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What is Bluetooth?“Bluetooth wireless technology is an open specification for alow-cost, low-power, short-range radio technology for ad-hocwireless communication of voice and data anywhere in theworld.”One of the first modules (Ericsson) A recent module
Bluetooth Goals & Vision• Originally conceived as a cable replacementtechnology• Short-Range Wireless Solutions• Open Specification• Voice and Data Capability• Worldwide Usability
Present wireless technology like Infra Red datacommunication has two problems :1)Line of Sight2) One to OneBLUETOOTH OVERCOMES THESE PROBLEMS
Bluetooth vs. IRDBluetooth• Point to Multipoint• Data & Voice• Easier Synchronization due toomni-directional and no LOSrequirement• Devices can be mobile• Range 10 mIRD• Point to point• Intended for Data Communication• Infrared, LOS communication• Both devices must be stationary,for synchronization• Range 1 m
Logo• A Scandinavian firm originally designed the logo at the time the SIG(Special Interest Group) was formally introduced to the public• The logo unites the Runic alphabetic characters "H", which lookssimilar to an asterisk, and a "B", which are the initials for HeraldBluetooth
Bluetooth HistoryWhen does it appear?1994 – Ericsson study on a wireless technology to linkmobile phones & accessories.5 companies joined to form the Bluetooth Special InterestGroup (SIG) in 1998.First specification released in July 1999.
Timeline1994 : Ericsson study complete / vision1995 : Engineering work begins1997 : Intel agrees to collaborate1998 : Bluetooth SIG formed: Ericsson, Intel, IBM, Nokia & Toshiba1999 : Bluetooth Specification 1.0A SIG promoter group expanded2000 : Bluetooth Specification 1.0B, 2000+ adopters2001 : First retail products released, Specification 1.12003 : Bluetooth Specification 1.22005 : Bluetooth Specification 2.0
Special Interest GroupThe Bluetooth Special Interest Group comprises more than 1000companies:
Different Versions of Bluetooth• Bluetooth 1.1:Offers Only some Basic Features. The first Bluetooth corespecification version 1.1 was introduced in 1998• Bluetooth 1.2:New features to eliminate radio frequency interferencethrough frequency hopping and added greater security. It wasreleased in 2003.• Bluetooth 2.0:In 2004,Bluetooth version 2.0 + EDR(Enhanced data rate)was introduced
Different Versions of Bluetooth• Bluetooth 2.1:The SIG then introduced version 2.1, which improvedpairing without the need for a PIN, requires even lowerpower consumption, and offers more security.• Bluetooth 3.0:Created in 2009, Bluetooth 3.0 added the ability to use aWi-Fi connection to increase data transmission speeds• Bluetooth 4.0:Most recent is Bluetooth 4.0. Its major feature is BluetoothLow Energy, essentially strong power management skills.
The Basic Idea• Bluetooth is a standard for a small , cheap radio chip tobe plugged into computers, printers, mobile phones, etc• Bluetooth chip is designed to replace cables.Information normally carried by the cable, istransmitted at a special frequency to a receiverBluetooth chip.• These devices can form a quick ad-hoc secure “piconet”and start communication.• Connections in the “piconets” can occur even whenmobile.
Requirements• Low cost as cables – chip $5• Secure as cables – must support authentication andencryption• Must support both data and voice.• Must connect to a variety of devices.• Must be able to function in a noisy environment.• Data rates – 721kbps , using the 2.45Ghz radiofrequency band –I.S.M (Industrial, scientific andmedical)• Must support many simultaneous and private“piconets”.• Must be low power, compact and global.
Bluetooth ClassesThe following table compares the availableBluetooth classes:
Bluetooth Classes• If you wish to communicate over the 100m range, youwill need a class 3 Bluetooth device at both ends.• If you wish to communicate over the 10m range, you canhave a class 2 device at both ends.
Piconet-word• Pico- Small• Net- NetworkThe word “Piconet" literally means "very small network."
Piconet• A piconet is an ad-hoc computer network linking a wirelessuser group of devices using Bluetooth technology protocols.A collection of devices connected viaBluetooth technology in an ad hoc fashion
Piconet….cont.• A piconet starts with two connected devices, and may growto eight connected devices.• Master• Slaves (up to 7)One of the Bluetooth devices as a main controllingunit or MASTER unitOther devices that follow the master unit are SLAVE units.
