Wi-Fi

Wi-Fi is short for wireless fidelity and is way to network computers without using wires. This website will explain Wi-FI in depth and will explain the development of this technology.

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Wi-Fi Introduction
Wi-Fi (also WiFi, Wi-fi, Wifi, or wifi) is a set of product compatibility standards for wireless local area networks (WLAN) based on the IEEE 802.11 specifications. New standards beyond the 802.11 specifications, such as 802.16(WiMAX), are currently in the works and offer many enhancements, anywhere from longer range to greater transfer speeds.

Wi-Fi was originally intended to be used for mobile computing devices and LANs, but is now used in many other instances as well, including Internet access or basic connectivity of consumer electronics. It enables the device, often a wireless-enabled computer or personal digital assistant (PDA), to connect to the Internet remotely when in close proximity to an access point. The geographical region covered by one or several access points is called a hotspot.

Hotspots

Hotspots are locations that allow users to access networked services, such as the internet, without a cabled connection. These are increasingly useful given the popularity of mobile computers (such as laptops and PDAs). Hotspots are often found near restaurants, train stations, airports, cafes, libraries and other public places where users tend to gather.

Originally, Wi-Fi certification was applicable only to products using the 802.11b standard. Today, Wi-Fi can apply to products that use any 802.11 standard. The 802.11 specifications are part of an evolving set of wireless network standards known as the 802.11 family. The particular specification under which a Wi-Fi network operates is called the "flavor" of the network. Wi-Fi has gained acceptance in many businesses, agencies, schools, and homes as an alternative to a wired LAN. Many airports, hotels, and fast-food facilities offer public access to Wi-Fi networks as a means of attracting customers. As mentioned earlier, these locations are known as hotspots. Many businesses that offer wireless access to hotspots charge a daily or hourly rate for access, but some are free. An interconnected area of hotspots and network access points is known as a hotzone.

The increasing availability of hotspots and hotzones has made internet access practically universal. One of the drawbacks to this development is the chance to have your wireless access point pirated by an unauthorized user. Unless adequately protected, a Wi-Fi network can be highly susceptible to access by unauthorized users looking for a free Internet connection. The activity of locating and exploiting security-exposed wireless LANs is called wardriving and is an increasing concern among wireless users. Any entity that has a wireless LAN should use security safeguards such as the Wired Equivalent Privacy (WEP) encryption standard, the more recent Wi-Fi Protected Access (WPA), Internet Protocol Security (IPsec), or a virtual private network (VPN).

As Wi-Fi becomes the main mode of access among prevailing culture, an identifying iconography is emerging. This iconography, called warchalking, is a means of letting other users know that an open Wi-Fi wireless network is nearby. Warchalking consisted of drawing a symbol on a wall or nearby pavement to alert users of the Wi-Fi network. Though it did not gain popularity amongst unauthorized users, warchalking was almost immediately adopted by businesses offering Wi-Fi and is now used as a type of shorthand in logos and ads.

Specifications

Wi-Fi is based on the IEEE 802.11 specifications. There are currently four deployed 802.11 variations: 802.11a, 802.11b, 802.11g, and 802.11n. The b specification was used in the first Wi-Fi products. The g and n variants are the ones most often sold as of 2005.

In most of the world, the frequencies used by Wi-Fi do not require user licenses from local regulators (e.g. the Federal Communications Commission in the U.S.). 802.11a equipment, using a higher frequency, has reduced range, all other things being equal.

The most widespread version of Wi-Fi in the U.S. market today (based in IEEE 802.11b/g) operates in the 2,400 MHz to 2,483.50 MHz range. It allows operation in 11 channels (5 MHz each), centered on the following frequencies:

Channel 1 – 2,412 MHz;

Channel 2 – 2,417 MHz;

Channel 3 – 2,422 MHz;

Channel 4 – 2,427 MHz;

Channel 5 – 2,432 MHz;

Channel 6 – 2,437 MHz;

Channel 7 – 2,442 MHz;

Channel 8 – 2,447 MHz;

Channel 9 – 2,452 MHz;

Channel 10 – 2,457 MHz;

Channel 11 – 2,462 MHz

Europe, France, Spain, and Japan have adopted their own allowed channels sets.

Wi-Fi channels are 22 MHz wide, and thus channels with spacing less than 22 MHz (five 5 MHz channels) apart will overlap. This can result in interference, with the amount of interference decreasing with channel separation. (Thus channels 1 and 3 interfere less with each other than channels 1 and 2.) For minimum interference between different Wi-Fi networks, use Channels 1, 6, and 11, which do not overlap. To increase the available channels, which can help in multiple access point deployments, a slightly overlapping four channel configuration of 1, 4, 8, and 11, results in relatively little interference, as explained in "4 Simultaneous Channels Okay For 802.11b".

