wireless technology in day to day life

8/9/2019 Wireless Technology in Day to Day Life

1/36

WIRELESS TECHNOLOGY IN DAY-TO-DAY LIFE

PROJECT REPORT

Submitted by:

GROUP NO:

II - YEAR, EEE

Submitted to:

DEPARTMENT OF ENGLISH

AMRITA SCHOOL OF ENGINEERING

ETTIMADAI

COIMBATORE-641105

MARCH 2009


2/36

DECLARATION

I hear by declare that this submission is my own work and that, to best of my

knowledge and belief, it contains no material previously published or written by another

person not material which has been accepted for the award of any other degree or

diploma of the university or other institute of higher learning, except where view

acknowledgment has been made in the text.

Place: Signature

Date: Name : ANUVIND B

Register Number : CB107EE008

Signature

Name : HARSHAVARDHAN


Signature

Name : SHIVARAM K V


Signature

Name : SREEJITH RAJAMOHAN



3/36

INTRODUCTION

Wireless communication is the transfer of information over a distance withoutthe use of electrical conductors or "wires".[1] The distances involved may be short (a fewmeters as in television remote control) or long (thousands or millions of kilometers for

radio communications). When the context is clear, the term is often shortened to"wireless". Wireless communication is generally considered to be a branch oftelecommunications.

It encompasses various types of fixed, mobile, and portable two way radios,cellular telephones, personal digital assistants (PDAs), and wireless networking. Otherexamples ofwireless technology include GPS units, garage door openers and or garagedoors, wireless computer mice, keyboards and headsets, satellite television and cordlesstelephones.

Wireless operations permits services, such as long range communications, that are

impossible or impractical to implement with the use of wires. The term is commonly usedin the telecommunications industry to refer to telecommunications systems (e.g., radiotransmitters and receivers, remote controls, computer networks, network terminals, etc.)which use some form of energy (e.g. radio frequency (RF), infrared light, laser light,visible light, acoustic energy, etc.) to transfer information without the use of wires.[2]

Information is transferred in this manner over both short and long distances.

The term "wireless" has become a generic and all-encompassing word used to

describe communications in which electromagnetic waves or RF (rather than some form

of wire) carry a signal over part or the entire communication path.

Wireless networking is one of several ways to connect the computers in yourhome. It creates a network by sending radio-frequency signals between your computers toshare information.

Wireless networking technologies take the concept of "no new wires" one stepfurther. In a wireless network, all of the computers in your home broadcast theirinformation to one another using radio signals. This can make networking extremely east,especially if you have computers all over house. It also makes it a whole lot simpler tomove computers around.

HISTORY

The term "Wireless" came into public use to refer to a radio receiver ortransceiver(a dual purpose receiver and transmitter device), establishing its usage in thefield of wireless telegraphy early on; now the term is used to describe modern wirelessconnections such as in cellular networks and wireless broadband Internet. It is also usedin a general sense to refer to any type of operation that is implemented without the use of
http://g/wiki/Wirehttp://g/Wireless.html#cite_note-0#cite_note-0http://g/Wireless.html#cite_note-0#cite_note-0http://g/wiki/Telecommunicationshttp://g/wiki/Two_way_radiohttp://g/wiki/Mobile_phonehttp://g/wiki/Personal_Digital_Assistanthttp://g/wiki/Wireless_networkhttp://g/wiki/Global_Positioning_Systemhttp://g/wiki/Garage_door_openerhttp://g/wiki/Garage_door_openerhttp://g/wiki/Computer_mousehttp://g/wiki/Computer_keyboardhttp://g/wiki/Headset_(telephone/computer)http://g/wiki/Satellite_televisionhttp://g/wiki/Telephonehttp://g/wiki/Radio_frequencyhttp://g/wiki/Infraredhttp://g/wiki/Laserhttp://g/Wireless.html#cite_note-FS1037C-1#cite_note-FS1037C-1http://vidya1/beyond2/HSW/radio.htmhttp://g/wiki/Transceiverhttp://g/wiki/Wirehttp://g/Wireless.html#cite_note-0#cite_note-0http://g/wiki/Telecommunicationshttp://g/wiki/Two_way_radiohttp://g/wiki/Mobile_phonehttp://g/wiki/Personal_Digital_Assistanthttp://g/wiki/Wireless_networkhttp://g/wiki/Global_Positioning_Systemhttp://g/wiki/Garage_door_openerhttp://g/wiki/Garage_door_openerhttp://g/wiki/Computer_mousehttp://g/wiki/Computer_keyboardhttp://g/wiki/Headset_(telephone/computer)http://g/wiki/Satellite_televisionhttp://g/wiki/Telephonehttp://g/wiki/Radio_frequencyhttp://g/wiki/Infraredhttp://g/wiki/Laserhttp://g/Wireless.html#cite_note-FS1037C-1#cite_note-FS1037C-1http://vidya1/beyond2/HSW/radio.htmhttp://g/wiki/Transceiver


4/36

wires, such as "wireless remote control" or "wireless energy transfer", regardless of thespecific technology (e.g. radio, infrared, ultrasonic) that is used to accomplish theoperation.

David E. Hughes, eight years before Hertz's experiments, induced electromagnetic wavesin a signaling system. Hughes transmitted Morse code by an induction apparatus. In

1878, Hughes's induction transmission method utilized a "clockwork transmitter" totransmit signals. In 1885, T. A. Edison used a vibrator magnet for induction transmission.In 1888, Edison deploys a system of signaling on the Lehigh Valley Railroad. In 1891,Edison attains the wireless patent for this method using inductance (U.S. Patent465,971 ).

In the history of wireless technology, the demonstration of the theory ofelectromagneticwaves by Heinrich Rudolf Hertz in 1888 was important.[3][4] The theory ofelectromagnetic waves were predicted from the research ofJames Clerk Maxwell andMichael Faraday. Hertz demonstrated that electromagnetic waves could be transmittedand caused to travel through space at straight lines and that they were able to be receivedby an experimental apparatus.[3][4]The experiments were not followed up by Hertz. Thepractical applications of the wireless communication and remote control technology wereimplemented byNikola Tesla.
http://g/wiki/Radiohttp://g/wiki/Infraredhttp://g/wiki/Ultrasonichttp://g/wiki/David_E._Hugheshttp://g/wiki/Electromagnetic_inductionhttp://g/wiki/Thomas_Alva_Edisonhttp://patft.uspto.gov/netacgi/nph-Parser?patentnumber=465971http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=465971http://g/wiki/Electromagnetic_wavehttp://g/wiki/Electromagnetic_wavehttp://g/wiki/Heinrich_Rudolf_Hertzhttp://g/Wireless.html#cite_note-Story-2#cite_note-Story-2http://g/Wireless.html#cite_note-Story-2#cite_note-Story-2http://g/Wireless.html#cite_note-katz-3#cite_note-katz-3http://g/wiki/James_Clerk_Maxwellhttp://g/wiki/Michael_Faradayhttp://g/wiki/Transmission_(telecommunications)http://g/wiki/Receiver_(radio)http://g/Wireless.html#cite_note-Story-2#cite_note-Story-2http://g/Wireless.html#cite_note-katz-3#cite_note-katz-3http://g/Wireless.html#cite_note-katz-3#cite_note-katz-3http://g/wiki/Nikola_Teslahttp://g/wiki/Radiohttp://g/wiki/Infraredhttp://g/wiki/Ultrasonichttp://g/wiki/David_E._Hugheshttp://g/wiki/Electromagnetic_inductionhttp://g/wiki/Thomas_Alva_Edisonhttp://patft.uspto.gov/netacgi/nph-Parser?patentnumber=465971http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=465971http://www.pat2pdf.org/pat2pdf/foo.pl?number=465971http://g/wiki/Electromagnetic_wavehttp://g/wiki/Electromagnetic_wavehttp://g/wiki/Heinrich_Rudolf_Hertzhttp://g/Wireless.html#cite_note-Story-2#cite_note-Story-2http://g/Wireless.html#cite_note-katz-3#cite_note-katz-3http://g/wiki/James_Clerk_Maxwellhttp://g/wiki/Michael_Faradayhttp://g/wiki/Transmission_(telecommunications)http://g/wiki/Receiver_(radio)http://g/Wireless.html#cite_note-Story-2#cite_note-Story-2http://g/Wireless.html#cite_note-katz-3#cite_note-katz-3http://g/wiki/Nikola_Tesla


5/36


6/36

The Wireless Ethernet Compatibility Alliance (WECA) has gone in a completelydifferent drection from HomeRF. Targeted more at office use than home networks, Wi-Fi(for "wireless fidelity", like Hi-Fi for "high fidelity" in audio equipment) is essentially aseal of approval that says the manufacturer's product is compliant with a variation of theIEEE 802.11 specification known as IEEE 802.11b. This specification drops FHSS and

focuses on DSSS because of the higher data rate it can attain. Under 802.11b, devicescommunicate at a speed of 11 Mbps whenever possible. If signal strength or interferenceis disrupting data, the devices will drop back to 5.5 Mbps, then 2 Mbps and finally downto 1 Mbps. Though it may occasionally slow down, this keeps the network stable andvery reliable.
http://showimage%28%27http//www.wirelessethernet.com');http://showimage%28%27http//www.wirelessethernet.com');


7/36


http://showimage%28%27http//www.wirelessethernet.com');http://showimage%28%27http//www.wirelessethernet.com');


8/36



Photo courtesy Nexland

The ISB Wavebase by Nexland allows you to connect

wireless devices to your fast Internet connection.

Here are the advantages of Wi-Fi:

It's fast (11 Mbps).

It's reliable.

It has a long range (1,000 ft / 305 m in open areas, 250 to 400 ft / 76 to 122 m inclosed areas)

It's easily integrated into existing wired-Ethernet networks.

It's compatible with original 802.11 DSSS devices.

Here are the disadvantages:

It's expensive.

It requires an access point.

It can be difficult to set up.

Speed can fluctuate significantly.Wi-Fi offers Ethernet speeds without the wires, but you pay for it. Access points varygreatly in cost, from about $300 to $1,400. Most access points have an integratedEthernet controller to connect to an existing wired-Ethernet network. It also has an omni-directional antenna to receive the data transmitted by the wireless transceivers. Applesells an inexpensive ($299 list) and easy-to-configure access point called Airport. Airporthas to be connected to an Apple computer (iMac, PowerMac, iBook), but it will accept
http://showimage%28%27http//www.wirelessethernet.com');http://showimage%28%27http//www.apple.com/airport');http://showimage%28%27http//www.wirelessethernet.com');http://showimage%28%27http//www.apple.com/airport');


9/36

signals from any 802.11b-compatible wireless-network card, whether its PC or Mac-based.


