Information AboutWi-fi |
|
Wi-Fi (also '''WiFi''', '''Wi-fi''', '''Wifi''', or '''wifi''') is a brand originally licensed by the Wi-Fi Alliance to describe the underlying technology of Wireless Local Area Network s ( WLAN ) based on the IEEE 802.11 specifications. Wi-Fi is now so pervasive, and the term so generic, that the brand is no longer protected and it appears on Webster's dictionary. Wi-Fi was intended to be used for mobile computing devices, such as laptops, in LAN s, but is now often used for increasingly more applications, including Internet access, gaming, and basic connectivity of consumer electronics such as televisions and DVD players. There are even more standards in development that will allow Wi-Fi to be used by cars in highways in support of an Intelligent Transportation System to increase safety, gather statistics, and enable mobile commerce (IEEE 802.11p) . A person with a Wi-Fi device, such as a computer, telephone, or Personal Digital Assistant (PDA) can connect to the Internet when in proximity of an Access Point . The region covered by one or several access points is called a Hotspot . Hotspots can range from a single room with a single person connecting to the internet, to large metropolitan areas, such as Philadelphia and San Francisco, who are creating citywide hotspots to allow free internet access among all socioeconomic groups. Wi-Fi also allows connectivity in peer-to-peer mode, which enables devices to connect directly with each other. This connectivity mode is useful in consumer electronics and gaming applications. When the technology was first commercialized there were many problems because consumers could not be sure that products from different vendors would work together. The Wi-Fi Alliance began as a community to solve this issue so as to address the needs of the end user and allow the technology to mature. The Alliance created another brand "Wi-Fi CERTIFIED" to denote products are Interoperable with other products displaying the "Wi-Fi CERTIFIED" brand. History Wi-Fi is a Direct-sequence Spread Spectrum radio technology, part of the larger family of Spread Spectrum technology. Unlicensed spread spectrum was first authorized 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. These regulations then enabled the development of Wi-Fi, its onetime competitor HomeRF , and Bluetooth . 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 1 Mbit/s to 2 Mbit/s. Vic Hayes , who was the inventor of Wi-Fi and has been named the 'father of Wi-Fi,' was involved in designing standards such as IEEE 802.11b, 802.11a and 802.11g. In 2003, Vic retired from Agere Systems. Agere Systems suffered from strong competition in the market even though their products were cutting edge, as many opted for cheaper Wi-Fi solutions. 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. Origin and Meaning of the Term "Wi-Fi" Despite the similarity between the terms "Wi-Fi" and " contradict the popular conclusion that "Wi-Fi" stands for "Wireless Fidelity". According to Mr. Belanger, the Interbrand Corporation developed the brand "Wi-Fi" for the Wi-Fi Alliance to use to describe WLAN products that are based on the IEEE 802.11 standards. In Mr. Belanger's words, ''"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'."'' The Wi-Fi Alliance themselves invoked the term "Wireless Fidelity" with the marketing of a tag line, "The Standard for Wireless Fidelity," but later removed the tag from their marketing. The Wi-Fi Alliance now discourages propagation of the notion that "Wi-Fi" stands for "Wireless Fidelity". Wi-Fi: How it works 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 100 ms. The beacons are transmitted at 1 Mbit/s, and are relatively short and therefore are not of influence on performance. Since 1 Mbit/s is the lowest rate of Wi-Fi it assures that the client who receives the beacon can communicate at at least 1 Mbit/s. Based on the settings (i.e. the SSID), the client may decide whether to connect to an AP. Also the Firmware running on the client Wi-Fi card is of influence. Say two AP's of the same SSID are in range of the client, the firmware may decide based on Signal Strength to which of the two AP's it will connect. The Wi-Fi standard leaves connection criteria and roaming totally open to the client. This is a strength of Wi-Fi, but also means that one wireless adapter may perform substantially better than the other. In Windows XP, there is a feature called ''zero configuration'' which makes the user show any network available and let the end user connect to it on the fly. In the future, wireless cards will be more and more controlled by the operating system. Microsoft's newest feature called ''SoftMAC'' will take over from on-board firmware. Wi-Fi transmits in the air, it has the same properties as non-switched ethernet network. Even collisions can therefore appear like in non-switched