1. D ELAY / FAULT -T OLERANT M OBILE S ENSOR N ETWORK ( DFT - MSN ) : A N EW P ARADIGM FOR P ERVASIVE I NFORMATION G ATHERING IEEE TRANSACTION ON MOBILE COMPUTING 2008 Y U W ANG, H ONGYI W U U NIVERSITY OF L OUISIANA P RESENTATION : PARK HAN JIN( 박한진 ) C OMPUTER N ETWORK L AB CS 710

2. I NTRODUCTION  D ELAY /F AULT -T OLERANT M OBILE S ENSOR N ETWORK  N ODAL M OBILITY  S PARSE C ONNECTIVITY  D ELAY T OLERABILITY  F AULT T OLERABILITY  L IMITED B UFFER  H OW TO ACHIEVE RELIABILITY ?  R EDUNDANCY ( MULTIPLE COPIES OF A DATA MESSAGE ) CS 710 1 / 15

3. D IRECT T RANSMISSION  G ATHERED MESSAGES ARE INSERTED INTO A FIFO Q UEUE  W HENEVER THE SENSOR MEETS A SINK, IT TRANSMITS D IRECTLY TO THE S INK NODE CS 710 2 / 15 S 1 3 2 4 5 6 7 S S 8 9

4. S IMPLE F LOODING  S ENSOR BROADCASTS THE DATA MESSAGES IN ITS QUEUE TO NEARBY SENSORS  N EIGHBOR SENSORS KEEP MESSAGES IN QUEUE, AND REBROADCAST THEM  R EPLICATION WITH M ULTIPLE COPIES CS 710 3 / 15 S 1 3 2 4 8 9 5 6 7 5 6

5. O BSERVATION  T RADE - OFF  W HEN SHOULD DATA MESSAGE BE TRANSMITTED ?  W HICH MESSAGES SHOULD BE TRANSMITTED ?  W HICH MESSAGES SHOULD BE DROPPED ? D IRECT T RANSMISSION F LOODING B ASED T RANSMISSION O VERHEAD L OW H IGH D ELIVERY R ATIO /D ELAY B AD G OOD (?) CS 710 4 / 15

6. RED[1/3]  R EPLICATION -B ASED E FFICIENT D ATA D ELIVERY S CHEME (RED)  N ODAL D ELIVERY P ROBABILITY  E STIMATE P ROBABILITY THAT A SENSOR CAN DELIVERY A MESSAGE TO SINK  D ECISION ON DATA TRANSMISSION IN BASED ON DELIVERY PROBABILITY  I NITIALIZE WITH ZERO AND UPDATE UPON AN EVENT OF EITHER MESSAGE TRANSMISSION OR TIMER EXPIRATION i k S CS 710 5 / 15

7. RED[2/3]- D ATA T RANSMISSION  R EPLICATED BY THE SOURCE NODE VIA ERASURE CORDING i 1 3 2 1 i 1 3 2 1a2 4 5 6 7 S 4 5 6 7 S i 3 2 4 5 6 7 S 1 2a i 3 2 4 5 6 7 S 1 3 i 3 2 4 5 6 7 S 1 3a i 3 24 6 7 S 1 5 Node ‘i’ learns neighbor’s delivery probability and available buffer space via simple handshaking Node ‘i’ transmits its message to the neighbor, ‘2’, which has the highest delivery probability and available space CS 710 6 / 15

8. RED[3/3]  E RASURE CODING APPROACH 12354 O NE M ESSAGE  b BLOCKS E NCODING (s X b BLOCKS ) 111221232231323342415152535554 O PPORTUNISTIC F ORWARDING 12121323242425252 D ECODING 12354 M ESSAGE N BLOCKS Erasure coding improves delivery ratio PARAMETERS : b, s CS 710 7 / 15

