ROUTING IN BLUETOOTH SCATTERNET

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ROUTING IN BLUETOOTH SCATTERNET

• Supervisor Mr. Gil Zussman.
• Hadar Vorenshtein
• Amit Balderman

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Project Goals

• Establish a physical Bluetooth Scatternet.
• Implement a routing algorithm.

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Overview

• Bluetooth
• BT is a short range radio-technology using a
  frequency hopping scheme in the ISM band.
• Originally developed as a cable replacement
  technology ,enabling people and machines to
  interact at short range. And hence can be used to
  form a close range wireless network (Personal
  Area Network).

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Overview (cont.)

• PAN(Personal Area Network)
• We will divide it into a Piconet and a Scatternet
• Piconet
• Is a collection of up to seven slave devices
  operating together with one common master.
• All devices on the piconet follow the
  frequency hopping sequence and timing of the
  master.

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Scatternet.

• When a number of piconets cover the same area and
  reception space and there are some units that are
  participating in inter- piconet connections a
  Scatternet is formed.

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RIP protocol

• RIP is a distance vector protocol
• Each host that implements RIP is assumed to have
  a routing table.
• This table has one entry for every destination.
  Each entry contains at least the following
  information
• The address of the destination
• A metric, which represents the total cost of
  getting from the host to the destination.
• The address of the next gateway
• Various timers

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Working Environment

• Ericsson Rok BT units
• Ericsson multi-point BT units
• Linux RedHat 7.2 (2.4.17 kernel)
• BlueZ 2.0
• Merlin Bluetooth Packet Analyzer.

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Achievements of Part A

• Learning the bluetooth and BlueZ topics
• Setting up the working environment and tools
• Using the L2CAP and HCI for communicating with
  the BT units and between the BT units
• Writing code for communicating within a piconet
• Transmitting messages from one unit to another
  via an intermediate unit and thus establishing a
  basic piconet.

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Achievements of Part B

• Learning how to pass any HCI command.
• Establishing a working Scatternet.
• Implementing a simple routing algorithm.
• Setting up a basic network initialization
  protocol.

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Main Stages to Solution Part A

• Choosing the working environment
• Building the working environment .
• Establishing a connection between two Ericsson BT
  units.
• Establishing a connection between two Digianswer
  BT units .
• Establishing a connection between a Digianswer
  unit and an Ericsson unit .
• Writing the code.
• Experimenting with the network .

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Main Stages to Solution Part B

• Putting the units into HOLD- using built in
  commands.
• Putting the units into HOLD- using our own code.
• Analyzing the networks traffic.
• Network experiments.
• Converting Blue_net into a server like structure.
• Implementing a routing algorithm.
• Implementing an initialization mechanism.

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The Scatternet (cont.)

• Our first attempts to create a Scatternet were
  based on the common concept that states that a
  slave should be put in the HOLD mode in piconet
  A, and during the time of the HOLD ,be active in
  piconet B. In this way all messages that need to
  pass from one piconet to the other would pass
  through this slave.
• It is commonly accepted that it should be a slave
  unit that acts as a relay unit , since putting
  a master in HOLD would disrupts the whole
  piconets activity.

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The Scatternet (cont.)

• However we discovered that
• Our BT units cannot work properly in the hold
  mode.
• A multi-point unit can be simultaneously a master
  of one piconet and a slave in another.

These discoveries led us to the tree like network
structure, as was described previously.
It is important to emphasize that although we
have a working Scatternet, we still do not
understand how it works, even after several
experiments and analysis (using the packet
analyzer).
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Piconet A
The Scatternet
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The Routing AlgorithmBlue_Net

• This application has three main functions
• Initializing and creating a network based on the
  Scatternet implementation that was described in
  the previous section.
• Running a routing algorithm based on the RIP
  protocol
• Routing the traffic in the network.

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Blue_Net Structure-Block Diagram.
MAIN
STATION
LOOP
ROUTER_LOOP
ROUTER TIMER LOOP
DO CONNECT
TABLE LOOP
DO LISTEN
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Initialization of the Network.
An example of a start condition when initializing
a network. We assume all slaves have awakened
and master I awakens first (prompted with
gtblue_net m L).
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Initialization is begun ,by master, by first
performing an inquiry routine.
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Initialization of the Network.
Master I created a connection to one slave. Now
master II is prompted by gtblue_net m .
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Initialization of the Network.
Master II created a connection to two slaves and
to the master that is in the C state, master I.
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Initialization of the Network.
This figure shows the tree-like hierarchy that is
created after master III connects to the network.
It is easy to see that master III is the master
of its own piconet and a master of master II,
which is in turn a master of its own piconet and
also a master of master I.
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Routing Table Building Update
Master
Piconet
Inter piconet Communication.
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Routing Table
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Data Messages
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Layer Model
Application (eg-ftp)
Blue_Net
Network Layer
L2CAP and HCI
Transport Layer Data Link Layer
BlueZ stack.
Bluetooth Hardware.
Physical Layer
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Summary

• A functional Scatternet and inter-piconet
  communications have been achieved.
• Weve learned a great deal about the Bluetooth
  protocol, mechanisms and limitations and how to
  interface with hardware in the Linux environment
  using BlueZ.
• We feel that greater achievements can be made
  with better hardware.