Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 1 CHAPTER 1 INTRODUCTION 1.1 Origin of the Name Harald Blatand, also known as Harald Bluetooth, supposedly named for his unusually dark complexion, was a Viking and also the King of Denmark from 940 to 981.He was known for his ability to get people to talk to each other and during his reign DenmarkandNorwaywereChristianizedandunited.Today,Bluetoothwireless technology enables electronic devices to talk to each other, but this time by means of a low-cost, short-range radio link.The developers of the Bluetooth technology hoped that it would unite the world as Harald Bluetooth united Norway and Denmark, and thus they decided to name this new technology after the Viking King Harald Bluetooth. 1.2 History of BluetoothThe idea that resulted in the Bluetooth wireless technology was born in 1994 when Ericsson decided to investigatethe feasibility of a low-power, low-cost radio interface between mobile phones and their accessories. As the idea grew, a special interest group (SIG) was formed to create a standard for this technology. The original SIG, formed in 1998, consisted of five companies: Ericsson IBM Intel Nokia Toshiba Four othermajorcompanies(Microsoft,3Com,Lucent,andMotorola)laterjoined this founding group to form the Bluetooth Promoter Group. Many more companies have sincebecomepartoftheBluetoothrevolution,expandingontheoriginalvision,and helping drive the development of this new technology. Theideawasthatasmallradiobuiltintoboththecellulartelephoneandthe laptop would replace the cumbersome cable used today to connect the two devices. Today, the Bluetooth wireless technology is supported bytheBluetoothSIG(Special InterestGroup.Currently,thereareabout16000companiesjoinedtheBluetooth Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 2 Special Interest Group (SIG). The backing and support from these companies ensures that Bluetooth will receive a chance to gain acceptance in todays wireless market. 1.3 What exactly is Bluetooth ? AccordingtoDictionary.com,BluetoothisAspecificationforshort-rangeradio links between mobile computers, mobile phones, digital cameras,andotherportable Devices. Bluetooth is an open standard specification for a low cost, low power, radio frequencytechnologyforshort-rangeCommunications.Itcanbeusedtoreplacethe cablesconnectingportable/fixedelectronicdevices,buildad-hocnetworksorprovide data/voiceaccesspoints.Ithasbeenadoptednotonlybyallmajorplayersinthe telecom, computer and home entertainment industry, but also in such diverse areas as the automotive industry, health care, automation, and toy industries. Fig 1.1: Bluetooth module Frequency2.4GHz ISM band, Frequency hopping ModulationGaussian shaped BFSK Data rate723Kbps Operating range10m~100m Size28mmx15mmx2mm(MitsumiWML-C05) CostLong term: $5/endpoint SecurityGood. FHSS. Link layer authentication and encryption AcceptanceSIGhaveabout16000member companies Table 1.1: Bluetooth summary Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 3 CHAPTER 2 TECHNICAL ASPECTS OF BLUETOOTH 2.1 Working of a Bluetooth device Bluetooth networking transmits data via low-power radio waves. It communicates on a frequency of 2.45 gigahertz (actually between 2.402 GHz and 2.480 GHz, to be exact). This frequency band has been set aside by international agreement for the use of industrial, scientific and medical devices (ISM). Anumberofdevicesthatyoumayalreadyusetakeadvantageofthissame radio-frequency band. Baby monitors, garage-door openers and the newest generation ofcordlessphonesallmakeuseoffrequenciesintheISMband.Makingsurethat Bluetooth and these other devices don't interfere with one another has been a crucial part of the design process. OneofthewaysBluetoothdevicesavoidinterferingwithothersystemsisby sending out very weak signals of about 1 milliwatt. By comparison, the most powerful cellphonescantransmitasignalof3watts.Thelowpowerlimitstherangeofa Bluetoothdevicetoabout10meters(32feet),cuttingthechancesofinterference between your computer system and your portable telephone or television. Even with the low power, Bluetooth doesn't require line of sight between communicating devices. The wallsinyourhousewon'tstopaBluetoothsignal,makingthestandardusefulfor controlling several devices in different rooms. Bluetoothcanconnectuptoeightdevicessimultaneously.Withallofthose devices in the same 10-meter (32-foot) radius, you might think they'd interfere with one another, but it's unlikely. Bluetooth uses a technique called spread-spectrum