10/36

Bluetooth is a standard developed by a group of electronics manufacturers that allowsany sort of electronic equipment -- from computers and cell phones to keyboards andheadphones -- to make its own connections, without wires, cables or any direct actionfrom a user. Bluetooth is intended to be a standard that works at two levels:

It provides agreement at the physical level -- Bluetooth is a radio-frequency

standard.

It also provides agreement at the next level up, where products have to agree onwhen bits are sent, how many will be sent at a time and how the parties in aconversation can be sure that the message received is the same as the messagesent.

The companies belonging to the Bluetooth Special Interest Group, and there are more

than 1,000 of them, want to let Bluetooth's radio communications take the place of wires

for connecting peripherals, telephones and computers.

There are already a couple of ways to get around using wires. One is to carry information

between components via beams oflight in the infrared spectrum. Infrared refers to lightwaves of a lower frequency than human eyes can receive and interpret. Infrared is used inmost television remote control systems, and with a standard called IrDA (Infrared DataAssociation) it's used to connect some computers with peripheral devices. For most ofthese computer and entertainment purposes, infrared is used in a digital mode -- thesignal is pulsed on and off very quickly to send data from one point to another.

Infrared communications are fairly reliable and don't cost very much to build into adevice, but there are a couple of drawbacks. First, infrared is a "line of sight" technology.For example, you have to point the remote control at the television orDVD playertomake things happen. The second drawback is that infrared is almost always a "one toone" technology. You can send data between your desktop computer and yourlaptop

computer, but not your laptop computer and your PDA at the same time.

These two qualities of infrared are actually advantageous in some regards. Becauseinfrared transmitters and receivers have to be lined up with each other, interferencebetween devices is uncommon. The one-to-one nature of infrared communications isuseful in that you can make sure a message goes only to the intended recipient, even in aroom full of infrared receivers.

The second alternative to wires, cable synchronizing, is a little more troublesome thaninfrared. If you have a Palm Pilot, a Windows CE device or a Pocket PC, you know aboutsynchronizing data. In synchronizing, you attach the PDA to your computer (usually witha cable), press a button and make sure that the data on the PDA and the data on the

computer match. It's a technique that makes the PDA a valuable tool for many people, butsynchronizing the PDA with the computer and making sure you have the correct cable orcradle to connect the two can be a real hassle.

Bluetooth is intended to get around the problems that come with both infrared and cablesynchronizing systems. The hardware vendors, which include Siemens, Intel, Toshiba,Motorola and Ericsson, have developed a specification for a very small radio module tobe built into computer, telephone and entertainment equipment. From the user's point ofview, there are three important features to Bluetooth:
http://192.168.9.3/beyond2/HSW/cell-phone.htmhttp://192.168.9.3/beyond2/HSW/radio-spectrum.htmhttp://192.168.9.3/beyond2/HSW/light.htmhttp://192.168.9.3/beyond2/HSW/eye.htmhttp://192.168.9.3/beyond2/HSW/dvd.htmhttp://192.168.9.3/beyond2/HSW/laptop.htmhttp://192.168.9.3/beyond2/HSW/laptop.htmhttp://192.168.9.3/beyond2/HSW/cell-phone.htmhttp://192.168.9.3/beyond2/HSW/radio-spectrum.htmhttp://192.168.9.3/beyond2/HSW/light.htmhttp://192.168.9.3/beyond2/HSW/eye.htmhttp://192.168.9.3/beyond2/HSW/dvd.htmhttp://192.168.9.3/beyond2/HSW/laptop.htmhttp://192.168.9.3/beyond2/HSW/laptop.htm


11/36

It's wireless. When you travel, you don't have to worry about keeping track of abriefcase full of cables to attach all of your components, and you can design youroffice without wondering where all the wires will go.

It's inexpensive.

You don't have to think about it. Bluetooth doesn't require you to do anythingspecial to make it work. The devices find one another and strike up a conversationwithout any user input at all.

Bluetooth communicates on a frequency of2.45 gigahertz, which has been set aside byinternational agreement for the use of industrial, scientific and medical devices (ISM). Anumber of devices that you may already use take advantage of this same radio-frequencyband. Baby monitors, garage-door openers and the newest generation of cordless phonesall make use of frequencies in the ISM band. Making sure that Bluetooth and these otherdevices don't interfere with one another has been a crucial part of the design process.

BEHIND THE NAME

Harald Bluetooth was king of Denmark around the turn of the last millennium. He

managed to unite Denmark and part of Norway into a single kingdom then introduced

Christianity into Denmark. He left a large monument, the Jelling rune stone, in memory

of his parents. He was killed in 986 during a battle with his son, Svend Forkbeard.

Choosing this name for the standard indicates how important companies from the Baltic

region (nations including Denmark, Sweden, Norway and Finland) are to the

communications industry, even if it says little about the way the technology works.


12/36

Avoiding Interference


13/36

One of the ways Bluetooth devices avoid interfering with other systems is by sending outvery weak signals of 1 milliwatt. By comparison, the most powerful cell phones cantransmit a signal of 3 watts. The low power limits the range of a Bluetooth device toabout 10 meters, cutting the chances of interference between your computer system andyour portable telephone or television. Even with the low power, the walls in your house

won't stop a Bluetooth signal, making the standard useful for controlling several devicesin different rooms.With many different Bluetooth devices in a room, you might think they'd interfere withone another, but it's unlikely that several devices will be on the same frequency at thesame time, because Bluetooth uses a technique called spread-spectrum frequencyhopping. In this technique, a device will use 79 individual, randomly chosen frequencieswithin a designated range, changing from one to another on a regular basis. In the case ofBluetooth, the transmitters change frequencies 1,600 times every second, meaning thatmore devices can make full use of a limited slice of the radio spectrum. Since everyBluetooth transmitter uses spread-spectrum transmitting automatically, its unlikely thattwo transmitters will be on the same frequency at the same time. This same technique

minimizes the risk that portable phones or baby monitors will disrupt Bluetooth devices,since any interference on a particular frequency will last only a tiny fraction of a second.

When Bluetooth-capable devices come within range of one another, an electronicconversation takes place to determine whether they have data to share or whether oneneeds to control the other. The user doesn't have to press a button or give a command --the electronic conversation happens automatically. Once the conversation has occurred,the devices -- whether they're part of a computer system or a stereo -- form a network.Bluetooth systems create a personal-area network (PAN), orpiconet, that may fill a roomor may encompass no more distance than that between the cell phone on a belt-clip andthe headset on your head. Once a piconet is established, the members randomly hopfrequencies in unison so they stay in touch with one another and avoid other piconets thatmay be operating in the same room.
http://192.168.9.3/beyond2/HSW/radio-spectrum.htmhttp://192.168.9.3/beyond2/HSW/radio-spectrum.htm


14/36

An Example


15/36

Lets take a look at how the Bluetooth frequency hopping and personal-area networkkeep systems from becoming confused. Lets say youve got a typical modern livingroom with the typical modern stuff inside. Theres an entertainment system with a stereo,a DVD player, a satellite TV receiver and a television; there's a cordless telephone and apersonal computer. Each of these systems uses Bluetooth, and each forms its own piconet

to talk between main unit and peripheral.The cordless telephone has one Bluetooth transmitter in the base and another in thehandset. The manufacturer has programmed each unit with an address that falls into arange of addresses it has established for a particular type of device. When the base is firstturned on, it sends radio signals asking for a response from any units with an address in aparticular range. Since the handset has an address in the range, it responds, and a tinynetworkis formed. Now, even if one of these devices should receive a signal fromanother system, it will ignore it since its not from within the network. The computer andentertainment system go through similar routines, establishing networks among addressesin ranges established by manufacturers. Once the networks are established, the systemsbegin talking among themselves. Each piconet hops randomly through the available

frequencies, so all of the piconets are completely separated from one another.Now the living room has three separate networks established, each one made up ofdevices that know the address of transmitters it should listen to and the address ofreceivers it should talk to. Since each network is changing the frequency of its operationthousands of times a second, its unlikely that any two networks will be on the samefrequency at the same time. If it turns out that they are, then the resulting confusion willonly cover a tiny fraction of a second, and software designed to correct for such errorsweeds out the confusing information and gets on with the networks business.Most of the time, a network or communications method either works in one direction at atime, called half-duplex communication, or in both directions simultaneously, calledfull-duplex communication. A speakerphone that lets you either listen or talk, but notboth, is an example of half-duplex communication, while a regular telephone handset is afull-duplex device. Because Bluetooth is designed to work in a number of differentcircumstances, it can be either half-duplex or full-duplex. The cordless telephone is anexample of a use that will call for a full-duplex (two-way) link, and Bluetooth can senddata at more than 64,000 bits per second in a full-duplex link -- a rate high enough tosupport several human voice conversations. If a particular use calls for a half-duplex link-- connecting to a computer printer, for example -- Bluetooth can transmit up to 721kilobits per second (Kbps) in one direction, with 57.6 Kbps in the other. If the use callsfor the same speed in both directions, a link with 432.6-Kbps capacity in each directioncan be made.
http://192.168.9.3/beyond2/HSW/satellite.htmhttp://192.168.9.3/beyond2/HSW/radio.htmhttp://192.168.9.3/beyond2/HSW/cordless-telephone.htmhttp://192.168.9.3/beyond2/HSW/inkjet-printer.htmhttp://192.168.9.3/beyond2/HSW/satellite.htmhttp://192.168.9.3/beyond2/HSW/radio.htmhttp://192.168.9.3/beyond2/HSW/cordless-telephone.htmhttp://192.168.9.3/beyond2/HSW/inkjet-printer.htm


16/36

Here are some specification details from the Bluetooth Web site The devices in a piconet share a common communication data channel. The

channel has a total capacity of 1 megabit per second (Mbps). Headers andhandshaking information consume about 20 percent of this capacity.

In the United States and Europe, the frequency range is 2,400 to 2,483.5 MHz,

with 79 1-MHz radio frequency (RF) channels. In practice, the range is 2,402MHz to 2,480 MHz. In Japan, the frequency range is 2,472 to 2,497 MHz with 231-MHz RF channels.

A data channel hops randomly 1,600 times per second between the 79 (or 23) RFchannels.

Each channel is divided into time slots 625 microseconds long. A piconet has a master and up to seven slaves. The master transmits in even time

slots, slaves in odd time slots. Packets can be up to five time slots wide. Data in a packet can be up to 2,745 bits in length. There are currently two types of data transfer between devices: SCO

(synchronous connection oriented) and ACL (asynchronous connectionless). In a piconet, there can be up to three SCO links of 64,000 bits per second each. To

avoid timing and collision problems, the SCO links use reserved slots set up bythe master.

