BLUETOOTH WIRELESS TECHNOLOGY

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BLUETOOTH WIRELESS TECHNOLOGY

• Maureen Stella B. Lim

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What is Bluetooth?

• A way to form connections between electronic
  devices in close proximity
• Cable-replacement technology
• It is a radio-frequency technology that uses the
  2.4 GHz Industrial-Scientific-Medical (ISM) band
• To be Bluetooth certified, a device must pass
  interoperability testing by the Bluetooth Special
  Interest Group (SIG), thus assuring that products
  meeting the specification will be able to
  interact with all other Bluetooth-certified
  products.

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Bluetooth

• ideal for small devices, short range, and low
  power radio links
• fit for connecting PCs and laptop computers,
  phones, printers, and
  cameras.
• Low power Bluetooth devices have a range of about
  30 feet.

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Bluetooth Features

• Wireless and automatic
• Inexpensive
• The ISM band that Bluetooth uses is regulated,
  but unlicensed.
• Handles both voice and data
• Signals are omni-directional
• Uses frequency hopping

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Network Topology
Piconet
Scatternet
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Packets

• All data on the piconet channel are conveyed in
  packets
• Each packet consists of three entities
• Acces Code used for timing synchronization,
  offset compensation, paging and inquiry
• Header information for packet acknowledgment,
  numbering, flow control, slave address, error
  check
• Payload voice field or data field

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Radio Frequency and Spectrum Hopping

• Uses fast acknowledgment and frequency-hopping
• Bluetooth divides the 2.4 GHz frequency band into
  79 channels (from 2.402 to 2.480 GHz)
• Jumps to a new frequency after every packet

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Physical Channel

• Piconets are formed by two or more Bluetooth
  devices using the same channel
• The channel is represented by a pseudo-random
  hopping sequence
• Hopping sequence - unique for each piconet and
  determined by the Bluetooth device address of the
  master
• Phase - determined by the Bluetooth clock of the
  master

Master Slave
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Physical Channel

• The channel is divided into time slots, each 625
  microseconds long
• Time-division multiplexing (TDM) scheme a
  master device always uses an even-numbered slot
  when it transmits, and a slave uses an
  odd-numbered slot.

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Physical Links

• 1. Synchronous Connection Oriented (SCO)
• Symmetric point-to-point link
• Carries voice information
• Reserved time slots to guarantee timely
  transmission
• Works at 64 Kb/s

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Physical Links

• 2. Asynchronous Connection Less (ACL)
• Primarily for data
• Established on a per-slot basis
• Support point-to-multipoint transmissions
• A slave can only transmit only after receiving a
  packet from a master
• For this purpose, the master can send a polling
  packet
• Can transmit as much as 721 Kb/s in one direction

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Physical Links
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Connection Set-up

• Step 1 Inquiry procedure
• Source inquiry state sends out inquiry packets
• Destination inquiry scan state
• Destination inquiry response state sends an
  inquiry reply to the source

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Connection Set-up

• Step 2 Paging Procedure
• Source pages another device
• Destination receives page
• Destination replies
• Source sends an FHS packet to the destination
• Destination sends second reply
• Destination and source then switch to the source
  channel parameters

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Error Checking

• 1/3 Forward Error Checking (FEC)
• Implemented by repeating three bits at a time
• 2/3 FEC
• Generator polynomial is used to encode 10 bit
  code to 15 bit code
• Automatic Repeat Request
• requires that the header error and cyclic
  redundancy checks are okay

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Whose teeth are blue?

• 10th century Scandinavian king, Harald Bluetooth
  managed to unite several unruly kingdoms. Thus,
  Bluetooth is a reference to the taming of a
  myriad of unruly competing standards by defining
  one world-wide specification.