1. Mesh-based Geocast Routing Protocols in an Ad Hoc Network
指導教授：許子衡 教授
報告學生：馬敏修
2010/5/21

2. Outline Introduction Geocast via a Mesh Performance Evaluation
3.1Simulation Environment
3.2Simulation Results
3.2.1Overhead/Load
3.2.2Performance
3.3Observations
3.4Network Reliability
Random Waypoint Model
Conclusions
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3. Introduction
The goal of a geocasting protocol is to deliver a packet to a set of nodes within a specified geographical area.
Unlike multicast communication for an ad hoc network, membership in a geocast group changes whenever a mobile node (MN) moves in or out of the geocast region.
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4. Geocast via a Mesh(1/7)
Protocols that use a mesh for multicasting in an ad hoc environment have been proposed in order to provide redundant paths between the source and the group members.
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5. Geocast via a Mesh(2/7)
Use JOIN-DEMAND packets, instead of the conventional JOIN-REQUEST packets of multicast protocols, to insist that all MNs in the geocast region join the geocast group.
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6. Geocast via a Mesh(3/7)
FLOOD approach
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7. Geocast via a Mesh(4/7)
BOX approach
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8. Geocast via a Mesh(5/7)
CONE approach
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9. Geocast via a Mesh(6/7)
A JOIN-DEMAND packet is forwarded in the ad hoc network until it reaches an MN in the geocast region.
Once the JOIN-DEMAND packet reaches an MN in the geocast region, a JOIN-TABLE is unicast back to the source following the reverse route taken by the JOIN-DEMAND.
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10. Geocast via a Mesh(7/7)
MNs on the edge of the geocast region become a part of the mesh.
These nodes then use a localized flooding algorithm to transmit each geocast data packet to all reachable nodes within the geocast region.
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11. Performance Evaluation
Consider the following performance metrics: protocol overhead, network-wide data load, end-to-end delay, and goodput ratio.
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12. Simulation Environment(1/2)
Simulation environment is a 500 * 500 meter region.
Geocast region is a 100 * 100 meter region
The geocast source transmits 20 data packets (512 bytes each) to the geocast region every second for 500 seconds
Each simulation trial has 300 MNs whose initial locations are randomly chosen from a uniform distribution
Node mobility uses the random waypoint model
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13. Simulation Environment(2/2)
The geocast source transmits a JOIN-DEMAND packet every second in order to create and maintain the geocast mesh.
MN removes itself from the mesh if it does not receive a JOIN-TABLE at least every five seconds.
Each MN's communication channel bandwidth is limited to 1 Mbps, and each MN has a finite buffer which allows it to save a maximum of 20 unprocessed packets until its next opportunity to communicate.
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14. Simulation Results
MN's speed from an average of 0 to 20 m/s in increments of 5 m/s.
MN's pause time from an average of 0 to 20 seconds in increments of 5 seconds.
The average amount of data generated is approximately 9,750 packets in one simulation trial.
The average number of hops from the source to the geocast region was 2.54.
The average number of neighbors for each MN was approximately 16.
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15. Overhead/Load(1/3)
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16. Overhead/Load(2/3)
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17. Overhead/Load(3/3)
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18. Performance
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19. Performance
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20. Observations(1/2)
Observation A: Reducing the area of the forwarding zone reduces control overhead, network-wide data load, end-to-end delay, and network reliability.
Observation B: At one fixed average pause time, increasing average node speed results in decreased control overhead and decreased network-wide data load.
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21. Observations(2/2)
Observation C: At one fixed average pause time, increasing average node speed results in decreased end-to-end delay.
Observation D: At one fixed average pause time, increasing average node speed results in decreased network reliability
Observation E: At one fixed average speed, increasing average node pause time results in increased network reliability.
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22. Network Reliability
All three forwarding approaches decrease approximately 40% of the network reliability
Two other mesh-based routing protocols for an ad hoc network exist in the literature: the On-Demand Multicast Routing Protocol (ODMRP) and the Core-Assisted Mesh protocol (CAMP)
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23. Random Waypoint Model(1/3)
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24. Random Waypoint Model(2/3)
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25. Random Waypoint Model(3/3)
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26. Conclusions(1/2)
The FLOOD approach has the highest amount of control overhead and network-wide data load, but provides the highest level of reliability.
The CONE approach has the smallest amount of control overhead and network-wide data load, but provides the smallest level of reliability.
The CONE approach has the smallest end-to-end delay
The FLOOD approach has the largest end-to-end delay
The BOX approach fall between the FLOOD and CONE
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