Bluetooth

1
Bluetooth

• By Christian Doyle

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Overview

• What is Bluetooth?
• Whats with the name?
• Establishing a connection
• Multiplexing
• Piconets
• Scatternets
• Architecture
• Routing
• Sources

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What is Bluetooth?

• First version released in 1999
• Short range radio ISM (industrial scientific
  medical) 2.4GHz
• 79 channels at 1MHz each
• 1Mbps data rate
• Originally created as a replacement for cables
• Inexpensive chips
• Create mobile ad hoc networks of many different
  types of devices

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More on Bluetooth

• Frequency hopping physical layer
• Multiple channels, each defined by frequency
  hopping sequence
• 802.11 uses a single channel broadcast
• Channels are shared using polling to allocate
  time slots to slaves
• Devices must be on same frequency in order to
  communicate
• Link layer uses ARQ and FEC

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Whats with the name?

• Named after the 10th century Danish King Harald
  Blatand or Harold Bluetooth in English
• Harold united warring factions in what is now
  Norway, Sweden, and Denmark
• Similarly Bluetooth technology is supposed to
  unite different types of devices such as PDAs,
  laptops and mobile phones

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Establishing a connection

• Asymmetric processes, involve two types of nodes
  senders and receivers
• Nodes broadcast on predetermined frequency
• Inquiry phase
• Senders discover and collect neighborhood info
  about receivers
• Paging phase
• Senders connect to receivers that were discovered
  during the inquiry phase

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TDD

• Time division duplexing
• Single slave communication
• Master sends on even numbered slots
• Slave sends on odd numbered slots
• Multiple slave communication
• Master sends on even numbered slots
• Slave only sends if the last even numbered slot
  was addressed to it (polling)

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Piconet

• One hop network
• All nodes must be on same hopping frequency
• One master
• Any number of slaves
• There may only be seven active slaves at any
  given time
• In order to talk to other slaves, master must
  park one of them

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Piconet
Master
Slave
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Scatternet

• Connection of piconets is called a scatternet
• Nodes can only be active in one piconet
• Nodes must change hopping frequency in order to
  be active in another piconet
• Nodes can not communicate unless they are in the
  same piconet, even if they can physically receive
  each others messages

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Scatternet

• A bridge node connects two piconets
• Bridge nodes can be a slave in one piconet and a
  master in another
• Nodes can only be a master in one piconet

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Scatternet
Master
Slave
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Architecture

• Goal is to form fully connected scatternets
• Switching frequency creates performance problem
• Bluetree
• One Blueroot
• Every master only has at most two slaves
• Other options
• Bridge may only connect two piconets
• Minimize number of piconets
• Connected
• Two piconets should share only one bridge

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Bluetree
Master
Slave
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Other architectures
Master
Slave
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Routing

• Because devices are mobile an optimal path may
  not be optimal in a few moments
• Routing is very reliant on the application and
  architecture
• Reactive routes created when needed
• Random IPs

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Sources

• Bluetrees Scatternet Formation to Enable
  Bluetooth-Based Ad Hoc Networks
• Zaruba et al
• Distributed Topology Construction of Bluetooth
  Personal Area Networks
• Salonidis et al
• Performance Aspects of Bluetooth Scatternet
  Formation
• Miklos et al
• Bluetooth an Enabler for Personal Area
  Networking
• Kazantzidis et al
• Data Communication and Networking
• Forouzan, Behrouz
• www.Bluetooth.org