GeoTORA: A Protocol for Geocasting in Mobile Ad Hoc Networks

1. GeoTORA: A Protocol for Geocasting in Mobile Ad Hoc Networks Authors: Young-Bae Ko, IBM T.J. Watson Nitin H. Vaidya, Texas A&M University Speaker: Gavin Holland, Texas A&M University

2. Mobile Ad hoc Networks (MANETs) • Network of mobile wireless nodes • Do not require fixed infrastructure to communicate • Form their own mobile routing infrastructure • Characteristics • Dynamic topology • Low link bandwidth • Limited power • Applications • Personal area networking • Wireless home networking • Search and rescue operations

3. Geocasting • Packets are delivered to all nodes within a geographical region • Compared to multicasting • Multicasting: nodes may join/leave group as desired • Geocasting: nodes join/leave group by entering/leaving the geocast region • Useful for delivering location-dependent information • Sending fire emergency messages to a certain region Geocast Region K L C D A B G J F E

4. Geocasting in MANET • Navas and Imielinski [Navas97] proposed the notion of geocasting in the traditional internet • Need new protocols for geocasting in MANETs • Ko and Vaidya[Ko99] proposed several flooding-based geocasting protocols • Geocast flooding • Location-Based Multicast (LBM)

5. Location-Based Multicasting Geocast Region • Limit flooding of geocasts to forwarding zone • Good when geocasting is performed infrequently • High overhead A A C C Z Z B B W W Y Y Forwarding Zone X X

6. Proposed: GeoTORA • Based on TORA (Temporally Ordered Routing Algorithm) [Park and Corson 97] • Unicast routing algorithm for MANETs • Destination-oriented directed acyclic graphs (DAGs) • Uses “Link-Reversal” techniques to maintain DAGs • GeoTORA • Modify TORA to do anycasting • Modify further to do geocasting

7. TORA(Temporally Ordered Routing Algorithm) • A DAG is maintained for each destination • Alogical direction is imposed on the links towards the destination • Starting from any node in the graph, a destination can be reached by following the directed links B C A D G F E

8. TORA – Link Reversal • When a node has no downstream links, it reverses the direction of one or more links B B C C A D A D G G F F E E B B C C A D A D G G F F E E

9. Anycasting with Modified TORA • In GeoTORA, the TORA protocol is modified to be able to perform anycast • Anycast -deliver to any one node in the anycast group • Protocol • Maintain a DAG for eachanycast group • Make each member of the anycast group a sink • No logical direction for links between sinks • Following the directed links results in packets being delivered to any onesink

10. Anycasting Example Anycast group = {A, B, C, D}, DAG structure for the anycast group K K K L L L C D C D C D A B A B A B G J J J G G F F F E E E

11. Geocasting using Modified Anycasting • Small variation on the previous anycasting • All nodes within a specified geocasting region are made sinks • Maintain a single DAG for a given geocast group • Source first performs an anycast to the geocast group members • When a group member receives a packet, it floods it within the geocast region K Geocast Region L C D A B G J F E

12. L B B B G G J J F F E E GeoTORA - Considerations Links may have to be updated K when node C leaves geocast region when node K enters geocast region L C D K L C C A K G D J D F E A A

13. Performance Evaluation • Simulation Model (NS2 w/ CMU extensions) • 30 nodes in a 700x700 unit arena • 1000 geocasts towards a 200x200 geocast region • Data packet (512 bytes) and Control packet (32 bytes) • Random waypoint mobility model • Performance Metrics • Accuracyof geocast delivery • Overhead of geocast delivery • average number of packets received by each node per geocast • average number of bytes received “ “ “ “ “ • Performance compared to geocast flooding and LBM

14. Simulation Results • Effect of varying pause time • Accuracy of GeoTORA is reasonably high, but not as high as flooding or LBM • Local flooding in GeoTORA may not deliver packets to all nodes in the group • Delays required to establish a route to the geocast group can be another reason A Does not receive geocast Z C B W X Y

15. Simulation Results • Overhead of geocast delivery • The overhead is consistently lower for GeoTORA as compared to the other two protocols • The main reason for increasing overhead in GeoTORA is the control packets, not the data packets

16. Simulation Results • Paper also evaluates impact of mobile speed and frequency of geocast • Results are similar to previous slides

17. Conclusions • GeoTORA • TORA unicast routing is modified for anycasting to nodes in the geocast region • Geocasting is achieved by flooding within the region • By integrating TORA and flooding, GeoTORA can significantly reduce the geocast overhead • However, GeoTORA may provide relatively lower accuracy than flooding and LBM • Needs future work

18. Thank You • For more information, contact: Young-Bae Ko (youngko@us.ibm.com) T.J. Watson Research Center, NY, USA Nitin H. Vaidya (vaidya@cs.tamu.edu) Texas A&M University, TX, USA

19. References • [Navas97] J.C. Navas and T. Imielinski, “Geocast-geographic addressing and routing,” MOBICOM’97 • [Ko99] Y.-B. Ko and N.H. Vaidya, “Geocasting in mobile ad hoc networks: Location-based multicast algorithms,” IEEE WMCSA’99 • [Park97] V.D. Park and M.S. Corson, “A highly adaptive distributed routing algorithm for mobile wireless networks,” INFOCOM’97

20. Simulation Results • Effect of varying moving speed • Impact for varying speed can be negligible here, too. • Accuracy of geocast delivery

21. Simulation Results • Overhead of geocast delivery • Geocast flooding and LBG suffer from a significantly higher overhead than GeoTORA for all moving speed.

22. Simulation Results • Effect of varying geocast frequency • Accuracy of geocast delivery

23. Simulation Results • Overhead of geocast delivery • For GeoTORA, the overhead due to data packets is almost constant. • However, GeoTORA overhead becomes poor for low geocast frequency due to higher control packet overhead to maintain DAGs

24. TORA – Basic Functions • Route Creation: demand driven “query/reply” • A query packet (QRY) is flooded through network • An update packet (UPD) propagates back if routes exist • Route Maintenance: “link-reversal” algorithm • React only when necessary • Reaction to link failure is localized in scope • Route Erasure: • A clear packet (CLR) is flooded through network to erase invalid routes

25. B C B C A D G A D G F E F E TORA – Conceptual Description B A C SRC DEST D G E F C B A D G E F