Wi-Fi
Ashwin A
Roll no-0718104
Department of computer science and information technology
Government College of technology
Anna University, Coimbatore

1. Abstract:
For years, it has been understood that the acronym wi-fi was short for “wireless fidelity”. Recently, however, there has been a dust up of debate about whether this is really the case. The recent debate on this issue stems from the fact that “wireless fidelity” literally means, well, absolutely nothing. It was just a convenient way of fusing “wireless” with “high-fidelity”.
But think a little deeper and you’ll realize that the very name wi-fi is nonexistent. It’s just a pun on an earlier phrase that happened to include the word “fidelity”.
2. Introduction:
Wi-fi is the trade name for the popular wireless technology used in home networks, mobile phones, video games and more. In particular, it covers the various ieee 802.11 technologies (including 802.11n, 802.11b, 802.11g, and 802.11a).
Wi-fi technologies are supported by nearly every modern personal computer operating system and most advanced game consoles, printers, and other peripherals.
3. Purpose:
The purpose of wi-fi is to hide complexity by enabling wireless access to applications and data, media and streams. The main aims of wi-fi are the following:
Make access to information easier
Ensure compatibility and co-existence of devices
Eliminate cabling and wiring
Eliminate switches, adapters, plugs, pins and connectors
4. History:
Wi-fi uses both single carrier direct-sequence spread spectrum radio technology and multi-carrier ofdm (orthogonal frequency division multiplexing) radio technology. The regulations for unlicensed spread spectrum enabled the development of wi-fi, its onetime competitor homerf, Bluetooth, and many other products such as some types of cordless telephones.
Unlicensed spread spectrum was first made available in the us by the federal communications commission in 1985 and these FCC regulations were later copied with some changes in many other countries enabling use of this technology in all major countries. The fcc action was proposed by Michael Marcus of the fcc staff in 1980 and the subsequent regulatory action took 5 more years. It was part of a broader proposal to allow civil use of spread spectrum technology and was opposed at the time by main stream equipment manufacturers and many radio system operators.
The precursor to wi-fi was invented in 1991 by ncr corporation/at&t in nieuwegein, the Netherlands. It was initially intended for cashier systems; the first wireless products were brought on the market under the name wavelan with speeds of 1 mbit/s to 2 mbit/s. Vic hayes, who held the chair of ieee 802.11 for 10 years and has been named the 'father of wi-fi,' was involved in designing standards such as ieee 802.11b, and 802.11a.
5. City wide wi-fi:
Sunnyvale, California became the first city in the united states to offer city wide free Wi-Fi, [20]corpus Christi, Texas had offered free wi-fi until may 31, 2007 when the network was purchased by EarthLink. Philadelphia is also trying to save the EarthLink wifi for its city. New Orleans had free city wide wi-fi shortly after hurricane Katrina.[23] city wide Wi-Fi is available in nine cities in the uk, Newcastle upon tyne being the first uk city host, others include Leeds, Liverpool, Norwich and London. Other cities, such as the Minneapolis metro area, have a large number of wi-fi hotspots so you can receive good signals anywhere, even if from different sources. In Europe, the city of Luxembourg has a city-wide wi-fi network.
In Latin America, Mexico City downtown has a public wi-fi network. Also, many public squares in towns of Puerto Rico are offering wi-fi internet access.
As compared to wireless mesh, wimax provides over 4 times the number of subcarriers over a variable bandwidth of 1 to 28 MHz with more subcarriers and a variable length guard interval, the spectral efficiency has increased from 15% to 40% compared to wireless mesh. The error vector magnitude of wireless mesh is higher than wimax. This makes wimax have a longer range. Wireless mesh transmits and receives functions on the same channel where as wimax transmits and receives functions at a different channel and at a different time. In wireless mesh the output power is virtually fixed however in wimax the devices closer to the base stations emit less output power whereas the ones further away emit maximum output power.
Wi-fi can overpower wimax if the city is meshed with hot spots. A very easy way to do it would be if mobile carriers integrate hot spots with their mobile base stations as wimax chips are not as integrated as the wi-fi chips.
6. Origin and meaning of the term "wi-fi":
The term "wi-fi" suggests "wireless fidelity", comparing with the long-established audio recording term "high fidelity" or "hi-fi", and "wireless fidelity" has often been used in an informal way, even by the wi-fi alliance itself, but officially the term does not mean anything.
