Sensor and Data Communication Networks

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Sensor and Data Communication Networks

• Sripriya Vasudevan
• DAWN Research Lab
• 01/26/2001

2
Network
Intercluster Region (forwarding nodes)
D
B
BS
A
E
C
F
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Forwarding - Concerns

• Path is multi-hop through the clusters
• Load distribution among nodes in the inter
  cluster region
• Reasonable guarantee that the messages are
  forwarded from one cluster to another
• Desired number of forwarding nodes are selected
  for each round of communication to ensure
  connectivity between clusters

4
Route Point Graph Method

• Introduced by A.Sen, M.L. Huson
• Ad Hoc network is modeled as a graph like a wired
  network
• Each cluster of devices represent one node in the
  graph
• If there are overlapping nodes between two
  clusters(within transmission range), then there
  is a line connecting these two nodes

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Point Graph
A
B
D
BS
E
F
C
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Route Stored

• All routes are periodically determined by the
  base station by sending out beacons for
  connectivity information between the clusters
• Routes given by the base station are used for
  forwarding data to the base station through
  multiple hops among the clusters

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System Design

• Primarily a data gathering network
• 25 Node Network 25 25 m
• 50 Node Network 50 50 m
• 100 Node Network 100 100 m
• Random generation of nodes in all the above cases
• Base station located at various distances for the
  above topologies

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System Design (Contd.)

• Each sensor node has a unique identifier
• Nodes are organized into clusters
• Some clusters are within transmission range of
  each other
• Base station has the point graph of these
  clusters
• Base station maintains the route from each of the
  clusters

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1.All nodes forward

• Broadcast to the inter-cluster nodes
• All nodes in the inter-cluster region forward by
  broadcast
• Advantage No selection of a forwarding node
• Disadvantage Redundancy, resulting in wastage of
  power

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Reduce redundancy

• Forwarding node is selected
• For each round
• For x number of packets
• For a specified time span
• After which a new node is selected again by the
  algorithm
• Use the broadcast and synchronous property of the
  network

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2.Selected by Base station

• Base station maintains information of the nodes
  in each inter-cluster region
• For every round, the base station selects a
  forwarding node which is sent to the clusters
  along with the route
• Route may look like
• A(10)-gt C(23)-gt E(30)-gt BS
• Only these nodes that are specified in the route
  forward to the next cluster

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3.Randomization Algorithm

• For each round, all the inter cluster nodes
  participate in selection of a forwarding node
• Processors draw pseudo identifiers drawn from a
  range
• Pseudo identifier 2 is chosen with the
  probability 1/n (n is the number of nodes)
• Pseudo identifier 1 is chosen with the
  probability (1-1/n)
• This selection of pseudo-identifiers determine
  the execution

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3.Randomization(Contd.)

• The pseudo-identifier selected is sent to all
  nodes in the intercluster region
• The node with the highest pseudo-identifier
  becomes elected
• All other nodes change their status to
  non-elected
• The elected node is the only node to forward
  between clusters for the next round

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4.Selection by Power

• Depending on the power of each inter-cluster node
  after each round
• Node with the highest power level is selected as
  the forwarding node for each round
• Could be done by the base station or by the nodes
  themselves
• Can be used by anonymous networks too

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Metrics Studied

• Energy per packet
• Delay per packet
• Energy Delay metric

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Why is this arch. Better?

• Generic routing protocol, not just for
  information gathering
• For large networks, 2 level hierarchy is not
  scalable so this architecture is used
• Broadcast clusters may make MAC coordination
  easier
• Rendezvous might be easier as coordination is
  between clusters, not nodes

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Conclusion

• Simulation is being done in C
• Performance results will be compared to other
  transmission mechanisms, especially in terms of
  energy conservation
• Future work Rendezvous mechanism will be
  incorporated into the algorithm