1、Bluetooth TechniquesChapter 15OverviewnUniversal short-range wireless capabilitynUses 2.4-GHz bandnAvailable globally for unlicensed usersnDevices within 10 m can share up to 720 kbps of capacitynSupports open-ended list of applicationsnData,audio,graphics,videoBluetooth Application AreasnData and v
2、oice access pointsnReal-time voice and data transmissionsnCable replacementnEliminates need for numerous cable attachments for connectionnAd hoc networkingnDevice with Bluetooth radio can establish connection with another when in rangeBluetooth Standards DocumentsnCore specificationsnDetails of vari
3、ous layers of Bluetooth protocol architecturenProfile specificationsnUse of Bluetooth technology to support various applicationsProtocol ArchitecturenBluetooth is a layered protocol architecturenCore protocolsnCable replacement and telephony control protocolsnAdopted protocolsnCore protocolsnRadionB
4、asebandnLink manager protocol(LMP)nLogical link control and adaptation protocol(L2CAP)nService discovery protocol(SDP)Protocol ArchitecturenCable replacement protocolnRFCOMMnTelephony control protocolnTelephony control specification binary(TCS BIN)nAdopted protocolsnPPPnTCP/UDP/IPnOBEXnWAE/WAPUsage
5、ModelsnFile transfernInternet bridgenLAN accessnSynchronizationnThree-in-one phonenHeadsetPiconets and ScatternetsnPiconetnBasic unit of Bluetooth networkingnMaster and one to seven slave devicesnMaster determines channel and phasenScatternetnDevice in one piconet may exist as master or slave in ano
6、ther piconetnAllows many devices to share same areanMakes efficient use of bandwidthWireless Network ConfigurationsRadio SpecificationnClasses of transmittersnClass 1:Outputs 100 mW for maximum rangenPower control mandatorynProvides greatest distancenClass 2:Outputs 2.4 mW at maximumnPower control o
7、ptionalnClass 3:Nominal output is 1 mWnLowest powerFrequency Hopping in BluetoothnProvides resistance to interference and multipath effectsnProvides a form of multiple access among co-located devices in different piconetsFrequency HoppingnTotal bandwidth divided into 1MHz physical channelsnFH occurs
8、 by jumping from one channel to another in pseudorandom sequencenHopping sequence shared with all devices on piconetnPiconet access:nBluetooth devices use time division duplex(TDD)nAccess technique is TDMAnFH-TDD-TDMAFrequency HoppingPhysical Links between Master and SlavenSynchronous connection ori
9、ented(SCO)nAllocates fixed bandwidth between point-to-point connection of master and slavenMaster maintains link using reserved slotsnMaster can support three simultaneous links nAsynchronous connectionless(ACL)nPoint-to-multipoint link between master and all slavesnOnly single ACL link can existBlu
10、etooth Packet FieldsnAccess code used for timing synchronization,offset compensation,paging,and inquirynHeader used to identify packet type and carry protocol control informationnPayload contains user voice or data and payload header,if presentTypes of Access CodesnChannel access code(CAC)identifies
11、 a piconetnDevice access code(DAC)used for paging and subsequent responsesnInquiry access code(IAC)used for inquiry purposesAccess CodenPreamble used for DC compensationn0101 if LSB of sync word is 0n1010 if LSB of synch word is 1nSync word 64-bits,derived from:n7-bit Barker sequencenLower address p
12、art(LAP)nPseudonoise(PN)sequencenTrailern0101 if MSB of sync word is 1n1010 if MSB of sync word is 0Packet Header FieldsnAM_ADDR contains“active mode”address of one of the slavesnType identifies type of packetnFlow 1-bit flow controlnARQN 1-bit acknowledgmentnSEQN 1-bit sequential numbering schemesn
13、Header error control(HEC)8-bit error detection codePayload Format nPayload headernL_CH field identifies logical channelnFlow field used to control flow at L2CAP levelnLength field number of bytes of datanPayload body contains user datanCRC 16-bit CRC codeError Correction Schemesn1/3 rate FEC(forward
14、 error correction)nUsed on 18-bit packet header,voice field in HV1 packetn2/3 rate FECnUsed in DM packets,data fields of DV packet,FHS packet and HV2 packetnARQnUsed with DM and DH packetsARQ Scheme ElementsnError detection destination detects errors,discards packetsnPositive acknowledgment destinat
15、ion returns positive acknowledgmentnRetransmission after timeout source retransmits if packet unacknowledgednNegative acknowledgment and retransmission destination returns negative acknowledgement for packets with errors,source retransmitsLogical ChannelsnLink control(LC)nLink manager(LM)nUser async