ethernet LAN's. Wi-Fi vs. cellular Some argue that Wi-Fi and related consumer technologies hold the key to replacing Cellular Telephone networks such as GSM . Some obstacles to this happening in the near future are missing Roaming and Authentication features (see 802.1x , SIM cards and RADIUS ), the narrowness of the Available Spectrum and the limited range of Wi-Fi. It is more likely that WiMax could compete with other cellular phone protocols such as GSM , UMTS or CDMA . However, Wi-Fi is ideal for VoIP applications like in a corporate LAN or SOHO environment. Early adopters were already available in the late '90s, though not until 2005 did the market explode. Companies such as Zyxel , UT Starcomm , Samsung , Hitachi and many more are offering VoIP Wi-Fi phones for reasonable prices. In 2005 ADSL ISP started to offer VoIP services to their customers (eg. the dutch ISP XS4All ). Since calling via VoIP is low-cost and more often being free, VoIP enabled ISPs have the potential to open up the VoIP market. GSM phones with integrated Wi-Fi & VoIP capabilities are being introduced into the market and have the potential to replace land line telephone services. Currently it seems unlikely that Wi-Fi will directly compete against cellular. Wi-Fi-only phones have a very limited range, so setting up a covering network would be too expensive. Additionally, cellular technology allows the user to travel while connected, bouncing the connection from tower to tower (or "cells") as proximity changes, all the while maintaining one solid connection to the user. Current Wi-Fi offerings do not do this, and connect to only one access point at a time. Therefore once you are out of range of one "hotspot", the connection will drop and will need to be re-connected to the next one each time. For these reasons, Wi-Fi phones may be best reserved for local use such as corporate networks. However, devices capable of multiple standards (also known as UMA) may well compete in the market. Commercial Wi-Fi Commercial Wi-Fi services are available in places such as Internet Cafe s, coffee houses and airports around the world (commonly called Wi-Fi-cafés), although coverage is patchy in comparison with Cellular :
Universal Efforts Another business model seems to be making its way into the news. The idea is that users will share their bandwidth through their personal ; and ''aliens'' buy access from bills. Thus the system can be described as a Peer-to-peer sharing service, which we usually relate to software. Although FON has received some financial support by companies like Google and Skype , it remains to be seen whether the idea can actually work. There are three main challenges for this service at the moment. The first is that it needs much media and community attention first in order to get though the phase of "early adoption" and into the mainstream. Then comes the fact that sharing your Internet connection is often against the terms of use of your ISP . This means that in the next few months we can see ISPs trying to defend their interests in the same way music companies united against free MP3 distribution. And third, the FON software is still in Beta-version and it remains to be seen if it presents a good solution of the imminent security issues... Free Wi-Fi While commercial services attempt to move existing business models to Wi-Fi, many groups, communities, cities, and individuals have set up free Wi-Fi networks, often adopting a common peering agreement in order that networks can openly share with each other. Free Wireless Mesh Network s are often considered the future of the internet. Many municipalities have joined with local community groups to help expand free Wi-Fi networks (see Mu-Fi ). Some community groups have built their Wi-Fi networks entirely based on volunteer efforts and donations. For more information, see Wireless Community Network , where there is also a list of the free Wi-Fi networks one can find around the globe. OLSR is one of the protocols used to set up free networks. Some networks use static routing; others rely completely on OSPF . Wireless Leiden developed their own routing software under the name LVrouteD for community wi-fi networks that consist of a completely wireless backbone. Most networks rely heavily on open source software, or even publish their setup under an open source license. Some smaller countries and municipalities already provide free Wi-Fi hotspots and residential Wi-Fi internet access to everyone. Examples include the Kingdom Of Tonga or Estonia which have already a large number of free Wi-Fi hotspots throughout their countries. In Paris, France, OzoneParis offers free Internet access for life to anybody who contributes to the Pervasive Network’s development by making their rooftop available for the Wi-Fi Network. Annapolis, Maryland is in the early phases (as of April 2006) of a pilot program to provide