frequency hoppingthatmakesitrareformorethanonedevicetobetransmittingonthesame frequency at the same time. In this technique, a device will use 79 individual, randomly chosenfrequencieswithinadesignatedrange,changingfromonetoanotherona regular basis. In the case of Bluetooth, the transmitters change frequencies 1,600 times everysecond,meaningthatmoredevicescanmakefulluseofa limitedsliceofthe radiospectrum.SinceeveryBluetoothtransmitterusesspread-spectrumtransmitting automatically,itsunlikelythattwotransmitterswillbeonthesamefrequencyatthe Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 4 sametime.Thissametechniqueminimizestheriskthatportablephonesorbaby monitors will disrupt Bluetooth devices, since any interference on a particular frequency will last only a tiny fraction of a second. WhenBluetooth-capabledevicescomewithinrangeofoneanother,anelectronic conversation takes place to determine whether they have data to share or whether one needs to control the other. The user doesn't have to press a button or give a command --theelectronicconversationhappensautomatically.Oncetheconversationhas 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), or piconet, that may fill a room or may encompass no more distance than that between the cell phone on a belt-clipandtheheadsetonyourhead.Onceapiconet isestablished,themembers randomly hop frequencies in unison so they stay in touch with one another and avoid other piconets that may be operating in the same room. Let's check out an example of a Bluetooth-connected system. 2.2 Example for working of a Bluetooth systemLet's say you have a typical modern living room with typical modern stuff inside. There'sanentertainmentsystemwithastereo,aDVDplayer,asatelliteTVreceiver and a television; there's also a cordless telephone and a personal computer. Each of these systems uses Bluetooth, and each forms its own piconet to talk between the main unit and peripheral. The cordless telephone has one Bluetooth transmitter in the base and another in thehandset.Themanufacturerhasprogrammedeachunitwithanaddressthatfalls into a range of addresses it has established for a particular type of device. When the base is first turned on, it sends radio signals asking for a response from any units with anaddressinaparticularrange.Sincethehandsethasanaddressintherange,it responds,andatinynetworkisformed.Now,evenifoneofthesedevicesshould receiveasignalfromanothersystem,itwillignoreitsinceit'snotfromwithinthe network.Thecomputerandentertainmentsystemgothroughsimilarroutines, establishing networks among addresses in ranges established by manufacturers. Once thenetworksareestablished,thesystemsbegintalkingamongthemselves.Each piconethopsrandomlythroughtheavailablefrequencies,soallofthepiconetsare completely separated from one another. Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 5 Now the living room has three separate networks established, each one made up of devices that know the address of transmitters it should listen to and the address of receivers it should talk to. Since each network is changing the frequency of its operation thousands oftimesasecond,it'sunlikelythatanytwonetworkswillbeon thesame frequency at the same time. If it turns out that they are, then the resulting confusion will only cover a tiny fraction of a second, and software designed to correct for such errors weeds out the confusing information and gets on with the network's business. 2.3 Frequency band and RF channels of bluetooth Works in ISM band: 2.4~2.4835 GHz (US, Europe and most other countries)Carrier frequency: f=2402+k MHz k=0...78Hopping rate: 1 hop/packet. 1600 hop/s for 1 slot packet Channel bandwidth: 1MHz(-20dB) 220KHz(-3dB) Bluetoothuses2.4GHzISMbandbecauseitisanunlicensedband,and availableinmostcountries.Atthisfrequency(=12.3cm),averysmallantennais possible. And higher frequency band may cause high cost on RF. For some countries withdifferentbandwidthallocations,areducedhop(23hops)systemisdefined. According to current version of Bluetooth specs, 79/23 hops system cant communicate to each other. This is a big problem for the original goal of global standard.However, Bluetooth SIG has been actively lobbying those countries with different regulations.FranceandJ apanrecentlyreleasedthefullISMband.Spainisalso working on it. It is very likely to use the same band globally in the future. In the 2.4GHz ISMband,theuseofspreadspectrumismandatory.AlthoughDSSScanachieve higher data rate (11Mbps for 802.11b standard), FHSS has its