Advisor : Prof. Yu-Chee Tseng Student : Yi-Chen Lu 12009/06/26

 Introduction  Related Work  Motivation  Goal  Protocol Design  Simulation  Conclusion 2

 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 3

 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 4 Fruits Area Drinks Area Join banana group Join coke group

 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 5

 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 6 Region bounded by MaxNonMemberRadius Member Another Member  Drawbacks of ZigBee multicast  Heavy traffic overhead  High energy cost  Unreliable

 Introduction  Related Work  Overlay Multicast  Geographic Multicast  Relay-Selection Multicast  Motivation  Goal  Protocol Design  Simulation  Conclusion 7

 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 8 redundant 6 transmissions4 transmissions Destination List & Forwarder List

 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 9

 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 10

 Introduction  Related Work  Motivation  Goal  Protocol Design  Simulation  Conclusion 11

 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 12

 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) 13

 Introduction  Related Work  Motivation  Goal  Protocol Design  Simulation  Conclusion 14

 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 15

 Introduction  Related Work  Motivation  Goal  Protocol Design  Simulation  Conclusion 16

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

18 MIT Maitenance Radom Backoff Radom Backoff Discard Forward Rebroadcast Ack Mechanism Forwarding Strategy Initiate A Multicast Receive A Multicast Packet Coverage Over Cost Ratio Residual Energy Wait for t wait Backoff for t b Multicasting

 Introduction  Related Work  Motivation  Goal  Protocol Design  MIT Maintenance  Multicasting  Simulation  Conclusion 19

 Multicast Information Table (MIT)  Reachable members within MaxNonMemberRadius hops  Hop distances to the reachable members 20 MIT MemberHop Count m1m1 h1h1 m2m2 h2h2 …… mnmn hnhn

21 MIT MIT MIT MIT MIT MaxNonMemberRadius = 2 MIT keeps the information of only the members located within the region bounded by MaxNonMemberRadius hops

 Introduction  Related Work  Motivation  Goal  Protocol Design  MIT Maintenance  Multicasting  Simulation  Conclusion 22

23 MIT Maitenance Radom Backoff Radom Backoff Discard Forward Rebroadcast Ack Mechanism Forwarding Strategy Initiate A Multicast Receive A Multicast Packet Coverage Over Cost Ratio Residual Energy Wait for t wait Backoff for t b 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 24

Random Backoff Packet Forwarding 25 Probabilistic Anycast Coverage Over Cost Ratio Residual Energy Coverage Over Cost Ratio Residual Energy Forwarding Strategy Ack Mechanism Forwarding Strategy Ack Mechanism

26 Multicast to {m 1, m 2, m 3 } Hop distance to them is {2, 2, 3 } The average residual energy of my neighbors is E avg Destination Set M = {m 1, m 2, m 3 } Distance Set H = {2, 2, 3 } Average residual energy of the neighbors = E avg MIT m1m1 2 m2m2 2 m3m3 3

27 MIT m1m1 1 m2m2 3 m3m3 2 SX Remove member originator/previous hop to avoid loop Remove the members which are further from me than from the previous hop to avoid detours MIT m1m1 2 m2m2 2 m3m3 3 Generate a random Backoff period

28 Random Backoff Packet Forwarding Probabilistic Anycast Coverage Over Cost Ratio Residual Energy Coverage Over Cost Ratio Residual Energy

 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 29 X A B YC B A Number of covered members Estimated energy cost Superior in forwarding

 The backoff timer interval t b is generated randomly within the range [ 0, T]  With greater f value, T should be smaller  The single-node failure problem is still unsolved 30

 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 31 Superior in forwarding

32 Random Backoff Packet Forwarding Probabilistic Anycast Forwarding Strategy Ack Mechanism Forwarding Strategy Ack Mechanism

 During the backoff period, any member covered by other nodes is removed from M  When the backoff period expires, and M is not Φ  Rebroadcast the packet with up-to-date M, H and E avg 33

 After sending out the multicast packet, the sender waits for a period of time t wait to confirm the forwarding status of the destination members  If not all the members in set M of the sender are forwarded when t wait expires, the sender retransmits the multicast packet 34

 Introduction  Related Work  Motivation  Goal  Protocol Design  Simulation  Conclusion 35

Simulation Environment Simulation Duration10 5 sec Area35m * 35m Number of Nodes100~500 (Random deployment) Number of Members10 (Randomly generated) MaxNonMemberRadius5 Transmission Range6m MACIEEE MAC with unslotted CSMA-CA Max Backoff Interval5ms Transmission Rate250Kbps 36

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 Introduction  Related Work  Motivation  Goal  Protocol Design  Simulation  Conclusion 38

 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 39

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