"wi-fi" was coined by a brand consulting firm called Interbrand corporation that had been hired by the alliance to determine a name that was "a little catchier than 'ieee 802.11b direct sequence'." Interbrand invented "wi-fi" as simply a play-on-words with "hi-fi", as well as creating the yin yang style wi-fi logo.
The wi-fi alliance initially complicated matters by stating that it actually stood for "wireless fidelity", as with the advertising slogan "the standard for wireless fidelity", but later removed the phrase from their marketing. The wi-fi alliance's early white papers still held in their knowledge base: "… a promising market for wireless fidelity (wi-fi) network equipment." and "a short history of wlans." the yin yang logo indicates that a product had been certified for interoperability.
The alliance has since downplayed the connection to "hi-fi". Their official position is that it is merely a brand name that stands for nothing in particular, and they now discourage the use of the term "wireless fidelity".
7. Hardware-standard devices:
A wireless access point connects a group of wireless devices to an adjacent wired LAN. An access point is similar to a network hub, relaying data between connected wireless devices in addition to a (usually) single connected wired device, most often an Ethernet hub or switch, allowing wireless devices to communicate with other wired devices.
Wireless adapters allow devices to connect to a wireless network. These adapters connect to devices using various external or internal interconnects such as pci, miniPCI, usb, express card, card bus and pc card. Most new laptop computers are equipped with internal adapters. Internal cards are generally more difficult to install.
Wireless routers integrate a wap, Ethernet switch, and internal router firmware application that provides ip routing, nat, and dns forwarding through an integrated wan interface. A wireless router allows wired and wireless Ethernet lan devices to connect to a (usually) single wan device such as cable modem or dsl modem. A wireless router allows all three devices (mainly the access point and router) to be configured through one central utility. This utility is most usually an integrated web server which serves web pages to wired and wireless LAN clients and often optionally to wan clients. This utility may also be an application that is run on a desktop computer such as apple's airport.
Wireless network bridges connect a wired network to a wireless network. This is different from an access point in the sense that an access point connects wireless devices to a wired network at the data-link layer. Two wireless bridges may be used to connect two wired networks over a wireless link, useful in situations where a wired connection may be unavailable, such as between two separate homes.
Wireless range extenders or wireless repeaters can extend the range of an existing wireless network. Range extenders can be strategically placed to elongate a signal area or allow for the signal area to reach around barriers such as those created in l-shaped corridors. Wireless devices connected through repeaters will suffer from an increased latency for each hop. Additionally, a wireless device connected to any of the repeaters in the chain will have a throughput that is limited by the weakest link between the two nodes in the chain from which the connection originates to where the connection ends.
8. Embedded systems:
Embedded serial-to-wi-fi module
Wi-fi availability in the home is on the increase. This extension of the internet into the home space will increasingly be used for remote monitoring. Examples of remote monitoring include security systems and tele-medicine. In all these kinds of implementation, if the wi-fi provision is provided using a system running one of operating systems mentioned above, then it becomes unfeasible due to weight, power consumption and cost issues.
Increasingly in the last few years (particularly as of early 2007), embedded wi-fi modules have become available which come with a real-time operating system and provide a simple means of wireless enabling any device which has and communicates via a serial port. This allows simple monitoring devices – for example, a portable ecg monitor hooked up to a patient in their home – to be created. This wi-fi enabled device effectively becomes part of the internet cloud and can communicate with any other node on the internet. The data collected can hop via the home's wi-fi access point to anywhere on the internet.
These wi-fi modules are designed so that designers need minimal wi-fi knowledge to wireless-enable their products.
9. Network security:
During the early popular adoption of 802.11, providing open access points for anyone within range to use was encouraged to cultivate wireless community networks; particularly since people on average use only a fraction of their upstream bandwidth at any given time. Later, equipment manufacturers and mass-media advocated isolating users to a predetermined white list of authorized users—referred to as "securing" the access point.
Measures to deter unauthorized users include suppressing the ap's ssid broadcast, allowing only computers with known Mac addresses to join the network, and various encryption standards. Suppressed ssid and Mac filtering are ineffective security methods as the ssid is broadcast in the open in response to a client ssid query and a Mac address can easily be spoofed. If the eavesdropper has the ability to change his Mac address, then he can potentially join the network by spoofing an authorized address.
