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E-ODMRP: Enhanced ODMRP with Motion Adaptive Refresh

E-ODMRP: Enhanced ODMRP with Motion Adaptive Refresh. Soon Y. Oh, Joon-Sang Park, Mario Gerla Computer Science Dept. UCLA. Multicasting in ad hoc nets. Why multicast in ad hoc nets? Group (1-to-many) communication Wireless “broadcast” medium ODMRP: On Demand Multicast Routing Protocol

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E-ODMRP: Enhanced ODMRP with Motion Adaptive Refresh

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  1. E-ODMRP: Enhanced ODMRP with Motion Adaptive Refresh Soon Y. Oh, Joon-Sang Park, Mario Gerla Computer Science Dept. UCLA

  2. Multicasting in ad hoc nets • Why multicast in ad hoc nets? • Group (1-to-many) communication • Wireless “broadcast” medium • ODMRP: On Demand Multicast Routing Protocol • One of the most widely used ad hoc multicast routing protocol • Simple yet high-performing

  3. F F F F ODMRP: Initialization Phase Join Query Join Reply Forwarding Node Link Multicast Route • On-demand approach: A source initiates JOIN QUERY flooding only when it has data to send • The sender periodically floods JOIN QUERY control messages • All intermediate nodes set up route to sender (backward pointer) • Members send Join Reply messages following backward pointers • Routes from sources to receivers build a mesh of nodes called “forwarding group”. Forwarding Group R S R R R

  4. Forwarding Group S1 R S R R S2 R F F F F Generalize to multiple sources • To make the procedure scalable to large number of sources: • stagger “join query” floods • aggregate join replies

  5. Forwarding Group R S R R S2 R ODMRP: operation • Source broadcasts data packet to neighbors • Forwarding Group nodes forward multicast packets via “restricted” flooding on the forwarding mesh • Soft state • No explicit receiver join/leave messages • Forwarding nodes clear state upon timeout • Extremely robust to mobility, fast fading, obstacles, jamming

  6. Comparison: Packet Delivery Ratio

  7. Problem: ForwardGroup maintenance • Mesh is very resilient to: • Short term disruptions (jamming, fading, obstacles) • Medium term (connectivity) disruptions, eg FG node moving out of field • FG maintenance • To overcome connectivity disruptions, need frequent mesh refresh • Short refresh interval (proportional to FG node longevity) needed to keep connectivity in the face of motion • Problem: Short refresh interval leads to high overhead • Refresh rate is a key performance parameter

  8. Solution: motion adaptive refresh + local route recovery • Adaptive route refreshing • Route refresh rate is adjusted on-the-fly to environment, i.e., node mobility • Adjustment is based on receivers’ loss reports to source • Local route recovery • Receiver estimates packet interval and calculate time out eg. Interval * n • If time out expires, the disconnected node proactively grafts onto the FG mesh instead of waiting until next route refresh

  9. Local Route Recovery • Ring search with limited TTL • Disconnected node (say node A) floods RECEIVER JOIN locally, e.g. set packet TTL to 1 • On reception of RECEIVER JOIN, a Listener node, a neighbor of any forwarder or receiver nodes, sets itself up as a Temporary Forwarders and start forwarding next several data packets • Node A sends passive ACKs to one of Temporary Forwarders (say node B) • Node B becomes a Forwarder and others clear their status and go back to Listeners

  10. Source Receiver Join Forwarders Data flow Receivers Listeners D B A C Local Route Recovery

  11. Source Receiver Join Forwarders Data flow Receivers Listeners D B A C Local Route Recovery

  12. Source Receiver Join Forwarders Data flow Receivers Listeners D B A C Local Route Recovery

  13. Local Route Recovery (Cont.) • If failed Local Recovery, the disconnected node floods entire network with REFRESH REQUEST • On reception of REFRESH REQUEST, sources refresh FG by flooding JOIN QUERY

  14. Adaptive Route Refresh • Refresh interval varies between min and max value, e.g. 3 sec and 30 sec • On reception of REFRESH REQUEST (RR), refresh interval is adjusted to: Max > Rfr >Min ( route lifetime/F, 3 sec) • Route lifetime is the time difference between the two events: last JOIN Query arrival and link breakage detection • F is a reduction coefficient, e.g. F=2 • If no RR during a refresh interval, linearly and slowly increase refresh interval

  15. Passive ACK and Pruning • Intermediate nodes overhear packet transmission from downstream nodes • Data packets serve as passive ACKs • If a Forwarder misses several passive ACKs, it prunes itself from the mesh • Passive ACK suppression technique; a leaf node skips sending a passive ACK if it receives duplicated packets • Other node may send a passive ACK • A leaf node is changing a upstream forwarder due to mobility

  16. Forwarders Passive ACK Data flow Receivers Passive ACK Suppression & Pruning

  17. Forwarders Passive ACK Data flow Receivers Passive ACK Suppression & Pruning

  18. Forwarders Passive ACK Data flow Receivers Passive ACK Suppression & Pruning

  19. Simulation Results • Settings • NS2.1b8 • 100 nodes on 1200x800m2 • Random Way Point mobility model • 512 byte/packet • Constant bit rate traffic (4 packet/sec) • 300 seconds simulation time • Scenario 1: Varying mobility • Varying max speed (1 ~ 30m/s) and 0 sec pause time • 1 group, 1 source, and 20 receivers

  20. Simulation Results (Cont.) • Scenario 2: Varying number of receivers • Varying number of receivers (10 ~ 50) • 20 m/s max speed and 0 sec pause time • Scenarios 3: Varying data rate • Varying data rate 4pkts/sec ~ 30pkts/sec • 20 m/s max speed and 0 sec pause time • 1 group, 1 source, and 20 receivers • Scenarios 4: Varying number of sources • Varying number of sources (1 ~ 6) • 20 m/s max speed and 0 sec pause time • 1 group and 20 receivers

  21. Results in various mobility cases Packet Delivery Ratio E-ODMRP maintains PDR degradation within 1% to ODMRP and surpasses ADMR’s PDR

  22. Results in various mobility cases Normalized Packet Overhead E-ODMRP reduces the normalized overhead by 50% to ODMRP’s

  23. Results in various group size Packet Delivery Ratio E-ODMRP scales with the number of receivers and shows best PDR with 50 receivers

  24. Results in various group size Normalized Packet Overhead E-ODMRP normalized overhead is superior to ODMRP and ADMR

  25. Results in various Data Rate Packet Delivery Ratio E-ODMRP outperforms ODMRP and ADMR in high packet sending rate

  26. Results in various Data Rate Normalized Packet Overhead E-ODMRP keeps lowest normalized overhead in high packet sending rate

  27. Results in various number of Sources Packet Delivery Ratio PDR lines decrease by different factors and E-ODMRP surpasses others when there are more than three sources

  28. Results in various number of Sources Normalized Packet Overhead E-ODMRP overhead is near-flat line, but ADMR’s overhead slope suddenly change

  29. Conclusion • E-ODMRP : Enhanced ODMRP with motion adaptive refresh • E-ODMRP reduces normalized packet overhead up to 50% yet keeping similar PDR compared to ODMRP • E-ODMRP surpasses ADMR in any case • E-ODMRP achieves high packet delivery ratio with low overhead

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