In all areas, the maximum radio transmitter power and the maximum effective radiated power (essentially the power output at the antenna) are strictly limited. In the U.S., maximum transmitter power is 1 watt and maximum effective radiated power is 4 watts (an antenna which concentrates 1 watt of transmitter energy into 1/4 of an "omnidirectional" sphere will achieve 4 watts of effective power); in most of Europe these limits are somewhat lower. Most Wi-Fi equipment (e.g. MiniPCI, Cardbus, PCMCIA cards for laptops, PCI cards for desktop equivalent computers, or standalone units often with other functions included) has transmitter power levels of between 15 mW and perhaps 200 mW, (the last part of this sentence is confusing. I don’t know how to edit it because I don’t know what you’re saying. Also, don’t use the word so if you can avoid it) so antennas with some gain are permissible.

New standards beyond the 802.11 specifications are currently in the works and offer many enhancements, from wider access range to greater transfer speeds. One example is WiMAX, with a range of several miles and data rates of up to 70 Mbit/s. 802.16a permits operation between 2 and 11 GHz, increasing the probability of developing some interoperability between 802.11 units and some 802.16a units.

History and origin
Wi-Fi was invented in 1991 by NCR Corporation/AT&T (later, Lucent & Agere Systems) in Nieuwegein, the Netherlands. Initially meant for cashier systems, the first wireless products were brought on the market under the name WaveLAN with speeds of 1Mbps/2Mbps. Vic Hayes, the inventor and ‘father’ of Wi-Fi, was part of a team involved in designing standards such as IEEE 802.11b, 802.11a and 802.11g. In 2003, Vic retired from Agere Systems, which was suffering from strong market competition. Although their products were leading edge, cheap Wi-Fi solutions were voted by many (this sentence makes no sense). Agere's 802.11abg all-in-one chipset (code named: WARP) never hit the market and Agere Systems decided to quit the Wi-Fi market in late 2004.

Contrary to popular belief, Wi-Fi did not originally stand for Wireless-Fidelity. The term "Wi-Fi" was developed by the Wi-Fi Alliance along with the Interbrand Corporation to describe WLAN products that are based on the IEEE 802.11 standards. Phil Belanger of the Wi-Fi Alliance quoted, "Wi-Fi and the yin yang style logo were invented by Interbrand. We (the founding members of the Wireless Ethernet Compatibility Alliance, now called the Wi-Fi Alliance) hired Interbrand to come up with the name and logo that we could use for our interoperability seal and marketing efforts. We needed something that was a little catchier than “IEEE 802.11b Direct Sequence”. Later, the term "Wireless Fidelity" was coined with the marketing of a new tag line, "The Standard for Wireless Fidelity”. This new tag line was soon dropped due to confusion among customers and consumers.

Technical aspect – How does Wi-Fi work?
The typical Wi-Fi setup contains one or more Access Points (APs) and one or more clients. An AP broadcasts its *SSID (Service Set Identifier, Network name) via packets that are called beacons, which are broadcasted every 100ms. The beacons are transmitted at 1Mbps and are relatively short, giving them no influence over performance. Because 1Mbps is the lowest rate of Wi-Fi, this assures that clients who receive the beacon can communicate at a minimum of 1Mbps. Based on the specific settings and the *firmware of the the client (i.e. the SSID), the user may decide whether to connect to an AP. For instance, if APs of the same SSID are in range of the client, the firmware may decide based on signal strength (*Signal-to-noise ratio) which of the two APs is more feasible. The Wi-Fi standard leaves connection criteria and roaming totally open to the client. This is the strength of Wi-Fi, but also means that one wireless adapter may perform substantially better than another. Windows XP offers a feature called zero configuration that allows the end user to visualize all available networks and connect to them at will. In the future, wireless cards will become increasingly controlled by the operating system. Microsoft's newest feature, called SoftMAC, will take over for on-board firmware. Moreover, roaming criteria will be totally controlled by the operating system. Because Wi-Fi transmits in the air, it has the same properties as a non-switched ethernet network, allowing collision to appear similar to those in non-switched ethernet LAN's.

SSID

In Wi-Fi Wireless LAN computer networking, a service set identifier (SSID) is a code attached to all packets on a wireless network to identify each packet as part of that network. The code consists of a maximum of 32 alphanumeric characters. All wireless devices attempting to communicate with each other must share the same SSID. Apart from identifying each packet, SSID also serves to uniquely identify a group of wireless network devices used in a given "Service Set".

