Architecture Overview of Bluetooth

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Architecture Overview of Bluetooth

• Presented by Chih-Liang Huang
• 10/11/00

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Objective

• Be able to answer What is Bluetooth?
• Behavior/Functional Overview
• Architecture Overview
• Implementation

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• What is Bluetooth?
• Bluetooth is the term used to describe the
  protocol of a short range (10 meter)
  frequency-hopping radio link between devices.
  These
• devices are then termed Bluetooth - enabled.

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In the Office
You arrive at the office and put down your
briefcase. While in your office, your Personal
Digital Assistant (PDA) automatically
synchronizes with your desktop PC and transfers
files, e-mails and schedule information.
While in a meeting, you access your PDA to send
your presentation to the electronic whiteboard.
You record meeting minutes on your PDA and
wirelessly transfer these to the
attendees before they leave the meeting.
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At home
Upon arriving at your home, the door
automatically unlocks for you, the entry way
lights come on, and the heat is adjusted to your
pre-set preferences.
An alarm notifies you that your toddler has just
left the house.
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During the travel
You enter the airport waiting lounge, equipped
with Bluetooth-enabled Internet ports. Via the
ports, you and other guests use Bluetooth-enabled
laptops, PDAs, and other devices to access your
office or home-based servers via the airline
server.
You get on the Rent-A-Car bus. Your reservation
is automatically transferred to the Rent-A-Car
database, and you are dropped off at your car.
You get in the Bluetooth-enabled rental car. Your
hotel reservations are automatically queried
from your PDA and the GPS system offers you
directions to your hotel.
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In the car
As you enter a national park, a map of the park
appears on your display. You can view the
schedule of activities for the park and your own
personal electronic tour guide is downloaded to
your vehicle.
You receive a new message en route, which is
verbally transmitted to you via the vehicle's
speakerphone.
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What is the Bluetooth? The Bluetooth is a
wireless technology to solve a simple problem
replace the cables used on mobile devices with
radio frequency waves. The Bluetooth system is
a universal radio interface on the globally
available unlicensed ISM 2.4 GHz frequency band
facilitating wireless communication of data and
voice in both stationary and mobile environments.
and avoid interference from other signals by
hopping to a new frequency after transmitting or
receiving a packet. Its key features are
robustness, low complexity, low power and low
cost.
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Technology Evolution Traditionally, the wireless
network has been used for voice communication,
where voice-mail is one of the most popular
value-added services. The focus has now moved
towards mobile data technologies and the demand
for wireless data communication has increased. As
a result, the end-user wants wireless technology
that will support all or most of their needs
e-mail internet access e-commerce ALL of
the services can use the Bluetooth technology
enabled devices to satisfy the end-users need.
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History The Bluetooth Special Interest Group
(SIG) was launched in May 1998. Goal to develop
the specifications for a low-powered, short
range, RF-based wireless communication technology.
Today, over 1800 companies have joined as
members.
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Application and usage modes There are many
practical applications or usage models where
Bluetooth technology can be used today. For
example
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The features of Bluetooth Syatem 1. Worldwide
Operation 2. Transmission of Voice and data 3.
Small, low power, low cost radio transceiver 4.
Security
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Bluetooth Architecture Core Specification
Discuss how the technology works. (hardware
oriented) Profile specification focus on how to
build interoperating devices using the core
technologies. (software oriented)
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Radio Frequency Layer Antenna power of 0dBm
(1mW) up to 20dBm (100mW) worldwide. The radio
used Frequency Hopping to spread the energy
across the ISM spectrum in 79 hops displaced by 1
MHz, starting at 2.402 GHz and stopping at 2.480
GHz. Therefore, there are 79 channel radio to
work in most of the countries. (Japan, Spain and
other countries used different of channels.)
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The ISM band ranges from 2,400 to 2,483.5 MHz in
the US and Europe (only parts of this band are
available in France and Spain), and from 2,471 to
2,497 MHz in Japan.
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The application of the ISM frequency band is like
his name implied Industrial, Scientific,
Medical which is used in baby monitors, garage
door openers cordless phones and microwave ovens.
The microwave is the strongest interference.
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The Bluetooth Baseband The radio operates in a
frequency-hopping manner in which the 2.4 GHz ISM
band is broken into 79 one-MHz channels that the
radio randomly hops through while transmitting
and receiving data.
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Every slot is 625 usec. the Bluetooth channel is
represented by a pseudo random hopping sequence
through the entire 79 (or 23) RF frequencies -
with a nominal hop rate of 1600 hops per
second.The dashed line shows the master hopping
on its transmission frequency only.
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Each channel is divided into 625 µs time slots. A