advantage of low cost, lowpower,bettersecurity.FHSSalsohandlesnear-farproblembetter,sinceitwill effectively block out-of-band signals.ConsideringthepossibleapplicationsofBluetooth,FHSSisabettersolution. ThehoppingsequenceiscalculatedusingthemastersBluetoothDeviceAddress.It hops to every 1MHz channel with equal probability. Its 1600hops/sec fast hopping rate isenoughtoovercomeslowfadinginmostindoorenvironment,whichhasDoppler spread of 0.1~6Hz. The RMS delay spread usually ranges from 100ns to 10s. A typical 0.25sRMSdelayspreadcorrespondsto640KHzcoherentbandwidth.Sodifferent 1MHzchannelswillhavedifferentradiocharacteristics,andtheFHSSwilleffectively solve the multipath and fading problem. For 1MHz channel, the 1Msps symbol rate is alreadyfullyexploitingthebandwidth.The1MHzchannelbandwidthwasthe Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 6 requirementofFCC,butrecentdecisionfromFCCchangedthatto5MHz.Thiswill probably enable the future version protocol to get higher data rate.HomeRFisalreadytakingadvantageofthis5MHzchanneltoget10Mbps throughput.2.4GHzISMbandisfreetoall, somanyapplicationsnowareusingthis band.Theseapplicationsincludedigitalcordlessphone,WLAN(802.11b),HomeRF, RFID,microwaveovenandmanyotherproprietarytechnologies.Althoughspread spectrumismandatoryfordeviceswithatransmitpowerover0dBm,consideringthe possiblelargenumberofunitsworking inthesameband,manypeopleareworrying that the interference will make this band a garbage band. WLAN is trying to migrate to the 5.7GHz band. 2.4 Transmitter characteristics Forhigherbandwidthefficiency,GaussianshapedbinaryFSKisusedin Bluetooth. The bandwidth time product BT=0.5. The nominal modulation index is 0.3. A binary zero is represented by negative frequency deviation, and one is represented by positive frequency deviation. The frequency deviation is no less than 115 KHz. Fig 2.1: GFSK modulation GFSK is constant-envelope modulation, which enables the use of class C power amplifierforhighpowerefficiency.Itsalsoeasiertoimplementcomparedtoother modulation techniques. Bluetooth devices are divided to 3 power classes: Class 1: maximum output power of 20 dBm Class 2: maximum output power of 4 dBm Class 3: maximum output power of 0 dBm Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 7 2.5 Receiver characteristics Forarawbiterrorrateof0.1%,Bluetoothdevicesshouldhaveaminimum sensitivity of -70dBm, maximum-usable signal level of -20dBm. Thats a dynamic range of 50dB. Compared to that of many cellular phones, the sensitivity level of Bluetooth is much higher. The purpose is to allow higher substrate noise and low current LNA, thus to minimize the cost. A noise figure as large as 23 dB is allowed in Bluetooth receiver. Thehighnoisefigureallowstheuseofinexpensivecomponents,andon-chipinterference for single chip implementation.Forarawbiterrorrateof0.1%,Bluetoothdevicesshouldstandaco-channel interferenceofcarriertointerferenceratioCIR=11dB,1MHzadjacentchannel interference of CIR=0dB, 2MHz adjacent channel interference of CIR=-30dB and 3MHz adjacentchannelinterferenceofCIR=-40dB.Theserequirementstranslatetophase noise requirement for the VCO of 124dBc/Hz, this is less demanding than most cellular systems.Thisallowssimpleon-chipVCOimplementation.ReceiverSignalStrength Indicator (RSSI) is an optional feature, but most vendors selected to implement it, since this will help reduce the power consumption. It compares the received signal power to upperandlowerthresholdstoseeifitswithinthegoldenrangeandnotifiesthe transmitter via LMP. Fig 2.2: Diagram of Bluetooth tranceiver Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 8 RF design currently is a big hurdle for the Bluetooth single chip implementation. ThecostofRFchipisthemajorpartofmostBluetoothsolutionsnow.Themajor difficulties to integrate RF circuit to deep sub-micron CMOS chip include lack of good RF model for CMOS circuit, and making high quality passive components. For the down converter,VeryLowIFandDirectConversionReceiveraregainingmoresupport, because they have low requirements on filters and are easy to be integrated into CMOS chip. The low IF also eliminates the requirement for in-band image rejection filter, thus reduces the cost and power consumption. 