Firmware

In computing, firmware is software that is embedded in a hardware device. It is often provided in flash ROMs or as a binary image file that can be uploaded onto existing hardware by a user.

Firmware is defined as:

the computer program in a read-only memory (ROM) integrated circuit (a hardware configuration is usually used to represent the software);

the erasable programmable read-only memory (EPROM) chip, whose program may be modified by special external hardware, but not by [a general purpose] application program.

Signal-to-noise ratio

Signal-to-noise ratio (often abbreviated SNR or S/N) is meaningful both in the context of information theory and, informally, for Usenet or other newsgroup-like services.

Signal-to-noise ratio is an engineering term for the power ratio between a signal (meaningful information) and the background noise. Because many signals have a very wide dynamic range, SNRs are usually expressed in terms of the logarithmic decibel scale. In decibels, the SNR is 20 times the base-10 logarithm of the amplitude ratio, or 10 times the logarithm of the power ratio, where P is average power and A is RMS amplitude. Both signal and noise power are measured within the system bandwidth.

Signal-to-noise ratio is closely related to the concept of dynamic range, where dynamic range measures the ratio between noise and the greatest un-distorted signal on a channel. SNR measures the ratio between noise and an arbitrary signal on the channel, not necessarily the most powerful signal possible. Because of this, measuring a signal-to-noise ratio requires the selection of a representative or reference signal. In audio engineering, this reference signal is usually a sine wave, sounding a tone at a recognized and standardized magnitude, such as 1 kHz at 1.228 VRMS (+4 dBu).

Often the signals being compared are electromagnetic in nature, though it is also possible to apply the term to sound stimuli. Due to the definition of decibel, the SNR gives the same result independent of the type of signal which is evaluated (such as power, current, or voltage).

SNR is usually taken to indicate an average signal to noise ratio, as it is possible that (near) instantaneous signal to noise ratios will be considerably different. In general, higher signal to noise is better (i.e. cleaner).

In image processing, the SNR of an image is usually defined as the ratio of the mean pixel value to the standard deviation of the pixel values. Related measures are the "contrast ratio" and the "contrast to noise ratio".

What are the advantages and disadvantages of Wi-Fi anyway?

Advantages

Unlike packet radio systems, Wi-Fi uses unlicensed radio spectrum and does not require regulatory approval for individual users.

Wi-Fi allows LANs to be deployed without cabling, potentially reducing the costs of network deployment and expansion. Wireless Lans allow networks to be access in spaces where cable cannot be run, such as outdoor areas or historically protected sites.

Wi-Fi products are widely available in the market. Different brands of access points and client network interfaces are interoperable at a basic level of service.

Competition amongst vendors has lowered prices considerably since their inception.

Wi-Fi networks support roaming, in which a mobile client station such as a laptop computer can move from one access point to another as the user moves around a building or area.

Many access points and network interfaces support various degrees of encryption to protect traffic from interception.

Wi-Fi is a global set of standards. Unlike cellular carriers, the same Wi-Fi client works in different countries around the world.

Disadvantages

Use of the 2.4 GHz Wi-Fi band does not require a license in most areas, provided that one stays below the 100 mW limit and accepts interference from other sources; including interference which causes devices to no longer function. Some believe, albeit incorrectly, that Amateur Radio operators are an exception to the otherwise limited power output ceilings. This is based on the belief that they may boost power output from their Wi-Fi routers up to the legal maximum for the Amateur Radio license class, often 100 watts for spread spectrum operation (roughly 1,000 times that of a normal router).

Spectrum assignments and operational limitations are not consistent worldwide; most of Europe allows for an additional 2 channels beyond those permitted in the US; Japan has one more on top of that, while some countries, like Spain, prohibit use of the lower-numbered channels. Furthermore, users are sometimes required to possess a 'general authorization' (or operator registration) for any WiFi used outside an operator's own premises; such is the case in Italy. Users in Europe can consult http://www.ero.dk for an annual report on the additional restrictions imposed by European countries.

The 802.11b and 802.11g flavors of Wi-Fi use the unlicensed 2.4 GHz spectrum, which is crowded with other devices such as Bluetooth, microwave ovens, cordless phones (900 MHz or 5.8 GHz are alternative phone frequencies one can use for a Wi-Fi network), or video sender devices, among many others. This density of users may negatively affect performance. Other devices which use microwave frequencies such as certain types of cell phones can also cause degradation in performance. However, many Wi-Fi cards have Microwave-robustness algorithms on-board which make the problems non-existent in most cases.

Power consumption is fairly high compared to other standards, making battery life and heat a concern.

