1. A Scalable Approach for Reliable Downstream Data Delivery in Wireless Sensor Networks Seung-Jong Park, Ramanuja Vedantham, Raghupathy Sivakumar and Lan F. Akyildiz School of Electrical and Computer Engineering Georgia Institute of Technology ACM MobiHoc 2004 Speaker: Hao-Chun Sun

2. Outline Introduction Introduction GARUDA Overview GARUDA Overview GARUDA Framework GARUDA Framework Performance Evaluation Performance Evaluation Conclusion Conclusion

3. Introduction -background- Introduction -background- Sink to the sensors Sink to the sensors The need for reliability in a sensor network is dependent upon the specific application the used for. The need for reliability in a sensor network is dependent upon the specific application the used for. Sensor Network Downstream Sink

4. Introduction -background- Introduction -background- Security application for reconfigurable sensors Security application for reconfigurable sensors Sink upgrades software (control code) to sensor. Sink upgrades software (control code) to sensor. Sink sends target database to sensor. Sink sends target database to sensor. Sink sends a query. Sink sends a query. Sensor Network Downstream Sink Reliability

5. Introduction -Motivation- Introduction -Motivation- Reliable downstream point-to-multipoint data delivery from sink to the sensors. Reliable downstream point-to-multipoint data delivery from sink to the sensors. Sensor network Challenges — Sensor network Challenges — Environment considerations Environment considerations Message considerations Message considerations Reliability considerations Reliability considerations

6. Introduction -Motivation- Introduction -Motivation- Sensor network Challenges — Sensor network Challenges — Environment considerations Environment considerations Limited life time Limited life time Low bandwidth, energy Low bandwidth, energy Message considerations Message considerations Small sized messages Small sized messages Reliability considerations Reliability considerations Traditionally, reliability notion is a simple 100% reliable data delivery. Traditionally, reliability notion is a simple 100% reliable data delivery. WSNs might require other notions of reliability. WSNs might require other notions of reliability.

7. Introduction -Motivation- Introduction -Motivation- WSNs reliability notions WSNs reliability notions

8. GARUDA Overview GARUDA design elements GARUDA design elements Core node Core node Instantaneous construction Instantaneous construction A single packet flood. A single packet flood. Approximation of the minimum dominating set (MDS) Approximation of the minimum dominating set (MDS) Used for the loss recovery Used for the loss recovery On a per-message basis On a per-message basis

9. GARUDA Overview GARUDA design elements GARUDA design elements Loss recovery process Loss recovery process Two-stage loss recovery Two-stage loss recovery Loss recovery for Core Nodes Loss recovery for Core Nodes Loss recovery for Non-core Nodes Loss recovery for Non-core Nodes Reasons for two-stage — Reasons for two-stage — Precluding any non-core nodes ’ contention Precluding any non-core nodes ’ contention When the core nodes perform retransmission for other core nodes, this core node ’ s neighbors can receive the packets. When the core nodes perform retransmission for other core nodes, this core node ’ s neighbors can receive the packets. Only core nodes are performing retransmissions, the chances for collisions are minimized. Only core nodes are performing retransmissions, the chances for collisions are minimized.

10. GARUDA Overview GARUDA design elements GARUDA design elements Loss recovery process Loss recovery process NACK based NACK based Cannot handle all packets in a message being lost. Cannot handle all packets in a message being lost. NACK implosion NACK implosion In-sequence forwarding In-sequence forwarding Out-of sequence forwarding with A-map propagation Out-of sequence forwarding with A-map propagation A-map (Availability Map) — representing availability of packets with bit set. A-map (Availability Map) — representing availability of packets with bit set. Ex:1 message=5 packets  A-map:(01010) Ex:1 message=5 packets  A-map:(01010)

11. GARUDA Overview GARUDA design elements GARUDA design elements Reliable Single/First Packet Delivery Reliable Single/First Packet Delivery Wait-for-First-Packet (WFP) pulse Wait-for-First-Packet (WFP) pulse Short duration pulses Short duration pulses The amplitude that is much larger than that of a regular data transmission. The amplitude that is much larger than that of a regular data transmission. Sink inform the sensors about an impending message. Sink inform the sensors about an impending message. It enables sensors to require for retransmission. It enables sensors to require for retransmission. Time Tp Ts P pulses Tp<Td<Ts

12. GARUDA Overview GARUDA design elements GARUDA design elements Multiple Reliability Semantics Multiple Reliability Semantics Require reliable delivery to a subset Gs of the nodes in the graph G. Require reliable delivery to a subset Gs of the nodes in the graph G. Gs is consisted of K components. Gs is consisted of K components. Sink MDS Shortest Path Tree

13. GARUDA Framework Single/First Packet Delivery Single/First Packet Delivery NACK reliability problem NACK reliability problem Core instantaneous construction Core instantaneous construction A B Sink S A B Ts Forced WFP Pulse Data Packet DIFS Data Packet DIFS Data Packet

14. GARUDA Framework Single/First Packet Delivery Single/First Packet Delivery Loss detection and recovery Loss detection and recovery A B Sink S A B Ts Forced WFP Pulse Data Packet DIFS Data Packet DIFS Data Packet X Forced WFP Pulse Data Packet DIFS

15. GARUDA Framework Single/First Packet Delivery Single/First Packet Delivery Loss detection and recovery Loss detection and recovery Tc=i × Δ × Td, i: hop number; Δ: max node degree Tc=i × Δ × Td, i: hop number; Δ: max node degree A B A B Forced WFP Pulse Data Packet DIFS Data Packet X Forced WFP Pulse Data Packet DIFS Tc

