BlueTooth

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BlueTooth

• George Reilly
• and
• Lin Mouv

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Bluetooth - overview

• Motivation
• In 1994 the L.M. Ericsson company wanted
• to connect mobile phones to other devices
• without using cables.

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Bluetooth - overview

• Special Interest Group (SIG)
• L.M. Ericsson
• IBM
• Intel
• Nokia
• Toshiba

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Bluetooth overview

• Etymology
• Harald Blaatand II ( translated
  Bluetooth)
• A Viking king that unified (conquered) Denmark
  and Norway in 940 981.

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Bluetooth - overview

• Goals of the Bluetooth SIG
• Wireless standard (unification) for the
  interconnection of computing and communication
  devices.
• Inexpensive
• Short range
• Wireless radios

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Bluetooth - overview

• Change in Bluetooth original scope
• From Getting rid of cables between devices
• To Becoming more like a wireless LAN

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Bluetooth - overview

• In 1999 the Bluetooth SIG published a 1500 page
  document describing V 1.0.
• IEEE assigned designation 802.15 and used the V
  1.0 specification as its basis. Then they began
  to modify parts of it.

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Bluetooth - overview

• Differences between V 1.0 and 802.15
• V 1.0 is a complete specification from
  application layer to physical layer
• 802.15 is only standardizing (modifying) the
  physical and data link layers.

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Bluetooth - overview

• The Bluetooth 802.15 specification not only
  creates competition for other wireless
  technologies, namely 802.11, but the two occupy
  most of the same 2.4 GHz spectrum and thus
  interfere with each other.
• (More on this later)

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Bluetooth - architecture

• Piconet the basic unit of a Bluetooth
  system.
• 1 Master node
• 1 to 7 active slave nodes
• 0 to 255 parked nodes

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Bluetooth - architecture

• Parked node
• a slave device in a low power state to conserve
  the drain on the devices batteries
• In this state the device can only respond to the
  beacon from the master node

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Bluetooth - architecture

• Node range
• Slave nodes need to be within 10 meters of the
  master node.
• Why design such a short range?

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Bluetooth - architecture

• Answer Money, Money Money !!!
• The designers wanted this technology to be used
  widely (i.e. to sell product).
• Bluetooth chips under 5.00

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Bluetooth - architecture

• Communication
• Only possible between master and slave nodes
• Piconet uses centralized Time Division
  Multiplexing.
• The master node controls the clock and determines
  which devices occupy which time slot.

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Bluetooth - architecture

• How can such a limited range architecture really
  provide competition for 802.11 (WiFi)?

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Bluetooth - architecture

• How can such a limited range architecture really
  provide competition for 802.11 (WiFi)?
• Answer Scatternets

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Bluetooth architecture
Tanenbaum, Andrew S., Computer Networks 4th Ed.
figure 4-35
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Bluetooth - profiles

• Bluetooth is different from most network
  protocols.
• Most network protocols focus defining how the
  channels are to be used and leave application
  designers to define what they will be used for.
• Bluetooth V 1.1 defines 13 specific profiles
  (applications) that will be supported along with
  the different protocol stacks for each of them.

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Bluetooth profiles

• Generic access profile
• provides secure channels between the master and
  slave.
• Service discovery profile
• allows devices to discover what services are
  available from other devices.

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Bluetooth profiles

• Serial port profile
• for applications that need a serial port
  communication
• Generic object exchange profile
• provide support for the client/server model.
• note that a slave can be a client or a server.

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Bluetooth profiles

• LAN access profile
• is a direct competitor of 802.11.
• allows a Bluetooth device to connect to a fixed
  network.
• Dialup access profile
• Ericssons original motivation
• allows a notebook computer to communicate to a
  mobile phone without wires
• Fax profile
• allows fax machines to connect to mobile phones
  wirelessly to send and receive faxes

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Bluetooth profiles

• Cordless Telephony Profile
• connect a cordless telephone handset to a base
  station without wires.
• Intercom profile
• allows two telephones to connect like
  walkie-talkies
• Headset Profile
• good for hands free telephony I.E. while driving
  a car

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Bluetooth profiles

• The last three profiles are for wireless devices
  to exchange a wide variety of data
• Object Push profile for simple objects
• File transfer profile - general file transfer
• Synchronization profile - was designed to
  facilitate the exchange of data in both
  directions between a P.C. and a P.D.A.

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Bluetooth profiles

• There is a feeling that the 13 profiles are an
  overly complicated solution to achieve the
  desired goal.
• A more simplistic solution could have been the
  use of one protocol stack for file transfer and
  one for streaming real-time communication.
• So how did it get to be so complicated?

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Bluetooth profiles

• Answer In the 1968 April issue of Datamation
  magazine, Melvin Conway proposed If you assign
  n people to design a compiler then you will wind
  up with an n-pass compiler.
• Said another way, the resulting software
  structure mirrors the structure of the group that
  created it.

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Bluetooth profiles

• The groups of designers of Bluetooth
• each focused on solving a specific problem.
• Each generated a profile.
• Next, lets take a look at how all of these
  profiles fit together (The 802.15 protocol stack
  architecture).