2.6 Classes of BluetoothClassRange Power consumption Application 1 Upto330 ft(100m) Greater Typicallyusedbydevicesthatrequire extendedrange,suchasBluetoothtoUSB Adapters (IOGEAR GBU311) and more. 2 Upto66ft (20m) Lesser Typicallyusedbydeviceswhichdonot requiregreatrangeandshouldconserve notebookbatterypower,suchasBluetooth MiniMice(IOGEARGME225B),Bluetooth GPS (IOGEAR GBGPS201), Printer Adapters (IOGEAR GBP201) 3 Upto33ft (10m) Least Usedbydevicesrequireveryshortrange, such as cell phones, PDAs Table 2.1: Bluetooth classes 2.7 Bluetooth protocols J ust like in most other high frequency wireless communication systems, Bluetooth alsoworksbasedonalargecollectionofcommandsandresponsesknownasa protocol.Any Bluetooth device needs exactly four parts (fig 2.3) to operate properly. These include a radio frequency for receiving and transmitting dataa module with a baseband microprocessor memory an interface to the host device Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 9 Fig 2.3: Bluetooth hardware For any device to be qualified as a Bluetooth device, it must satisfy these seven protocols (Fig 2.4). Fig 2.4: Bluetooth protocol stack These seven protocols includeradio protocol baseband protocol LMP protocol HCI protocol L2CAP protocol RFCOMM protocol SDP protocol Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 10 2.7.1 Radio protocol The radio protocol is basically what makes Bluetooth a wireless device byservingasthedigitalsignal-processingcomponentofthesystem.Itworksverysimilartootherwirelesstechnologieswehavetoday.Bluetoothdevicestransmitdata,whichismadeupofbits(onesandzeros),overaradiofrequency,whichisanelectromagneticwavefrequencyfoundbetweenaudioandinfrared. BluetoothdevicesuseGaussianFrequencyShiftKeyingorGFSKforshortdistance communication. Thismeans thatabinary one is represented bya positivefrequency deviationandthatabinaryzeroisrepresentedbyanegativefrequencydeviation.A receiveronanotherBluetooth device will pick up the bits that are being sent through air.The frequency assigned to Bluetooth devices in the United States and in Europe is from 2,402 MHz to 2480 MHz. This frequency may differ in other places.2.7.2 Baseband ProtocolThis brings us to the baseband, which processes the signals that are received andtransmittedbytheradio.Italsocontrolsthelinks,packets,channels,error correction, and flow control. 2.7.3 Link Manager ProtocolNext, there is the LMP or the link manager protocol.The Link Manager controlsormanageslinksetup,authentication,linkconfigurationandotherlowlevelprotocols.ItdiscoversotherremotelinkmanagersandcommunicateswiththemviatheLinkManagerProtocol.Itbasically,withthehelpoftheBaseband, establishes all the connections for all Bluetooth devices 2.7.4 Host Controller Interface Protocol Then, there is the HCI protocol. The HCI provides a command interface to the basebandcontrollerand linkmanager. The HCI alsoprovidesaccesstohardware status and control registers. Essentially this interfaceprovidesa uniformmethod of accessing the Bluetooth baseband capabilities, which is important for all devices to be able to utilize the Bluetooth technology. The HCI exists across three sections, the host,transport layer,and thehostcontroller. Each ofthe sections has a different role to play in the HCI system. Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 11 2.7.5 Logical Link Control and Adaptation Layer ProtocolThe Logical Link Control and Adaptation Layer Protocol (L2CAP) is layered overthe Baseband Protocol and resides in the data link layer. The L2CAP is basically aprocessorthatprovidesconnection oriented and connectionless data services to upperlayerprotocolswithprotocolmultiplexingcapability,segmentationandreassemblyoperation,andgroup abstractions. In other words, other protocols, such as IP, can send their packets through the Bluetooth device, and the L2CAP will break their packets down into the correct size for Bluetooth transmission, which happens to haveamaximumsizeof64kilobytes.Whenthepacketpassesthroughanother BluetoothdevicesL2CAP,itwillbeputbackinitsoriginalform.L2CAPpermits higher-level protocols and applications to transmit and receiveL2CAPdatapackets up to 64 kilobytes in length. 