Reader Collision Problem in RFID Networks with Mobile Readers

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Reader Collision Problem in RFID Networks with
Mobile Readers

• Presented By
• Shailesh M. Birari
• Guided By
• Prof. Sridhar Iyer

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Problem Definition

• Develop an anti-collision protocol for a mobile
  ad hoc network of RFID readers
• Reader Collision Problem
• Reader Reader Interference
• Reader tag Interference

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Interesting Features

• The passive tags, where the collision may take
  place, are not able to take part in the collision
  resolution as in hidden terminal problem
• Here T is not able to send a CTS in response to
  an RTS from a reader

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Interesting Features (contd...)

• In case multiple readers try to read the same
  tag, the tag cannot select a particular reader to
  respond to

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Problem Definition..... Precisely

• Aim is to increase the overall read rate of the
  rfid system
• 2 aspects of the solution
• Increase the throughput of the tag identification
  protocol
• Reduce the reader-reader collision (wastage of
  bandwidth)

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Problem Definition..... Precisely

• System under consideration
• Readers form an Ad hoc network
• All readers have unrestricted mobility
• Readers may frequently join and leave the network

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Approaches Considered

• Registration at the access point (query response)
• Transmit Neighbour information to AP along with
  request to transmit
• AP scans the status of the neighbours and
  responds accordingly

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Approaches Considered (contd.)

• Centralised graph coloring at Access Point
• All nodes transmit neighbour information to the
  AP
• AP applies a graph coloring to allocate time-slots

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Final Chosen Strategies

• NAK Based solution
• Beacon Based solution
• Variable Power

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NAK Based Solution

• Assumptions
• Separate control channel between readers
• The range in the control channel is sufficient
  for a reader to communicate with all the possible
  readers that might interfere in the data channel

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NAK Based Solution

• A reader sends an RTS to its neighbours
• If any neighbour is busy(reading tags), then it
  sends a NAK
• Thus if the reader receives atleast one NAK, then
  it differs its access to the data channel

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NAK Based Solution
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Beacon Based Solution

• Assumptions
• Separate control channel between readers
• The range in the control channel is sufficient
  for a reader to communicate with all the possible
  readers that might interfere in the data channel

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Beacon Based Solution (contd...)

• A reader while reading tag, periodically sends a
  beacon on the control channel

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Beacon Based Solution (contd...)
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Variable Power Readers

• Double the read range after every 'x' reads
• On collision, reduce the read range by certain
  probability 'p'

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Related work Colorwave

• Distributed TDMA protocol
• Each node chooses a color from 0,Maxcolors
  indicating the timeslot to transmit
• Maxcolors is increased if the collisions become
  more than certain threshold
• Maxcolors is decreased if the collisions fall
  below certain threshold

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Comparison

• Compare the proposed algorithms with Colorwave
  algorithm
• Performance metrics
• overall read rate for the system
• time to first read
• read rate of nodes (Fairness to the nodes)

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Road Ahead......
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Questions???
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(No Transcript)
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Publications Targeted