The most common wireless encryption standard, Wired Equivalent Privacy or WEP, has been shown to be breakable even when correctly configured (caused by weak-key generation). Although most new wireless products support the much improved Wi-Fi Protected Access (WPA) protocol, many first-generation access points cannot be upgraded in the field and have to be replaced to support it. The adoption of the 802.11i (AKA WPA2) standard in June 2004 made available a further improved security scheme, which has become available on the latest equipment. Both schemes require stronger passwords in personal mode than most users typically employ. Many enterprises have deployed additional layers of encryption (such as VPNs) to protect against interception.

Wi-Fi networks have limited range. A typical Wi-Fi home router using 802.11b or 802.11g might have a range of 45m (150 ft) indoors and 90m (300 ft) outdoors. Range also varies, as Wi-Fi is no exception to the physics of radio wave propagation, with frequency band. Wi-Fi in the 2.4 GHz frequency block has better range than WiFi in the 5 GHz frequency block, and less range than the oldest Wi-Fi (and pre-Wi-Fi) 900 MHz block.

Interference of a closed or encrypted access point by other open access points on the same or a neighboring channel can prevent access to the open access points by other users in the area. This can pose a problem in high-density areas such as large apartment buildings where many residents are operating Wi-Fi access points.

Access points can be used to steal personal information transmitted by Wi-Fi users.

Interoperability issues between brands or deviations in the standard can cause limited connection or lower throughput speeds.

Free access points (or improperly configured access points) may be used by the malicious to anonymously initiate an attack that would be impossible to track beyond the owner of the access point.

Will Wi-Fi ever replace cell phones one day?
Some expect that Wi-Fi and related consumer technologies will replace cellular telephone networks such as 3G and GSM. The current generation of Wi-Fi still lacks roaming and authentication features (see 802.1x, SIM cards and RADIUS) and the limited range of Wi-Fi as well as the narrowness of the available spectrum are holding back its proliferation as a 3G replacement. However, the bandwidth and overall capabilities of Wi-Fi are already exceeding those once promised by 3G cellular telephone standards. Users have adopted the term 4G in reference to Wi-Fi as a telling example of the believed superiority of the technology.

Companies like BroadVoice, UTStarcom, ZyXEL, SocketIP and Symbol Technologies are already offering Wi-Fi VoIP phones and telephony platforms (Central Office replacements and terminals (phones) that use Wi-Fi VoIP.

Many vendors now sell mobile Internet products that link Wi-Fi and cellular radio systems in a more or less transparent way, in order to take advantage of the benefits of both systems. Future wireless systems are expected to routinely switch between a variety of radio systems.

The main difference between cellular and Wi-Fi is their basis in licensed or unlicensed spectrums, Wi-Fi using the unlicensed and cellular using the licensed. The economic basis for its implementation is therefore completely different. The success of Wi-Fi has made many look to the unlicensed spectrumm with its potential to lower costs and expand service coverage, as the future of wireless access.

Wi-Fi Troubleshooting Guide
If you encounter a Wi-Fi problem at a coffee shop, airport lounge, or book store, it's often easy to fix it yourself. Here's how.

Open Your Web Browser
It is a common misconception that a user must only turn on their computer and connect to the wireless network in order to take advantage of a free Wi-Fi hotspot. Often, this is not enough. Most commercial hotspots, such as those in hotels, require a user to sign on to their wireless network, which must be done through your Web browser. When launching your browser, the hotspot service provider's sign-up page should automatically appear. At that point, a user will be asked to sign on with a user name, password, credit-card number, or other information. However, this protection is not all encompassing, as some free public hotspots do not require a user to do anything but open their browser to access a network.

Change Your Default Home Page
If your default home page is blank, the hotspot service provider's sign-up page isn't likely to appear automatically when you launch the browser. To get around this, change your browser's default home page to a specific website, such as "http://www.pcworld.com," close the browser, then reopen it. This time, the sign-up page should appear when you launch your browser.

To change Microsoft Internet Explorer's default home page, go to Tools, Internet Options. On the General tab, type a Web site address into the "Home page" section's address field, then click OK.

Get the Latest Password
Many free Wi-Fi hotspot providers require you to enter a password to use the network. For security reasons, a password that worked on Tuesday may have been changed by Sunday. To make sure you're up-to-date, ask someone in charge for the latest password; at a hotel, for instance, you might ask the front-desk clerk.

Restart the Connection
Occasionally, the software and hardware for a mobile computer’s Wi-Fi adapter don’t always get along with Windows XP. Wi-Fi connections suddenly drop, without apparent reason, sometimes causing problems as a user attempts to connect.
One workaround is to stop and restart the wireless network service using the Microsoft Management Console in Windows. Begin by going to Start, Control Panel, "Performance and Maintenance"; if you're in Category View, select Administrative Tools then Services. On the right side of the two-pane dialog box, scroll down to Wireless Zero Configuration. Click "Stop the service" then "Start the service" to restart the service.