Masters can support up to three SCO links with one, two or three slaves. Slots not reserved for SCO links can be used for ACL links. One master and slave can have a single ACL link. ACL is either point-to-point (master to one slave) or broadcast to all the slaves. ACL slaves can only transmit when requested by the master.

WIRELESS ENERGY TRANSFER

Wireless energy transfer orwireless power transmission (also known as the TeslaEffect) is the process that takes place in any system where electrical energy is transmittedfrom apower source to an electrical load, without interconnecting wires in an electricalgrid. Wireless transmission is ideal in cases where instantaneous or continuous energytransfer is needed, but interconnecting wires are inconvenient, hazardous, or impossible.Though the physics of both are related, this is distinct from wireless transmission for thepurpose of transferring information (such as radio) through waves, where the percentageof thepowerthat is received is only important if it becomes too low to successfullyrecover the signal. With wireless energy transfer, the efficiency is a more critical

parameter and this creates important differences in these technologies.The most common and the most viable form of wireless power transfer is carried outusing Inductive Power Transfer. The other viable technologies for Wireless Power arebased on Microwaves and Lasers.Size, distance, and efficiency

The size of the components is dictated by the distance from transmitterto receiver, thewavelength and the Rayleigh Criterion orDiffraction limit, used in standard RF (RadioFrequency) antenna design, which also applies to lasers.
http://showimage%28%27http//www.bluetooth.com/developer/specification/core.asp');http://g/wiki/Electrical_energyhttp://g/wiki/Power_supplyhttp://g/wiki/Electrical_loadhttp://g/wiki/Electrical_gridhttp://g/wiki/Electrical_gridhttp://g/wiki/Informationhttp://g/wiki/Radiohttp://g/wiki/Power_(physics)http://g/wiki/Technologyhttp://g/wiki/Microwave_power_transmissionhttp://g/wiki/Beam-powered_propulsionhttp://g/wiki/Transmitterhttp://g/wiki/Receiverhttp://g/wiki/Wavelengthhttp://g/wiki/Rayleigh_Criterionhttp://g/wiki/Diffractionhttp://g/wiki/RFhttp://g/wiki/Radio_Frequencyhttp://g/wiki/Radio_Frequencyhttp://g/wiki/Antenna_(radio)http://showimage%28%27http//www.bluetooth.com/developer/specification/core.asp');http://g/wiki/Electrical_energyhttp://g/wiki/Power_supplyhttp://g/wiki/Electrical_loadhttp://g/wiki/Electrical_gridhttp://g/wiki/Electrical_gridhttp://g/wiki/Informationhttp://g/wiki/Radiohttp://g/wiki/Power_(physics)http://g/wiki/Technologyhttp://g/wiki/Microwave_power_transmissionhttp://g/wiki/Beam-powered_propulsionhttp://g/wiki/Transmitterhttp://g/wiki/Receiverhttp://g/wiki/Wavelengthhttp://g/wiki/Rayleigh_Criterionhttp://g/wiki/Diffractionhttp://g/wiki/RFhttp://g/wiki/Radio_Frequencyhttp://g/wiki/Radio_Frequencyhttp://g/wiki/Antenna_(radio)


17/36

The Rayleigh Criterion dictates that any beam will spread (microwave or laser) andbecome weaker and diffuse over distance, The larger the transmitter antenna or laseraperture, the tighter the beam and the less it will spread as a function of distance (andvice versa). Smaller antennae also suffer from excessive losses due to side lobes.Then the power levels are calculated by combining the above parameters together, and

adding in the gains and losses due to the antenna characteristics and the transparency ofthe medium through which the radiation passes. That process is known as calculating alink budget.Ultimately,beamwidth is physically determined by diffraction due to the dish size inrelation to the wavelength of the electromagnetic radiation used to make the beam.Microwave power beaming can be more efficient than lasers, and is less prone toatmospheric attenuation caused by dust orwater vaporlosing atmosphere to vaporize thewater in contact.Resonant induction

"Resonant inductive coupling" has key implications in solving the main problemassociated with non-resonant inductive coupling and electromagnetic radiation;

specifically, the dependence of efficiency on transmission distance. Electromagneticinduction works on the principle of aprimary coil generating a predominantly magneticfield and a secondary coil being within that field so a current is induced in the secondary.This results in a relatively short range due to the amount of power required to produce anelectromagnetic field. Over greater distances the non-resonant induction method isinefficient and wastes much of the transmitted energy. This is where the resonance comesin and helps efficiency dramatically by "tunneling" the magnetic field to a receiver coilthat resonates at the same frequency. Unlike the multiple-layer secondary of a non-resonant transformer, such receiving coils are single layersolenoids with closely spacedcapacitorplates on each end, which in combination allow the coil to be tuned to thetransmitter frequency thereby eliminating the wide energy wasting "wave problem" and

allowing the energy used to focus in on a specific frequency increasing the range.Beginning in the early 1960s resonant inductive wireless energy transfer was usedsuccessfully in implantable medical devices[13]including such devices as pacemakers andartificial hearts. While the early systems used a resonant receiver coil later systems [14]

implemented resonant transmitter coils as well. These medical devices are designed forhigh efficiency using low power electronics while efficiently accommodating somemisalignment and dynamic twisting of the coils. The separation between the coils inimplantable applications is commonly less than 20 cm. Today resonant inductive energytransfer is regularly used for providing electric power in many commercially availablemedical implantable devices.[15]

Wireless electric energy transfer for experimentally powering electric automobiles and

buses is a higher power application (>10kW) of resonant inductive energy transfer. Highpower levels are required for rapid recharging and high energy transfer efficiency isrequired both for operational economy and to avoid negative environmental impact of thesystem. An experimental electrified roadway test track built circa 1990 achieved 80%energy efficiency while recharging the battery of a prototype bus at a specially equippedbus stop [16][17]. The bus could be outfitted with a retractable receiving coil for greater coilclearance when moving. The gap between the transmit and receive coils was designed tobe less than 10 cm when powered. In addition to buses the use of wireless transfer has
http://g/wiki/Diffusehttp://g/wiki/Side_lobehttp://g/wiki/Gainshttp://g/wiki/Losseshttp://g/wiki/Transparency_(optics)http://g/wiki/Link_Budgethttp://g/wiki/Beamwidthhttp://g/wiki/Attenuationhttp://g/wiki/Water_vaporhttp://g/wiki/Inductive_couplinghttp://g/wiki/Electromagnetic_radiationhttp://g/wiki/Electromagnetic_inductionhttp://g/wiki/Electromagnetic_inductionhttp://g/wiki/Primary_coilhttp://g/wiki/Magnetic_fieldhttp://g/wiki/Magnetic_fieldhttp://g/wiki/Solenoidshttp://g/wiki/Capacitorhttp://g/Wireless_energy_transfer.html#cite_note-12#cite_note-12http://g/Wireless_energy_transfer.html#cite_note-12#cite_note-12http://g/Wireless_energy_transfer.html#cite_note-12#cite_note-12http://g/Wireless_energy_transfer.html#cite_note-13#cite_note-13http://g/Wireless_energy_transfer.html#cite_note-14#cite_note-14http://g/Wireless_energy_transfer.html#cite_note-14#cite_note-14http://g/Wireless_energy_transfer.html#cite_note-15#cite_note-15http://g/Wireless_energy_transfer.html#cite_note-15#cite_note-15http://g/Wireless_energy_transfer.html#cite_note-16#cite_note-16http://g/wiki/Diffusehttp://g/wiki/Side_lobehttp://g/wiki/Gainshttp://g/wiki/Losseshttp://g/wiki/Transparency_(optics)http://g/wiki/Link_Budgethttp://g/wiki/Beamwidthhttp://g/wiki/Attenuationhttp://g/wiki/Water_vaporhttp://g/wiki/Inductive_couplinghttp://g/wiki/Electromagnetic_radiationhttp://g/wiki/Electromagnetic_inductionhttp://g/wiki/Electromagnetic_inductionhttp://g/wiki/Primary_coilhttp://g/wiki/Magnetic_fieldhttp://g/wiki/Magnetic_fieldhttp://g/wiki/Solenoidshttp://g/wiki/Capacitorhttp://g/Wireless_energy_transfer.html#cite_note-12#cite_note-12http://g/Wireless_energy_transfer.html#cite_note-13#cite_note-13http://g/Wireless_energy_transfer.html#cite_note-14#cite_note-14http://g/Wireless_energy_transfer.html#cite_note-15#cite_note-15http://g/Wireless_energy_transfer.html#cite_note-16#cite_note-16


18/36

been investigated for recharging electric automobiles in parking spots and garages aswell.Some of these wireless resonant inductive devices operate at low milliwatt power levelsand are battery powered. Others operate at higher kilowatt power levels. Currentimplantable medical and road electrification device designs achieve more than 75%

transfer efficiency at an operating distance between the transmit and receive coils of lessthan 10 cm.In November 2006, Marin Soljai and other researchers at the Massachusetts Institute ofTechnology applied the near field behaviour well known in electromagnetic theory to awireless power transmission concept based on strongly-coupled resonators.[18][19][20] In atheoretical analysis,[21] they demonstrate that, by designing electromagnetic resonatorsthat suffer minimal loss due to radiation and absorption and have a near field with mid-range extent (namely a few times the resonator size), mid-range efficient wireless energy-transfer is possible. The reason is that, if two such resonant objects are brought in mid-range proximity, their near fields (consisting of so-called 'evanescent waves') couple(evanescent wave coupling) and can allow the energy to tunnel/transfer from one object

to the other within times much shorter than all loss times, which were designed to belong, and thus with the maximum possible energy-transfer efficiency. Since the resonantwavelength is much larger than the resonators, the field can circumvent extraneousobjects in the vicinity and thus this mid-range energy-transfer scheme does not requireline-of-sight. By utilizing in particular the magnetic field to achieve the coupling, thismethod can be safe, since magnetic fields interact weakly with living organisms.

Laser

With a laser beam centered on its panel of photovoltaic cells, a lightweight model plane

makes the first flight of an aircraft powered by a laser beam inside a building at NASA

Marshall Space Flight Center.In the case of electromagnetic radiation closer to visible region of spectrum (10s ofmicrons (um) to 10s ofnm), power can be transmitted by converting electricity into alaserbeam that is then pointed at a solar cell receiver. This mechanism is generallyknown as "PowerBeaming" because the Power is Beamed at a receiver that can convert itto usable electrical energy.Its drawbacks are:

1. Conversion to light, such as with a laser, is moderately inefficient (althoughquantum cascade lasers improve this)

2. Conversion back into electricity is moderately inefficient, with photovoltaic cellsachieving 40%-50% efficiency.[26](Note that conversion efficiency is rather

higher with monochromatic light than with insolation of solar panels).3. Atmospheric absorption causes losses.4. As with microwave beaming, this method requires a direct line of sight with the

target.There are also a few unique advantages ofLaserbased energy transfer that outweigh thedisadvantages.