2.7.6 RFCOMM protocol RFCOMMisasimpletransportprotocol,whichprovidesemulationofRS232 serial ports over the L2CAP protocol. The protocol is based on the ETSI standard TS 07.10. The RFCOMM protocol supports up to 60 simultaneous connections betweentwoBluetoothdevices.These60differentconnectionsaresimilartoportsonaserver.Thereisadifferentservicerunningoneachoftheports.ThisallowstwoBluetoothdevicestohaveupto60simultaneousconnections.ThenumberofconnectionsthatcanbeusedsimultaneouslyinaBluetoothdeviceisimplementation-specific,meaningitisbasedonwhatprofileisbeingused.Someprofileswillnoteveruseallofthe60differentports.ForthepurposesofRFCOMM,acompletecommunicationpathinvolvestwoapplicationsrunningondifferent devices with a communication segment between them.2.7.7 Service Discovery ProtocolFinally, the Service Discovery Protocol, or SDP, is a simple protocol with minimal requirementsontheunderlyingtransport.Itcanfunctionoverareliablepacket transport.If the client implements timeouts and repeats requests as necessary, SDP canfunctionoveranunreliablepackettransport.SDPusesa request/responsemodelwhereeachtransactionconsistsofone request protocoldata unit (PDU) and one response PDU.In the case where SDP is used with the Bluetooth L2CAP transport protocol, only one SDP request PDU per connection to a given SDP server may be outstanding at a Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 12 giveninstant.Inotherwords,aclientmustreceivearesponsetoeachrequest before issuing another request on the same L2CAP connection. Limiting SDP to sending one unacknowledged request PDU provides a simple form of flow control. 2.8 Bluetooth Security In any wireless networking setup, security is a concern. Devices can easily grab radiowavesoutoftheair,sopeoplewhosendsensitive informationoverawireless connectionneedtotakeprecautionstomakesurethosesignalsaren'tintercepted. Bluetooth technology is no different -- it's wireless and therefore susceptible to spying andremoteaccess,justlikeWiFiissusceptibleifthenetworkisn'tsecure.With Bluetooth,though,theautomaticnatureoftheconnection,which is ahugebenefit in terms of time and effort, is also a benefit to people looking to send you data without your permission. Bluetoothoffersseveralsecuritymodes,anddevicemanufacturersdetermine whichmodetoincludeinaBluetooth-enabledgadget.Inalmostallcases,Bluetooth users can establish "trusted devices" that can exchange data without asking permission. When any other device tries to establish a connection to the user's gadget, the user has todecidetoallowit.Service-levelsecurityanddevice-levelsecurityworktogetherto protectBluetoothdevicesfromunauthorizeddatatransmission.Securitymethods includeauthorizationandidentificationproceduresthatlimittheuseofBluetooth servicestotheregistereduserandrequirethatusersmakeaconsciousdecisionto open a file or accept a data transfer. As long as these measures are enabled on the user's phone or other device, unauthorized access is unlikely. A user can also simply switchhisBluetoothmodeto"non-discoverable"andavoidconnectingwithother Bluetoothdevicesentirely.Ifa usermakes useof theBluetooth networkprimarilyfor synching devices at home, this might be a good way to avoid any chance of a security breach while in public. Still,earlycell-phoneviruswritershavetakenadvantageofBluetooth's automatedconnectionprocesstosendoutinfectedfiles.However,sincemostcell phonesuseasecureBluetoothconnectionthatrequiresauthorizationand authentication before accepting data from an unknown device, the infected file typically doesn'tgetveryfar. Whenthevirusarrives intheuser'scellphone,theuserhasto Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 13 agree to open it and then agree to install it. This has, so far, stopped most cell-phone viruses from doing much damage. See How Cell-phone Viruses Work to learn more. Otherproblemslike"bluejacking,""bluebugging"and"CarWhisperer"have turnedupasBluetooth-specificsecurityissues.BluejackinginvolvesBluetoothusers sending a business card (just a text message, really) to other Bluetooth users within a 10-meter(32-foot)radius.Iftheuserdoesn'trealizewhatthemessageis,hemight allowthecontacttobeaddedtohisaddressbook,andthecontactcansendhim messagesthatmightbeautomaticallyopenedbecausethey'recomingfromaknown contact.Bluebuggingismoreofaproblem,becauseitallowshackerstoremotely accessauser'sphoneanduseitsfeatures,includingplacingcallsandsendingtext messages, and the user doesn't realize it's happening. The Car Whisperer is a piece of softwarethatallowshackerstosendaudiotoandreceiveaudiofromaBluetooth-enabled car stereo. Like a computer security hole, these vulnerabilities are an inevitable resultoftechnologicalinnovation,anddevicemanufacturersarereleasingfirmware upgrades that address new problems as they arise. 