Young-ri Choi, Mohamed G. Gouda, Hongwei Zhang and Anish Arora

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Routing on a Logical Grid in Sensor Networks

• Young-ri Choi, Mohamed G. Gouda, Hongwei Zhang
  and Anish Arora
• The University of Texas at Austin, Austin, TX
  78712-0233, U.S.A.
• Technical Report TR04-49-2004
• speaker Chung Lung Chen

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Outline

• Introduction
• Logical grid routing protocol
• Experiment
• Conclusion

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Introduction

• Gathering data from sensor nodes via multi-hop
  routing to the sink node.
• Propose a protocol
• Grid based spanning tree.
• Distributed working.
• Periodically maintained spanning tree.
• Assume node knows its position.

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Drawback of grid base

• Initial setup requirement
• Limited communication patterns
• Limited connectivity
• No support for mobility

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Contributions

• Simplicity
• Load balancing
• Increasing the network lifetime
• Fast fault recovery
• Supporting a broadcast protocol

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Logical grid routing protocol

• Sensors are deployed arbitrarily in the area.
• Each sensor has a unique ID if the sensors formed
  an MN logical 2-D grid
• The unique id is indicated by S(i , j) where
  i0M-1,j0N-1
• Sink node is at S(0,0).

sink
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Build the spanning tree

• 1. Organize the grid, the tree root is the sink
  node at S(0,0).
• 2. Assign the unique id of each sensor.
• 3. Each sensor calculates potential parents set
  of its own.
• 4. Each sensor connects with its parent.

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Potential Parents (PP)

• S(i,j) is a potential parent of S(i,j)
• if (i-j) (j-j) H, where ii and jj
• and H is a static positive integer.

At most H1
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Potential Parents (PP)

• Suppose H2 , the PP of(2,2) are

(0,2) (1,1) (2,0)
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Potential Parents (PP)
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Connects with parents

• Terms
• Connected(i,j) S(i,j) sends connect(i,j) to
  other nodes which means S(i ,j) connected with
  the spanning tree(BS). 2 4 bytes
• Trc remaining time to connected , time T.
• In the beginning ,sink S(0,0)is in the spanning
  tree
• Sink sends connected(0,0) packets every T
  seconds.

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Foster parent

• If S(i,j) has no parent and receives a connect
  packet S(i,j) which is not a pp of S(i,j)
• S(i,j) to be a foster parent of S(i,j)
• S(i,j) stop broadcasting connect packets.

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S(i,j) acts
S(i,j) received connect packet within 3T seconds?
Get any connect packet but not pp?
No
No
S(i,j) disconnect with spanning tree.Stop
broadcasting.
For ex get S(i,j)
Yes
Yes
No
S(I,j) be a foster parent of S(i,j) S(I,j)
stop broadcasting connect packet
Is S(i,j) a PP of S(i,j)?
Yes
connect change S(i,j)s parent to
S(i,j) Broadcast connect packet every T sec.
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Experiment

• 80 MICA2 motes were deployed to monitor a field
  forming a 77 grid with 5-feet separation
• the base station (0,0) is the mote at the
  left-bottom corner of the grid

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• Even if 50 of the sensors in a network
  fail-stop, 84 of the remaining sensors can still
  route data messages

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individual delivery ratio
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Conclusion

• Propose a logical grid routing protocol
  periodically maintains an spanning tree to the
  sink.
• Localized algorithm(scalable).
• Simple and load balancing for sensor networks.
• Highly recovery when node failures.