1. collimated monochromatic wavefront propagation allows narrow beam cross-section area for energy confinement over large ranges.
http://g/wiki/Marin_Solja?i?http://g/wiki/MIThttp://g/wiki/MIThttp://g/Wireless_energy_transfer.html#cite_note-MIT_theory_news-17#cite_note-MIT_theory_news-17http://g/Wireless_energy_transfer.html#cite_note-MIT_Physics_World_1-18#cite_note-MIT_Physics_World_1-18http://g/Wireless_energy_transfer.html#cite_note-MIT_NewScientist_2006-19#cite_note-MIT_NewScientist_2006-19http://g/Wireless_energy_transfer.html#cite_note-20#cite_note-20http://g/wiki/Resonancehttp://g/wiki/Evanescent_wave_couplinghttp://g/wiki/Quantum_tunnelinghttp://g/wiki/Micrometrehttp://g/wiki/Nanometerhttp://g/wiki/Laserhttp://g/wiki/Solar_cellhttp://g/wiki/Quantum_cascade_laserhttp://g/Wireless_energy_transfer.html#cite_note-25#cite_note-25http://g/Wireless_energy_transfer.html#cite_note-25#cite_note-25http://g/Wireless_energy_transfer.html#cite_note-25#cite_note-25http://g/wiki/Laserhttp://g/wiki/Collimatedhttp://g/wiki/Wavefronthttp://g/wiki/File:ED03-0249-18.jpghttp://g/wiki/Marin_Solja?i?http://g/wiki/MIThttp://g/wiki/MIThttp://g/Wireless_energy_transfer.html#cite_note-MIT_theory_news-17#cite_note-MIT_theory_news-17http://g/Wireless_energy_transfer.html#cite_note-MIT_Physics_World_1-18#cite_note-MIT_Physics_World_1-18http://g/Wireless_energy_transfer.html#cite_note-MIT_NewScientist_2006-19#cite_note-MIT_NewScientist_2006-19http://g/Wireless_energy_transfer.html#cite_note-20#cite_note-20http://g/wiki/Resonancehttp://g/wiki/Evanescent_wave_couplinghttp://g/wiki/Quantum_tunnelinghttp://g/wiki/Micrometrehttp://g/wiki/Nanometerhttp://g/wiki/Laserhttp://g/wiki/Solar_cellhttp://g/wiki/Quantum_cascade_laserhttp://g/Wireless_energy_transfer.html#cite_note-25#cite_note-25http://g/wiki/Laserhttp://g/wiki/Collimatedhttp://g/wiki/Wavefront


19/36

2. compact size ofsolid state lasers-photovoltaics semiconductor diodes allows easeof integration into products with small form factors.

3. ability to operate with zero radio-frequency interference to existingcommunication devices i.e. wi-fi and cell phones.

4. control of Wireless Energy Access, instead ofomnidirectional transfer where

there can be no authentication before transferring energy.These allow laser-based Wireless Energy Transfer concept to compete with conventionalenergy transfer methods.The Laser "PowerBeaming" technology has been mostly explored in military weapons[27][28][29]and aerospace[30][31] applications and is now being developed for commercial andconsumer electronics Low-Power applications. Wireless energy transfer system usinglaser for consumer space has to satisfy Laser safety requirements standardized under IEC60825.To develop an understanding of the trade-offs of Laser "a special type of light wave"based system:[32][33][34][35]

1. Propagation of a laser beam[36][37][38] (on how Laser beam propagation is much

less affected by diffraction limits)2. Coherence and the range limitation problem (on how spatial and spectralcoherence characteristics of Lasers allows better distance-to-power capabilities[39])

3. Airy disk(on how most fundamentally wavelength dictates the size of a disk withdistance)

4. Applications of laser diodes (on how the laser sources are utilized in variousindustries and their sizes are reducing for better integration)

Geoffrey Landis[40][41][42] is one of the pioneers ofSolar Power Satellite[43] and Laser-based transfer of energy especially for Space and Lunar missions. The continuouslyincreasing demand for safe and frequent space missions has resulted in serious thoughtson a futuristic Space elevator[44][45]that would be powered by Lasers. NASA's Spaceelevator need wireless power to be beamed to it, for it to climb a tether[46].NASA's Dryden Flight Research Center has demonstrated flight of a lightweightunmanned model plane powered by a laser beam [47]. This concept allows a periodicrecharging using Laser beam and an unlimited time in air.

WITRICITY

WiTricity, aportmanteau for wireless electricity, is a term which describes wireless

energy transfer, the ability to provide electrical energy to remote objects without wires.

The term was coined initially in 2005 by Dave Gerding and later used for the project of a

MIT research team led by Prof. Marin Soljai in 2007
http://g/wiki/Solid_state_laserhttp://g/wiki/Photovoltaicshttp://g/wiki/Radio-frequencyhttp://g/wiki/Wi-fihttp://g/wiki/Cell_phonehttp://g/wiki/Omnidirectionalhttp://g/wiki/Authenticationhttp://g/wiki/Directed-energy_weaponhttp://g/Wireless_energy_transfer.html#cite_note-26#cite_note-26http://g/Wireless_energy_transfer.html#cite_note-27#cite_note-27http://g/Wireless_energy_transfer.html#cite_note-28#cite_note-28http://g/Wireless_energy_transfer.html#cite_note-28#cite_note-28http://g/Wireless_energy_transfer.html#cite_note-28#cite_note-28http://g/wiki/Laser_propulsionhttp://g/Wireless_energy_transfer.html#cite_note-29#cite_note-29http://g/Wireless_energy_transfer.html#cite_note-30#cite_note-30http://g/Wireless_energy_transfer.html#cite_note-30#cite_note-30http://g/wiki/Consumer_electronicshttp://g/wiki/Laser_safetyhttp://g/Wireless_energy_transfer.html#cite_note-31#cite_note-31http://g/Wireless_energy_transfer.html#cite_note-32#cite_note-32http://g/Wireless_energy_transfer.html#cite_note-33#cite_note-33http://g/Wireless_energy_transfer.html#cite_note-34#cite_note-34http://g/wiki/Diffraction#Propagation_of_a_laser_beamhttp://g/Wireless_energy_transfer.html#cite_note-35#cite_note-35http://g/Wireless_energy_transfer.html#cite_note-36#cite_note-36http://g/Wireless_energy_transfer.html#cite_note-36#cite_note-36http://g/Wireless_energy_transfer.html#cite_note-36#cite_note-36http://g/Wireless_energy_transfer.html#cite_note-37#cite_note-37http://g/wiki/Coherence_(physics)#Quantum_coherence_and_the_range_limitation_problemhttp://g/Wireless_energy_transfer.html#cite_note-38#cite_note-38http://g/wiki/Airy_diskhttp://g/wiki/Laser_diode#Applications_of_laser_diodeshttp://g/wiki/Geoffrey_A._Landishttp://g/Wireless_energy_transfer.html#cite_note-39#cite_note-39http://g/Wireless_energy_transfer.html#cite_note-40#cite_note-40http://g/Wireless_energy_transfer.html#cite_note-40#cite_note-40http://g/Wireless_energy_transfer.html#cite_note-40#cite_note-40http://g/Wireless_energy_transfer.html#cite_note-41#cite_note-41http://g/wiki/Solar_Power_Satellitehttp://g/Wireless_energy_transfer.html#cite_note-42#cite_note-42http://g/wiki/Space_elevatorhttp://g/Wireless_energy_transfer.html#cite_note-43#cite_note-43http://g/Wireless_energy_transfer.html#cite_note-44#cite_note-44http://g/Wireless_energy_transfer.html#cite_note-44#cite_note-44http://g/Wireless_energy_transfer.html#cite_note-44#cite_note-44http://g/Wireless_energy_transfer.html#cite_note-45#cite_note-45http://g/Wireless_energy_transfer.html#cite_note-45#cite_note-45http://g/Wireless_energy_transfer.html#cite_note-45#cite_note-45http://g/Wireless_energy_transfer.html#cite_note-46#cite_note-46http://g/wiki/Portmanteauhttp://g/wiki/Electricityhttp://g/wiki/Wireless_energy_transferhttp://g/wiki/Wireless_energy_transferhttp://g/wiki/Electrical_energyhttp://g/wiki/Marin_Solja?i?http://g/wiki/Solid_state_laserhttp://g/wiki/Photovoltaicshttp://g/wiki/Radio-frequencyhttp://g/wiki/Wi-fihttp://g/wiki/Cell_phonehttp://g/wiki/Omnidirectionalhttp://g/wiki/Authenticationhttp://g/wiki/Directed-energy_weaponhttp://g/Wireless_energy_transfer.html#cite_note-26#cite_note-26http://g/Wireless_energy_transfer.html#cite_note-27#cite_note-27http://g/Wireless_energy_transfer.html#cite_note-28#cite_note-28http://g/wiki/Laser_propulsionhttp://g/Wireless_energy_transfer.html#cite_note-29#cite_note-29http://g/Wireless_energy_transfer.html#cite_note-30#cite_note-30http://g/wiki/Consumer_electronicshttp://g/wiki/Laser_safetyhttp://g/Wireless_energy_transfer.html#cite_note-31#cite_note-31http://g/Wireless_energy_transfer.html#cite_note-32#cite_note-32http://g/Wireless_energy_transfer.html#cite_note-33#cite_note-33http://g/Wireless_energy_transfer.html#cite_note-34#cite_note-34http://g/wiki/Diffraction#Propagation_of_a_laser_beamhttp://g/Wireless_energy_transfer.html#cite_note-35#cite_note-35http://g/Wireless_energy_transfer.html#cite_note-36#cite_note-36http://g/Wireless_energy_transfer.html#cite_note-37#cite_note-37http://g/wiki/Coherence_(physics)#Quantum_coherence_and_the_range_limitation_problemhttp://g/Wireless_energy_transfer.html#cite_note-38#cite_note-38http://g/wiki/Airy_diskhttp://g/wiki/Laser_diode#Applications_of_laser_diodeshttp://g/wiki/Geoffrey_A._Landishttp://g/Wireless_energy_transfer.html#cite_note-39#cite_note-39http://g/Wireless_energy_transfer.html#cite_note-40#cite_note-40http://g/Wireless_energy_transfer.html#cite_note-41#cite_note-41http://g/wiki/Solar_Power_Satellitehttp://g/Wireless_energy_transfer.html#cite_note-42#cite_note-42http://g/wiki/Space_elevatorhttp://g/Wireless_energy_transfer.html#cite_note-43#cite_note-43http://g/Wireless_energy_transfer.html#cite_note-44#cite_note-44http://g/Wireless_energy_transfer.html#cite_note-45#cite_note-45http://g/Wireless_energy_transfer.html#cite_note-46#cite_note-46http://g/wiki/Portmanteauhttp://g/wiki/Electricityhttp://g/wiki/Wireless_energy_transferhttp://g/wiki/Wireless_energy_transferhttp://g/wiki/Electrical_energyhttp://g/wiki/Marin_Solja?i?


