Introduction to bluetooth
Jan 01, 2016
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