Piconet….cont.• The master device acts as the hub, meaning the slave devices mustcommunicate through the master device in order to communicate witheach other. In most piconets, the computer serves as the master device.• one master device interconnect with up to seven active slave devices usinga three-bit MAC address. In addition to this a further 255 slave devices canbe connected in an "inactive", or "parked" mode, which can be made"active" at any time by the master device.Each active device within a piconet is identifiable by a 3-bitactive device address.
• A master is the only one that may initiate a Bluetooth communication link.However, once a link is established, the slave may request a master/slaveswitch to become the master. Slaves are not allowed to talk to each otherdirectly. All communication occurs within the slave and the master.• Where higher number of Bluetooth enabled devices need to communicatefor data exchange, the master Bluetooth-enabled device is capable ofswapping the active slaves for the parked slaves in a round robin sequence,normally based of priority assigned.
How Piconet Works?• Bluetooth piconets utilize frequency hopping.• 79 frequencies are used and The frequency hopping is doneat a rate of 1600 times a second.• Devices use an assigned frequency of 2.45 GHz, a frequencyset aside for this purpose by the ISM(Industrial Scientific andMedical) frequency band.
Working…Cont.• Each piconet has a unique master with it’s>>Unique Bluetooth device address (BD_ADDR)>>Clock• Therefore, each piconet has its unique frequency hoppingsequence.• When a connection is initiated by Bluetooth enabled devices,the master device’s clock along with the device address(BD_AAR) is transmitted to the slave devices in a packet knownas Frequency-Hop Synchronization Packet (FHS packet).
The device address of the master device is used to calculate thesequence of frequency hops which all devices within apiconet, follow. The clock of the master device assigns thesequence of the frequency hops.
All devices within a piconet use the difference between theirown native clock and the master’s native clock to make use ofparticular frequency in order to transmit or receive radiosignals on a particular moment.• Using this method, the Bluetooth devices within a piconet areable to avoid one another’s transmission by persistentlychanging frequency channels.
Piconet…Features• A piconet typically has a range of about 30 feet (or 10 meters).Piconet range varies according to the class of the Bluetoothdevice. Data transfer rates vary between about 200 and2100 kilobits per second.• Because the Bluetooth system hops over 79 channels, the probability ofinterfering with another Bluetooth system is less than 1.5%. This allowsseveral Bluetooth Piconets to operate in the same area at the same timewith minimal interference.
After a Bluetooth device has been added to the temporary network (thePiconet), each device is assigned a specific time period to transmit andthey do not collide or overlap with other units operating within the samePiconet.• Piconets can be setup to interact with other Piconets to form largernetworks called Scatternets. Scatternets allow the master in one Piconet tooperate as a slave in another Piconet. While this allows Bluetooth devicesin one Piconet to communicate with devices in another Piconet.
Piconet… Safety• A Bluetooth piconet has encryption and verification built in tothe devises upon which it resides.• There are error-correction schemas and a 4-digit PIN is usedon the master device to authenticate the user. However,other devices may not be equipped with a PINauthentication.
Bluetooth ApplicationsBluetooth provides support for three general applicationareas:• Data and voice access points• Cable replacement• Ad hoc networking
Usage ModelsSet of protocols that implement a particular Bluetooth-basedapplication. Some of the highest priority usage models are:• File transfer• Internet bridge• LAN access• Synchronization• Three-in-one phone• Headset
File Transfer• one of the most fundamental and useful applications• simple point-to-point links to exchange files and other dataobjects• removes the need for cables• much easier to form temporary links between devices toquickly exchange data• also includes the capability to browse folders on a remotedevice.
Internet Bridge• PC is wirelessly connected to a mobile phone or cordlessmodem to provide dial-up networking and fax capabilities.• AT-commands (Attention commands) are needed to controlthe Mobile phone or modem.
Synchronization• It provides a device-to-device (phone, PDA, computer, etc.)synchronization of the PIM (personal informationmanagement) information such as phonebook, calendar,message and note information.• It requires task information to be transferred and processedby devices utilizing a common protocol and format.
