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Wi-Fi, Devices, Rules, Enhancement, Range
WiFi Standard Devicesstyle="margin-left: 40px; font-family: Verdana; text-align: justify;">Wireless access pointsconnects a group of wireless devices to an adjacent wired LAN.An access point is similar to an ethernet hub,relaying data between connected wireless devices in addition to a(usually) single connected wired device, most often an ethernet hub orswitch, allowing wireless devices to communicate with other wireddevices. style="margin-left: 40px; font-family: Verdana; text-align: justify;"> Wi-FiResource style="margin-left: 40px; font-family: Verdana; text-align: justify;">Wireless adaptersallow devices to connect to a wireless network. These adapters connectto devices using various external or internal interconnects such as PCI, miniPCI,USB,ExpressCard, Cardbus and PCcard. Most newer laptop computers are equipped with internaladapters. Internal cards are generally more difficult to install. style="margin-left: 40px; font-family: Verdana; text-align: justify;">Wirelessroutersintegrate WAP, ethernet switch, and internal Routerfirmware application that provides IP Routing,NAT,and DNSforwarding through an integrated WANinterface. A wireless router allows wired and wireless ethernet LANdevices to connect to a (usually) single WAN device such as cable modem or DSLmodem.A wireless router allows all three devices (mainly the access point androuter) to be configured through one central utility. This utility ismost usually an integrated web serverwhich serves web pages to wired and wireless LAN clients and oftenoptionally to WAN clients. This utility may also be an application thatis run on a desktop computer such as Apple's AirPort. style="margin-left: 40px; font-family: Verdana; text-align: justify;">WirelessEthernet bridgesconnect a wired network to a wireless network. This is different froman access point in the sense that an access point connects wirelessdevices to a wired network at the data-link layer.Two wireless bridges may be used to connect two wired networks over awireless link, useful in situations where a wired connection may beunavailable, such as between two separate homes. style="margin-left: 40px; font-family: Verdana; text-align: justify;">Wirelessrange extenders or wirelessrepeaterscan extend the range of an existing wireless network. Range extenderscan be strategically placed to elongate a signal area or allow for thesignal area to reach around barriers such as those created in L-shapedcorridors. Wireless devices connected through repeaters will sufferfrom an increased latency for each hop. Additionally, a wireless deviceat the end of chain of wireless repeaters will have a throughput thatis limited by the weakest link within the repeater chain. style="margin-left: 40px; font-family: Verdana; text-align: justify;">Mostcommercial devices (routers, access points, bridges, repeaters)designed for home or business environments use either RP-SMAor RP-TNC antenna connectors. PCIwireless adapters also mainly use RP-SMAconnectors. Most PC card and USBwireless only have internal antennas etched on their printed circuit boardwhile some have MMCX connector or MC-Cardexternal connections in addition to an internal antenna. A few USBcards have a RP-SMA connector. Most MiniPCI wireless cards utilize Hirose U.FLconnectors, but cards found in various wireless appliances contain allof the connectors listed. Many high-gain (and homebuilt antennas)utilize the Type N connector morecommonly used by other radio communications methods. style="margin-left: 40px; font-family: Verdana; text-align: justify;"> Non-StandardDevicesstyle="margin-left: 40px; font-family: Verdana; text-align: justify;">USB-Wi-Fiadapters, food container "Cantennas",parabolic reflectors, and many other types of self-built antennae areincreasingly made by do-it-yourselvers. For minimal budgets, as low asa few dollars, signal strength and range canbe improved dramatically. style="margin-left: 40px; font-family: Verdana; text-align: justify;">Thereis also a type of optimization by polarizing the signal toachieve a planar coverage like a plate. Many of these high-gainaftermarket modifications are technically illegal under FCC and otherregulatory guidelines. style="margin-left: 40px; font-family: Verdana; text-align: justify;">Asof 2007, long range Wi-Fikits have begun to enter the market. Companies like BroadbandXpressoffer long range, inexpensive kits that can be setup with limitedknowledge. These kits utilize specialized antennas which increase therange of Wi-Fi dramatically, in the case of the world record 137.2miles (220 km). These kits are commonly used to get Broadband internetto a place that cannot access the service itself.[6] style="margin-left: 40px; font-family: Verdana; text-align: justify;">Thelongest link ever achieved was by the Swedish space agency. Theyattained 310 km, but used 6 watt amplifiers to reach an overheadstratospheric balloon.