Bluetooth

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Bluetooth

• A low-cost, low-power, short-range approach to
  ad-hoc Personal-Area Networks

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Bluetooth Summary

• Designed for ad-hoc personal-area networking
• Small size (including phones PDAs)
• Low cost (few dollars/chip)
• Low power levels (allowing long battery life)
• Support for both voice and data traffic
• Up to three 64 kbps synchronous voice channels
• Up to 721 kbps asynchronous data (with 57.6 kbps
  return)
• Total gross rate limited to 1 Mbps (3 Mbps for
  version 2.0 EDR)
• Deterministic, centralized networking protocols
• Piconet 1 master communicates with up to 7
  slaves
• Scatternet two or more piconets connected
  through a common device
• Full seven-layer standards with profiles
  targeting common application areas
• Cable replacement is a pervasive theme
• Standardized/coordinated by Bluetooth SIG and
  IEEE 802.15.1

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Bluetooth can connect many types of devices
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Bluetooth Versions

• Bluetooth 1.1 (2001)
• 1 Mbps
• Bluetooth 1.2 (2003)
• Improved 802.11 b/g co-existence
• Improvements for voice, QoS
• Bluetooth 2.0 EDR (11/2004)
• EDR Enhanced Data Rate (3 Mbps)
• Products expected starting 2005

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Bluetooth Radios

• Spread spectrum (FH-CDMA), frequency shift keying
  (FSK), 1600 hops/sec across 79 frequencies from
  2.402 2480 GHz (most countries)
• Class 1 20 dBm (100 mW), 50-100 meters
• Class 2 4 dBm (2.5 mW), 20 meters
• Class 3 0 dBm (1 mW), 10 meters
• These are maximum levels--radios adapt their
  power levels as needed

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Frequency Hopping
























79 Frequencies









1600 Hops/Second (each 625 microseconds long)
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Traffic Supported

• Up to 3 synchronous connection-oriented (SCO)
  links for voice _at_ 64 kbps each (point-to-point,
  circuit switched)
• One asynchronous connectionless link (ACL) for
  data _at_ up to 721 kbps one way 57.6 kbps back
  (point to multipoint, packet switched)
• Various combinations of the above
• Enhanced data rate of 3 Mbps in version 2.0

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Voice and data transmissions
SCO
ACL
ACL
SCO
SCO
ACL
ACL
ACL
Master
Slave
Slave
Slave
http//ing.ctit.utwente.nl/WU4/Documents/307,16,Vo
ice and data transmissions
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Piconets
M
M
S
S
S
S
M master, S slave (A device can function as
master or slave as required) Each piconet has
its own frequency hopping pattern determined by
the master.
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Scatternet
M
M
S
S
S
S
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Scatternet
M
M
S
S
S
S
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Masters are in Control . . .

• Masters poll slaves slaves synchronize with
  masters timing and frequency hopping sequence
• Slaves can be in several states
• Active
• Sniff (listen only to sniff slots)
• Hold (master lets slave sleep for a specified
  time slave can participate in other piconets)
• Park (slave gives up its 3-bit active member
  address, gets an 8-bit parked member address,
  remains synchronized to the masters
  channel--this lets a master attend to more than 7
  slaves)

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Basic Connection Sequence

• Units in standby mode wake up every 1.28 seconds
  and listen on one of 32 hop frequencies
• Master units send out inquiries to which slaves
  respond with ID and clock information
• After inquiry, masters can page slaves (128 pages
  on first 16 frequencies, another 128 on 2nd 16 if
  needed)
• Successful paging results in a connection

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Connection State Machine
Standby
Not connected
Inquiry (unknown address)
Page (known address)
Connecting
Transmit (AMA)
Connected (AMA)
Active
Park (PMA)
Sniff (AMA)
Power save
Hold (AMA)
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Simplified Bluetooth Stack
Applications
Profiles
SW
RFCOMM
TCP/IP
Audio
Service Discovery Protocol
Logical Link Control and Adaptation Protocol
Host Controller Interface
Link Manager (managing slaves, connections, power
. . .)
HW
Baseband Controller (timing, framing, flow
control . . .)
RF (Radio transceiver)
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Bluetooth Packets
Access Code (72 bits)
Header (54 bits)
Payload (0 - 2745 bits)
Preamble, channel, synchronization information
3-bit address,4-bit packet type,1-bit flow
control,1-bit ack,1-bit sequence , Forward
Error Correction
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Profiles

• Provide interoperability for defined functions
  and services
• Define allowable messages and procedures
• Configures the protocol stack for particular
  purposes

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Profile Examples

• Generic Access
• Service Discovery
• Networking
• LAN Access
• Serial Port/Telephony
• Dial-Up Networking
• Fax
• Headset
• Generic Object Exchange
• File Transfer
• Object Push
• Synchronization
• Human Interface Device
• Keyboards, mice, joysticks . . .

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Bluetooth Security

• Generic Access Profile security modes
• 1 non-secure
• 2 service-level enforced security
• 3 link-level enforced security
• Authentication (128-bit random link key)
• Authorization (1 to 16 octet PIN is used to
  generate an initialization key)
• Confidentiality/Encryption (8 to 128-bit,
  negotiated)

Vastly simplifiedthere are many complex
options and variants.
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Some Bluetooth Limitations

• Speeds insufficient for broadband
• Only 8 devices per piconet
• Masters are bottlenecks
• No real routing protocols

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For More Information

• http//www.bluetooth.org (standards)
• http//www.bluetooth.com (marketing)
• http//www.cs.uno.edu/golden/6990MC/MobilePapers/
  bluetooth.pdf (vision, goals, architecture)
• http//www.palowireless.com/infotooth/ (general)
• http//h18000.www1.hp.com/products/wireless/wpan/f
  iles/WhitePaper_BluetoothTechnologyOverview-QA.pdf
  (HP iPaq
• http//www.palmos.com/dev/tech/bluetooth/palm_blue
  tooth_mwp_r1.pdf (Palm)