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A Case for Resource Heterogeneity in Large Sensor Networks

A Case for Resource Heterogeneity in Large Sensor Networks. Srikanth Kandula MIT. with Jennifer Hou, Lui Sha (UIUC). IEEE MILCOM Nov 1, 2004. Lot of energy wasted in forwarding alerts. Increased wireless collisions. Problem. Blindly suppressing alerts is bad

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A Case for Resource Heterogeneity in Large Sensor Networks

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  1. A Case for Resource Heterogeneity in Large Sensor Networks Srikanth Kandula MIT with Jennifer Hou, Lui Sha (UIUC) IEEE MILCOMNov 1, 2004

  2. Lot of energy wasted in forwarding alerts Increased wireless collisions Problem • Blindly suppressing alerts is bad • Dissemination Trees  process alerts at intermediate sensors? • may not see all alerts • may not have cpu/memory to correlate Need dedicated entities that process sensor data close to point of origin IEEE MILCOM 04

  3. Resource-Heterogeneous networks Tunnelled Digest Resource-rich Accumulator Also provides fine-grained control Serve as a spine for the n/w HowTo co-ordinate and control sensors using a random deployment of accumulators? IEEE MILCOM 04

  4. Accumulator-centered clusters IEEE MILCOM 04

  5. Accumulator-centered clusters Cluster sensors around closest accumulator Many sizes Multiple hops An overlay of accumulators Digests are routed along the overlay Tunneled Path Improves network lifetime and goodput of updates IEEE MILCOM 04

  6. Accumulator centered clusters– Level 1 Cluster sensors around closest accumulator Clusters vary in size Multiple hops An overlay of accumulators Digests are routed along the overlay Tunneled Path How to efficiently form these clusters? IEEE MILCOM 04

  7. Contributions • Detailed design of a sensor n/w architecture hinged on resource-rich nodes • Protocols for efficient clustering and routing • Demonstrate several distinct benefits through ns2 simulations • Identify opportunities for load-sensitive routing IEEE MILCOM 04

  8. Talk Outline • Internal structure of Level-1 Clusters • Hop-by-hop forwarding of join messages • Routing • Results IEEE MILCOM 04

  9. Level-0 Hexagonal Cells • Idle radios consume power • Only the leader of a cell forwards traffic IEEE MILCOM 04

  10. Level-0 Hexagonal Cells • Idle radios consume power • Only the leader of a cell forwards traffic • Leadership exchanged among all nodes in a cell • Cell size chosen to maintain connectivity • Note: Equivalent Level-0 clusters e.g. SPAN can be used instead Level-0 clusters save power! IEEE MILCOM 04

  11. Talk Outline • Internal structure of Level-1 Clusters • Hop-by-hop forwarding of join messages • Routing • Results IEEE MILCOM 04

  12. Accumulator Broadcasts join messages One hop to accumulator A1 IEEE MILCOM 04

  13. Back-pointer to parent cell Grids store back-pointer to parent 1 1 1 1 1 1 IEEE MILCOM 04

  14. Join messages are re-broadcast! 1 1 1 Two hops to accumulator A1 1 1 1 IEEE MILCOM 04

  15. Join messages are re-broadcast! 1 1 1 Two hops to accumulator A1 1 1 1 Join messages to parent’s neighbors will propagate errors IEEE MILCOM 04

  16. Controlled Broadcast - 1 1 1 1 Two hops to accumulator A1 1 1 1 Suppress Join messages to neighbors of parent IEEE MILCOM 04

  17. Controlled Broadcast - 2 1 1 1 2 1 1 1 2 2 Suppress Join messages to a neighbor if there is a common neighbor of smaller hop count IEEE MILCOM 04