16、hronous(UA)nUser isochronous(UI)nUse synchronous(US)Channel ControlnStates of operation of a piconet during link establishment and maintenancenMajor statesnStandby default statenConnection device connectedChannel ControlnInterim substates for adding new slavesnPage device issued a page(used by maste
17、r)nPage scan device is listening for a pagenMaster response master receives a page response from slavenSlave response slave responds to a page from masternInquiry device has issued an inquiry for identity of devices within rangenInquiry scan device is listening for an inquirynInquiry response device
18、 receives an inquiry responseState Transition DiagramInquiry ProcedurenPotential master identifies devices in range that wish to participatenTransmits ID packet with inquiry access code (IAC)nOccurs in Inquiry statenDevice receives inquirynEnter Inquiry Response statenReturns FHS packet with address
19、 and timing informationnMoves to page scan statePage ProcedurenMaster uses devices address to calculate a page frequency-hopping sequencenMaster pages with ID packet and device access code(DAC)of specific slavenSlave responds with DAC ID packetnMaster responds with its FHS packetnSlave confirms rece
20、ipt with DAC IDnSlaves moves to Connection state Slave Connection State ModesnActive participates in piconetnListens,transmits and receives packetsnSniff only listens on specified slotsnHold does not support ACL packetsnReduced power statusnMay still participate in SCO exchangesnPark does not partic
21、ipate on piconetnStill retained as part of piconetBluetooth AudionVoice encoding schemes:nPulse code modulation(PCM)nContinuously variable slope delta(CVSD)modulationnChoice of scheme made by link managernNegotiates most appropriate scheme for applicationBluetooth Link SecuritynElements:nAuthenticat
22、ion verify claimed identitynEncryption privacynKey management and usagenSecurity algorithm parameters:nUnit addressnSecret authentication keynSecret privacy keynRandom numberLMP PDUsnGeneral responsenSecurity ServicenAuthenticationnPairingnChange link keynChange current link keynEncryptionLMP PDUsnT
23、ime/synchronizationnClock offset requestnSlot offset informationnTiming accuracy information requestnStation capabilitynLMP versionnSupported featuresLMP PDUsnMode controlnSwitch master/slave rolenName requestnDetachnHold modenSniff modenPark modenPower controlLMP PDUsnMode control(cont.)nChannel qu
24、ality-driven change between DM and DHnQuality of servicenControl of multislot packetsnPaging schemenLink supervisionL2CAPnProvides a link-layer protocol between entities with a number of servicesnRelies on lower layer for flow and error controlnMakes use of ACL links,does not support SCO linksnProvi
25、des two alternative services to upper-layer protocolsnConnection servicenConnection-mode serviceL2CAP Logical ChannelsnConnectionlessnSupports connectionless servicenEach channel is unidirectionalnUsed from master to multiple slavesnConnection-orientednSupports connection-oriented servicenEach chann
26、el is bidirectionalnSignalingnProvides for exchange of signaling messages between L2CAP entitiesL2CAP Packet Fields for Connectionless ServicenLength length of information payload,PSM fieldsnChannel ID 2,indicating connectionless channelnProtocol/service multiplexer(PSM)identifies higher-layer recip
27、ient for payloadnNot included in connection-oriented packets nInformation payload higher-layer user dataSignaling Packet PayloadnConsists of one or more L2CAP commands,each with four fieldsnCode identifies type of commandnIdentifier used to match request with replynLength length of data field for th
28、is commandnData additional data for command,if necessaryL2CAP Signaling Command CodesL2CAP Signaling CommandsnCommand reject commandnSent to reject any commandnConnection commands nUsed to establish new connectionsnConfigure commands nUsed to establish a logical link transmission contract between tw
29、o L2CAP entitiesL2CAP Signaling CommandsnDisconnection commands nUsed to terminate logical channelnEcho commandsnUsed to solicit response from remote L2CAP entitynInformation commandsnUsed to solicit implementation-specific information from remote L2CAP entityFlow Specification ParametersnService typenToken rate(bytes/second)nToken bucket size(bytes)nPeak bandwidth(bytes/second)nLatency(microseconds)nDelay variation(microseconds)