2.9 Technical challenges and solutions Like any other engineering practice, the design of Bluetooth has to compromise between different goals, like high throughput and low cost, large operation range and lowpowerconsumption.Throughoutthespecifications,youwillfindoutthemost deciding factors are low power and low cost. Thats the key for mobile applications. Technical ChallengesSolutions Global operation2.4GHz ISM band Interference from other devices using ISM band and other Bluetooth devices FHSS, Error correction coding Low power consumption Power control, Power-saving modes, Programmable packet length, Moderate data rate Low cost FHSS, TDMA, low receiver sensitivity, Relaxed link budget, Low IF Security FHSS, link layer security (Authentication and Encryption) High error probability of wireless linkARQ, FEC and CVSD (audio) Voice/Data supportCircuit/Packet Switching Table 2.2: Bluetooth technical solutions Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 14 CHAPTER 3 COMPARISON WITH COMPETITORS 3.1 Bluetooth vs. IrDA IrDAisusedforhigh-speed,short-range,line-of-sightandpoint-to-pointdata transfer. The range of IrDA is larger than 1 meter. It requires a narrow angle (30degree) point-and-shoot operation. The maximum data transfer speed is 4Mbps and 16Mbps is under development. It doesnt interfere with other wireless communications and also its immunetointerferencefromothers.Currentlyover150millionunitsareinstalled worldwide and this number is growing 40% annually. Its major applications are laptop computers, printers and LAN access among others.ThebiggestadvantageofIrDAoverBluetoothisitshighthroughput,which makesitsuitableforhigh-speedapplications.TheIrDAisalsocheaper.One manufacturer can get a whole solution with cost of about $1. Bluetooth provides users more mobility. For class 2 Bluetooth devices, its range can reach 10 meters, and it is omni-directional. It can effectively penetrate clothes and soft partitions. For examples, the user can leave his cellular phone in his pocket while using dial-up networking. This isimpossibleforIrDA.Bothofthemhavetheiradvantagesanddisadvantages,and neithercanfullyreplacetheother.InBluetoothspecifications,IrOBEXisdefinedto enable applications to work on both RF and IR media. ParameterBluetoothIrDA Technology 2.4GHz FHSS, Point to point/multipoint Infrared, Point to point Data Rate1Mbps4Mbps, 16Mbps underway Range100m(class 1)1m, line of sight DirectionalityOmni-directional30 degree SecurityVery goodGood Cost$5(long term)$1 Table 3.1: Bluetooth vs. IrDA Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 15 3.2 Bluetooth vs. WLAN (802.11) Aspartof802.xstandard,the802.11standardcoverstheMACandphysical layer. It supports 3 kinds of physical media: DSSS at 2.4GHz, FHSS at 2.4 GHz and IR. Unlike Bluetooths time-division scheme, 802.11 uses CSMA/CA to access the media. Currentversion802.11b(alsocalledWi-Fi)providesupto11Mbpsthroughput,50m operating range. The future version will use 5.7GHz band and can achieve date rates of up to 40Mbps.802.11busesDSSSonthree22MHzchannels.ItusesQPSKandCCK (complementary code keying) to achieve high data rate. It uses 1.375Msps symbol rate andachiprateof8.Thelargestpacketsizeis1500bytes.ComparedtoBluetooth, WLANhashigherimplementationcostbecauseitshigherthroughputneedmore powerfulDSPsandalsomorepowerconsumption.Currently,thecostofoneWLAN card can be as high as $150.802.11b uses DSSS technology, which is more sensitive to interference. There are reports that both Cisco and Lucents WLAN product failed to work when you use a Panasonic2.4GHzcordlessphonenearby.SoBluetoothismoresuitablefor applicationsinnoisyenvironments,likeinafactoryenvironment.Thesetwo technologies are not only competing for market share, but also fighting physically in the same 2.4GHz ISM band. ParameterBluetoothWLAN (802.11b) Technology 2.4GHz FHSS, 79 1MHz channels. TDMA 2.4GHz DSSS, 3 22MHz channels, CSMA/CA Data Rate1Mbps11Mbps Range100m(class 1)50m Power20mA(active)200mA(active) Cost$5(long term)$50 Robustness to interferenceGoodNot so good Table 3.2: Bluetooth vs. WLAN AccordingtoIntersilstest,thethroughputofa802.11systemcoulddropto 3.5MbpsinaBluetoothdenseenvironment.Bluetoothseemsperformingbetter. According to Ericssons test report, in a typical office environment with a large number of802.11terminalsdeployed,oneBluetoothunitoperatingin10mrangeislikelyto Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 16 possess a 24% probability of a 10% throughput reduction. But the Bluetooth throughput reduction will never be greater than 22% due to limited bandwidth overlapping. So the effect of 802.11 on Bluetooth is much less severe than that of Bluetooth on 802.11.AgroupofcompaniesintheWLANcampispetitioningtheFCCtorequest Bluetooth to use adaptive hopping. The adaptive hopping will avoid the frequencies that are used by WLAN, thus a frequency division may be achieved. But there are still many issues to address for this approach. 