20/36

Overview

WiTricity is based on strong coupling between electromagnetic resonant objects totransfer energy wirelessly between them. The system consists of transmitters andreceivers that contain magnetic loop antennas critically tuned to the same frequency. Dueto operating in the electromagnetic near-field, the receiving devices must be no more than

about a quarter wavelength from the transmitter (which is a few meters at the frequencyused by the example system). In their first paper, the group also simulated GHz dielectricresonators.Unlike the far field wireless power transmission systems based on traveling EM waves,WiTricity employs near fieldinductive coupling through magnetic fields,[clarification needed]

which interact far more weakly with surrounding objects, including biological tissue. Inparticular, it is based on using 'strongly-coupled' resonances to achieve a high power-transmission efficiency. Aristeidis Karalis, referring to the team's experimentaldemonstration, says that "the usual non-resonant magnetic induction would be almost 1million times less efficient in this particular system".[2] The researchers suggest that theexposure levels will be below the threshold for FCC safety regulations, and the radiated-

power levels will also comply with the FCC radio interference regulations.It is not known exactly why this technology had not been developed. Researchersattribute it to various reasons ranging from the limitations of well-known physical laws,to simply a lack of need. Only recently have modern consumers obtained a high numberof portable electronic devices which currently require batteries and plug-in chargers.[2]

Experimental demonstration

The MIT researchers successfully demonstrated the ability to power a 60-watt light bulbwirelessly, using two copper coils of 60 cm (24in) diameterthat were 2m (7ft) away, atroughly 45% efficiency.[3] The coils were designed to resonate together at 10MHz andwere oriented along the same axis. One was connected inductively to a power source, andthe other one to a bulb. The setup powered the bulb on, even when the direct line of sight

was blocked using a wooden panel.Applications

This technology can potentially be used in a large variety of applications, includingconsumer, industrial, medical and military. Its aim is to reduce our dependence onbatteries.Further applications for this technology include transmission of information it wouldnot interfere with radio waves and thus could be used as a cheap and efficientcommunication device without requiring a license or a government permit.

Wireless security is the prevention of unauthorized access or damage to computers usingwireless networks.

Wireless networks are very common, both for organizations and individuals. Many laptopcomputers have wireless cardspre-installed. The ability to enter a network while mobilehas great benefits. However, wireless networking has many security issues.[1]Hackershave found wireless networks relatively easy to break into, and even use wirelesstechnology to crack into wired networks. As a result, it's very important that enterprisesdefine effective wireless security policies that guard against unauthorized access toimportant resources.[2]
http://g/wiki/Wireless_energy_transferhttp://g/wiki/Magnetic_loophttp://g/wiki/Near-fieldhttp://g/wiki/Dielectric_resonatorhttp://g/wiki/Dielectric_resonatorhttp://g/wiki/Far_fieldhttp://g/wiki/Near_fieldhttp://g/wiki/Inductive_couplinghttp://g/wiki/Magnetic_fieldhttp://g/wiki/Wikipedia:Please_clarifyhttp://g/wiki/Wikipedia:Please_clarifyhttp://g/wiki/Wikipedia:Please_clarifyhttp://g/wiki/Electromagnetic_inductionhttp://g/Witricity.html#cite_note-MIT_experiment_news-1#cite_note-MIT_experiment_news-1http://g/Witricity.html#cite_note-MIT_experiment_news-1#cite_note-MIT_experiment_news-1http://g/Witricity.html#cite_note-MIT_experiment_news-1#cite_note-MIT_experiment_news-1http://g/Witricity.html#cite_note-MIT_experiment_news-1#cite_note-MIT_experiment_news-1http://g/wiki/Watthttp://g/wiki/Diameterhttp://g/Witricity.html#cite_note-2#cite_note-2http://g/wiki/Megahertzhttp://g/wiki/Information_transmissionhttp://g/wiki/Radio_waveshttp://g/wiki/Wirelesshttp://g/wiki/Wirelesshttp://g/wiki/Wireless_cardhttp://g/Wireless_security.html#cite_note-0#cite_note-0http://g/Wireless_security.html#cite_note-0#cite_note-0http://g/wiki/Black_hathttp://g/Wireless_security.html#cite_note-1#cite_note-1http://g/wiki/Wireless_energy_transferhttp://g/wiki/Magnetic_loophttp://g/wiki/Near-fieldhttp://g/wiki/Dielectric_resonatorhttp://g/wiki/Dielectric_resonatorhttp://g/wiki/Far_fieldhttp://g/wiki/Near_fieldhttp://g/wiki/Inductive_couplinghttp://g/wiki/Magnetic_fieldhttp://g/wiki/Wikipedia:Please_clarifyhttp://g/wiki/Electromagnetic_inductionhttp://g/Witricity.html#cite_note-MIT_experiment_news-1#cite_note-MIT_experiment_news-1http://g/Witricity.html#cite_note-MIT_experiment_news-1#cite_note-MIT_experiment_news-1http://g/wiki/Watthttp://g/wiki/Diameterhttp://g/Witricity.html#cite_note-2#cite_note-2http://g/wiki/Megahertzhttp://g/wiki/Information_transmissionhttp://g/wiki/Radio_waveshttp://g/wiki/Wirelesshttp://g/wiki/Wirelesshttp://g/wiki/Wireless_cardhttp://g/Wireless_security.html#cite_note-0#cite_note-0http://g/wiki/Black_hathttp://g/Wireless_security.html#cite_note-1#cite_note-1


21/36

The risks to users of wireless technology have increased as the service has become morepopular. There were relatively few dangers when wireless technology was firstintroduced. Crackers had not yet had time to latch on to the new technology and wirelesswas not commonly found in the work place. However, there are a great number ofsecurity risks associated with the current wireless protocols and encryption methods, and

in the carelessness and ignorance that exists at the user and corporate IT level.[3]

Crackingmethods have become much more sophisticated and innovative with wireless. Crackinghas also become much easier and more accessible with easy-to-use Windows orLinux-based tools being made available on the web at no charge.Some organizations that have no wireless access points installed do not feel that theyneed to address wireless security concerns. In-Stat MDR and META Group haveestimated that 95% of all corporate laptop computers that were planned to be purchasedin 2005 were equipped with wireless. Issues can arise in a supposedly non-wirelessorganization when a wireless laptop is plugged into the corporate network. A crackercould sit out in the parking lot and gather info from it through laptops and/or otherdevices as handhelds, or even break in through this wireless card-equipped laptop and

gain access to the wired networkWi-Fi versus BluetoothWi-Fi and Bluetooth are designed to coexist in the network, and although they certainlyhave overlapping applications, each has its distinct zones of advantage.The biggest differences between Wi-Fi and Bluetooth are

_Distance: Bluetooth is lower powered, which means its signal can only go shortdistances (up to 30 feet). 802.11 technologies can cover your home, and in some casesmore, depending on the antenna that you use.Note:New software for Bluetooth devices is enabling the creation of mesh networks inthe home, where interconnected Bluetooth devices can create a large mesh network thatcan be interconnected to the Internet thereby creating a network similar to an 802.11bnetwork in the home, for instance._Application: Bluetooth is designed as a replacement of cables: that is, trying to get ridof that huge tangle of cables that link your mouse, printer, monitor, scanner, and otherdevices on your desk and around your home. In fact, the first Bluetooth device was aBluetooth headset, eliminating that annoying cable to the telephone that got in the way oftyping. New cars are also becoming outfitted with Bluetooth so that you can use your cellphone in your car, with your cars stereo speakers and an onboard microphone serving asyour hands-free capability.RADIO WAVESRadio waves are electromagnetic waves occurring on the radio frequency portion of theelectromagnetic spectrum.Radio waves were first predicted by mathematical work done in 1865 by James ClerkMaxwell. Maxwell noticed wavelike properties of light and similarities in electrical andmagnetic observations. He then proposed equations that described light waves and radiowaves as waves of electromagnetism that travel in space. In 1887, Heinrich Hertzdemonstrated the reality of Maxwell's electromagnetic waves by experimentally
http://g/wiki/Encryptionhttp://g/Wireless_security.html#cite_note-2#cite_note-2http://g/Wireless_security.html#cite_note-2#cite_note-2http://g/wiki/Microsoft_Windowshttp://g/wiki/Linuxhttp://g/wiki/Access_pointhttp://g/wiki/Electromagnetic_radiationhttp://g/wiki/Radio_frequencyhttp://g/wiki/Electromagnetic_spectrumhttp://g/wiki/James_Clerk_Maxwellhttp://g/wiki/James_Clerk_Maxwellhttp://g/wiki/Heinrich_Hertzhttp://g/wiki/Encryptionhttp://g/Wireless_security.html#cite_note-2#cite_note-2http://g/wiki/Microsoft_Windowshttp://g/wiki/Linuxhttp://g/wiki/Access_pointhttp://g/wiki/Electromagnetic_radiationhttp://g/wiki/Radio_frequencyhttp://g/wiki/Electromagnetic_spectrumhttp://g/wiki/James_Clerk_Maxwellhttp://g/wiki/James_Clerk_Maxwellhttp://g/wiki/Heinrich_Hertz


22/36

generating radio waves in his laboratory. Many inventions followed, making practical theuse of radio waves to transfer information through space.Nikola Tesla and Guglielmo Marconi are credited with inventing systems to allow radiowaves to be used for communication

IEEE USPer IEEE Std 521-2002. Reaffirmed standard of 1984; originally dates back to WWII.

Band Frequency range Origin of name

HF band 3 to 30 MHz High Frequency

VHF

band30 to 300 MHz Very High Frequency

UHF

band300 to 1000 MHz

Ultra High Frequency

Frequencies from 216 to 450 MHz were sometimes called P-band: Previous, since early British radarused this band butlater switched to higher frequencies.

