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What is Wireless Internet?

Published:2020/10/24 18:02:48 Visits:


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Imagine for a moment if all the wireless connections in the world were instantly replaced by cables. You'd have cables stretching through the air from every radio in every home hundreds of miles back to the transmitters. You'd have wires reaching from every cellphone to every phone mast. Radio-controlled cars would disappear too, replaced by yet more cables. You couldn't step out of the door without tripping over cables. You couldn't fly a plane through the sky without getting tangled up. If you peered through your window, you'd see nothing at all but a cats-cradle of wires. That, then, is the brilliance of wireless: it does away with all those cables, leaving our lives simple, uncluttered, and free! Let's take a closer look at how it works.

From wireless to radio
Wireless started out as a way of sending audio programs through the air. Pretty soon we started calling it radio and, when pictures were added to the signal, TV was born. The word "wireless" had become pretty old-fashioned by the mid-20th century, but over the last few years it's made a comeback. Now it's hip to be wireless once again thanks to the Internet. Back in 2007, approximately half of all the world's Internet users were using some kind of wireless access. In 2019, over 80 percent of us use wireless to get online at home, which is hardly surprising now more of us now are using smartphones and tablets (54.8 percent) than desktop computers (45.2 percent). Wireless, mobile Internet is overwhelmingly popular in developing countries where traditional wired forms of access, based on telephone networks, are not available. Wireless Internet, perhaps best known to us as Wi-Fi?, has made the Internet more convenient than ever before. But what makes it different from ordinary Internet access?

From radio to Wi-Fi
Radio is an invisible game of throw-and-catch. Instead of throwing a ball from one person to another, you send information, coded as a pattern of electricity and magnetism, from a transmitter (the thrower) to a receiver (the catcher)—both of which are kinds of antennas. The transmitter is a piece of equipment that turns electrical signals (such as the sound of someone speaking, in radio, or a picture, in TV) into an oscillating electromagnetic wave that beams through the air, in a straight line, at the speed of light (300,000 km 186,000 miles per second). The receiver is a mirror-image piece of equipment that catches the waves and turns them back into electrical signals—so we can recreate the radio sounds or TV pictures. The more powerful the transmitter and receiver, the further apart they can be spaced. Radio stations use gigantic transmitters, and that's why we can pick up radio signals from thousands of miles away on the opposite side of Earth. Wireless Internet is simply a way of using radio waves to send and receive Internet data instead of radio sounds or TV pictures. But, unlike radio and TV, it is typically used to send signals only over relatively short distances with low-power transmitters.



Wi-Fi
If you have wireless Internet access at home, you probably have a little box called a router that plugs into your telephone socket. This kind of router is a bit like a sophisticated modem: it's a standalone computer whose job is to relay connections to and from the Internet. At home, you might use a router to connect several computers to the Internet at once (saving on the need for several separate modems). In other words, the router does two jobs: it creates a wireless computer network, linking all your computers together, and it also gives all your machines a shared gateway to the Internet.

Pie charts showing the vast growth in mobile phone and Internet access between 2000 and 2010

You can connect a router to all your different computers using ordinary network-connecting cables (for the technically minded, these are called RJ-45, Cat 5, or Ethernet cables). This creates what's called a LAN (local area network) linking the machines together. A computer network is a very orderly affair, more like an organized committee meeting, with carefully agreed rules of behavior, than a free-for-all cocktail party. The machines on the network have to be hooked up in a standard way and they communicate in a very orderly fashion. The rules that govern the network setup and the communication are based on an international standard called Ethernet (also known as IEEE 802.3).

A wireless router is simply a router that connects to your computer (or computers) using radio waves instead of cables. It contains a very low-power radio transmitter and receiver, with a maximum range of about 90 meters or 300 ft, depending on what your walls are made of and what other electrical equipment is nearby. The router can send and receive Internet data to any computer in your home that is also equipped with wireless access (so each computer on the wireless network has to have a radio transmitter and receiver in it too). Most new laptops come with wireless cards built in. For older laptops, you can usually plug a wireless adapter card into the PCMCIA or USB socket. In effect, the router becomes an informal access point for the Internet, creating an invisible "cloud" of wireless connectivity all around it, known as a hotspot. Any computer inside this cloud can connect into the network, forming a wireless LAN.

