Advisor : Prof. Yu- Chee Tseng Student : Yi-Chen Lu

1. Advisor : Prof. Yu-Chee Tseng Student : Yi-Chen Lu An Energy Efficient, Load Balanced Multicast Protocol with Probabilistic Anycast for ZigBee Wireless Sensor Networks

2. Outline • Introduction • Related Work • Motivation • Goal • Protocol Design • Simulation • Conclusion

3. Outline • Introduction • Related Work • Motivation • Goal • Protocol Design • Simulation • Conclusion

4. Introduction • A WSN is composed of numerous inexpensive wireless sensor nodes, each of which is normally powered by batteries and has limited computing ability • Wireless sensor nodes are capable of not only collecting, storing, processing environmental information, but also communicating with neighboring nodes • Many research works have been dedicated to WSNs, such as routing, self-organization, deployment, and localization

5. Introduction • Multicast is a fundamental routing service of network communication • In WSN, a single message can be delivered to multiple destinations efficiently via multicast communication • In WSN, members may dynamically join and leave the groups Fruits Area Join banana group Drinks Area Join coke group

6. Introduction • ZigBee is a cost-effective wireless networking solution that supports low data-rates, low-power consumption, security, and reliability • Most WSN industries have adopted ZigBee as their communication protocol and developed numerous products

7. ZigBee Multicast • In ZigBee, multicast members are physically separated by a hop distance of no more than MaxNonMemberRadius • ZigBee multicast exploits regional flooding to deliver the multicast message • Drawbacks of ZigBee multicast • Heavy traffic overhead • High energy cost • Unreliable Region bounded by MaxNonMemberRadius Another Member Member

8. Outline • Introduction • Related Work • Overlay Multicast • Geographic Multicast • Relay-Selection Multicast • Motivation • Goal • Protocol Design • Simulation • Conclusion

9. Overlay Multicast • PAST-DM (Wireless Networks 2007) • Applying unicast leads to excessive energy consumption and redundant transmissions • AOM (ICPPW 2007) • Applying broadcast eliminates redundant transmissions • Packet header overhead • Overlay multicast needs extra cost to support dynamic member actions • Fixed delivery paths lead to single-node failure problem Destination List & Forwarder List redundant 4 transmissions 6 transmissions

10. Geographic Multicast • GMREE (COMCOM 2007) • Cost over progress ratio • Drawbacks • Packet header overhead • Location information must be available • Suffer from the face routing cost • Do not support dynamic member joining/leaving • Single-node failure problem

11. Relay-Selection Multicast • Steiner-tree based multicast • BIP and MIP (MONET 2002) • Based on Prim’s algorithm to find a minimum-cost spanning tree • NJT and TJT (COMCOM 2007 ) • Minimum cost set cover heuristics • Single-node failure problem • Computing complexity is high • Centralized algorithm must keep global information • Do not support dynamic member joining/leaving • Source tree construction overhead 2 4 S 10 8 9 C1 C2 C3 C4 C5 6 1 3 1 2 3 4 5 6 7 5 7

12. Outline • Introduction • Related Work • Motivation • Goal • Protocol Design • Simulation • Conclusion

13. Motivation • Due to the limited power resource, energy efficient multicast is a critical issue in WSN • ZigBee multicast is not only energy inefficient but also unreliable • Many approaches have been proposed to study on the energy efficient multicast issues in WSN

14. Motivation • However, these proposed approaches either have significant drawbacks or are not compatible with ZigBee • Single-node failure problem (all) • Do not support dynamic member joining/leaving (all) • Packet header overhead (overlay & geographic) • Location information (geographic) • High computing complexity (geographic & relay) • Must keep global information (relay-selection)

15. Outline • Introduction • Related Work • Motivation • Goal • Protocol Design • Simulation • Conclusion

16. Goal • Propose a multicast routing protocol which has the following features • ZigBee Compatible • Energy efficient • Less energy consumption • Reliable • Higher delivery ratio • Load balanced • Avoid single-node failure problem • Prolong the network lifetime • Support dynamic member joining/leaving

17. Outline • Introduction • Related Work • Motivation • Goal • Protocol Design • Simulation • Conclusion

18. Protocol Overview Coverage Over Cost Ratio Probabilistic Anycast Random Backoff Multicast Information Table (MIT) Residual Energy Forwarding Strategy Packet Forwarding Ack Mechanism

19. Protocol Flow Coverage Over Cost Ratio MIT Maitenance Initiate A Multicast Residual Energy Multicasting Receive A Multicast Packet Radom Backoff Backoff for tb Ack Mechanism Forwarding Strategy Forward Wait for twait Rebroadcast Discard

20. Outline • Introduction • Related Work • Motivation • Goal • Protocol Design • MIT Maintenance • Multicasting • Simulation • Conclusion

