a bluetooth overview

A Bluetooth Overviewby N.G.Alexiou

School of Computing & Mathematics Sciences

Liverpool John Moores University

Liverpool John Moores UniversitySchool of Computing and Mathematical Sciences

A Bluetooth Overview 2

A Bluetooth OverviewWhat is Bluetooth?Bluetooth DevelopmentBluetooth Administrative StructureBluetooth Technology

Baseband LayerSingle & Multi-Slot FramePower Class TableThe Protocol StackNetwork TopologyConnection States

Forming a PiconetSecurity in BluetoothBluetooth Profile Structure

Bluetooth Vs Wireless TechnologiesBluetooth CompetitorsPlanned Future WorkReferences



What is Bluetooth? (i)

Bluetooth is a Radio System (Radio Frequency Standard) which defines the concept of PANs (Personal Area Network)Nominal Link Range up to 10m/ 0dBm (~100m with 20dBm)Transmitting between 2.402Ghz – 2.480Ghz (79 channels / on a frequency hopping scheme)Reaching Speeds up to 720KbpsNo line-of-sight RestrictionsHigh Security



What is Bluetooth? (ii)

A Bluetooth Network can consist of 7 slave devices and 1 master deviceUntil Bluetooth no other global cellular technology for mobile users existed Solve a simple problem, Replace cables used on mobile devices and their peripherals with radio frequency wavesThus Bluetooth tries to emulate cost, security and capabilities of cable for mobile users



Bluetooth DevelopmentBluetooth as a word derived from the 10th century king of Denmark (Harald Blatand)As a research started in 1994 by Ericsson Mobile Communications with one goal to relief cables carried by mobile phone usersIn February 1998 Bluetooth SIG (Special Interest Group) founded, under the core promoters of

Ericsson, Intel, IBM, Toshiba and NokiaIn 1999 more core promoters added

Microsoft, Agere, 3Com and MotorolaNow exceeding 2500 members



Bluetooth SIG Administrative Structure

Program Management Board

Regulatory Legal Committee

Japan Regulation

s

Marketing Bluetooth Qualification Review Board

Test & Interoperability

Architecture Review Board

Sub groupsRF Regulation

s

Aviation Regulation

s

Security Regulation

s

Management Services (ADMIN)

Bluetooth Technical Advisory

Board

Bluetooth Qualification

Admin

Bluetooth Qualification

Body

Technical Working Groups

Expert Groups

Errata owners and review pool

Bluetooth SIG Administrative Structure



Bluetooth Baseband Layer (i)

Bluetooth operates in ISM (Industrial Scientific Medical) band of 2.4GHzBetween 2.402GHz and 2.480GHz with the spacing of 1MhzUsing a Frequency Hopping Spread Spectrum (FHSS) instead of Direct Sequence Spread Spectrum (DSSS)The FHSS scheme provides 1600 hops / second and every hop is 625μsBluetooth packets can be multible slots, each packet can be composed of 1, 3 or 5 slots of 625μs each.



Bluetooth Baseband Layer (ii)

Voice and Data links in Bluetooth RF can be divided into two types ACL & SCO (Also a third type which combines both – DV):

ACL (Asynchronous Connection-Less)

Made for non-critical dataProvides largest data rate of 723.3 Kb/s in one directionAsynchronousPacket-switchedConstructed of 72 bit access code54 bit packet header and 16 bit CRC

SCO (Synchronous Connection Oriented)

SCO functionality is for critical data and voiceSCO occurs after the ACL if neededCircuit SwitchedA master can support up to 3 SCO LinksConstructed of 72 bit access code54 bit packet headerUses slot reservation at fixed intervalsData rate of 30b/sDoesn’t have CRC (Cyclic Redundancy Code)

DV (Data Voice)Has no flow Control or CRC (similar to SCO)The Data part supports flow control and retransmission



Bluetooth Single & Multi-Slot Frame

Master

Slave

625μs

F(1) F(5)

t

t

One Slot

F(2)+F(3)+F(4)

Multi slot

Bluetooth frame packets slots



Bluetooth Power Class Table

Power ClassMax Output

PowerMax Output

PowerExpected

RangeRange in

Free Space

Class 1 100mW 20dBm 42m 300m

Class 2 2.5mW 4dBm 16m 50m

Class 3 1mW 0dBm 10m 30m

Bluetooth Power Class Table



Bluetooth SIG Complete Protocol Stack (i)

vCard/vCal

OBEX

WAE

WAP

UDP TCP

IP

PPP

AT-Commands

RFCOMM

TCS BIN SDP

L2CAP

Host Controller Interface LMP

BaseBand

Bluetooth Radio/RF

Audio


Complete Protocol Stack


Bluetooth Protocol Stack (ii)

