What is Bluetooth

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What is Bluetooth?

• Bluetooth technology is a peripheral that
  connects to a variety of products in order to
  provide wireless connections.

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Why is it called Bluetooth?

• Harald Bluetooth was king of Denmark in the late
  900s. He managed to unite Denmark and part of
  Norway into a single kingdom then introduced
  Christianity into Denmark. He was killed in 986
  during a battle with his son, Svend Forkbeard.

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• Choosing this name for the standard indicates how
  important companies from the Baltic region
  (nations including Denmark, Sweden, Norway and
  Finland) are to the communications industry, even
  if it says little about the way the technology
  works.

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History of Bluetooth

• Technology was born in Swedish town of Lund in
  1994
  
• Research facility was tied to the local
  university
  
• The research that developed Bluetooth came about
  by accident

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History continued

• In Feb. 1998, 5 companies got together to and
  formed a SIG further the universitys research on
  Bluetooth and May 20, 1998 it was publicly
  announced as a marketable product

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• Bluetooth continued to thrive, although it didnt
  evolve into its current form until 4 companies
  joined the original 5, these include Motorola,
  Microsoft, Lucent and 3-Com

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How Bluetooth Works

• Bluetooth communicates on a frequency of 2.45
  gigahertz
  
• This frequency was allocated for industrial,
  scientific and medical devices (ISM)
  
• This band also works for baby monitors,
  garage-door openers, and the newer cordless phones

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Bluetooth and interference

• To prevent interference with other devices,
  Bluetooth sends out minute signals of 1 milliwatt
  
  
• This only allows units to send out signals for a
  distance of 10 meters, however this is strong
  enough to go through a normal wall

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Spread-spectrum frequency hopping

• In order to avoid crossing signals between
  devices, Bluetooth utilizes frequency hopping.
  
• Using 79 individual, random frequencies in an
  area, the device hops from one to another
  regularly.

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How Bluetooth interacts

• When 2 Bluetooth devices come within the range of
  each other, they electronically speak to each
  other to determine whether they have data to
  share or if one will control the other

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Piconet

• The devices then set up a personal-area network
  (PAN) or piconet.

• In a piconet network, one device is assigned the
  master role, and up to seven other devices are
  assigned to be slaves.

• The master transmits in the even time slots,
  slaves transfer in the odd time slots.

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Piconet data channels

• Devices in a piconet connect through a common
  data channel, which has a capacity of 1 Mbps
  
• A channel is divided into time slots of 625
  microseconds long
  
• Each data channel hops randomly 1,600 per second.

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Channel Control

• There are two major states in channel control
  Standby and Connection
  
• Standby the default low power state, only the
  native clock runs, and there is no interaction
  with the device
  
• Connection master and slave exchange packets
  using the masters access code and native clock

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IF CONNECTION STATE IS ACTIVE
Inquiry Phase
Page Procedure

• Inquiry enables a device to find other devices
  within range.

• Page procedure where an actual connection is
  made .

Inquiry Phase

• 1. Unit sends out inquiry packets and receives
  replies if anything is present
  
• 2. Receiving unit is hopefully in scan state to
  receive packets
  
• 3. Receiving unit then switches to response
  states and replies to sending source

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Paging Procedure

• 1. Source device pages destination device(s)
• 2. Destination receives the page
• 3. Destination replies to source
• 4. Source sends an FHS packet to destination
• 5. Destination sends its second reply to source
• 6. Destination and source then switch to source
  channel parameters

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Piconet modes

• Active Mode Bluetooth actively participates
• Sniff Mode slave listens to the piconet at
  reduced rates, reducing its duty cycle
  
• Hold Mode master unit can put a slave unit into
  hold mode where only the internal timer is
  running
  
• Park Mode a device is still synched but not
  actively participating in traffic
  

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Piconet Packets

• Packets can be up to five time slots wide

• Data in the packets can be up to 2,754 bits in
  length

• Data is transferred in two types in Bluetooth
  Devices Sychnronous connection oriented (SCO) or
  asynchronous connectionless (ACL)
  

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SCO link

• SCO link is a symmetric point-to-point link
  between a master and slave
  
• Master maintains the link by using reserved slots
  at regular intervals (circuit switch)
  
• Master can support up to 3 links, while slaves
  can maintain 2-3
  
• SCO is mainly used for voice info transferred at
  64/Kb
  

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ACL link

• ACL is a point-to-multipoint link between master
  and all the slaves in the network
  
• In the slots unused by the SCO, the master can
  create a ACL link on a per-slot basis to any
  slave (packet switch)
  
• Only a single ACL link can exist in a piconet

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Bluetooth Devices