Three-in-one PhoneTelephone handsets may connect to three different serviceproviders and act as a:• Walkie-talkie or handset extension• Cellular phone• Cordless phone connecting to a voice access point
The Ultimate Headset• Headset is wirelessly connected to act as a remote device’saudio input and output interface• Increases user’s freedom of movement• Headset must be able to send AT-commands (Attentioncommands) and receive result codes
AT Commands• AT is the abbreviation of Attention• AT commands are instructions used to control andcommunicate with a modem• These commands modify modems behavior or instructthe modem to do something specific, such as dialing atelephone number
Bluetooth Architecture• The Bluetooth technology is dividedinto two specifications:the core and the profile specifications.• The core specification discusses howthe technology works• The profile specification focuses onhow to build interoperating devicesusing the core technologies.
Bluetooth Architecture• RF(radio frequency):The Radio (layer) is the lowest definedlayer. It defines the requirementsof the Bluetooth transceiver deviceoperating in the 2.4GHz ISM band.Transmits data to and from the Baseband• Baseband:Establishes and manages the physicalradio frequency (RF) link betweenBluetooth units that form a piconet.
Bluetooth Architecture• LMP:Link management protocol responsiblefor control of radio links.• L2CAP:logical link control and adaptationprotocol provides multiplexing,Segmentation.• RFCOMM:radio frequency communication,serial port emulation.• HID:Human interface device for peripheral devices.
Types of links• Synchronous Connection Oriented(SCO) link.• Asynchronous Connectionless Link
Synchronous Connection Oriented(SCO) link• SCO is a type of communication link that provides for thecontinuous transfer of data in pre-assigned time periods.• Point to point full duplex link.• The SCO link reserves slots between the master and theslave.• Time slot is reserved at every fixed interval.• Used for a circuit switching voice connection.• Needs an asynchronous connectionless (ACL) type link to befirst established.
Asynchronous Connectionless Link• ACL is a type of communication link that can send data inbursts whenever data is ready to be sent.• when the communication channel (radio channel) isavailable (not transmitting another transmission).• ACL connections can use various types of flow control suchas reliable or time bounded.• This is a packet switched link between a master and slave.• The Bluetooth system has two types of ACL links control(ACL-C) and user data (ACL-U).
Bluetooth packets• Bluetooth supports a wide variety of packet typesdepending on the type of link, throughput and bit faulttolerance.• Data packetsSCO packet –for circuit switchingACL packet –for packet switching• On SCO links packets for low, medium and high qualityvoice as well as combined data and voice are supported.• For ACL links 1, 3 and 5 slot packets using medium andhigh data rates are supported.
Access code• The 72-bit access code is mainly used to identifypackets transmitted over a Bluetooth channel.• All data packets sent on the channel share the sameaccess code.• In addition the access code is used for device paging(finding out if a specific device is in range) andinquiries (used to discover new devices).
Header• The 18-bit packet header contains the followinginformation• A 3-bit target device address• A 4-bit type code. Identifies the type of data or controlpacket.• A 1-bit fields for flow control, sequencing and packetacknowledgement.• An 8-bit header error check• To protect the header from transmission errors each bitis repeated three times in yielding a total length of 54 bits
Payload• The payload part (0 to 2745 bits) of the packet carriesthe actual data.
Forward error correction(FEC)• FEC is a technique for detecting and correcting errors byadding a small number of extra bits.• FEC allows optical transmission over longer distances bycorrecting errors that can happen as the signal-to-noiseratio decreases with distance.• Within Bluetooth technology, there are 2 versions of this1/3 FEC and 2/3 FEC.• 1/3 FEC is a simple 3-times repetition of each info bit.• 2/3 FEC is a shortened Hamming code.
Automatic Repeat Request scheme• Also referred to as ”backward error correction”.• This is an error control technique in this every block of datareceived is checked using the error detection code used, andif the check fails, retransmission of the data is requestedthis may be done repeatedly, until the data can be verified.
“Things that think…don’t make sense unless they link.”- Nicholas Negroponte, MIT MediaLaboratory