Introduction to bluetooth

outline

Why bluetooth History Bluetooth stack and technology Reference

bluetooth

Why bluetooth?Cable replacement between devicesOpen SpecificationLow power consumptionConnection can be initiated without user

interactionDevices can be connected to multiple devices

at the same time

history

The technology was born in 1994

Standardized by the Bluetooth Special Interest Group (SIG),a consortium founded in spring 1998 by Ericsson,Intel,IBM,Nokia,and Toshiba

The first version was released July 1999

stack

stack

Bluetooth stack and OSI layers

stack

Bluetooth StackTransport Protocol group

Radio ,Baseband , L2CAP and HCI

Middleware Protocol group PPP , IP , TCP ,WAP , OBEX, IrDA RFCOMM, TCS, SDP

Application group

stack

stack

stack

Transport Protocol groupAllow Bluetooth devices to locate each other

manage physical and logical links with higher layer protocols and applications

support both asynchronous and synchronous transmission

stack

Middleware Protocol group includes third-party and industry-standard prot

ocols as well as Bluetooth SIG developed protocols

These protocols allow existing and new applications to operate over Bluetooth links

stack

Application groupConsists of actual applications that use Blueto

oth links

They can include legacy applications as well as Bluetooth-aware applications

radio

Primarily concerned with the design of the Bluetooth transceivers

Bluetooth devices operate on 2.4 GHz Industrial Scientific Medical band (ISM band)

Unlicensed in most countries

radio

Techniques to minimize packet loss:Frequency HoppingAdaptive power controlShort data packets

radio

TDD (Time Division Duplex)The channel is divided into time slots, each 62

5 μs in lenght, thus the nominal hop rate is 1600 hops/s

When in inquiry or page mode, it hops at 3200 hops/s with a residence time of 312.5 μ sec

radio

Master only transmits in odd slots Slaves only transmit in even slots

radio

FHSS (Frequency Hopping Spread Spectrum)Divides the ISM-band into 79 1-Mhz channels

Channel 0: 2402 MHz … channel 78: 2480 MHz

Communication between devices switches between available channels

radio

625 μs

radio

Three power classes defined with max output power from 1 mW (Class 1) to 100 mW (Class 3)

power class 1 : long range (~100m,~100mW)power class 2 : mid range (~10m,~2.5mW)power class 3 : short range (~1m,~1mW)

radio

Packet

radio

Access CodeChannel Access Code (CAC)Device Access Code (DAC) Inquiry Access Code (IAC)

GIAC ( Global IAC) DIAC ( Discovery IAC )

radio

Packet Header AM_ADDR : the active member address in piconet TYPE : kind of code FLOW : flow control ARQN : ACK,NAK SEQN : discriminate duplication of ARQN HEC : Header verify

Payload Data header , data and CRC

radio

Kind of code Normal

ID,NULL,POLL,FHS,DM1

SCO HV1,HV2,HV3,DV

ACL DM1,DH1,DM3,DH3,DM5,DH5,AUX1

radio

radio

Error Control 1/3FEC(Forward Error Correction) 2/3FEC(Forward Error Correction) ARQ(Automatic Repeat Request)

radio

ARQ scheme in the ACL link

baseband

Defines how Bluetooth devices search for and connect to other devices

Responsible for channel coding/decoding, timing and managing a Bluetooth link

baseband

Master/slavePiconet : A master and the slaves

piconet

baseband

Scatternet : multiple piconets connected together

scatternet

baseband

Communication is only possible between a master and its slaves.

Master determines hopping pattern , slaves have to synchronize

Each piconet has a unique hopping pattern Participation in a piconet = synchronization to hopping

sequence Each piconet has one master and up to 7 simultaneou

s slaves The maximum number of “parked” slaves is 255 per pi

conet

baseband

Device connection states

baseband

Inquire and Page

baseband

3 power saving modes sniff : slave listens to the channel at a reduced rate (d

ecreasing of duty cycle)-least power efficient Hold : data transfer is held for a specific time period -

medium power efficient park : synchronized to the piconet but does not partici

pate in traffic

baseband

link types Voice link – SCO (Synchronous Connection Oriented)

FEC (forward error correction), no retransmission, 64 kbit/s duplex, point-to-point, single-slot packet size

Data link – ACL (Asynchronous ConnectionLess) Asynchronous, point-to-multipoint, up to 433.9 kbit/s symmetr

ic or 723.2/57.6 kbit/s asymmetric, Variable packet size (1,3,5 slots)

baseband

baseband

The Link Manager Protocol(LMP)

LMP manages bandwidth allocation for general data bandwidth reservation for audio traffic trust relationships between devices encryption of data control of power usage

Host Controller Interface (HCI)

This layer is not a required part of the specification

Defines a standard interface for upper level applications to access the lower layers of the stack

Its purpose is to enable interoperability among devices and the use of existing higherlevel protocols and applications

Logical Link Control and Adaption (L2CAP)

Deals with multiplexing of different services

RFCOMM, SDP, telephony control

segmentation , reassembling of packets Quality of Service Group abstraction

Create/close group, add/remove member

only support ACL connection

Service Discovery Protocol (SDP)

Inquiry/response protocol for discovering services Searching for and browsing services in radio proximity Adapted to the highly dynamic environment Defines discovery only, not the usage of services Caching of discovered services

Reference

Praktikum Mobile und Verteilte Systeme im Sommersemester 2006 Prof. Dr. C. Linnhoff-Popien, Peter Ruppel, Georg Treu

Bluetooth Steffen Witt and Tobias Julius Neubert

Bluetooth Alessandro Leonardi

Bluetooth Dr.-Ing. H. Ritter,

“What is Bluetooth” Patricia McDermott-Wells