9. FAD[1/3]  M ESSAGE F AULT T OLERANCE -B ASED A DAPTIVE D ATA D ELIVERY S CHEME (FAD)  M ULTIPLE COPIES OF THE MESSAGES  REDUNDANCY  F AULT T OLERANT D EGREE (FTD)  P ROBABILITY THAT AT LEAST ONE COPY OF THE MESSAGE IS DELIVERED TO THE SINK  I NITIALIZE WITH ZERO AND UPDATE UPON AN EVENT OF EITHER MESSAGE TRANSMISSION  M ESSAGE WITH SMALLER FAULT TOLERANCE IS MORE IMPORTANT CS 710 8 / 15

10. FAD[2/3]- D ATA T RANSMISSION  R EPLICATED BY THE SOURCE AND INTERMEDIATE NODES. i 1 3 2 1 i 1 3 2 1a2 4 5 6 7 S 4 5 6 7 S i 1 3 2 4 5 6 7 S 2a i 1 3 2 5 6 7 S 3 i 13 2 5 6 7 S 3a i 1 3 2 5 6 7 S 4 44 Node ‘i’ learns neighbor’s delivery probability and available buffer space via simple handshaking Node ‘i’ multicasts its message ‘j’ to a subset of neighbors NODAL DELIVERY PROBABILITY > THRESHOLD (H) Intermediate node can replicate message CS 710 9 / 15

11. FAD[3/3]- Q UEUE M ANAGEMENT  RED’ S : FIFO, FAD’ S : FTD BASED QUEUE MANAGEMENT 0.98 j 0.01 0.3 0.45 0.56 0.86 S ORT THE MESSAGES BASED ON FTD. T HE SMALLER FTD, THE MORE IMPORTANT W HEN A NEW M ESSAGE COME TO QUEUE WITH ALREADY FULL, THEN DROP THE BOTTOM MESSAGE IN THE QUEUE I F FTD OF A MESSAGE IS LARGER THAN THRESHOLD, THEN DROP IT TO REDUCE TRANSMISSION COST 0.580.780.86 M1,M2,M3,M4,M5,M6,M7 New Message M8Drop M5, M6, M8 M1,M2,M3,M4,M5,M6,M8 10 2 CS 710 10 / 15 FTD < THRESHOLD (r), EX ) 0.57

12. E VALUATION [1/4]  S IMULATION T RANSMISSION RANGE : 10 M N UMBER OF SENSOR NODES : 100 N UMBER OF SINK NODES : 3 S IZE OF NETWORK AREA : 200 M X 200 M M AX QUEUE LENGTH : 120 MESSAGES M ESSAGE GENERATION RATE : 0.01/ S W HOLE MESSAGE LENGTH : 200 BITS B ANDWIDTH : 10 KBPS N ODAL MOVING SPEED : 0-5 M / S r : 0.9 H : 0.9 S MAX : 3 b MAX : 20 CS 710 11 / 15

13. E VALUATION [2/4] D ELIVERY R ATIO  RED IS SENSITIVE TO NODE DENSITY  P ROPAGATING MANY SMALL MESSAGES MAY INCUR FURTHER PROCESSING OVERHEAD AND INEFFICIENCY OF BANDWIDTH UTILIZATION  O PTIMIZATION OF ERASURE CODING PARAMETERS IS D IFFICULT CS 710 12 / 15

14. E VALUATION [3/4] A VERAGE D ELIVERY D ELAY  S CALABILITY  T HE MORE COPIES, THE LOWER DELAY  B UT THERE IS OVERHEAD ISSUE FOR REPLICATION CS 710 13 / 15

15. E VALUATION [4/4] A VERAGE C OPIES FOR E ACH M ESSAGE  F LOODING EXCLUDED BECAUSE OF ITS EXPONENTIAL REPLICATION  FAD : QUEUE MANAGEMENT BY M ESSAGES ’ FTD CS 710 14 / 15

16. C ONCLUSION & D ISCUSSION  D FT - MSN  T RADEOFF BETWEEN D ELIVERY R ATIO /D ELAY AND T RANSMISSION OVERHEAD  S ENSITIVITY OF T HRESHOLD ( H, r, s, b) CS 710 15 / 15

17. Thank You CS 710