wireless short range communicationdixon.hh.se/urbi/wcs/wcs2/bluetooth_slides.pdf · • originating...

Bluetooth™Wireless short range communication

Per-Arne Wiberg, Free2move

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Content• Background• Technology• Applications• Test and qualification• Case study

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Background

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History

• Originating from Ericsson• “Special Interest Group” is formed• “Promoter Company group”• “Early adopter group”

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Special Interest Group SIG-supporting organizations

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SIG- Early adopters

• Over 2500 companies listed• Open to all• Members yield their IPR• Free License is given in return

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Bluetooth™ functionality

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Technology

• Air interface• Base Band• Protocol

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Air Interface

• Operates in the 2.4 GHz ISM-band• Total band width: 80 MHz

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ISM-band

• Free available band in most countries• Interference can appear• Wireless LAN uses the 2.4 GHz ISM band• Microwave ovens operate in the band• How can a stable communication be achieved

under these circumstances?

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Band spreading

• Frequency hopping at 1600 hops per second• Gives time slots at different frequencies• Sender and receiver must be synchronized• A channel = en hopping sequence

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To create a channel

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Piconet• A Piconet= a channel = en

hopping sequence• A Piconet has en Master with

up to 7 active slaves• < 256 inactive slaves

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Piconet(2)

• 1 master, 7 active slaves• 10 Piconet in the same area

without significant loss of throughput

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Piconet(3)• Ad Hoc connection• A new unit is connected to

the Piconet in 1-4 seconds

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Piconet(4)• Asynchronous traffic : data• Synchronous traffic: voice

or sound

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Piconet(5)

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Addressing in BluetoothBluetooth device address BD_ADDR: 48 bitarEtehrnet adress (IEEE 802.11)

•LAP lower address part•UAP upper address part•NAP non-significant address part

LAP NAPUAP24 bitar 8 bitar 16 bitar

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Packet format

54 bit72 bit 0-2745 bit

Accesskod

Packetheader

Data

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Packet format Access code

54 bit72 bit 0-2745 bit

Preeamble Access kod Trailer

4 b 64 b 4 b

•CAC Channel access code•DAC Device access code•GIAC General Inquire access code

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Access code

• First part of the packet• The receiver correlates to the code• Important with big separation of

code words in the code

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Access code

• Different codes:– “Inquire access” code when

connecting– “Device access” code when the

address is known– “Channel access” code when the link

is established

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Access code

• Device access code DAC– Is used by Page and Page scan– Is calculated from LAP i BD_ADDR

• Channel access code CAC– Used by data transfer packages– Is calculated from LAP i BD_ADDR

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Access code (2)

• Inquiry access code IAC– Is used by Inquiry and Inquiry Scan– A number of pre defined codes

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Access procedure

• Page scan– The slave listens on 32 frequencies– Calculated from address and clock– Special hopping sequence

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Page

– The master sends 16 ID packets at the double frequency

– Hopping sequence = -8 - +7 of the estimated frequncy of the slave; takes 10 ms

– The transmission is repeated 128 times

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F´(1)

master

10 ms 128

F(1)slav F(2)

11,25 ms1,28 s

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FHS

F(k)F(k+1)F(k+1) G(m)

F´(k) F´(k+1) G(m+1)

Hoppsekvens för kanalenHoppsekvens för page

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Inquiry

– Works like page– The address is unknown– Uses a given hopping sequence– Uses GIAC alt. DIAC

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Packet header

54 bit72 bit 0-2745 bit

3 b 8 b4 b 1 b 1 b 1 b

1/3 FEC

AM-ADDR TYPE•FHS•NULL, POLL•HV1, HV2, HV3•DM1, DM3, DM5•DH1, DH3, DH5•AUX1

Flow ARQN SEQN HEC

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Data packet

54 bit72 bit 0-2745 bit

2 b 1 b

Header

5 b

HV paket har fix längd: 240 bitIngen header

L_CHlogical channel

Flow Length

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Error correction

• 1/3 FEC : bit repetition• 2/3 FEC : (15,10) Hamming code

• Retransmission (ARQ)– 1 bit ACK/NAK– 1 bit sequence number

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Packet types

General packets– ID-packet: ”Device access code” 68 bits– POLL-packet: Is sent periodicaly to the

slaves. Contains only access code and header is 126 bits. The slave must respond to this packet.

– NULL-packet: Same as the POLL-packet. Is used for ARQ and flow control.

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General packets (2)

• FHS Access code, packet header and data. Data is 240 bits 2/3 FEC coded. Data contains BD_ADDR and the clock of the master.

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SCO-packet (synchronous link)

• “High quality voice” HV1 packet– Data 240 bits 1/3 FEC (no CRC) : 10

information bytes

• HV2 packet– Data 240 bits 2/3 FEC : 20 information

bytes.

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SCO-packet(2)

• HV3 packet– Data 240 bits no FEC : 30 information

bytes.

• DV packet– 80 bits voice 32-150 bits data. 2/3 FEC

on data. ARQ on data.