free, add-based Wi-Fi to all its residents. A private company, Annapolis Wireless Internet, will administrate the network. Users will only see local adds upon accessing the network. {Link without Title} Unwire Jerusalem is a project to put free Wi-Fi access points at the main shopping centers of Jerusalem. Many universities provide free Wi-Fi internet access to their students, visitors, and anyone on campus. Similarly, some commercial entities such as Panera Bread and Culver's offer free Wi-Fi access to patrons. McDonald's Corporation also offers Wi-Fi access, often branded 'McInternet'. This was launched at their flagship restaurant in Oak Brook, Illinois and is also available in many branches in London, UK . However, there is also a third subcategory of networks set up by certain communities such as universities where the service is provided free to members and guests of the community such as students, yet used to make money by letting the service out to companies and individuals outside. An example of such a service is Sparknet in Finland. Sparknet also supports OpenSparknet , a project where people can name their own wireless access point as a part of Sparknet in return for certain benefits. Recently commercial Wi-Fi providers have built free Wi-Fi hotspots and hotzones. These providers hope that free Wi-Fi access would equate to more users and significant return on investment. Wi-Fi vs. amateur radio In the US, the 2.4 GHz Wi-Fi radio spectrum is also allocated to amateur radio users. FCC Part 15 rules govern non-licenced operators (i.e. most Wi-Fi equipment users). Amateur operators retain what the FCC terms "primary status" on the band under a distinct set of rules (Part 97). Under Part 97, licensed amateur operators may construct their own equipment, use very high-gain antennas, and boost output power to 100 watts on frequencies covered by Wi-Fi channels 2-6. However, Part 97 rules mandate using only the minimum power necessary for communications, forbid obscuring the data, and require station identification every 10 minutes. Therefore, expensive automatic power-limiting circuitry is required to meet regulations, and the transmission of any encrypted data (for example https) is questionable. In practice, microwave power amplifiers are expensive and decrease receive-sensitivity of link radios. On the other hand, the short wavelength at 2.4 GHz allows for simple construction of very high gain directional antennas. Although Part 15 rules forbid any modification of commercially constructed systems, amateur radio operators may modify commercial systems for optimized construction of long links, for example. Using only 200 mW link radios and two 24 dB gain antennas, an effective radiated power of many hundreds of watts in a very narrow beam may be used to construct reliable links of over 100 km with little radio frequency interference to other users. Advantages of Wi-Fi
Disadvantages of Wi-Fi
Wi-Fi in Gaming Some gaming consoles and handhelds make use of Wi-Fi technology to enhance the gaming eaperience.
Wi-Fi and free software
Trademark/Certification Wi-Fi and '''Wi-Fi CERTIFIED''' are trademarks of the ''' Wi-Fi Alliance ''' the trade organization that tests and certifies equipment compliance with the 802.11x standards. Unintended and intended use by outsiders The default configuration of most Wi-Fi access points provides no protection from unauthorized use of the network. Many business and residential users do not intend to secure their access points, instead leaving them open to users in the area. Some argue that it is proper etiquette to leave access points open for others to use just as one can expect to find open access points while on the road. Measures to deter unauthorized users include suppressing the AP's Service Set Identifier (SSID) broadcast, allowing only computers with known MAC Address es to join the network, and various Encryption standards. Older access points frequently do not support adequate security measures to protect against a determined attacker armed with a Packet Sniffer and the ability to switch MAC addresses. Recreational exploration of other people's access points has become known as Wardriving , and the leaving of Graffiti describing available services as Warchalking . It should be noted that these activities are illegal in many countries, including the United Kingdom. However, it is also common for people to unintentionally use others' Wi-Fi networks without authorization. Operating systems such as Windows XP and Mac OS X automatically connect to an available wireless network, depending on the network configuration. 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 (see DHCP and Zeroconf ) this can lead wireless users to send sensitive data to the wrong destination, as described by Chris Meadows in the February 2004 RISKS Digest . {Link without Title} See also External links
|