16. GARUDA Framework Core instantaneous construction Core instantaneous construction 0 Sink Sensor node Core node 3i+1 3i+2 3i 3i+1 3i+2 3i

17. GARUDA Framework Core instantaneous construction Core instantaneous construction 0 Sink Sensor node Core node 3i+1 3i+2 3i 3i+1 3i+2 3i

18. GARUDA Framework Core instantaneous construction Core instantaneous construction a c e 3i 3i+1 3(i+1) 3i+2 g ……… 3i+2 Core band d b f h i Boundary band Broadcast Unicast Anycast

19. GARUDA Framework Core instantaneous construction Core instantaneous construction

20. GARUDA Framework Two phase loss recovery Two phase loss recovery Loss detection Loss detection A-map A-map Loss Recovery Loss Recovery Loss recovery for core nodes Loss recovery for core nodes Loss recovery for non-core nodes Loss recovery for non-core nodes

21. (Cid+NCid+NCid, A-map, bid, vFlag) (Cid, A-map, bid, vFlag) (Cid+NCid, A-map, bid, vFlag) GARUDA Framework Two phase loss recovery Two phase loss recovery Loss recovery for core nodes phase Loss recovery for core nodes phase Upstream core nodes Downstream core nodes 3i 3(i+1) 3i+1 3i+2 a d b c If the number of id equal to three, then sets the vFlag to false. Downstream core node will check the A-map from Upstream. Unicast Broadcast If non-core node has the request packet, it intercepts the request and retransmits to downstream core.

22. GARUDA Framework Two phase loss recovery Two phase loss recovery Loss recovery for non-core nodes phase Loss recovery for non-core nodes phase A non-core node snoops all transmission from its core nodes. A non-core node snoops all transmission from its core nodes. Once it observes an A-map from its core node with all the bits set, it enters the non-core recovery phase by initiating retransmission requests to the core node. Once it observes an A-map from its core node with all the bits set, it enters the non-core recovery phase by initiating retransmission requests to the core node. If it doesn ’ t hear from its core node for the period core presence timer, it sends an request to the core node to which the core node responds with its current A-map. If it doesn ’ t hear from its core node for the period core presence timer, it sends an request to the core node to which the core node responds with its current A-map.

23. GARUDA Framework Supporting other reliability semantics Supporting other reliability semantics The variants differ in which subset of nodes receive the message delivery. The variants differ in which subset of nodes receive the message delivery. Referring to the problem of determining the subset as the candidacy problem. Referring to the problem of determining the subset as the candidacy problem. Candidate nodes Forced Candidate nodes (core band)

24. GARUDA Framework Supporting other reliability semantics Supporting other reliability semantics Candidate nodes selection Candidate nodes selection Sub-region Sub-region Sub-region information is piggybacked on the first packet. Sub-region information is piggybacked on the first packet. Cover sensing field Cover sensing field Sensing range ≦ Transmission range Sensing range ≦ Transmission range Non-core nodes seek permission from their core nodes to become candidate nodes. Non-core nodes seek permission from their core nodes to become candidate nodes. Probabilistic subset Probabilistic subset Local process: each node chooses itself as a candidate node with a probability of p. Local process: each node chooses itself as a candidate node with a probability of p.

25. GARUDA Framework Supporting other reliability semantics Supporting other reliability semantics Forced candidate nodes selection Forced candidate nodes selection Sink Sensor node Core node 3i+1 3i+2 3i 3i+1 3i+2 3i Forced candidate

26. Performance Evaluation Simulator: NS2 Simulator: NS2 Network Size: 650m x 650m Network Size: 650m x 650m Nodes Deployment — Nodes Deployment — First 100 nodes to ensure connectivity First 100 nodes to ensure connectivity Sink is located at the center of one of the edges of the square. Sink is located at the center of one of the edges of the square. Radio Range:67m Radio Range:67m Channel Capacity: 1Mbps Channel Capacity: 1Mbps Each message consists of 100 packets. Each message consists of 100 packets. Transmission rate: 25 packets/s Transmission rate: 25 packets/s Packet size: 1KB Packet size: 1KB

27. Performance Evaluation Single Packet Delivery Single Packet Delivery Latency Latency

28. Performance Evaluation Single Packet Delivery Single Packet Delivery Number of data packet sent Number of data packet sent

29. Performance Evaluation Single Packet Delivery Single Packet Delivery Energy consumption per node Energy consumption per node

30. Performance Evaluation Multiple Packet Delivery Multiple Packet Delivery Latency Latency

31. Performance Evaluation Multiple Packet Delivery Multiple Packet Delivery Number of data packet sent Number of data packet sent

32. Performance Evaluation Multiple Packet Delivery Multiple Packet Delivery Energy consumption per node Energy consumption per node

33. Performance Evaluation Evaluation of Variants Evaluation of Variants Sub-region Sub-region

34. Performance Evaluation Evaluation of Variants Evaluation of Variants Sub-region Sub-region

35. Performance Evaluation Evaluation of Variants Evaluation of Variants Minimal number of sensors Minimal number of sensors

36. Performance Evaluation Evaluation of Variants Evaluation of Variants Probability Probability

37. Conclusion It proposed a new framework for providing sink-to-sensors reliability in WSNs. It proposed a new framework for providing sink-to-sensors reliability in WSNs. GARUDA GARUDA WFP pulses WFP pulses Core node Core node A-map A-map Two stage recovery Two stage recovery Future work: Multi-sink Future work: Multi-sink