TDD scheme is used which means that the time
slots are used alternately for transmitting and
receiving. One packet can be transmitted per time
slot. The master transmits a packet on its time
slot 2k on frequency f(2k) to a slave. In the
next time slot 2k1 on frequency f(2k1) it
receives a packet from the slave before it
transmits again.
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The Bluetooth fram consists of a transmit packet
followed by a receive packet. Each packet can be
composed of multiple slots (1, 3, 5) of 625 us.
(Note the hop frequency is fixed for the
duration of the packet transmission.)
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Multi-slot frames allow higher data rates because
of the elimination of the turn-around time
between packets and the reduction in header
overhead.
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Example Consider four time slots 2k, 2k2, 2k4
and 2k6. Normally, these would be associated
with hop frequencies f(2k), f(2k2), f(2k4) and
f(2k6). We can see that more packets can be
sent within 7 time slots.
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Piconet Two or more Bluetooth devices that
establish a connection (and share a channel) form
a small wireless network known as a Piconet.
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To form a piconet, the Bluetooth radio needs to
understand two parameters (1) hopping pattern
(2) timing offset
Bluetooth radios each hqave a unique Global ID
that is used to create a hopping pattern.
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Master/Slave Timing/Synchronisation In forming a
piconet. The master radio shares its Global ID
with the other radios, which then become slaves
and provide all the radios with the correct
hopping pattern. The master also shares its clock
offset with the slaves in the piconet.All devices
participating on the same piconet adapt their
internal clock with a timing offset in order to
synchronize to this frequency hopping sequence.
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BD_ADDR Bluetooth Device Address AM_ADDR
Active Member Address PM_ADDR Parked Member
Address AR_ADDR Access Request Address The
hopping sequence is determined by the identity of
the piconet master (BD_ADDR) and the timing is
determined by the master unit's system clock.
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Packet format
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Piconet When a slave is not active but remains
synchronized with the piconet, it is in park mode
and is assigned a unique PM_ADDR. Once the slave
is activated, it loses the PM_ADDR and instead it
is assigned an AM_ADDR.
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Scatternet A group of piconets with overlapping
areas of coverage is called a scatternet. Each
piconet is identified by a different frequency
hopping sequence.
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Physical Links When in the connected state, the
Bluetooth radios can issue two types of
packets (1) Synchronous Connection-Oriented
(SCO) link (2) Asynchronous Connection-Less (ACL)
link
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Synchronous Connection-Oriented (SCO) SCO links
support symmetrical, circuit-switched,
point-to-point connections and are typically used
for voice transmission. An example of a SCO link
is the voice link between a cellular phone and
headset. SCO links reserve two consecutive slots
- one for transmission and one for reception - at
fixed intervals.
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Asynchronous Connection-Less (ACL) ACL links
support symmetrical or asymmetrical,
packet-switched, point-to-multipoint connections
and are typically used for data transmission.
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Inquire/Page/Standby The master device uses the
page procedure to activate and connect to a slave
device, if the slave's address (BD_ADDR) is
known. If the slave's address is unknown, a
connection is made using an inquiry procedure
followed by a page procedure.
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Inquire The inquiry procedure involves three
steps (1)inquiry Inquiry Access Code
(IAC) (2)inquiry scan (3)inquiry response
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Page The page procedure involves three steps
(1) page Device Access Code (DAC) (2) page scan
(3) master page response and slave page
response.
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After connection, there are four modes of
operation Active, Sniff, Hold and Park.
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Active Mode In active mode, a device actively
participates in the piconet channel by
continuously listening into the master-to-slave
time slots for packets containing its own AM_ADDR.
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Sniff Mode In sniff mode, a slave only listens
in at predefined time slots, called sniff time
slots. Slaves enter the sniff mode when ordered
by the master or if the slaves request to be
placed in sniff mode - for example, in order to
participate in another piconet.
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Hold Mode During a connection, a slave can be
put in a hold mode so that for a fixed time ACL
packets are not supported. However, SCO packets
are still supported. For example, a Bluetooth
phone in hold mode will support a voice link but
will not support text messages.
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Park Mode In park mode, a slave does not
participate in the piconet but remains
synchronised with the piconet. The park mode is
used to connect more than seven slaves to a
single master. This allows a slave to reduce its
power consumption.
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When paging is completed, a connection between
the two Bluetooth devices can be established.
This includes (1) link establishment (2)
channel establishment (3) connection
establishment
