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Delay/fault-Tolerant Mobile Sensor Network ( dft -msn) :

Delay/fault-Tolerant Mobile Sensor Network ( dft -msn) : A New Paradigm for Pervasive Information Gathering. IEEE TRANSACTION ON MOBILE COMPUTING 2008. Yu Wang, Hongyi Wu University of Louisiana. Presentation: PARK HAN JIN( 박한진 ) Computer Network Lab. Introduction.

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Delay/fault-Tolerant Mobile Sensor Network ( dft -msn) :

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  1. Delay/fault-Tolerant Mobile Sensor Network (dft-msn) : A New Paradigm for Pervasive Information Gathering IEEE TRANSACTION ON MOBILE COMPUTING 2008 Yu Wang, Hongyi Wu University of Louisiana • Presentation: PARK HAN JIN(박한진) Computer Network Lab CS 710

  2. Introduction • Delay/Fault-Tolerant Mobile Sensor Network • Nodal Mobility • Sparse Connectivity • Delay Tolerability • Fault Tolerability • Limited Buffer • How to achieve reliability? • Redundancy(multiple copies of a data message) CS 710

  3. Direct Transmission 2 9 8 S 1 7 3 5 S S 4 6 Gathered messages are inserted into a FIFO Queue Whenever the sensor meets a sink, it transmits Directly to the Sink node CS 710

  4. Simple Flooding 1 4 6 3 5 2 9 7 6 5 8 S Sensorbroadcaststhe data messages in its queue to nearby sensors Neighbor sensors keep messages in queue, and rebroadcast them Replication with Multiple copies CS 710

  5. Observation • Trade-off • When should data message be transmitted? • Which messages should be transmitted? • Which messages should be dropped? CS 710

  6. RED[1/3] i S k • Replication-Based Efficient Data Delivery Scheme(RED) • Nodal Delivery Probability • Estimate Probability that a sensor can delivery a message to sink • Decision on data transmission in based on delivery probability • Initialize with zero and update upon an event of either message transmission or timer expiration CS 710

  7. RED[2/3]- Data Transmission • Node ‘i’ learns neighbor’s delivery probability and available buffer space via simple handshaking 1 1 1a 2 1 i i 2 1 4 4 2 2 i 4 3 3 5 S 5 S 3 • Node ‘i’ transmits its message to the neighbor, ‘2’, which has the highest delivery probability and available space 5 6 6 7 7 6 S 7 2a 3 3a 1 1 1 4 2 2 2 4 i 4 i i 3 3 3 5 5 5 6 6 6 S S S 7 7 7 • Replicated by the source node via erasure cording CS 710

  8. RED[3/3] • Erasure coding improves delivery ratio • PARAMETERS: b, s 1 2 3 4 5 One Message  bblocks Encoding (s x b blocks) 11 12 21 22 23 31 32 33 41 42 51 52 53 54 55 Opportunistic Forwarding 11 21 32 42 52 Decoding 1 2 3 4 5 Message n blocks Erasure coding approach CS 710

  9. FAD[1/3] • Message Fault Tolerance-Based Adaptive Data Delivery Scheme(FAD) • Multiple copies of the messages  redundancy • Fault Tolerant Degree(FTD) • Probability that at least one copy of the message is delivered to the sink • Initialize with zero and update upon an event of either message transmission • Message with smaller fault tolerance is more important CS 710

  10. FAD[2/3]- Data Transmission • Node ‘i’ learns neighbor’s delivery probability and available buffer space via simple handshaking 1 1 1a i 2 1 i i 4 4 2 2 1 4 3 3 5 S 5 S • Node ‘i’ multicasts its message ‘j’ to a subset of neighbors nodal delivery probability > threshold(H) 3 5 6 6 7 7 2 6 S 7 • Intermediate node can replicate message i 2a i 4 3 i 4 3a 4 1 3 1 1 3 3 5 5 5 6 2 6 2 2 6 7 7 S S S 7 Replicated by the source and intermediate nodes. CS 710

  11. FAD[3/3]- Queue Management • When a new Message come to queue with already full, then drop the bottom message in the queue • Sort the messages based on FTD. The smaller FTD, the more important • If FTD of a message is larger than threshold, then drop it to reduce transmission cost M1,M2,M3,M4,M5,M6,M8 M1,M2,M3,M4,M5,M6,M7 Drop M5, M6, M8 New Message M8 j 10 2 • FTD < threshold(r), ex) 0.57 0.86 0.78 0.98 0.86 0.56 0.45 0.3 0.58 0.01 CS 710 RED’s : FIFO, FAD’s : FTD based queue management

  12. Evaluation[1/4] Simulation Transmission range : 10m Number of sensor nodes : 100 Number of sink nodes : 3 Size of network area : 200 m x 200m Max queue length : 120 messages Message generation rate : 0.01/s Whole message length : 200bits Bandwidth : 10kbps Nodal moving speed : 0-5m/s r : 0.9 H : 0.9 Smax : 3 bmax : 20 CS 710

  13. Evaluation[2/4] Delivery Ratio RED is sensitive to node density Propagating many small messages may incur further processing overhead and inefficiency of bandwidth utilization Optimization of erasure coding parameters is Difficult CS 710

  14. Evaluation[3/4] Average Delivery Delay Scalability The more copies, the lower delay But there is overhead issue for replication CS 710

  15. Evaluation[4/4] Average Copies for Each Message Flooding excluded because of its exponential replication FAD : queue management by Messages’ FTD CS 710

  16. Conclusion & Discussion • Dft-msn • Tradeoff between Delivery Ratio/Delay AND Transmission overhead • Sensitivity of Threshold(h, r, s, b) CS 710

  17. Thank You CS 710

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