1. www.eng.monash.edu A Low-Cost Flooding Algorithm for Wireless Sensor Networks Department of Electrical and Computer Systems Engineering Monash University, Australia WCNC 2007, Hong Kong Ou Liang, Ahmet Sekercioglu and Nallasamy Mani

2. www.eng.monash.edu 2 Sections 1.Flooding in WSNs. 2.Our Low-Cost Flooding algorithm. 3.Simulation study. 4.Conclusion and future work.

3. www.eng.monash.edu 3 Flooding in WSNs Flooding is the simplest way of routing. It requires each node in the network to broadcast a packet upon receiving it for the first time. Flooding is widely used in WSNs by many applications. Problems : Redundant packets — nodes receive multiple copies of a packet. Contention and collision — happen when using a contention MAC layer like IEEE 802.11. Energy wastage — redundant retransmissions consume energy. Section 1Section 2Section 3Section 4

4. www.eng.monash.edu 4 Redundant flooding S Section 1Section 2Section 3Section 4

5. www.eng.monash.edu 5 An efficient way of flooding S A C B Section 1Section 2Section 3Section 4

6. www.eng.monash.edu 6 Low-Cost Flooding Algorithm It aims to form a Connected Dominating Set (CDS) in a given network. It operates in two steps: Elects cluster-heads (dominators). Generates connectors to link all the dominators. Section 1Section 2Section 3Section 4

7. www.eng.monash.edu 7 Electing dominators Initially, all nodes in the network mark themselves as white nodes, and only the nodes in the white node state participate dominator election. Section 1Section 2Section 3Section 4 A node announces itself as the dominator if it has the largest node degree among its white node neighbors. Nodes that are covered by the dominators change their states to dominatees.

8. www.eng.monash.edu 8 Dominator election example DB F A E C G H I J O P N L K M T Node | Node degree D 6 h 5 P 5 Dominators are two hops or three hops apart from each other. Section 1Section 2Section 3Section 4

9. www.eng.monash.edu 9 Generating connectors Two types of connectors: Active-Connector – selected by dominators Passive-Connector – selected by dominators and active connectors. Section 1Section 2Section 3Section 4 Passive-Connectors connect two-hop away dominators. Active-Connectors + Passive-connectors connect three-hop away dominators.

10. www.eng.monash.edu 10 Connecting two-hop away dominators A dominator U selects a dominatee V as a passive- connector to connect two-hop away dominators based on two rules: U has a bigger node ID than all its two-hop away dominators that are covered by V. V covers the most number of two-hop away dominators of U. Section 1Section 2Section 3Section 4

11. www.eng.monash.edu 11 Selecting passive connectors W B A V U Dominator W Node A: { V } Node B: { U, V } Dominator V Node A: { W } Node B: { U, W } Dominator UNode B: { V, W } I am a Passive connector Selected by W Section 1Section 2Section 3Section 4

12. www.eng.monash.edu 12 Connecting three-hop away dominators Two steps to connect three-hop away dominators: A dominator U selects an active-connector V. Active-connector V selects other passive connectors to connect three-hop away dominators. Section 1Section 2Section 3Section 4

13. www.eng.monash.edu 13 New definitions Special-dominatee: A dominatee V marks another dominatee W as a special dominatee if W has no shared one-hop dominator with V. CA B VW U Dominatee U and V have a shared dominator C. Dominatee V and W have no shared dominators. V and W mark each other as the special-dominatees. Section 1Section 2Section 3Section 4

14. www.eng.monash.edu 14 New definitions Special-dominator: Dominatee V marks all the one-hop dominators of a special- dominatee W as the special-dominators. CA B VW U Dominatee V marks dominator A as the special-dominator. Dominatee W marks dominator B and C as the special-dominators. Section 1Section 2Section 3Section 4

15. www.eng.monash.edu 15 New definitions Isolated-dominator: A dominator C marks a special-dominator A of dominatee V as the isolated-dominator if A is neither a two-hop away dominator of C, nor a two-hop away dominator of any node in D 2 (C). Use D 2 (C) to represent the set of two-hop away dominators of a dominator C. CA B VW U Section 1Section 2Section 3Section 4

16. www.eng.monash.edu 16 Selecting active-connectors A dominator U selects a dominatee V as an active-connector if: U has marked some isolated-dominator from V. U has larger node ID than those marked isolated dominators. Dominator U will inform active-connector V about the isolated-dominators V needs to connect. Section 1Section 2Section 3Section 4

17. www.eng.monash.edu 17 Selecting passive-connectors (by active-connectors) An active-connector V selects a dominatee W as the passive-connector if: W connects to the most number of isolated-dominators. CA B VW U Connect isolated- dominator A I am a passive- connector Section 1Section 2Section 3Section 4

18. www.eng.monash.edu 18 Simulation study Section 1Section 2Section 3Section 4 SimulatorOMNeT++ with Mobility Framework. MAC protocolAssume a perfect MAC layer (error and collision free). Network area100m x 100m two dimensional area. Topology generation Randomly distribute nodes in the area. Each node is placed within the transmission range of a previously placed node to make sure connectivity. Total nodesRange from 100 to 500. Transmission range Two transmission ranges: 15m and 25m. Performance metrics Number o forwarding nodes, number of signaling messages, and signaling message size. Number of runs11 random topologies simulated for each network size.

19. www.eng.monash.edu 19 Simulation study Section 1Section 2Section 3Section 4 Number of forwarding nodes generated

20. www.eng.monash.edu 20 Simulation study Section 1Section 2Section 3Section 4 Number of signaling messages generated

21. www.eng.monash.edu 21 Simulation study Section 1Section 2Section 3Section 4 Signaling message size (in bytes) R=15m Total number of nodes in the network 100200300400500 LCF15.7925.5534.0343.1351.48 MOA17.5026.1531.9241.1051.49 GMPR28.9248.6965.2480.9194.01 MPR32.0252.4070.0686.91100.86 SIMPR32.0252.4070.0686.91100.86 EMPR 53.58 91.53125.08157.25183.95 EEMPR911.242653.064946.217809.19136.01

22. www.eng.monash.edu 22 Simulation study Section 1Section 2Section 3Section 4 Signaling message size (in bytes) R=25m Total number of nodes in the network 100200300400500 LCF16.3627.8535.4546.5155.52 MOA17.9428.2539.1450.2153.65 GMPR31.4252.4774.1192.74112.11 MPR34.4156.978.5198.93118.62 SIMPR34.4156.978.5198.93118.62 EMPR58.57101.06142.74182.43220.92 EEMPR1056.633096.985888.127464.248945.48

23. www.eng.monash.edu 23 Conclusion and future work Section 1Section 2 Section 3Section 4 We have proposed a Low-Cost Flooding (LCF) algorithm for wireless senor networks. The algorithm aims to minimize the redundant retransmissions in the network by generating a Connected Dominating Set (CDS). Future work: Design efficient routing protocols for sensor networks. Implement a real world sensor network test bed.

24. www.eng.monash.edu 24 Thank you for your attention!

25. www.eng.monash.edu 25 Flooding protocol designing considerations Scalability — flooding algorithms for WSNs need to be distributed and depends on localized information. Simplicity — flooding algorithms need to be simple in both computation and communication. Efficiency — flooding algorithms can dramatically reduce unnecessary redundant transmissions and save energy. Section 1Section 2Section 3Section 4