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Bluetooth protocol stack architectureTanenbaum,
Andrew S, Computer Networks 4th Ed. figure 4-37

• Does not fit any known models
• OSI, TCP/IP, including the 802 model
• Radio layer corresponds to the physical layer
• deals with radio transmission and modulation
• focuses on inexpensive implementation

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Bluetooth protocol stack architecture
Tanenbaum, Andrew S, Computer Networks 4th Ed.
figure 4-37

• Base band layer
• Combines part of the typical physical and data
  link layer roles.
• Specifically the MAC sub-layer of the data link
  layer.
• Focuses on how the master controls the time
  slots and how the slots are grouped into frames.

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Bluetooth protocol stack architecture
Tanenbaum, Andrew S, Computer Networks 4th Ed.
figure 4-37

• Link Manager
• logical channels between devices
• power management
• authentication
• quality of service

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BlueTooth protocol stack architecture
Tanenbaum, Andrew S, Computer Networks 4th Ed.
figure 4-37

• Logical link control adaptation protocol (L2CAP)
• shields upper layers from the details of
  transmission
• somewhat analogous to 802 LLC sub layer

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BlueTooth protocol stack architecture
Tanenbaum, Andrew S, Computer Networks 4th Ed.
figure 4-37

• Middleware layer
• RFcomm serial communications, mouse, keyboard
• Telephony speech oriented protocol
• Service Discovery locate services in the network

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Bluetooth protocol stack architecture
Tanenbaum, Andrew S, Computer Networks 4th Ed.
figure 4-37

• Audio
• controls audio, applications have direct access
• Control
• a control protocol, applications have direct
  access

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Bluetooth protocol stack architecture
Tanenbaum, Andrew S, Computer Networks 4th Ed.
figure 4-37

• The top layer is for application and profiles.
• each application need only use the necessary
  subset of the protocol stack to accomplish its
  task

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(No Transcript)
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More Bluetooth protocol layers

1. Radio Layer
2. Base band Layer
3. L2CAP Layer

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Radio Layer

• Low power system can operated up to 10 meter with
  the frequency in the 2.4 GHz ISM band
• Lowest defined layer of the Bluetooth
  specification
• Band is divided into 79 channels with 1 MHz each
• Frequency hopping spread spectrum at 1600
  hops/sec.

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Bluetooth Radio Specification
Modulation Gaussian frequency-shift keying (GFSK) Modulation index 0.28 to 0.35
Symbol rate 1 Msymbol per second Using the binary GFSK Transmission time 1 microsecond
Frequency hopping rate 1600 hops per second Residence time 625 nucrosecond per hops
Transmit power Class 3 0 dBm ( 1 mW) Class 2 4 dBm ( 2.5 mW) Class 1 20 dBm (100 mW) a typical Bluetooth radio, optical power control to below 30 dBm Optical power control to below 30 dBn Required power control to at least 4 dBm,
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The Bluetooth Base band Layer

• It lies on top of the Bluetooth radio layer
• It is the physical layer of the Bluetooth
• Each frame is transmitted over a logical channel
  called a linked between master slave
• Two kinds of links
• Asynchronous Connection less (ASL)
• Synchronous Connection Oriented (SCO)

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Asynchronous Connection less Synchronous
Connection Oriented

• Data comes from L2CAP layer on the sending side
  and delivered to the L2CAP on the receiver side
• Frame can be lost and may need to retransmitted

• Their channel is allocated a fixed slot in each
  direction
• Frame send are never retransmitted
• Forward error correction can be used to provide
  high reliability
• Can have up to 3 slave SCO links with its master
• Each SCO links can transmitted one 64000 bps PCM
  audio channel

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Logical Link Control and Adaptation Protocol
(L2CAP)

• There are 3 major functions
• I. It accepts packets up to 64 kB from the upper
  layers breaks them into frames for transmission
• II. It handles the multiplexing and
  demultiplexing of multiple packet source
• Packet has been reassemble the L2CAP layer can
  determines which upper-layer protocol to handle (
  RFcomm or telephony)
• III. The third major function is to handles the
  quality of service requirements when both links
  are established and during normal operation ( not
  all devices can handle the 64 kB maximum packet)

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The Bluetooth Frame Structure
Image taken from Class Textbook Tanenbaum,
Andrew S. Computer Networks 4th Ed. p.310-17.
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Bluetooth Frame Structure

• Access code (72 bits)
• Header (54 bits)
• Address field, type field, flow bit, acknowledge
  bit, sequence bit, and checksum
• Data ( 0-2744 bits)

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Conclusion

• Bluetooth is a wireless technology that
• was developed to be very low cost in hopes
• that it would become widely used.
• It is still yet to be seen whether or not it
  will
• become the standard that the initial SIG
• had hoped it would become.

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Bibliography

• Computer Network by Andrew S. Tanenbaum, 4th
  Edition p.310-17.
• Bluetooth Revealed by Brent A. Miller and
  Chatschik Bisdikian, Ph.D., 2nd Edition.
• http//www.palowireless.com/infotooth/tutorial/rad
  io.asp

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Any Questions!