L band 1 to 2 GHz Long waveS band 2 to 4 GHz Short wave

C band 4 to 8 GHz Compromise between S and X

X band 8 to 12 GHz Used in WW II forfire control, X for cross (as in crosshair)

Ku band 12 to 18 GHz Kurz-under

K band 18 to 27 GHz GermanKurz (short)

Ka band 27 to 40 GHz Kurz-above

V band 40 to 75 GHz

W band 75 to 110 GHz W follows V in the alphabet

mm band 110 to 300 GHz

FUTUREMany of us firmly believe that wireless technology is to computing what the PC was tocomputing back in the 80s, nothing short of a revolution. On the other hand, just likemany other emerging technologies before it, this one is not without its share ofchallenges.On one side, we have the visionaries, the evangelizers, preaching the benefits of mobiledata access and, specifically, wireless connectivity. There are more than a few earlyadopters, who have successfully mobilized business applications and are reaping thebenefits. On the other hand there are a few who are not so sure the promised return oninvestment is really there, or remain yet to be convinced that the technology is ready fortheir specific enterprise requirements.So then, what is the future for wireless technology?Will we be able to access applications and data anywhere, at anytime, updating data inreal-time, securely, efficiently, effectively, affordably? Will we see the end of messywires protruding from computers, printers, modems, scanners, projectors and otherperipherals? Will we be able to walk up to a wireless printer at an Airport, turn on ourPocket PC, tablet or laptop and print that proposal or presentation we need, perfectly
http://g/wiki/Nikola_Teslahttp://g/wiki/Guglielmo_Marconihttp://g/wiki/WWIIhttp://g/wiki/High_frequencyhttp://g/wiki/VHFhttp://g/wiki/VHFhttp://g/wiki/UHFhttp://g/wiki/UHFhttp://g/wiki/United_Kingdomhttp://g/wiki/Radarhttp://g/wiki/L_bandhttp://g/wiki/S_bandhttp://g/wiki/C_bandhttp://g/wiki/X_bandhttp://g/wiki/World_War_IIhttp://g/wiki/Fire-control_systemhttp://g/wiki/Crosshairhttp://g/wiki/Ku_bandhttp://g/wiki/Ku_bandhttp://g/wiki/Ku_bandhttp://g/wiki/K_bandhttp://g/wiki/German_languagehttp://g/wiki/Ka_bandhttp://g/wiki/Ka_bandhttp://g/wiki/Ka_bandhttp://g/wiki/V_bandhttp://g/wiki/W_bandhttp://g/wiki/Alphabethttp://g/wiki/Mm_wavehttp://g/wiki/Nikola_Teslahttp://g/wiki/Guglielmo_Marconihttp://g/wiki/WWIIhttp://g/wiki/High_frequencyhttp://g/wiki/VHFhttp://g/wiki/VHFhttp://g/wiki/UHFhttp://g/wiki/UHFhttp://g/wiki/United_Kingdomhttp://g/wiki/Radarhttp://g/wiki/L_bandhttp://g/wiki/S_bandhttp://g/wiki/C_bandhttp://g/wiki/X_bandhttp://g/wiki/World_War_IIhttp://g/wiki/Fire-control_systemhttp://g/wiki/Crosshairhttp://g/wiki/Ku_bandhttp://g/wiki/K_bandhttp://g/wiki/German_languagehttp://g/wiki/Ka_bandhttp://g/wiki/V_bandhttp://g/wiki/W_bandhttp://g/wiki/Alphabethttp://g/wiki/Mm_wave


23/36

formatted, regardless of the operating system or application we are running and printerdrivers we may have in our device? Will we be able to create a mobile version of ourexisting SAP, Siebel, Oracle or SQL-based application, without fuss, without it costing afortune, and run it over a 1XRTT or GPRS network, securely, dependably? Will we beable to make and receive phone calls, or manage our email and calendar from a hand-held

device, using voice over Wireless LAN or unified messaging technology while connectedto a WiFi network at an Airport, convention center or coffee shop?Let us analyze the situations outlined above for a moment. Wireless access anytime,anywhere? Is it real? Answer: not today. Maybe most of the time, from most places,but anytime, anywhere? Not yet, not for a while. And if anyone is telling youotherwise, they either do not understand the question, or do not know much aboutmobility and wireless solutions.Is it possible for corporate files and applications to be accessed and updated in real-time,securely, efficiently, effectively and affordably? Answer: yes. Sophisticate wirelessapplication gateways, middle-ware, no-coding-required application design tools, XML-libraries, single-login for multiple applications, encryption and secured access

functionality make it possible today. It is only getting easier, cheaper and faster towirelessly enable existing and/or create new mobile applications. To get close to theanytime, anywhere dream, there are reliable technology solutions available that allowusers to wirelessly and securely access and download data from a server to a device,create or change information while not on line, and then re-connect and synchronize backwith the server. Very effective when users need to access data or create transactions deepwithin a building or basement, or in areas outside cellular coverage. Add the righthardware and software technology to a well-defined business plan and a properlyorganized and executed systems integration strategy and you have the recipe for successin wireless.Are we going to see the end of messy wires protruding from computers, printers,modems, scanners, projectors and other peripherals? Answer: it depends. Subject to theinherent restrictions of battery life, the near future reality is one of devices totallyinterconnected without wires. Blue-tooth and 802.11b printers, projectors, printers andaccess devices, for example, make it possible. Unfortunately, the power cord is not goingaway anytime soon.What about voice over WLAN and unified messaging? Well, technology solutions areavailable today to make and receive phone calls, manage email and calendar and runother applications from one device while walking un-tethered within a WiFi hotspot. Notonly that, technology is available to allow users to walk away from an 802.11 networkand automatically connect to a GPRS or 1XRTT network, seamlessly maintaining thesame IP session. Imagine the possibilities once 3G networks start delivering consistentbandwidth. Wireless printing from any device? Coming soon to an Airport, ConventionCenter, Hotel or Coffee Shop near you.Availability isnt everythingNow, the fact that all this is available, reliable and surprisingly affordable does not meanthat it should be deployed, just to keep up with the pace of technology.One of the problems with the whole wireless and mobility story is that in many casestechnology objectives have overtaken business objectives. As a result, wireless andmobility projects have been implemented without solid planning, business cases, proper


24/36

cost/benefit analysis and obviously without executive management buying into or fullysupporting the project. Many still think wireless and mobility is about devices andnetworks rather than systems integration. Not unlike what has happened many times overin the IT world, the results have been predictable. Without executive managementsupport, projects are soon abandoned or, worse yet, crash and burn, with the associated

casualties and personal embarrassment making big news.Sadly, this situation has hampered the implementation of wireless and mobility solutionsin areas that could have substantial benefits for corporations, institutions or the public atlarge. The wireless industry is not without blame, at times being guilty of over-simplifying the work of implementing a wireless LAN or WAN. Setting up a wirelessLAN is often advertised as being as simple as purchasing a few Access Points, pluggingthem into an existing Ethernet LAN and turning on WEP encryption (or sometimes noteven that). Or purchasing a few Sierra Wireless cards, installing them into a laptop, tabletor Pocket PC, instantly creating a ready-made wireless environment. At first sight, theperceived benefits are immense. Imagine being able to access your intranet, search theweb for information from wherever the network allows you to connect and access all

those web-enabled applications your IT department has built over the years. Untilsomeone finds out, usually at the worst moment or in the worst possible way thatcorporate security, networking and other key guidelines have been ignored and a threat tocorporate data has been created. Or that after the initial $50 dollar a month, unlimitedaccess incentive plan has expired, usually after the first six months, the cost jumps to$500 or $600 per month in wireless data charges, or that making a voice call using aGSM or 1XRTT service costs substantially more than a regular cellular voice call.what is the future of wireless?Well, although the road has been bumpy, the future is bright. Some may think thatdeployment of wireless LAN/WAN solutions has stalled. I would beg to differ. It is onlystarting. Many are waiting for wireless LANs to become more secure. Well, many arestill waiting for the Internet to become more secure also. Others are taking full advantageof proven IT design, implementation and support techniques, reliable technology andcommon sense procedures and guidelines to deploy wireless networks that are as secureas any wired environment. And the list of success stories, corporations and institutionsrealizing important productivity gains as a result of deploying wireless technology keepsgrowing.

InfraRed Devices and Drivers

Infrared and IrDA connections in palmtops and computers.IrDA was designed for cheap, bidirectional, short range, fairly directional point to pointconnections. Initially up to 115.2kbps via additions to an RS232C serial port, and latter

up to 4 Mbps. They use baseband return to zero inverted modulation. The 4 Mbps schemeuses a 4 pulse position modulation scheme of two bits per pulse.Remote controls for TVs and similar are totally different. They use approximately 40 kHzsignals and pulse width modulation, with a variety of protocols. They are customised forlow speed, wide angle, one way, long range connections. These are not IrDA compliant.You can find one piece receiver transmitter packages for remote signals at low cost, anddrive these from TTL. IrDA can't normally do TV remote control signals, and are shorterrange, but you can often fake the signals in software. Infrared connections for keyboards


25/36

and the like do not have to follow any standard, as the manufacturer supplies both ends ofthe connection.

Uses

A roof mounted Wi-Fi antenna
http://en.wikipedia.org/wiki/File:WIFI_Amp_Setup.JPGhttp://en.wikipedia.org/wiki/File:WIFI_Amp_Setup.JPGhttp://en.wikipedia.org/wiki/File:Patras_Wireless_Network_1.jpghttp://en.wikipedia.org/wiki/File:Patras_Wireless_Network_1.jpg


26/36

A Wi-Fi antenna

A Wi-Fi enabled device such as a PC, game console,mobile phone,MP3 playerorPDAcan connect to the Internetwhen within range of a wireless networkconnected to theInternet. 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 toset upmesh networks, for example, in London.[1] Both architectures can operate incommunity networks.

In addition to restricted use in homes and offices, Wi-Fi can make access publiclyavailable at Wi-Fi hotspots provided either free of charge or to subscribers to variousproviders. Organizations andbusinesses such as airports, hotels and restaurants oftenprovide free hotspots to attract or assist clients. Enthusiasts or authorities who wish toprovide services or even to promote business in a given area sometimes provide free Wi-Fi access. Metropolitan-wide Wi-Fi (Muni-Fi) already has more than 300projects inprocess.[2] There were 879 Wi-Fi basedWireless Internet service providers in the Czech

Republicas of May 2008.[3][4]

Wi-Fi also allows connectivity inpeer-to-peer(wireless ad-hoc network) mode, whichenables devices to connect directly with each other. This connectivity mode can proveuseful in consumer electronicsand gaming applications.