21. Outline • Introduction • Related Work • Motivation • Goal • Protocol Design • MIT Maintenance • Multicasting • Simulation • Conclusion

22. MIT Maintenance • Multicast Information Table (MIT) • Reachable members within MaxNonMemberRadius hops • Hop distances to the reachable members

23. MIT Maintenance Example HELLO HELLO HELLO HELLO HELLO HELLO HELLO HELLO HELLO HELLO HELLO HELLO HELLO HELLO Region bounded by MaxNonMemberRadius = 2

24. MIT Maintenance Example • MIT keeps the information of only the members located within the region bounded by MaxNonMemberRadius hops MaxNonMemberRadius = 2

25. Outline • Introduction • Related Work • Motivation • Goal • Protocol Design • MIT Maintenance • Multicasting • Simulation • Conclusion

26. Protocol Flow Coverage Over Cost Ratio MIT Maitenance Initiate A Multicast Residual Energy Multicasting Receive A Multicast Packet Radom Backoff Backoff for tb Ack Mechanism Forwarding Strategy Forward Wait for twait Rebroadcast Discard

27. Multicasting • Our protocol adopts a probabilistic anycast mechanism based on the coverage over cost ratio and each node’s residual energy • Our protocol is similar to the relay-selection approaches • However, the selection of relay nodes is determined by the receivers, rather than by the senders

28. Probabilistic Anycast • Coverage Over Cost Ratio • Residual Energy Probabilistic Anycast • Forwarding Strategy • Ack Mechanism

29. Probabilistic Anycast Illustration To Z • Node S multicasts a message • Node S’s neighbors, A, B, and C receive the message • Node A, B, and C back off for an interval which is calculated according to • The coverage over cost ratio • Its own residual energy • When the backoff timer expires • The node forwards the message if its destination set is not empty • The node does not forward the message if its destination set is empty • After sending out the message, node S waits for a period of time twaitto confirm the forwarding status • Node S decides whether to retransmit the packet according to whether the forwarders cover all the destination members or not • As the network topology changes and the power of each node depletes, the set of forwarders will be different • Therefore, our protocol is able to achieve energy efficiency and load balance while avoiding single-node failure problem A No retransmission because A, B, and C have covered X,Y, and Z Candidate Relay To X, Y, Z To X, Y S B B covers all my reachable members {Y} Candidate Relay C Candidate Relay

30. Initiating A Multicast Multicast to {m1, m2, m3} ; the hop distance to them is {2, 2, 3} The average residual energy of my neighbors is Eavg Destination Set M = {m1, m2, m3} Distance Set H = {2, 2, 3} Average residual energy of the neighbors = Eavg

31. Upon Receipt of A Multicast Packet Remove the members which are further from me than from the previous hop to avoid detours Remove member originator/previous hop to avoid loop Generate a random backoff period Roger that! S X S 1 m2 3

32. Random Backoff • Coverage Over Cost Ratio • Residual Energy Probabilistic Anycast

33. Coverage Over Cost Ratio A A • Coverage Over Cost Ratio • The coverage over cost ratio is targeted at reaching as many member nodes as possible while consuming as little energy as possible Number of covered members X Y C Estimated energy cost B B Superior in forwarding

34. Radom Backoff • The backoff timer interval tb is generated randomly within the range [0, T] • With greater f value, T should be smaller • The single-node failure problem is still unsolved Normalize f to a parameter α to show the influence of coverage over cost ratio on the backoff interval

35. Random Backoff • We further introduce the idea of load balance to our protocol • Therefore, a node which has more energy and covers more destination members with less energy cost has a better chance to generate a shorter backoff interval • The data delivery paths are dynamically adjusted during each propagation according to the instant network condition Superior in forwarding

36. Packet Forwarding Probabilistic Anycast • Forwarding Strategy • Ack Mechanism

37. Packet Forwarding Generate a random backoff period Roger that! All the destination members are forwarded m1and m2 are forwarded by node Y Wait for a period of time twait m3 is forwarded by node X X twait Generate a random backoff period Roger that! S m1 Y 2 m2 2 The members I want to forward to are all covered by other nodes m3 3 Z m1 is covered by node Y Generate a random backoff period m1 1 Roger that!

38. Outline • Introduction • Related Work • Motivation • Goal • Protocol Design • Simulation • Conclusion

39. Simulation

40. Simulation

41. Outline • Introduction • Related Work • Motivation • Goal • Protocol Design • Simulation • Conclusion

42. Conclusion • Energy efficient multicast is a critical issue in WSN • Many approaches have been proposed, but they fail to achieve energy efficiency and load balance at the same time • We propose a ZigBee compatible multicast protocol • Energy efficient • Load balanced • Reliable • Support dynamic member joining/leaving • Simulation result shows that our protocol outperforms ZigBee in energy consumption and latency

43. Q&A Thanks