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ACL-packet (asynchronous link) en time slot

• DM1- ”Data Medium rate”: 2/3 FEC 18 information bytes, CRC code

• DH1 ”Data High rate”: no FEC, 28 information bytes, CRC code

• AUX1 no FEC, no CRC 30 information bytes

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ACL-packet (asynchronous link) 3 time

slots

• DM3- ”Data Medium rate”: 2/3 FEC 123 information bytes, CRC code

• DH3 ”Data High rate”: no FEC, 185 information bytes, CRC code

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ACL-packet (asynchronous link) 5 time slots

• DM5- ”Data Medium rate”: 2/3 FEC 226 information bytes, CRC code

• DH5 ”Data High rate”: no FEC, 341 information bytes, CRC code

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Data throughput Typ Symetrisk Asymetrisk

DM1 108.8 108.8 108.8

DH1 172.8 172.8 172.8

DM3 258.1 387.2 54.4

DH3 390.4 585.6 86.4

DM5 286.7 477.8 36.3

DH5 433.9 723.2 57.6

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Security

• Link level• Authentication • Encryption• Security in the application

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Security on link level

• Robust authentication and encryption– 128 bit key

• Frequency hopping on 79 frequency bands– 100 is considered to be military

security• Limited range

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Authentication

• The key is generated from a random number, the PIN code and BD_ADDR

• The PIN-code can be stored• The PIN-code can be entered in the

units when connecting.

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Encryption

• Encryption key is generated from the Authentication key

• Can be 8-128 bits depending on country

• Is changed at every encryption command to LM

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Scatternet

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Scatternet(2)

• Tme sharing in a slave.• For ACL: Hold, park or sniff in one

piconet• For SCO: only HV3 can be used.• The slave must handle two clocks.

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Bluetooth protocol stack

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Protocol stack(2)

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Host Control Interface HCI

HCI: A commandinterface to LM andBasband

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Link Manager Protocol LMP

• Link establishment• Security• QoS handling

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Link Manager Protocol LMP

• Adjustment of the clock– The Master estimates

the clock of the slave – Is used to make PAGE

SCAN faster

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Link Manager Protocol LMP

• Master-Slave switch• Connecting SCO• Name request• Disconnection• ”Hold mode”• ”Parked mode”• ”Sniff mode”

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Logical Link Control and Adaptation Protocol

L2CAP

• Multiplexing of protocols – Many protocols on top of

L2CAP• Segmentation and

joining of packets• Quality-of-Service• Groups

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Logical Link Control and Adaptation Protocol

L2CAP• Establishment of

channels– Connection

oriented 0-65535 bytes

– Connectionless

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”Connectionless channel”

• Amount of data: 0-65535 bytes• Transmission to a ”Group”• Delivery is not guarantied

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Service Discovery Protocol- SDP• Search for services in the

Bluetooth neighborhood • Give out service

description on command• Search for specific

services• Hierarchical search for

services• Example: Printer

• Laser printer– color

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Service Discovery Protocol- SDP• Client-Server protocol• The server has a data

base with services• The services are

represented by a 128 bit UUID.

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Example of SDP session

• Establish a channel to a device• Query the SDP database

– Search b.m.o UUID– Or Browse

• Retrieve service ID• Disconnect SDP channel• Establish a channel to the service

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RFCOMM

• Emulates RS-232• Is used in many

profiles

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RFCOMM

• Emulates many serial ports between two units

• Flow control• Status of the

serial transmission is monitored

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Object Exchange Protocol OBEX

• Synchronization• File transfere• ”Object push”

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Telephony Control Protocol

• Group calls, Establishmnet and disconnection of voice connection

• Management: Handling of Groups

• Signaling (connectionless)

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Relation between profiles

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Applications

•Integrate into Lap Tops

•Integrate into mobile phones

•Integrate into PDAs

•Headset

•Cameras

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Applications

Sensors and actuatos

Communication systems

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Industrial applications

•Measurement on moving objects•Reducing cabelcosts•Identification•Supervision•Maintenance

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Medical applications•Regulatory issues

•Big potential still to come

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Utveckling av Bluetooth produkter

• Komponenter• Kvalificeringsprocessen• Utvecklingsverktyg

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KomponenterLeverantör Produkt Tidplan Pris Beskrivnign

Alcatel Enchips-lösning

Q1 2001 Integreradantenn

Atmel Modul Q4 2000 Basbandsenhet

AtmelWireless

RF-krets Q1 2001

Ericsson Modul Q4 2000 100USD

Komplettlösning

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KomponenterLeverantör Produkt Tidplan Pris Beskrivning

Mitel Basbands-krets

Q4 2000 7USD

Basbandskrets

National Modul Q2 2001 Utvecklings-verktyg finns

National Basbands-krets

Q2 2001

National RF-krets Q2 2001

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Kvalificering/Test

TillverkareBQTF

BQB

BQA

Produkt

AnmälanDokumentation

Testprotokoll

Kan vara samma organisation