  18. Controlled Broadcast - 2 1 1 1 2 1 1 1 2 2 Three hops to accumulator A1 IEEE MILCOM 04

  19. BGP Inefficiencies 1 1 1 2 1 1 1 2 2 3 3 IEEE MILCOM 04

  20. Controlled Broadcast 1 1 1 2 1 1 1 2 Three hops to accumulator A1 2 3 3 IEEE MILCOM 04

  21. Multiple paths 1 1 1 2 1 1 3 1 2 2 3 3 3 A cell may have multiple parents IEEE MILCOM 04

  22. Multiple paths 1 1 1 2 Multiple dis-joint paths exist! 1 1 3 1 2 2 2 3 2 3 3 IEEE MILCOM 04

  23. Level-1 cluster boundary 1 1 1 2 1 1 3 1 2 One hop to accumulator A2 2 2 3 2 3 3 IEEE MILCOM 04

  24. Level-1 cluster boundary 1 1 1 2 Two hops to accumulator A2 1 1 3 1 2 2 2 3 1 2 3 1 1 3 1 1 1 IEEE MILCOM 04

  25. Level-1 cluster boundary 1 1 1 Cell changes allegiance! 2 1 1 3 1 2 2 2 2 2 1 2 3 1 1 3 2 1 1 1 IEEE MILCOM 04

  26. Level-1 cluster boundary 1 1 1 Three hops to accumulator A2 2 1 1 3 1 2 2 2 2 2 1 2 3 1 1 3 2 1 1 1 IEEE MILCOM 04

  27. Boundary notification 1 1 1 2 Negative Ack x hops from A1 1 1 3 1 2 2 2 2 2 1 2 3 1 1 3 2 1 1 1 IEEE MILCOM 04

  28. Boundary notification 1 Border Cell: 3 hops to A2 1 1 2 Negative Ack: x hops from A1 1 1 3 1 2 2 2 2 2 1 Border Cell: 3 hops to A1 2 3 1 1 3 2 1 1 1 IEEE MILCOM 04

  29. Level-1 Cluster formation: Summary • Controlled broadcast of join messages • Naïve O(N^2)  O(N) messages, N = # of cells • Routing information piggybacks over join messages • Multiple paths from a cell to closest accumulator • Multiple paths between adjacent accumulators • Join broadcasts are periodically repeated • Join messages route around holes IEEE MILCOM 04

  30. Talk Outline • Internal structure of Level-1 Clusters • Hop-by-hop forwarding of join messages • Routing • Results IEEE MILCOM 04

  31. Sensor Alerts  Accumulator 1 1 1 Alert follows parent pointers back to the accumulator 2 1 1 3 1 2 2 2 2 2 1 2 3 1 1 3 2 1 1 Sensor forwards alert to cell leader 1 IEEE MILCOM 04

  32. Accumulator  Accumulator  Sink 1 1 1 2 Accumulator forwards digests to some border cell 1 1 3 1 2 2 Digest crosses the border and follows parent pointers 2 2 2 1 2 3 1 1 3 2 1 1 1 IEEE MILCOM 04

  33. Accumulator  Accumulator  Sink Accumulators run OSPF on the overlay Pick one of many paths Improved resilience IEEE MILCOM 04

  34. Talk Outline • Internal structure of Level-1 Clusters • Hop-by-hop forwarding of join messages • Routing • Results IEEE MILCOM 04

  35. Power Savings – CDF of remaining power Homogenous Network Heterogeneous Clusters Probability Sensors that generate updates gain a little due to decreased forwarding load Remaining Power (J) IEEE MILCOM 04

  36. Power Savings – CDF of remaining power Homogenous Network Heterogeneous Clusters Probability Long-haul sensors gain more due to decrease in forwarded traffic Remaining Power (J) IEEE MILCOM 04

  37. Power Savings – CDF of remaining power Homogenous Network Heterogeneous Clusters Probability Idle sensors gain a lot by turning off their radios Remaining Power (J) IEEE MILCOM 04

  38. Improvement in Goodput 500 sensors spread over 4sq-km 357 Cells, 15 CBR sources Fraction of Updates Received 14 accum Zero accum A small number of accumulators is enough to improve goodput significantly Duration between generation of updates (s) IEEE MILCOM 04

  39. Improvement in Goodput 500 sensors spread over 4sq-km 357 Cells, 15 CBR sources Fraction of Updates Received 14 accum Zero accum More accumulators are needed when updates are generated faster Duration between generation of updates (s) IEEE MILCOM 04

  40. Reduction in join message overhead 500 sensors spread over 4sq-km 357 Cells Total number of join messages Controlled Broadcast Naïve Algo. Significantly reduces # of join messages when clusters are large Number of Accumulators IEEE MILCOM 04

  41. Reduction in join message overhead 500 sensors spread over 4sq-km 357 Cells Total number of join messages Controlled Broadcast Naïve Algo. Slightly beneficial even when Level-1 clusters are small Number of Accumulators IEEE MILCOM 04

  42. Related Work • We explore the use of heterogeneous sensors in designing better dissemination trees. • Clustering and Routing in Sensor Networks • Geographic Area Forwarding (GAF), SPAN, k-cluster based routing, ZRP, Spine, Min-ID/Max degree • Dissemination Trees in sensor networks • Diffusion, TTDD IEEE MILCOM 04

  43. Conclusion • A small number of resource-rich sensors • Improve network lifetime • Improve goodput of updates • Provide fine-grained control • Hierarchical clusters to use resource-rich sensors can be built efficiently • Scope to design robust routing protocols – more work to be done! IEEE MILCOM 04

  44. Questions? IEEE MILCOM 04

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