Wep encryption can protect against casual snooping, but may also produce a misguided sense of security since freely available tools such as air snort or air crack can quickly recover wep encryption keys. Once it has seen 5-10 million encrypted packets, air snort can determine the encryption password in under a second; newer tools such as aircrack-ptw can use Klein’s attack to crack a wep key with a 50% success rate using only 40,000 packets. The newer wi-fi protected access (wpa) and ieee 802.11i (wpa2) encryption standards resolve most of the serious weaknesses of wep encryption.
Attackers who have gained access to a wi-fi network can use dns spoofing attacks very effectively against any other user of the network, because they can see the dns requests made, and often respond with a spoofed answer before the queried dns server has a chance to reply.
One serious issue with wireless network security is not just encryption, but access to the network (signal reception). With wired networking it is necessary to get past either a firewall or the security guard & locked doors. With wireless it is only necessary to get reception and spend as long as you want, comfortably out of (easy) reach of the network owner. Most business networks protect sensitive data and systems by attempting to disallow external access. Thus being able to get wireless reception (and thus possibly break the encryption) becomes an attack vector on the network as well.
Recreational logging and mapping of other people's access points has become known as war driving. It is also common for people to use open (unencrypted) wi-fi networks as a free service, termed piggybacking. Indeed, many access points are intentionally installed without security turned on so that they can be used as a free service. These activities do not result in sanctions in most jurisdictions; however legislation and case law differ considerably across the world. A proposal to leave graffiti describing available services was called war chalking. In a Florida court case, owner laziness was determined not to be a valid excuse. [17]
Piggybacking is often unintentional. Most access points are configured without encryption by default, and operating systems such as windows xp sp2 and Mac os x may be configured to automatically connect to any available wireless network. A user who happens to start up a laptop in the vicinity of an access point may find the computer has joined the network without any visible indication. Moreover, a user intending to join one network may instead end up on another one if the latter's signal is stronger. In combination with automatic discovery of other network resources this could possibly lead wireless users to send sensitive data to the wrong middle man when seeking a destination. For example, a user could inadvertently use an insecure network to login to a website, thereby making the login credentials available to anyone listening, if the website is using an insecure protocol like http, rather than a secure protocol like https.
10. Wibro
Wibro (wireless broadband) is a wireless broadband internet technology being developed by the South Korean telecoms industry. Wibro is the South Korean service name for IEEE 802.16e (mobile wimax) international standard.
Wibro adopts tdd for duplexing, ofdma for multiple access and 8.75 mhz as a channel bandwidth. Wibro was devised to overcome the data rate limitation of mobile phones (for example cdmassss 1x) and to add mobility to broadband internet access. In February 2002, the Korean government allocated 100 MHz of electromagnetic spectrum in the 2.3 - 2.4 GHz band, and in late 2004 wibro phase 1 was standardized by the tta of Korea and in late 2005 itu reflected wibro as ieee 802.16e (mobile wimax). Two South Korean telco (kt, skt) launched commercial service in June 2006, and the tariff is around us$30.
Wibro base stations will offer an aggregate data throughput of 30 to 50 mbit/s and cover a radius of 1-5 km allowing for the use of portable internet usage. In detail, it will provide mobility for moving devices up to 120 km/h (74.5 miles/h) compared to wireless LAN having mobility up to walking speed and mobile phone having mobility up to 250 km/h. From testing during the apec summit in busan in late 2005, the actual range and bandwidth were quite a bit lower than these numbers. The technology will also offer quality of service. The inclusion of qos allows for wibro to stream video content and other loss-sensitive data in a reliable manner. These all appear to be (and may be) the stronger advantages over the fixed wimax standard (802.16a). Some telcos in many countries are trying to commercialize this mobile wimax (or wibro). For example, ti (Italia), tva (brazil), omnivision (Venezuela), portus (Croatia), and aria link (Michigan) will provide commercial service after test service around 2006-2007. While wibro is quite exacting in its requirements from spectrum use to equipment design, wimax leaves much of this up to the equipment provider while providing enough detail to ensure interoperability
Uses
A wi-fi enabled device such as a pc, game console, mobile phone, mp3 player or pda can connect to the internet when within range of a wireless network connected to the internet. The coverage of one or more interconnected access points — called a hotspot — can comprise an area as small as a single room with wireless-opaque walls or as large as many square miles covered by overlapping access points. Wi-fi technology has served to set up mesh networks, for example, in London. Both architectures can operate in community networks.
