes).

Where is WiFi heading?

WiFi has become very popular very quickly, to the point that in certain sectors of the economy it is almost a prerequisite for doing business. Some hotels would probably lose custom if they didn't offer WiFi to their guests, who expect to be able to log on before they nod off. WiFi-less coffee shops might be bypassed by laptop-toting latte drinkers wanting to connect while they caffeinate.

The number of uses to which WiFi could be put is almost limitless. In the home, electrical equipment such as the refrigerator, television, lighting system, microwave and stereo equipment could all be linked and regulated by WiFi. The technology also has exciting possibilities in environmental science (Box 2: Remote sensors and their applications).

But perhaps the single greatest advantage of wireless networks over wired technologies is that they are more flexible about the infrastructure required to set them up. That's why community groups have latched onto them, and it is also why they are being pursued in developing countries, where they can be used to bypass the very expensive business of laying cables.

WiFi technology is not without problems, security being one of the biggest (Box 3: Security and encryption). But few people think it is a passing fad. So where is WiFi heading?

Predicting the evolution of information technology is not easy, especially given its current extraordinary rate of change: this month's boom product might be next month's landfill. But a few things about WiFi seem certain: speeds will increase ,the range of uses to which it is put will broaden and its availability will continue to spread. It will also face more competition.

Keeping tuned

The array of wireless technology already in use can be confusing. Consumers have a huge range of choices but often insufficient information on which to base their purchasing decisions. Can your laptop do WiFi and WiMAX, and does it need to? What does the shop assistant mean when she asks if you want a PDA with bluetooth? Do you need a WiFi rice-cooker? The proliferation of the technology does have one advantage: if you don't understand it and want to find out what it all means, you can at least research it – from almost anywhere!