[citation needed]The longest link without amplification was 279 km in Venezuela, 2006. [7] style="margin-left: 40px; font-family: Verdana; text-align: justify;"> Manufacturersstyle="margin-left: 40px; font-family: Verdana; text-align: justify;">Thereare many vendors now manufacturing and selling 802.11n products. Theyinclude: style="margin-left: 40px; font-family: Verdana; text-align: justify;"> Embeddedsystemsstyle="margin-left: 40px; font-family: Verdana; text-align: justify;">Wi-Fiavailability in the home is on the increase. This extension ofthe Internet into the home space will increasingly be used for remotemonitoring. Examples of remote monitoring include security systems andtele-medicine. In all these kinds of implementation, if the Wi-Fiprovision is provided using a system running one of operating systemsmentioned above, then it becomes unfeasible due to weight, powerconsumption and cost issues. style="margin-left: 40px; font-family: Verdana; text-align: justify;">Increasinglyin the last few years (particularly as of early 2007),embedded Wi-Fi modules have become available which come with areal-time operating system and provide a simple means of wirelessenabling any device which has and communicates via a serial port. style="margin-left: 40px; font-family: Verdana; text-align: justify;">Thisallows simple monitoring devices -- for example, a portable ECGmonitor hooked up to a patient in their home -- to be created. ThisWi-Fi enabled device effectively becomes part of the internet cloud andcan communicate with any other node on the internet. The data collectedcan hop via the home's Wi-Fi access point to anywhere on the internet. style="margin-left: 40px; font-family: Verdana; text-align: justify;">TheseWi-Fi modules are designed so that minimal Wi-Fi knowledge is requiredby designers to wireless enable their product. Unintendedand intended use by outsiders Wikinewshas related news: style="margin-left: 40px; font-family: Verdana; text-align: justify;">Measuresto deter unauthorized users include suppressing the AP's service set identifier(SSID) broadcast, allowing only computers with known MAC addresses to join thenetwork, and various encryption standards. Accesspoints and computers using no encryption are vulnerable toeavesdropping by an attacker armed with packet sniffer software. Ifthe eavesdropper has the ability to change his MAC address then he canpotentially join the network by spoofing an authorisedaddress. style="margin-left: 40px; font-family: Verdana; text-align: justify;">WEPencryption can protect against casual snooping but may also produce amisguided sense of security since freely available tools such as AirSnortcan quickly recover WEP encryption keys. Once it has seen 5-10 millionencrypted packets, AirSnort will determine the encryption password inunder a second.[8]The newer Wi-Fi Protected Access(WPA) and IEEE 802.11i (WPA2) encyptionstandards do not have the serious weaknesses of WEP encryption, butrequire strong passphrases for full security. style="margin-left: 40px; font-family: Verdana; text-align: justify;">Recreationalexploration of other people's access points has become known as wardriving, and the leaving of graffitidescribing available services as warchalking. These activitiesmay be illegal in certain jurisdictions, but existing legislation andcase-law is often unclear. style="margin-left: 40px; font-family: Verdana; text-align: justify;">However,it is also common for people to unintentionally use others'Wi-Fi networks without explicit authorization. Operating systems suchas Windows XP SP2 and MacOS Xautomatically connect to an available wireless network, depending onthe network configuration. A user who happens to start up a laptop inthe vicinity of an access point may find the computer has joined thenetwork without any visible indication. Moreover, a user intending tojoin one network may instead end up on another one if the latter'ssignal is stronger. In combination with automatic discovery of othernetwork resources (see DHCPand Zeroconf) this could possiblylead wireless users to send sensitive data to the wrong destination.[citation needed] style="margin-left: 40px; font-family: Verdana; text-align: justify;">InSingapore, using anotherperson's Wi-Fi network is illegalunder the Computer Misuse Act. A 17 year old has been arrested forsimply tapping into his neighbor's wireless Internet connection andfaces up to 3 years' imprisonment and a fine.[9] Wi-Fivs. amateur radiostyle="margin-left: 40px; font-family: Verdana; text-align: justify;">Inthe US, Canada and Australia, a portion of the 2.4 GHz Wi-Firadio spectrum is also allocated to amateur radiousers. In the US, FCC Part 15 rules govern non-licensed operators (i.e.most Wi-Fi equipment users). Under Part 15 rules, non-licensed usersmust "accept" (i.e. endure) interference from licensed users and notcause harmful interference to licensed users. Amateur radio operatorsare licensed users, and retain what the FCC terms "primary status" onthe band, under a distinct set of rules (Part 97). Under Part 97,licensed amateur operators may construct their own equipment, use veryhigh-gain antennas, and boost output power to 100 watts on frequenciescovered by Wi-Fi channels 2-6. However, Part 97 rules mandate usingonly the minimum power necessary for communications, forbid obscuringthe data, and require station identification every 10 minutes.Therefore, output power control is required to meet regulations, andthe transmission of any encrypted data (for example https) isquestionable. style="margin-left: 40px; font-family: Verdana; text-align: justify;">Inpractice, microwave power amplifiers are expensive. On the other hand,the short wavelengthat 2.4 GHz allows for simple construction of very high gaindirectionalantennas. Although Part 15 rules forbid any modification ofcommercially constructed systems, amateur radio operators may modifycommercial systems for optimized construction of long links, forexample. Using only 200 mW link radios and high gain directionalantennas, a very narrow beam may be used to construct reliable linkswith minimal radio frequency interference to other users. style="margin-left: 40px; font-family: Verdana; text-align: justify;">Courtesy of Wikipedia. Alltext is available under the terms of the GNUFree Documentation License. (See Copyrights for details.)
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