In addition to restricted use in homes and offices, wi-fi can make access publicly available at wi-fi hotspots provided either free of charge or to subscribers to various providers. Organizations and businesses such as airports, hotels and restaurants often provide free hotspots to attract or assist clients. Enthusiasts or authorities who wish to provide services or even to promote business in a given area sometimes provide free wi-fi access. Metropolitan-wide wi-fi already has more than 300 projects in process, there were 879 wi-fi based wireless internet service providers in the Czech republic as of may 2008.
Wi-fi also allows connectivity in peer-to-peer (wireless ad-hoc network) mode, which enables devices to connect directly with each other. This connectivity mode can prove useful in consumer electronics and gaming applications.
When wireless networking technology first entered the market many problems ensued for consumers who could not rely on products from different vendors working together. The wi-fi alliance began as a community to solve this issue — aiming to address the needs of the end-user and to allow the technology to mature. The alliance created the branding wi-fi certified to reassure consumers that products will interoperate with other products displaying the same branding.
Many consumer devices use wi-fi. Amongst others, personal computers can network to each other and connect to the internet, mobile computers can connect to the internet from any wi-fi hotspot, and digital cameras can transfer images wirelessly.
routers which incorporate a dsl-modem or a cable-modem and a wi-fi access point, often set up in homes and other premises, provide internet-access and internetworking to all devices connected (wirelessly or by cable) to them. One can also connect wi-fi devices in ad-hoc mode for client-to-client connections without a router.
As of 2007 wi-fi technology had spread widely within business and industrial sites. In business environments, just like other environments, increasing the number of wi-fi access-points provides redundancy, support for fast roaming and increased overall network-capacity by using more channels or by defining smaller cells. Wi-fi enables wireless voice-applications (vowlan or wvoip). Over the years, wi-fi implementations have moved toward "thin" access-points, with more of the network intelligence housed in a centralized network appliance, relegating individual access-points to the role of mere "dumb" radios. Outdoor applications may utilize true mesh topologies. As of 2007 wi-fi installations can provide a secure computer networking gateway, firewall, dhcp server, intrusion detection system, and other functions.
Advantages and challenges
Wi-Fi allows LANs (local area networks) to be deployed without cabling for client devices, typically reducing the costs of network deployment and expansion. Spaces where cables cannot be run, such as outdoor areas and historical buildings, can host wireless LANs.
In 2008, wireless network adapters are built into most modern laptops. The price of chipsets for wi-fi continues to drop, making it an economical networking option included in ever more devices. Wi-fi has become widespread in corporate infrastructures.
Different competitive brands of access points and client network interfaces are inter-operable at a basic level of service. Products designated as "wi-fi certified" by the wifi alliance are backwards compatible. Wi-Fi is a global set of standards. Unlike mobile telephones, any standard wifi device will work anywhere in the world.
Wi-Fi is widely available in more than 220,000 public hotspots and tens of millions of homes and corporate and university campuses worldwide. WPA is not easily cracked if strong passwords are used and wpa2 encryption has no known weaknesses. New protocols for quality of service make wifi more suitable for latency-sensitive applications, and power saving mechanisms, improve battery operation.
Limitations
Spectrum assignments and operational limitations are not consistent worldwide. Most of Europe allows for an additional 2 channels beyond those permitted in the us. For the 2.4 GHz band. Japan has one more on top of that (1–14). Europe, as of 2007, was essentially homogeneous in this respect. A very confusing aspect is the fact that a wifi signal actually occupies five channels in the 2.4 GHz band resulting in only three non-overlapped channels in the bus.: 1, 6, 11, and three or four in Europe: 1, 5, 9, 13 can be used if all the equipment on a specific area can be granted not to use 802.11b at all, even as fallback or beacon.

Reference:
1. “The Genesis of Unlicensed Wireless Policy" by George Mason University-Robert Clooney
2. “Wireless Vulnerabilities & Exploits” by Dr. Eric Brewer from Berkeley University
3. “Long Distance Wifi Trial" by Kelly Brooks from Osmania University.