Restart Your Notebook
When I'm having difficulty making a wireless connection, restarting my notebook sometimes solves the problem. Why? It's a bit mysterious, but in general, some utilities and applications may conflict with one another or hog system resources. Restarting can flush out whatever ails your Wi-Fi connection, giving you a fresh start.

Get Closer
If you're having problems making or keeping connections at a particular hotspot, your notebook could be too far from the wireless network access point. For instance, some hotel guests have reported that, even though they stayed in a hotel with in-room Wi-Fi, the wireless signal was too weak in their room to connect. If this happens, ask the front-desk clerk to move you to another room. Or, if you're in a coffee shop or other public setting, ask an employee where the wireless signal is strongest.

Extend Your Range
The antenna for built-in notebook Wi-Fi adapters is usually--no surprise here--built into the notebook, too. If you frequently have difficulty getting a strong signal, you might have better luck using a Wi-Fi adapter with a movable, external antenna. In some cases, an external antenna may be able to pick up weaker signals from nearby access points.

I've had good results with the Linksys WUSB12 (about $60). The compact USB adapter for 802.11b networks features a small, folding antenna. The adapter can be connected directly to your notebook's USB port or, via a USB cable, positioned farther away to provide a stronger signal.

Upgrade to Windows XP Service Pack 2
For easier wireless network connectivity, diagnostics, and repair, consider installing the recent upgrade to the Windows XP operating system. Windows XP SP2 includes several wireless network enhancements, including a new Wireless Network Setup Wizard for easier setup and an enhanced Repair Wireless Network Connection tool. I've found that the latter can help make a wireless connection work when other efforts have failed. To access the tool, right-click the Wireless Connection icon in the system tray on the bottom or right end of the Windows taskbar. From the context menu, select Repair to launch the tool.

Be aware, however, that many PC users continue to shy away from Windows XP SP2. The operating system upgrade includes enhanced networking and security features but can cause some applications installed on your PC to not work properly. (Windows XP SP2 came preinstalled on my current notebook, so I've not experienced any problems.) Read "Businesses Still Wary of XP SP2" for more about the ongoing problems.

Competing Technologies

Bluetooth - an industrial specification for wireless personal area networks (PANs)

European Installation Bus - intelligent electrical installation networking

HomePlug - Focused on broadband applications

INSTEON - (http://www.insteon.net) Smarthome's peer-to-peer mesh networking product that features a hybrid radio/powerline transmission. Designed for home usage, and interoperates with X10.

nanoNET - (http://www.nanotron.com/) A proprietary set of wireless sensor protocols, designed to compete with ZigBee.

OBEX - A communications protocol that facilitates the exchange of binary objects between devices.

RadioRa - (http://www.lutron.com/radiora/) A proprietary two-way RF protocol, developed by Lutron for use in residential lighting control.

TinyOS - (http://www.tinyos.net/) A mesh network OS using the NesC language.

UPB - (http://www.pcslighting.com/UPBMain.htm) A new powerline protocol that offers improved performance and reliability over X10.

Wi-Fi - A trademark for sets of product compatibility standards for wireless local area networks (WLANs).

Wireless USB - wireless extension to USB

X10 - A powerline protocol first introduced in the 1970s.

Z-wave - (http://www.z-wavealliance.com/) A proprietary protocol for wireless home control networking.

ZigBee - a set of high level protocols designed for low power digital radio.

How secure is my Wi-Fi connection?
Wi-Fi equipment can be used to steal personal information (passwords, financial information, identity information, and so on) transmitted by Wi-Fi users, if sensible protections are not enabled.

Some users report that open access points in a particular area or channel can cause interference in a closed or encrypted access point, resulting in the inability to gain access to said open access points by other users in the area. This can pose a problem in high-density areas such as large apartment buildings where many residents are operating Wi-Fi access points.

Large corporations are often concerned about the security risk posed to a company network by an unauthorized wireless access point, also known as a rogue access point. With the advent of inexpensive wireless routers and their increased availability at consumer electronics stores, employees will occasionally connect an unauthorized access point out of ignorance or malice, thereby exposing the secure corporate network to anyone who may be "wardriving" nearby. To alleviate the potential risk of rogue access points, some large organizations have begun (as of 2005) to install wireless intrusion detection systems. These systems are designed to monitor the premises for wireless signals and immediately report the presence of any unauthorized access points.

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