The Bluetooth protocol stack may differs from application to application, depending on the needs of the implementing Bluetooth Chip.Bluetooth Radio/RF: Broadcasting in between 79 channels (2.402GHz-2.480GHz) on a FHSS (Frequency Hopping Spread Spectrum) scheme at 1600 hops/secBaseband Layer: Prepares the packets and arranges the communication channels (ACL-SCO)LMP (Link Manager Protocol): Responsible for setting up the link between two Bluetooth radios (Security aspects and control issues on Baseband packet sizes) – Also LMP in charge of Bluetooth power modes and connection states.L2CAP (Logical Link Control & Adaptation Protocol): L2CAP acts as a bridge between the upper layer protocols and the baseband layer. Adapts data and converts them into different packet sizes. Sometimes works in parallel with LMP, only for ACL links.SDP (Service Discovery Protocol): Provides service discovery and is required in all usages models, by SDP we can interact-query other Bluetooth devices in the area about their status and their services.



Bluetooth Protocol Stack (iii)

RFCOMM Protocol: Cable replacement protocol, emulates RS-232 control and signals, thus provides transport to data for upper layer services such as OBEX or PPP.TCP (Telephony Control Protocol):

Telephony Control Binary: Defines the call control signalling for establishments of speech and data cellsTelephony Control AT Commands: Controls the modem and the mobile phone commands

(Adopted Protocols)PPP (Peer-to-Peer Protocol): Mainly for peer-to-peer networking usageTCP/UDP/IP (Transfer Control Protocol/User Datagram Protocol/Internet Protocol): Mainly for usage on internetOBEX (IrOBEX): Emulates the HTTP (HyperText Transfer Protocol), in common word is the web browser of the Bluetooth.WAP (Wireless Application Protocol): Supports the usage of wireless Computer applications developed for WAE (WAP Application Environment)VCARD & VCalendar: Type of format which data supported, not a protocol or mechanism



Bluetooth Network Topology

M

S

i) Piconet (Point-to-Point)

M

SS

S

S

ii) Piconet (Multipoint)

M

S S S

M

S S

Master/Slave

iii) Scatternet

Bluetooth devices have the ability to work as a slave or a master in an ad hoc network. The types of network configurations for Bluetooth devices can be three.

i. Single point-to-point (Piconet): In this topology the network consists of one master and one slave device.

ii. Multipoint (Piconet): Such a topology combines one master device and up to seven slave devices in an ad hoc network.

iii. Scatternet: A Scatternet is a group of Piconets linked via a slave device in one Piconet which plays master role in other Piconet.



Bluetooth Connection States


E

A

G

H

C

D

I

H

C

B

F

Master

There are four Connection states on Bluetooth Radio:

1. Active: Both master and slave participate actively on the channel by transmitting or receiving the packets (A,B,E,F,H)

2. Sniff: In this mode slave rather than listening on every slot for master's message for that slave, sniffs on specified time slots for its messages. Hence the slave can go to sleep in the free slots thus saving power (C)

3. Hold: In this mode, a device can temporarily not support ACL packets and go to low power sleep mode to make the channel available for things like paging, scanning etc (G)

4. Park: Slave stays synchronized but not participating in the Piconet, then the device is given a Parking Member Address (PMA) and it loses its Active Member Address (AMA) (D,I)

Bluetooth Connection States


Bluetooth Forming a Piconet


Master

Inquiry

Inquiry Scan

Inquiry Response

Page

Page Scan

Slave Response

Master Response

ConnectionConnection

Slave1. Inquiry: Inquiry is used to find the identity of the Bluetooth devices in the close range.

2. Inquiry Scan: In this state, devices are listening for inquiries from other devices.

3. Inquiry Response: The slave responds with a packet that contains the slave's device access code, native clock and some other slave information.

4. Page: Master sends page messages by transmitting slave's device access code (DAC) in different hop channels.

5. Page Scan: The slave listens at a single hop frequency (derived from its page hopping sequence) in this scan window.

6. Slave Response: Slave responds to master's page message

7. Master Response: Master reaches this substate after it receives slave's response to its page message for it.

3

2

4

1

5

7

6

Forming a Piconet Procedures


Bluetooth Security

Three Security Modes Available in Bluetooth:Security Mode 1- This is the most insecure security mode in which the Bluetooth device does not initiate any security procedure. Security Mode 2- This mode enforces security after establishment of the link between the devices at the L2CAP level. Security Mode 3- This mode enforces security controls such as authentication and encryption at the Baseband level itself, before the connection is set up.