When wireless networking technology first entered the market many problems ensuedfor 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 theneeds of the end-userand to allow the technology to mature. The Alliance created thebranding 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 computerscan network toeach other and connect to the Internet,mobile computers can connect to the Internet fromany 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
http://en.wikipedia.org/wiki/Personal_computerhttp://en.wikipedia.org/wiki/Game_consolehttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/MP3_playerhttp://en.wikipedia.org/wiki/Personal_digital_assistanthttp://en.wikipedia.org/wiki/Personal_digital_assistanthttp://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Wireless_networkhttp://en.wikipedia.org/wiki/Wireless_access_pointhttp://en.wikipedia.org/wiki/Hotspot_(Wi-Fi)http://en.wikipedia.org/wiki/Wireless_mesh_networkhttp://en.wikipedia.org/wiki/Wireless_mesh_networkhttp://g/New%20Folder/WiFi.html#cite_note-0http://en.wikipedia.org/wiki/Wireless_community_networkhttp://en.wikipedia.org/wiki/Hotspot_(Wi-Fi)http://en.wikipedia.org/wiki/Businesshttp://en.wikipedia.org/wiki/Municipal_wireless_networkhttp://en.wikipedia.org/wiki/Projecthttp://g/New%20Folder/WiFi.html#cite_note-1http://en.wikipedia.org/wiki/Wireless_Internet_service_providerhttp://en.wikipedia.org/wiki/Wireless_Internet_service_providerhttp://en.wikipedia.org/wiki/Czech_Republichttp://en.wikipedia.org/wiki/Czech_Republichttp://en.wikipedia.org/wiki/Czech_Republichttp://g/New%20Folder/WiFi.html#cite_note-2http://g/New%20Folder/WiFi.html#cite_note-3http://en.wikipedia.org/wiki/Peer-to-peerhttp://en.wikipedia.org/wiki/Wireless_ad-hoc_networkhttp://en.wikipedia.org/wiki/Consumer_electronicshttp://en.wikipedia.org/wiki/Consumer_electronicshttp://en.wikipedia.org/wiki/Wireless_networkinghttp://en.wikipedia.org/wiki/Communityhttp://en.wikipedia.org/wiki/End-userhttp://en.wikipedia.org/wiki/End-userhttp://en.wikipedia.org/wiki/Interoperablehttp://en.wikipedia.org/wiki/Personal_computerhttp://en.wikipedia.org/wiki/Personal_computerhttp://en.wikipedia.org/wiki/Personal_computerhttp://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Mobile_computerhttp://en.wikipedia.org/wiki/Mobile_computerhttp://en.wikipedia.org/wiki/Digital_camerahttp://en.wikipedia.org/wiki/Routerhttp://en.wikipedia.org/wiki/Digital_subscriber_linehttp://en.wikipedia.org/wiki/Cable_modemhttp://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Internetworkinghttp://en.wikipedia.org/wiki/File:Patras_Wireless_Network_1.jpghttp://en.wikipedia.org/wiki/File:Patras_Wireless_Network_1.jpghttp://en.wikipedia.org/wiki/Personal_computerhttp://en.wikipedia.org/wiki/Game_consolehttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/MP3_playerhttp://en.wikipedia.org/wiki/Personal_digital_assistanthttp://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Wireless_networkhttp://en.wikipedia.org/wiki/Wireless_access_pointhttp://en.wikipedia.org/wiki/Hotspot_(Wi-Fi)http://en.wikipedia.org/wiki/Wireless_mesh_networkhttp://g/New%20Folder/WiFi.html#cite_note-0http://en.wikipedia.org/wiki/Wireless_community_networkhttp://en.wikipedia.org/wiki/Hotspot_(Wi-Fi)http://en.wikipedia.org/wiki/Businesshttp://en.wikipedia.org/wiki/Municipal_wireless_networkhttp://en.wikipedia.org/wiki/Projecthttp://g/New%20Folder/WiFi.html#cite_note-1http://en.wikipedia.org/wiki/Wireless_Internet_service_providerhttp://en.wikipedia.org/wiki/Czech_Republichttp://en.wikipedia.org/wiki/Czech_Republichttp://g/New%20Folder/WiFi.html#cite_note-2http://g/New%20Folder/WiFi.html#cite_note-3http://en.wikipedia.org/wiki/Peer-to-peerhttp://en.wikipedia.org/wiki/Wireless_ad-hoc_networkhttp://en.wikipedia.org/wiki/Consumer_electronicshttp://en.wikipedia.org/wiki/Wireless_networkinghttp://en.wikipedia.org/wiki/Communityhttp://en.wikipedia.org/wiki/End-userhttp://en.wikipedia.org/wiki/Interoperablehttp://en.wikipedia.org/wiki/Personal_computerhttp://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Mobile_computerhttp://en.wikipedia.org/wiki/Digital_camerahttp://en.wikipedia.org/wiki/Routerhttp://en.wikipedia.org/wiki/Digital_subscriber_linehttp://en.wikipedia.org/wiki/Cable_modemhttp://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Internetworking


27/36

all devices connected (wirelessly or by cable) to them. One can also connect Wi-Fidevices in ad-hoc mode for client-to-client connections without a router. Wi-Fi alsoenables places which would traditionally not have network to be connected, for examplebathrooms, kitchens and garden sheds. The "father of Wi-Fi", Vic Hayes, stated thatbeing able to access the internet whilst answering a call of nature was "one of life's most

liberating experiences".

As of 2007 Wi-Fi technology had spread widely within business and industrial sites. Inbusiness environments, just like other environments, increasing the number of Wi-Fiaccess-points provides redundancy, support for fastroaming and increased overallnetwork-capacity by using more channels or by defining smallercells. Wi-Fi enableswireless voice-applications (VoWLAN or WVOIP). Over the years, Wi-Fiimplementations have moved toward "thin" access-points, with more of the networkintelligence housed in a centralized network appliance, relegating individual access-points to the role of mere "dumb" radios. Outdoor applications may utilize true meshtopologies. As of 2007 Wi-Fi installations can provide a secure computer networking

gateway, firewall,DHCPserver,intrusion detection system, and other functions.

[edit] Advantages and challenges

A keychain size Wi-Fi detector.

[edit] Operational advantages

Wi-Fi allows local area networks(LANs) to be deployed without wires for client devices,typically reducing the costs of network deployment and expansion. Spaces where cablescannot be run, such as outdoor areas and historical buildings, can host wireless LANs.

Wireless network adapters are now built into most laptops. The price ofchipsets for Wi-Fi continues to drop, making it an economical networking option included in even moredevices. 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 Wi-FiAlliance are backwards compatible. Wi-Fi is a global set of standards. Unlike mobiletelephones, any standard Wi-Fi device will work anywhere in the world.
http://en.wikipedia.org/wiki/Ad-hochttp://en.wikipedia.org/wiki/Bathroomhttp://en.wikipedia.org/wiki/Kitchenhttp://en.wikipedia.org/wiki/Garden_shedhttp://en.wikipedia.org/wiki/Garden_shedhttp://en.wikipedia.org/wiki/Roaminghttp://en.wikipedia.org/wiki/Roaminghttp://en.wikipedia.org/wiki/Cellular_networkhttp://en.wikipedia.org/wiki/Cellular_networkhttp://en.wikipedia.org/wiki/Voice_over_WLANhttp://en.wikipedia.org/wiki/Intelligence_(disambiguation)http://en.wikipedia.org/wiki/Mesh_networkhttp://en.wikipedia.org/wiki/Gateway_(computer_networking)http://en.wikipedia.org/wiki/Gateway_(computer_networking)http://en.wikipedia.org/wiki/Firewallhttp://en.wikipedia.org/wiki/Firewallhttp://en.wikipedia.org/wiki/DHCPhttp://en.wikipedia.org/wiki/DHCPhttp://en.wikipedia.org/wiki/Intrusion_detection_systemhttp://en.wikipedia.org/wiki/Intrusion_detection_systemhttp://en.wikipedia.org/w/index.php?title=Wi-Fi&action=edit&section=2http://en.wikipedia.org/w/index.php?title=Wi-Fi&action=edit&section=3http://en.wikipedia.org/wiki/Local_area_networkhttp://en.wikipedia.org/wiki/Local_area_networkhttp://en.wikipedia.org/wiki/Chipsethttp://en.wikipedia.org/wiki/Mobile_telephonehttp://en.wikipedia.org/wiki/Mobile_telephonehttp://en.wikipedia.org/wiki/Mobile_telephonehttp://en.wikipedia.org/wiki/File:WiFi-detector.jpghttp://en.wikipedia.org/wiki/File:WiFi-detector.jpghttp://en.wikipedia.org/wiki/Ad-hochttp://en.wikipedia.org/wiki/Bathroomhttp://en.wikipedia.org/wiki/Kitchenhttp://en.wikipedia.org/wiki/Garden_shedhttp://en.wikipedia.org/wiki/Roaminghttp://en.wikipedia.org/wiki/Cellular_networkhttp://en.wikipedia.org/wiki/Voice_over_WLANhttp://en.wikipedia.org/wiki/Intelligence_(disambiguation)http://en.wikipedia.org/wiki/Mesh_networkhttp://en.wikipedia.org/wiki/Gateway_(computer_networking)http://en.wikipedia.org/wiki/Gateway_(computer_networking)http://en.wikipedia.org/wiki/Firewallhttp://en.wikipedia.org/wiki/DHCPhttp://en.wikipedia.org/wiki/Intrusion_detection_systemhttp://en.wikipedia.org/w/index.php?title=Wi-Fi&action=edit&section=2http://en.wikipedia.org/w/index.php?title=Wi-Fi&action=edit&section=3http://en.wikipedia.org/wiki/Local_area_networkhttp://en.wikipedia.org/wiki/Chipsethttp://en.wikipedia.org/wiki/Mobile_telephonehttp://en.wikipedia.org/wiki/Mobile_telephone


28/36

Wi-Fi is widely available in more than 220,000 public hotspots and tens of millions ofhomes and corporate and university campuses worldwide.[5]Wi-Fi Protected Accessencryption (WPA and WPA2) is not easily cracked if strong passwords are used. Newprotocols for Quality of Service (WMM) make Wi-Fi more suitable for latency-sensitiveapplications (such as voice and video), and power saving mechanisms (WMM Power

Save) improve battery operation.