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Link Establishment Once paging is completed, a
physical link between the laptop and cellular
phone is established using the Link Manager
Protocol (LMP).
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Channel Establishment After the establishment of
a physical link, a logical link between the
laptop and cellular phone is then established to
setup a Bluetooth channel between the two
devices. Note logical channel A logical
channel that provides a signaling path within an
information channel or within a physical
signaling channel. signaling path In a
transmission system, a path used for system
control, synchronization, checking, signaling,
and service signals used in system management and
operations rather than for the data, messages, or
calls of the users.
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Connection Establishment Finally, a connection
between the applications on the two Bluetooth
devices is then established. In the case of the
connection between the cellular phone and laptop,
a serial port based application, RFCOMM is
initialized and a connection is established
between the devices.
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Security To ensure user protection and
information confidentiality, a Bluetooth device
implements authentication and encryption
techniques. As such, link layer and application
layer security are part of the basic Bluetooth
radio requirements.
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The shared secret key used in authentication is a
random number known as the 'link key'. The link
key can be either temporary or semi-permanent. A
temporary link key is used in the current session
only, and cannot be re-used at a later time. Once
a semi-permanent link key is defined, it may be
used in the authentication of several subsequent
connections between the devices sharing it.
Devices sharing a semi-permanent link key are
called paired devices.
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Four types of link key have been defined for
different types of application (1) Unit key KA
(2) Combination
key KAB (3) Initialisation key Kinit (4)
Temporary key Kmaster
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Link layer security architecture
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Bluetooth Architecture Overview The Bluetooth
baseband specification defines packet formats,
physical and logical channels and the different
modes of operation which support the transfer of
voice and data between devices. Audio is needed
to transfer voice. The specification for the
Bluetooth voice interface follows both ITU-T and
GSM recommendations.
The Link Manager (LM) is specified software that
handles link authentication, piconet management,
link set-up and configuration.
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The Host Controller Interface (HCI) provides a
common interface between the Bluetooth host
device, for example, a laptop and the Bluetooth
module. The Link Layer Control and Adaptation
Layer Protocol (L2CAP) is specified to provide a
common base for data communication.
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RFCOMM is a simple transport protocol which
emulates serial ports and is used, for example,
in a laptop to printer connection. The Telephony
Control protocol Specification (TCS) is used to
define the call control signalling for
the establishment of voice and data calls between
Bluetooth devices.
The Service Discovery Protocol (SDP) allows
applications to discover which services are
available through or provided by a Bluetooth
device, and to determine the characteristics of
these services.
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A number of protocols are available for
different applications or user scenarios.
Ex OBEX (Object Exchange Protocol) is used in
file transfer applications and to synchronize
multiple devices. TCP/IP is used for Internet
applications. A set of AT commands are defined to
support user terminal control. For example,
entering a PIN for authentication.
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Host application software is designed to support
a variety of hardware applications, to enable
legacy applications and to utilize existing
protocols and specifications where possible.
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For example, the 'headset' profile uses AT
Commands and the RFCOMM protocol and is one of
the profiles used in the "Ultimate Headset" usage
model.
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Ericsson's Implementation The Ericsson Bluetooth
module is the first fully functional solution for
Bluetooth applications and is compliant with the
Bluetooth Specification version 1.0. The Ericsson
Bluetooth module consists of a Bluetooth radio
Link Controller (LC) or baseband processor
Link Manager (LM)
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Ericsson's Implementation The Bluetooth radio is
a short wave radio transceiver with external
antenna. The Bluetooth radio has a short-range
radio link coverage of 10m or 100m, depending on
the radio amplifier strength.
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Ericsson's Implementation The Link Controller
(LC) includes the baseband processor,
micro-processor, memory and I/O interfaces (UART
and USB). LC performs baseband functions such as
packet handling, frequency hopping and
encryption. The Link Manager (LM) is stored in
flash memory. LM manages packets and flow control
on the link.
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Cunclusion

• globally available 2.4 GHz frequency band
• wireless communication of data and voice
• small, low power, low cost radio transceiver
• spread spectrum technique 79 (or 23) RF
  frequencies with 1600 hops per secon

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Reference Http//infotooth.tripod.com/tutorial.ht
m Http//www.palowireless.com/bluetooth/ Http//ww
w.bluetooth.com/ Http/developer.intelcom/ technol
ogy/itj/q22000/articles/art_1.htm Http//www.bluet
ooth.com/developer/download/download.asp?doc172