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
Good morning, everyone (ladies and gentlemen, Sir and Madam). My name is Young-Bae ko and I am very glad to be here with you today. I am gonna

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
A mobile ad hoc network, so called MANET, is a set of wireless mobile nodes forming
Nodes communicate directly with each other over either radio frequency or intrared wireless links

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 E F

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 A A C C Z Z B B W W Y Y
Forwarding
Zone X X
Limit flooding of geocasts to forwarding zone
Good when geocasting is performed infrequently
High overhead

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)B C
A DAG is maintained for each destination
A logical 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 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 C B C A D G A D G F F E E B C B 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 each anycast 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 one sink

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

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
Accuracy of 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
Several optimizations are possible to achieve more efficient performance of the basic location-aided routing protocol.

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
Several optimizations are possible to achieve more efficient performance of the basic location-aided routing protocol. A Z
Does not
receive
geocast C B W Y X

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
Several optimizations are possible to achieve more efficient performance of the basic location-aided routing protocol.

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
T.J. Watson Research Center, NY, USA
Nitin H. Vaidya
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
Several optimizations are possible to achieve more efficient performance of the basic location-aided routing protocol.

21. Simulation Results Overhead of geocast delivery
Geocast flooding and LBG suffer from a significantly higher overhead than GeoTORA for all moving speed.
Several optimizations are possible to achieve more efficient performance of the basic location-aided routing protocol.

22. Simulation Results Effect of varying geocast frequency
Accuracy of geocast delivery
Several optimizations are possible to achieve more efficient performance of the basic location-aided routing protocol.

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
Several optimizations are possible to achieve more efficient performance of the basic location-aided routing protocol.

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