BluetoothLectured By:Vivek Dimri

Asst Professor CSE Deptt. SET

IntroductionBluetooth is a wireless protocol utilizing

short-range communications technology facilitating data transmission over short distances from fixed and mobile devices, creating wireless personal area networks (PANs).

Bluetooth uses a radio technology called frequency hopping spread spectrum.

It chops up the data being sent and transmits chunks of it on up to 79 different frequencies.

Communication and ConnectionA master Bluetooth device can communicate with up

to seven devices. This network group of up to eight devices is called a

Piconet.A Piconet is an ad-hoc computer network, using

Bluetooth technology protocols to allow one master device to interconnect with up to seven active devices.

Up to 255 further devices can be inactive, or parked, which the master device can bring into active status at any time.

At any given time, data can be transferred between the master and one other device.

Communication and ConnectionThe Bluetooth specification allows connecting

two or more piconets together to form a scatternet, with some devices acting as a bridge by simultaneously playing the master role in one piconet and the slave role in another.

Peak transmission rate is 1 Mbps.

Communication and Connection

Bluetooth ChannelsThe piconet channel is represented by a pseudo-

random hopping sequence (through 79/23 RF frequencies)

The hopping sequence is unique for the piconet and is determined by the device address of the master of the piconet.

The phase is determined by the master clock.Channel is divided into time slots - 625 microsecs each .Each slot corresponds to a different hop frequency.Time Division Duplex - master and slave alternately

transmit/listen.Packet start aligned with slot start

Bluetooth Channels

m

s1

625 sec

f1 f2 f3 f4

Physical LinkSynchronous Connection Oriented (SCO)

Link :symmetric point-to-point link between M and Sreserved 2 consecutive slots at regular intervalsmaster can support up to 3 simultaneous SCO linksmainly for audio/voicenever retransmitted

Asynchronous Connection-less (ACL) Linksymmetric/asymmetric point-to-multipoint between master and all slaveson a per-slot basis (polling scheme for control)only one ACL link per piconetpackets retransmitted (ARQ)

PacketsAll data on the piconet channel is

conveyed in packets3 packet types are defined for the

Baseband layerControl packets (ID, NULL, FHS, POLL)Voice packets (SCO)Data packets (ACL)

Packet format - (68/72 bits) Access Code, (54 bits) Header, (0-2745 bits) Payload.

PacketsAccess code

Header Payload

Voice data

header CRC

SCO ACL

1/3/5 slot packetsUnprotected/ 2/3 FECARQ scheme – retran-smit lost data pkts

Single-slot packets64 kbpsUnprotected/ 1/3 or 2/3 FECNever retransmittedRobust CVSD encodingused

Bluetooth AddressBluetooth Device Address (BD_ADDR)

Unique 48 bit addressActive Member Address (AM_ADDR)

3 bit address to identify active slave in a piconet

MAC address of Bluetooth deviceAll 0 is broadcast address

Parked Member Address (PM_ADDR)8 bit parked slave address

Setting up ConnectionAny Bluetooth device will transmit the

following information on demand:Device name. Device class. List of services. Technical information, for example, device

features, manufacturer, Bluetooth specification used, clock offset.

Bluetooth ArchitectureBluetooth is both a hardware-based radio

system and a software stack that specifies the linkages between layers.

In this section, you’ll learn about:The Bluetooth protocol stack. The protocol

stack is the core of the Bluetooth specification that defines how the technology works.

The Bluetooth profiles. The profiles define how to use Bluetooth technology to accomplish specific tasks.

Bluetooth Architecture

Bluetooth ArchitectureLower Layer

Radio Layer Responsible for modulation/demodulation Define physical characteristics

Baseband or Link Controller Layer Responsible for properly formatting of data for transmission. Handles synchronization of link

Link Manager Protocol Translates HCI commands into baseband level operations Responsible for maintain and establish links and manage power

change request.Host Control Interface

Act as boundary between low layer protocol stack and upper layers

Bluetooth ArchitectureUpper Layer

L2CAP (Logical Link Control and Adaptation Protocol) layer:

Establishing connections across existing ACL links or requesting an ACL link if one does not already exist.

Multiplexing between different higher layer protocols, such as RFCOMM and SDP, to allow many different applications to use a single ACL link.

Repackaging the data packets it receives from the higher layers into the form expected by the lower layers.

RFCOMM (Radio frequency communications) layer: It connects to the lower layers of the Bluetooth protocol stack

through the L2CAP layer. RFCOMM is the cable replacement protocol used to create a

virtual serial data stream. RFCOMM provides a simple reliable data stream to the user,

similar to TCP.

Bluetooth ArchitectureUpper Layer

SDP (Service Discovery Protocol): It defines actions for both servers and clients of Bluetooth

services. Used to allow devices to discover what services each other

support, and what parameters to use to connect to them.

OBEX (object exchange): It is a transfer protocol that defines data objects and a

communication protocol two devices can use to easily exchange those objects.

Telephone control protocol-Binary (TCS-Bin): It’s a bit oriented protocol. It defines the call control signaling for the establishment of

voice and data calls between Bluetooth devices. TCS BIN defines mobility management procedures for handling

groups of Bluetooth TCS devices

Connection EstablishmentTwo step process :

Inquiry – to get device address.Paging – for Synchronization

Connection Establishment: InquiryNo master and slaves at this point

Inquiry Inquiry Scan

Inquiry Response

Inquiry pkt

FHS pkt

Device A Device B

Connection Establishment: PaggingMaster Slave

Page Page Scan

Master PageResponse

Slave PageResponse

Connected Connected

Page pkt

ID pkt

FHS pkt

ID pkt

POLL

NULL

Uses FHS to getCAC and clk info

Assigns active addr

Connection Establishment Time

ConnectedPagingInquiry

Typical

Max

5.12 s

15.36 s

0.64 s

7.38 s

Connection ModesActive Mode :

Device actively participates on the piconet channel

Power Saving modesSniff Mode :

Slave device listens to the piconet at a reduced rate . Least power efficient.

Hold Mode : The ACL link to the slave is put on hold. SCO links are still supported. Frees capacity for inquiry, paging, participation in another piconet.

Park Mode : The slave gives up its active member address. But remains synchronized (beacon channel). Listens to broadcasts. Most power efficient.