Exploiting spatial diversity for routing in sensor networks

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Exploiting spatial diversity for routing in
sensor networks

• Rahul C. Shah,
• Prof. Adam Wolisz Prof. Jan Rabaey
• BWRC Summer Retreat 2003

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Multipath routing a typical example

• Why does this occur?
• Fading channel
• Inter-packet times are longer than the channel
  coherence time
• Fast channel changes need adaptation at MAC,
  rather than network layer
• ?Cross-layer routing design!

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Routing at the MAC layer?
Path-based routing Network specifies next hop
One-hop neighbors

• List-based routing
• Network specifies forwarding region
• MAC chooses next-hop based on connectivity

Forwarding region
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Model assumptions

• Uniform random distribution of nodes
• Circular disk model for radio range
• Channels to all nodes are completely independent
• All nodes have identical probability of
  successful transmission
• Every transmission takes an identical amount of
  energy
• The optimization metric is the total number of
  transmissions

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Forwarding region
Open question What is the optimal forwarding
region?
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Parameter optimization
? 0.1
Optimum angle (degrees)
Probability of packet success
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Comparison of forwarding regions
Avg. of transmissions (end-to-end)
Rmax 10m D 100m ? 0.05
Probability of packet success
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Location uncertainty
Radial uncertainty model
Actual position
?Rmax
Perceived position equally likely in circle. Rmax
is the maximum radio range

• Nodes inside forwarding region perceive they are
  outside
• Nodes outside forwarding region perceive they are
  inside

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Progress with location uncertainty
Avg. progress towards destination (m)
Sector-based routing Rmax 10m
Uncertainty factor (?)
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Conclusions future work

• Perfect location information
• Energy and delay analysis for different
  forwarding regions
• Optimal forwarding region
• Location uncertainty
• Performance of different forwarding regions
• Using 2nd hop neighbor information effectively
• Protocol issues
• Transmitter vs. receiver based MAC
• Design efficient protocol based on the scheme
• Simulation implementation of the protocol
• Can duty cycling with opportunistic routing
  achieve network lifetime goals?