Just as computers connected to a wired LAN use Ethernet, machines on a wireless LAN use the wireless equivalent, which is called Wi-Fi (or, more technically, IEEE 802.11). Wireless Internet is improving all the time, so better forms of Wi-Fi are constantly evolving. You may see wireless equipment marked 802.11a, 802.11b, 802.11g or 802.11n: these are all broadly compatible variants of 802.11, with 802.11n, 802.11g and 802.11a somewhat faster than 802.11b. Other more recent variants are named 802.11a with an extra letter added on the end (such as 802.11ax, 802.11ay, and so on). For example, 802.11ah is designed to work with the so-called Internet of Things, 802.11ax is for high-efficiency LANs, and 802.11az is concerned with "location services" (finding the accurate position of mobile devices).

Wi-Fi is where the expression Wi-Fi hotspot comes from. A Wi-Fi hotspot is simply a public place where you can connect your computer wirelessly to the Internet. The hotspots you find in airports, coffee bars, bookshops, and college campuses use one or more wireless routers to create wireless Net access over a large area. Even bigger networks can be created by using tens or hundreds of access points to span entire university campuses, for example. Since the mid-2000s, many cities worldwide have turned huge areas into public hotspots (an idea sometimes known as Municipal Wi-Fi, Muni Wi-Fi, or Muni-Fi). Wi-Fi hotspots continue to pop up all over the world and the number is growing at an astonishing rate. By 2007, there were estimated to be around 180,000 in the United States alone; at the time this artice was last updated (August 2019), according to Statista, the worldwide total was around 362 million.

Wi-Fi Direct?: Let's cut out the middleman!
People sometimes confuse Wi-Fi and Bluetooth. Both are methods of connecting gadgets without wires, so what exactly is the difference? Broadly speaking, Bluetooth is a way of connecting two relatively nearby gadgets without the hassle of using a cable, whereas Wi-Fi is a method of linking wireless computers (and particularly mobile ones, such as laptops, tablets, and smartphones) to the Internet through a shared connection point—your router—which typically makes a wired connection to a telephone or cable line. At least, that's how things used to be.

Ad-hoc networks
Comparison between Wi-Fi infrastructure and ad-hoc modes and Wi-Fi Direct

Artwork: Wi-Fi modes: Left: In infrastructure mode, all your devices communicate wirelessly with a central router that talks (usually via a wired connection) to the Internet. Here, three tablets and a laptop are talking to a router in the middle. Right: In ad-hoc mode (or with Wi-Fi Direct), devices communicate directly over a temporary network without any kind of central router. In this example, two tablets are talking to one another and to a shared printer using Wi-Fi Direct.

But nothing says Wi-Fi can't also link two laptops or smartphones directly instead of Bluetooth. Normally, Wi-Fi uses infrastructure mode, in which various gadgets and devices communicate through a router or central access point. But Wi-Fi also has what's called an ad-hoc mode, which allows gadgets to communicate directly without a router. Typically, an ad-hoc network is created as a temporary form of communication—as the name ad-hoc suggests—whereas infrastructure-mode is a more permanent thing. (The Wi-Fi network I'm using at the moment, for example, is one I set up about a decade ago using infrastructure mode and a central router as the access point.) Ad-hoc networks tend to be hard to set up, slower, and less reliable because the various devices using them all have to communicate with each other and manage the networking (unlike infrastructure networks, which are managed by the router that also handles the communications between them).

Wi-Fi Direct?
Some household gadgetry relies on a mixture of Wi-Fi and Bluetooth, which can be a bit confusing—and prompts the question "Why can't Wi-Fi do the short-range, ad-hoc bit as well?" With a bolt-on addition to the basic Wi-Fi spec known as Wi-Fi Direct?, it can. The basic idea is to use secure, encrypted Wi-Fi in a much more informal way for things like printing from a tablet or sharing photos with someone else's smartphone. Putting it a bit more technically, Wi-Fi Direct is an ad-hoc, peer-to-peer form of networking between pairs of nearby devices (sometimes multiple devices) that doesn't rely on an Internet connection. It works in a similar way to traditional Wi-Fi: each device lets others nearby know that you can connect to it (much like the way access points let you know about available Wi-Fi networks nearby). Some devices can connect both to Wi-Fi Direct and a Wi-Fi network at the same time; others can only do one or the other at a time.


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