3.3 Bluetooth vs. HomeRF TheHomeRFis aimedatthehomenetworkingmarket.Itprovidesupto8toll quality(32ADPCM)voicechannels,8prioritizedstreamingmediasessionsanddata rate up to 10Mbps(20Mbps in 2002). This makes it verysuitable for media-rich home environment. It could be used to connect audio and video sources, where Bluetooth is notcapable.ItsMAClayerisoptimizedforcombineddataandvoicetraffic.Ituses reserved slots (TDMA) for voice and CSMA/CA for data. Its physical layer uses 2.4GHz ISM band FHSS. Similar to Bluetooth, it has 75 1MHz channels, but it can combine five channels together to form a 5MHz SuperChannel for high-speed traffic. And also unlike Bluetoothsfixedhoppingsequence,itcanadaptitshopingsequencetothe environment. This technique is very useful to reduce the interference from other static interferers like microwave oven. HomeRF also provides very good security. It uses 32-bitIV(initializationvector)and128-bitencryption.Bluetoothuses8-128bitsvariable size encryption, and 802.11b uses 64-bit encryption. ParameterBluetoothHomeRF Technology 2.4GHz FHSS, 1MHz, channels, TDMA 2.4GHz FHSS, 1MHz/5MHz channels, TDMA, CSMA/CA Data Rate1Mbps10Mbps(20Mbps in 2002) Range100m(class 1)50m Power20mA(active)350mA(transmit) Cost$5(long term)$20 Robustness to interferenceGoodVery good Streaming media support3 64kbps voice channels 8 stream sessions 8 32kbps ADPCM channels Table 3.3: Bluetooth vs. HomeRF Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 17 HomeRFisaverypromisingtechnology;ithasgainedsupportfromover100 companies including Compaq, Intel and Motorola. HomeRF has many advantages over Bluetooth, but they do not come for free. The physical layer specification of HomeRF is largely adopted from 802.11 and modified to reduce cost. But its high throughput and complex MAC layer make it impossible to compete with Bluetooth on price. Currently, onecangetaHomeRFadapterforabout $80.Also itspowerconsumptionismuch largerthanthatofBluetooth.SoitsbelievedthatBluetoothwilldominatethemobile applications like cellular phones and laptop computers. Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 18 CHAPTER 4 APPLICATIONS OF BLUETOOTH Some of the applications of Bluetooth are By installing a Bluetooth network in your office you can do away with the complex andtedioustaskofnetworkingbetweenthecomputingdevices,yethavethe powerofconnecteddevices.No longerwouldyoubeboundtofixedlocations whereyoucanconnecttothenetwork.EachBluetoothdevicecouldbe connected to 200 other devices making the connection of every device with every other possible. Since it supports both point to point and point to multipoint it will virtually make the maximum number of simultaneously linked devices unlimited. The Bluetooth technology connects all your office peripherals wirelessly. Connect your PC or notebook to printers, scanners and faxes without the ugly and trouble somecableattachments.Youcanincreaseyourfreedombyconnectingyour mouse or the keyboard wirelessly to your computer. If your digital cameras in Bluetooth enabled, you can send still or video images from any location to any location without the hassle of connecting your camera to the mobile phone on the wireline phone. Bluetooth allows us to have three way phones. At home, your phone functions as a portable phone (fixed line charge). When you're on the move, it functions as a mobilephone(cellularcharge).Andwhenyourphonecomeswithinrangeof another mobile phone with built-in Bluetooth wireless technology it functions as a walkie-talkie (no telephony charge). In meetings and conferences you can transfer selected documents instantly with selectedparticipants,andexchangeelectronicbusinesscardsautomatically, without any wired connections. Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 19 Connectyourwirelessheadsettoyourmobilephone,mobilecomputerorany wired connection to keep your hands free for more important tasks when you're at the office or in your car. Haveautomaticsynchronizationofyourdesktop,mobilecomputer,notebook (PC-PDAandPC-HPC)andyourmobilephone.For instance,assoon asyou enter your office the address list and calendar in your notebook will automatically be updated to agree with the one in your desktop, or vice versa. Automatic Message Delivery: Compose e-mails on your portable PC while you're on an airplane. As soon as you've landed and switched on your mobile phone, all messages are immediately sent. Unwired communication between the input and output devices of a computer is possible by means of Bluetooth technology. Some game consoles use Bluetooth for their wireless controllers. Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 20 CHAPTER 5 ADVANTAGES AND DISADVANTAGES OF BLUETOOTH 5.1 Advantages Firstly, it is wireless, thus eliminating all the cords used in connections. Line of sight is not required, as opposed to that in Infrared communication. This unwired form of communication reduced the clutter of wires to a great extent. Secondly, with Bluetooth headsets, you can communicatehands-free. You can use your cell phone without the use of your hands. That makes it safe to talk on phone while your hands are engaged in other activities. Bluetoothdevicesarefairlyinexpensive.Thereisnospecialcostincurredin using this technology. Thenextconcernisinteroperability.Bluetoothisastandardizedspecification. Bluetooth-enableddevicesarehighlycompatiblewitheachother.They 'understand'eachothersowell,thatnohumaninterventionisrequired. When within range, they sense each other and start communicating on their own. The process of connection setup is automatic. Thencomesefficiency!Bluetoothuseslowpowersignals,thusrequiringless energy.Duetospread-spectrumfrequencyhopping,interferencewithother wireless devices is not a question at all. Bluetooth Special Interest Group has been working on upgraded versions, which are backward compatible. So higher versions are no cause of worry. Moreover,Bluetoothcommunicationissecure.Securityruleswillnotallowthe devices to communicate unless pre-approved by the user. Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 21 5.2 Disadvantages CommunicationspeedisnotthatgreatwithBluetoothtechnology.Wi-Fiand Infrared communication can happen at much higher speeds compared to that of Bluetooth. ThoughBluetoothcommunicationisconsideredsecure,ifauserhappensto leavehis/herdeviceinthe'discoverable'mode,ahackercaneavesdropor establishaconnectionwiththe'discovered'devicewithouttheuserknowing about it. IfBluetooth is in theONmode,itdoesdrainthebattery.So oneneedsto be careful about switching Bluetooth ON only for the time span of communication andturnitOFFafterthecommunicationends.Thispracticealsoreducesthe security risk involved with Bluetooth technology. Interference with other devices that may use the same frequency, such as baby monitors,garagedooropeners,cordlessphones,microwaveovens,andother wireless technologies which use the same frequency Relatively short range Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 22 CHAPTER 6 CONCLUSION Bluetoothisalowcost,lowpowerRFtechnologyforshort-range communications.Itcouldbeusedtoreplacecablesconnectingportabledevices. Compared to other similar wireless technologies, its biggest advantage is the low power and low cost, which makes it suitable for mobile applications. But its low data rate keeps it away from high-speed applications like real time video. A higher data rate version of Bluetooth is under discussion. It shares the 2.4GHz ISM band with many other products. Interference among theseunitsisanimportanttopicforresearch.Thereishugemarketpotentialfor Bluetooth products. The market will reach $1 billion around 2005. It has gained support from thousands of companies. There are a few commercial products available, and its believed many more will roll out next year. It can be said that the name Bluetooth refers not only to a technology, but also to astandardandaspecification.AndfewstandardshavetakenoffasBluetoothhas, capturingtheattentionanddevelopmentmoneyofmajorcorporationsthroughoutthe world. If it can live up to its expectations and meet the needs of a global marketplace in an easy-to-use, straightforward manner, it promises to become (like its eponymous King Harald) a uniting force in the wireless communications world.Ultimately, the real winners are the hundreds of millions of Bluetooth customers around the world who simply enjoy the connected convenience Bluetooth brings to their lives. Life sure is better with Bluetooth. Bluetooth Technology Department of Electronics and Communication, SJCE, MysorePage 23 CHAPTER 7 REFERENCES 7.1 Books Future of Bluetooth Technology, by J ustin Blasdel, Kian Pokorny Overview of Bluetooth Technology, by Hongfeng Wang Bluetooth- Application Guide, edited by IOGEAR 7.2 Websites http://electronics.howstuffworks.com/bluetooth.htm http://www.buzzle.com/articles/how-does-bluetooth-work.html http://en.wikipedia.org/wiki/Bluetooth http://www.mobileinfo.com/Bluetooth/applic.htm