And three Security Controls for restricting access to services:Access to Services would need Authorization (Authorization always includes authentication). Only trusted devices would get automatic access.Access to Services would need only Authentication. I.e. the remote device will need to get authenticated before being able to connect to the applicationAccess to Services would need Encryption. The link between the two devices must be encrypted before the application can be accessed.



Bluetooth Profile Structure

Generic Access Profile TCS-BIN-based ProfilesCordless Telephony Profile

Intercom ProfileService Discovery Profile

Serial Port ProfileDial-up Networking Profile

Fax Profile

Headset Profile

LAN Access Profile

Generic Object Exchange Profile

File Transfer Profile

Object Push Profile

Synchronization Profile


Bluetooth Profile Structure


Bluetooth Vs Wireless Technologies


HyperLAN2

DECT – DMAP (DependedOn the Antenna)

IEEE802.11(Depended on the Antenna)

Gro

ss

Da

ta R

ate

Distance to Access Point

1 Mbps

100 Kbps

10 Mbps

100 Mbps

10 m 100 m 1000 m 10000 m

IrDA V1.0(SIR)

IrDA V1.1(FIR)

IrDA(VFIR)

Bluetooth

HomeRF1.2

HomeRF2.0

HomeRF2.1IEEE802.11b

HyperLan

GSM / WAP

GPRS

UMTS (FDD)

UMTS (TDD)

IEEE802.11a

Wireless Technologies Graph – Distance Vs Data Rate


Bluetooth WLANs Competitors


Bluetooth HomeRF 802.11b HyperLAN 802.11aHyperLAN

2Frequency Band 2.4GHz 2.4GHZ 2.4GHz 2.4GHz 5GHz 5GHz

TechnologyFrequency

Hopping Spread Spectrum

Frequency Hopping Spread

Spectrum

Direct Sequence

Spread Spectrum

Guassian Minimum

Shift Keying

Orthogonal Frequency

Division Multiplexing

Orthogonal Frequency

Division Multiplexing

Performance 720Kbps 1.6Mbps 11Mbps 23Mbps ~50Mbps ~50Mbps

Range 10-100 m 50 m ~100-1000 m ~100-500m ~100-1000m ~100-1000m

Power Very Low Medium Medium Medium Medium/High Medium/High

Relative Cost Low/Very Low Medium/Low Medium Medium High High

Target Applications

Cable Replacement, Wireless Data, Wireless Voice,

PANs

Wireless Data, Wireless Voice

Wireless Data Wireless Data Wireless Data Wireless Data

Key FeaturesVery Low Power,

Low Cost,

Voice & Data

Voice & Data,

Moderate CostGood

PerformanceGood

PerformanceHigh

PerformanceHigh

Performance

Promoters 2500+ <50 ~100 <50 ~100 <50

Regional Support Global US US/Asia Europe US Europe

Comparison Table of the most popular WLANs Technologies


Planned Future WorkPlanned Future work will concentrate on:

•Analyzing and studying deeper the capabilities on Bluetooth Technology Vs the Rest Wireless Family•Verifying that currently developed Bluetooth technology covers all the needs & necessities required for such a technology (If any further development could be done in major areas such as security or protocols)•Visualizing the procedures followed by a Bluetooth Master device to create a Piconet, in order to specify how Bluetooth interacts in Real-Time Environments•Creating a middleware platform able to interact “openly” in a Master Bluetooth device for monitoring communication issues between the Master Device and Slave Devices in a Bluetooth Piconet



ReferencesSpecification of Bluetooth System, Profiles Version 1.1, February 22 2001, Specification Volume 2, Bluetooth SIG (www.bluetooth.org)Bluetooth Architecture Overview, James Kardach, Mobile Computing Group, Intel CorporationDirect Sequence vs. Frequency Hopping, Wave Wireless Networking, 2000, www.wavewireless.comBluetooth Security Architecture, Version 1.0, 15 July 1999, Thomas Muller, (www.bluetooth.org)How Bluetooth’s unusual operating characteristics impact test decisions, Teit Poulsen, September 1 2002, PRIMEDIA Business Magazines & MediaBluetooth Protocol Architecture, Version 1.0, August 25th 1999, Riku Mettala, (www.bluetooth.org)Bluetooth Security, 2000-05-25, Juha T. Vainio, Department of Computer Science and Engineering Helsinki University of Technology


a bluetooth overview

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