1. Time-stable geocast for ad hoc networks and its application with virtual warning signs Volume 27, Issue 11, 1 July 2004, Pages 1065-1075 Applications and Services in Wireless Networks 作者： Christian Maiho¨fer*, Reinhold Eberhardt 指導教授：許子衡 教授 報告學生：馬敏修 2010/4/21

2. Outline 1. Introduction 2. Background and related work 3. Overview on abiding geocast 4. Design space of abiding geocast 5. Abiding geocast approaches  Server approach  Election approach  Neighbor approach 6. Simulations 7. Summary 2010/4/22

3. Introduction(1/2) Geocast ： the transmission of a message to some or all nodes within a geographical area. Virtual warning signs are attached to a certain geographical position or area. Virtual warning sign service need a time-stable geocast solution. 2010/4/23

4. Introduction(2/2) 4

5. Background and related work For geographical unicast routing protocols, three basic forwarding strategies can be identified: 1) Greedy forwarding 2) Restricted directional flooding 3) Hierarchical forwarding 2010/4/25

6. Overview on abiding geocast An inherent question of the abiding geocast semantics is the duration of storage and delivery availability. We provide an best effort service without guarantees, which means that we cannot provide guarantees about the duration availability. 2010/4/26

7. Design space of abiding geocast(1/2) For a stored geocast solution we identify four building blocks ： 1) The underlying geocast routing protocol 2) The storage of geocast messages 3) The hand over of abiding geocast messages 4) The delivery of an abiding geocast messages to new nodes inside the destination region. 2010/4/27

8. Design space of abiding geocast(2/2) 2010/4/28

9. Abiding geocast approaches(1/10) Server approach The geocast server uses a geocast routing protocol to deliver the message to the destination region. 2010/4/29

10. Abiding geocast approaches(2/10) Moving node does not know about the defined destination region of geocast messages stored on the server. Server requires moving nodes to periodically send their position to the geocast server. 2010/4/210

11. Abiding geocast approaches(3/10) 2010/4/211

12. Abiding geocast approaches(4/10) Election approach Each node in the destination region is a candidate for the election process. 2010/4/212

13. Abiding geocast approaches(5/10) Geocast message delivery is done as follows ： 1) The sender of a geocast message uses a geocast routing protocol to deliver the message. 2) All nodes receive the geocast message and start the election process. 3) The elected node stores the message and periodically or on request delivers the message. 2010/4/213

14. Abiding geocast approaches(6/10) 2010/4/214

15. Abiding geocast approaches(7/10) Opposing event geocast is used to address the whole destination region of the abiding geocast message that is to be discarded. 2010/4/215

16. Abiding geocast approaches(8/10) Neighbor approach Each node stores all geocast packets destined for its location and keeps a table of all neighbor nodes and their location. The neighbor approach simply makes use of the exchanged neighbor information for unicast routing. 2010/4/216

17. Abiding geocast approaches(9/10) 2010/4/217

18. Abiding geocast approaches(10/10) 2010/4/218

19. Simulations(1/4) 2010/4/219

20. Simulations(2/4) 2010/4/220

21. Simulations(3/4) 2010/4/221

22. Simulations(4/4) 2010/4/222

23. Summary Virtual warning signs are attached to a certain geographical position or area. An abiding geocast is a time-stable geocast delivered to all nodes. The design space of abiding geocast has the four dimensions: geocast protocol, geocast storage, geocast hand over and geocast delivery. Three reasonable approaches ： Server approach, Election approach and Neighbor approach. 2010/4/223