[edit] Limitations

Spectrum assignments and operational limitations are not consistent worldwide. Most ofEurope allows for an additional 2 channels beyond those permitted in the U.S. for the 2.4GHz band. (113 vs. 111); Japan has one more on top of that (114). Europe, as of2007, was essentially homogeneous in this respect. A very confusing aspect is the factthat a Wi-Fi signal actually occupies five channels in the 2.4 GHz band resulting in onlythree non-overlapped channels in the U.S.: 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 guaranteed not to use

802.11b at all, even as fallback or beacon. Equivalent isotropically radiated power(EIRP)in the EU is limited to 20 dBm (100 mW).

[edit] Reach

See also: Long-range Wi-Fi

Wi-Fi networks have limited range. A typical Wi-Fi home routerusing 802.11bor802.11g with a stock antenna might have a range of 32 m (120 ft) indoors and 95 m (300ft) outdoors. Range also varies with frequency band. Wi-Fi in the 2.4 GHz frequencyblock has slightly better range than Wi-Fi in the 5 GHz frequency block. Outdoor rangewith improved (directional) antennas can be several kilometres or more with line-of-sight.

Wi-Fi performance decreases roughly quadratically as the range increases at constantradiation levels.

Due to reach requirements for wireless LAN applications, power consumption is fairlyhigh compared to some other low-bandwidth standards. Especially ZigbeeandBluetoothsupporting wireless PAN applications refer to much lesser propagation range of


29/36

[edit] Mobility

Speed vs. Mobility of wireless systems: Wi-Fi, HSPA, UMTS, GSM

Because of the very limited practical range of Wi-Fi, mobile use is essentially confined tosuch applications as inventory taking machines in warehouses or retail spaces,barcodereading devices at check-out stands or receiving / shipping stations. Mobile use of Wi-Fiover wider ranges is limited to move, use, move, as for instance in an automobile movingfrom one hotspot to another (Wardriving). Other wireless technologies are more suitableas illustrated in the graphic.

[edit] Threats to security

The most common wireless encryption standard, Wired Equivalent Privacy or WEP, hasbeen shown to be easily breakable even when correctly configured.Wi-Fi ProtectedAccess (WPA and WPA2), which began shipping in 2003, aims to solve this problem andis now available on most products. Wi-Fi Access Pointstypically default to an "open"(encryption-free) mode. Novice users benefit from a zero-configuration device that worksout of the box, but this default is without any wireless securityenabled, providing openwireless access to their LAN. To turn security on requires the user to configure thedevice, usually via a software graphical user interface (GUI). Wi-Fi networks that areopen (unencrypted) can be monitored and used to read and copy data (including personalinformation) transmitted over the network, unless another security method is used tosecure the data, such as a VPN or a secure web page. (SeeHTTPS/Secure Socket Layer.)

[edit] Population

Many 2.4 GHz 802.11b and 802.11g access points default to the same channel on initialstartup, contributing to congestion on certain channels. To change the channel ofoperation for an access point requires the user to configure the device.

[edit] Channel pollution

For more details on this topic, see Electromagnetic interference at 2.4 GHz.
http://en.wikipedia.org/w/index.php?title=Wi-Fi&action=edit&section=6http://en.wikipedia.org/wiki/HSPAhttp://en.wikipedia.org/wiki/UMTShttp://en.wikipedia.org/wiki/GSMhttp://en.wikipedia.org/wiki/Barcodehttp://en.wikipedia.org/wiki/Barcodehttp://en.wikipedia.org/wiki/Wardrivinghttp://en.wikipedia.org/w/index.php?title=Wi-Fi&action=edit&section=7http://en.wikipedia.org/wiki/Wired_Equivalent_Privacyhttp://en.wikipedia.org/wiki/Wi-Fi_Protected_Accesshttp://en.wikipedia.org/wiki/Wi-Fi_Protected_Accesshttp://en.wikipedia.org/wiki/Wi-Fi_Protected_Accesshttp://en.wikipedia.org/wiki/Wireless_Access_Pointhttp://en.wikipedia.org/wiki/Wireless_Access_Pointhttp://en.wikipedia.org/wiki/Encryptionhttp://en.wikipedia.org/wiki/Wireless_security#Counteracting_riskshttp://en.wikipedia.org/wiki/Wireless_security#Counteracting_riskshttp://en.wikipedia.org/wiki/Graphical_user_interfacehttp://en.wikipedia.org/wiki/HTTPShttp://en.wikipedia.org/wiki/HTTPShttp://en.wikipedia.org/wiki/Transport_Layer_Securityhttp://en.wikipedia.org/wiki/Transport_Layer_Securityhttp://en.wikipedia.org/w/index.php?title=Wi-Fi&action=edit&section=8http://en.wikipedia.org/wiki/IEEE_802.11#802.11bhttp://en.wikipedia.org/wiki/IEEE_802.11#802.11ghttp://en.wikipedia.org/w/index.php?title=Wi-Fi&action=edit&section=9http://en.wikipedia.org/wiki/Electromagnetic_interference_at_2.4_GHzhttp://en.wikipedia.org/wiki/File:Wimax.svghttp://en.wikipedia.org/wiki/File:Wimax.svghttp://en.wikipedia.org/w/index.php?title=Wi-Fi&action=edit&section=6http://en.wikipedia.org/wiki/HSPAhttp://en.wikipedia.org/wiki/UMTShttp://en.wikipedia.org/wiki/GSMhttp://en.wikipedia.org/wiki/Barcodehttp://en.wikipedia.org/wiki/Wardrivinghttp://en.wikipedia.org/w/index.php?title=Wi-Fi&action=edit&section=7http://en.wikipedia.org/wiki/Wired_Equivalent_Privacyhttp://en.wikipedia.org/wiki/Wi-Fi_Protected_Accesshttp://en.wikipedia.org/wiki/Wi-Fi_Protected_Accesshttp://en.wikipedia.org/wiki/Wireless_Access_Pointhttp://en.wikipedia.org/wiki/Encryptionhttp://en.wikipedia.org/wiki/Wireless_security#Counteracting_riskshttp://en.wikipedia.org/wiki/Graphical_user_interfacehttp://en.wikipedia.org/wiki/HTTPShttp://en.wikipedia.org/wiki/Transport_Layer_Securityhttp://en.wikipedia.org/w/index.php?title=Wi-Fi&action=edit&section=8http://en.wikipedia.org/wiki/IEEE_802.11#802.11bhttp://en.wikipedia.org/wiki/IEEE_802.11#802.11ghttp://en.wikipedia.org/w/index.php?title=Wi-Fi&action=edit&section=9http://en.wikipedia.org/wiki/Electromagnetic_interference_at_2.4_GHz


30/36

Standardization is a process driven by market forces. Interoperability issues between non-Wi-Fi brands or proprietary deviations from the standard can still disrupt connections orlower throughput speeds on all user's devices that are within range, to include the non-Wi-Fi or proprietary product. Moreover, the usage of the ISM band in the 2.45 GHzrange is also common to Bluetooth, WPAN-CSS,ZigBee and any new system will take

its share.

Wi-Fi pollution, or an excessive number of access points in the area, especially on thesame or neighboring channel, can prevent access and interfere with the use of otheraccess points by others, caused by overlapping channels in the 802.11g/b spectrum, aswell as with decreased signal-to-noise ratio (SNR) between access points. This can be aproblem in high-density areas, such as large apartment complexes or office buildingswith many Wi-Fi access points. Additionally, other devices use the 2.4 GHz band:microwave ovens, security cameras,Bluetooth devices and (in some countries) Amateurradio, video senders, cordless phones and baby monitors, all of which can causesignificant additional interference. General guidance to those who suffer these forms of

interference or network crowding is to migrate to a Wi-Fi 5 GHz product, (802.11a, orthe newer802.11n if it has 5 GHz support) because the 5 GHz band is relatively unused,and there are many more channels available. This also requires users to set up the 5 GHzband to be the preferred network in the client and to configure each network band to adifferent name (SSID). It is also an issue when municipalities,[6] or other large entitiessuch as universities, seek to provide large area coverage. This openness is also importantto the success and widespread use of 2.4 GHz Wi-Fi.

[edit] Hardware

[edit] Standard devices

An embedded RouterBoard 112 with U.FL-RSMA pigtail and R52 mini PCI Wi-Fi

card widely used by wirelessInternet service providers (WISPs) in the Czech

Republic.
http://en.wikipedia.org/wiki/Bluetoothhttp://en.wikipedia.org/wiki/Personal_area_networkhttp://en.wikipedia.org/wiki/Chirp_spread_spectrumhttp://en.wikipedia.org/wiki/ZigBeehttp://en.wikipedia.org/wiki/ZigBeehttp://en.wikipedia.org/wiki/Signal-to-noise_ratiohttp://en.wikipedia.org/wiki/Bluetoothhttp://en.wikipedia.org/wiki/Bluetoothhttp://en.wikipedia.org/wiki/Amateur_radiohttp://en.wikipedia.org/wiki/Amateur_radiohttp://en.wikipedia.org/wiki/Video_senderhttp://en.wikipedia.org/wiki/Video_senderhttp://en.wikipedia.org/wiki/802.11ahttp://en.wikipedia.org/wiki/802.11nhttp://g/New%20Folder/WiFi.html#cite_note-5http://en.wikipedia.org/w/index.php?title=Wi-Fi&action=edit&section=10http://en.wikipedia.org/w/index.php?title=Wi-Fi&action=edit&section=11http://en.wikipedia.org/wiki/Embedded_systemhttp://en.wikipedia.org/wiki/U.FLhttp://en.wikipedia.org/wiki/SMA_connectorhttp://en.wikipedia.org/wiki/Mini_PCIhttp://en.wikipedia.org/wiki/Wirelesshttp://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Wireless_internet_service_providerhttp://en.wikipedia.org/wiki/Czech_Republichttp://en.wikipedia.org/wiki/Czech_Republichttp://en.wikipedia.org/wiki/File:RouterBoard_112_with_U.FL-RSMA_pigtail_and_R52_miniPCI_Wi-Fi_card.jpghttp://en.wikipedia.org/wiki/File:RouterBoard_112_with_U.FL-RSMA_pigtail_and_R52_miniPCI_Wi-Fi_card.jpghttp://en.wikipedia.org/wiki/Bluetoothhttp://en.wikipedia.org/wiki/Personal_area_networkhttp://en.wikipedia.org/wiki/Chirp_spread_spectrumhttp://en.wikipedia.org/wiki/ZigBeehttp://en.wikipedia.org/wiki/Signal-to-noise_ratiohttp://en.wikipedia.org/wiki/Bluetoothhttp://en.wikipedia.org/wiki/Amateur_radiohttp://en.wikipedia.org/wiki/Amateur_radiohttp://en.wikipedia.org/wiki/Video_senderhttp://en.wikipedia.org/wiki/802.11ahttp://e

wireless technology in day to day life

Documents