Xin Wang Assistant Professor Director, Wireless and Networking Systems Lab (WINS) SUNY, Buffalo

1. Scalable Geographic Routing for Mobile Ad-hoc Networks(Joint work with Xiaojing Xiang and Zehua Zhou) Xin Wang Assistant Professor Director, Wireless and Networking Systems Lab (WINS) SUNY, Buffalo http://www.cse.buffalo.edu/~xwang8

2. 4GRadios 4G AirInterface Future - Common Network, Common Applications 3G CellularNetworks RadioController AccessRouter UrbanNetworks • Outdoor Areas • High Mobility AggregationRouter • Broadband Distribution Networks • High Speed Pico Cells • Broadband • Wireless Presence EnterpriseNetworks Location AccessRouter • 802.11++ • Local Mobility • Packet Voice • High Data Rates Core InternetBackbone AggregationRouter AggregationRouter Authentication HomeNetworks AccessRouter • DSL/Cable • Community • wireless • networks Ad HocNetworks 4GRadios • Allow Peer-to-Peer Communications • Self Configuring

3. Talk Overview • Background and motivation • Part I: Self-adaptive geographic unicast routing • Part II: Scalable geographic multicast routing • On-going and future work

4. Background • Mobile Ad Hoc Networks (MANET) • Self organized networks with no fixed infrastructure • Example applications: disaster area, military, sensor networks, wireless mesh networks • May need to traverse many hops due to limited radio range • Routing: find a packet delivery path • Unicast: one-to-one • Multicast: one-to-many or many–to-many

5. Challenges of MANET Routing • Host mobility leads to dynamic topology • Rate of link failure/repair increases with moving speed • Topology and routing path maintenance become more difficult with the increase of path length and node density • Mobile devices have very limited energy, and small devices such as sensors have very limited per-node resources

6. Existing Unicast Routing Protocols • Proactive protocols (DSDV, OLSR) • Maintain routes continuously, large overhead when there is no traffic • Actively track network topology changes, not suitable for high mobility • Reactive protocols (DSR, AODV, TORA, FLR) • Maintain routes only if needed • May need network-wide flooding to discover routes, larger delay due to searching for path before sending packet • Hybrid protocols (ZRP, SHARP) • Combine the proactive and reactive approaches • Geographic routing protocols (GPSR, GFG) • Make use of location information to reduce routing overhead • Only need to be aware of local topology

7. Information Required for Geographic Routing • The position of the destination: determined through location service • A node’s own position: obtained through positioning service such as GPS • The positions of all neighbors: learned through periodic beacons sent by neighbors

8. Perimeter forwarding (GPSR) • Calculate a planar sub-graph (no crossed-edges exist) from the local topology • Route around the perimeter of void area (that does not have neighbor closer to the destination) until greedy forwarding can be resumed D x Forwarding Formats • Greedy forwarding • Make local optimal forwarding decision, choose the neighbor closest to the destination as next hop. D x

9. Problems with Classical Geographic Routing • Proactive fixed-interval beaconing for positions • Generate unnecessary overhead and consume energy • Create collisions with normal data transmissions • Beaconing interval affects accuracy of the local topology and routing performance • Outdated topology => non-optimal routing, transmission failures => more network resource consumption • Continuous retransmissions due to inaccurate position • Reduce link throughput and fairness, and increase collisions => further delay and energy consumption

10. Possible Performance Improvement • Change Beacon Sending Interval • Send out beacons only after moving a certain distance • Send beacons more frequently, e.g. piggyback position with packets (Are the sending nodes the best next hop? ) Does not consider traffic conditions. May generate unnecessary beacons. • Do not use Beacons (CBF’03, BLR’04) • Focus only on finding the next hop for greedy forwarding, and there is no recovery strategy • Do not have a good strategy to cache the path detected or perform any route optimization.

11. Talk Overview • Background and motivation • Part I: Self-adaptive geographic unicast routing • Part II: Scalable geographic multicast routing • On-going and future work

12. Our Contributions • Propose two self-adaptive routing protocols BIGR: Beaconless Interactive Geographic Routing BTGR: Beacon-on-Trigger Geographic Routing • On demand: alleviate unnecessary overhead due to proactive beacons • More flexible position distribution: more updated topology, more efficient routing and less failure • Self adaptive: adaptive to traffic pattern and robust to topology changes

13. r z R A B Importance of updated positions: some analysis • Positions obtained may become outdated • A mobile may move out of transmission range before the position is timed out and removed from neighbor table. • Analysis – assumptions • Node B sends beacons periodically to refresh its position at A • Neighbor area of A: centered at A, within transmission range R • Moving area of B: centered at B, within maximum distance r

14. r z R A B r z r A A z R R Different Scenarios R R r z z A B R r A B z B A r Same as this case

15. Probability of Moving Out of Range Case 1: Case 2: Case 3:

16. Probability of the mobile moving out-of-range (expressed in percentages) Timeout

17. Proposed Geographic Routing Protocols • BIGR: Beaconless Interactive Geographic Routing • BTGR: Beacon-on-Trigger Geographic Routing

18. Beaconless Interactive Geographic Routing (BIGR) • There is no beacon, routing path is built on-demand • Forwarding decision made through the cooperation of forwarding node and its neighbors • Forwarding path optimized jointly by sending node and its neighbors • Route searching phase • Route optimization phase How to find next hop without positions of neighbors?

19. Route Searching • After a route searching, a node keeps a record for next hop Next-hop position A F Next hop table for node B B C

20. How to find next hop? • When a node (C) does not have next hop information, broadcast REQ S E F B M L C J A G H D I K N Within neighborhood A node that receives a packet for the first time REQ message with

21. Forwarding Node Selection • Reply sending: nodes closer to destination respond after a competition delay, and the delay is smaller for a node closer to destination • Reply suppression: a node cancels its reply if it overhears packet forwarding, or overhears reply sent by node closer to destination • Multiple replies: select the node closer to the destination as next hop S E F B M L C J A G H D I K N REPLY message

22. Packet Sending • C’s next hop table S E F B M L C J A G H D I K N

23. Recovery from Local Void • Without local topology, cannot use perimeter forwarding. How to recover? • Broadcast REQ to N-hop neighbors E F S B M C L J A D H I G K N REQ message with

24. Finding Path in Recovery Mode • Reply sending: • If one-hop neighbor is nearer to destination, it replies with Hop = 1; Otherwise continues broadcasting REQ • A two-hop neighbor nearer to destination replies (reverse path), Hop = 2; • Reply suppression: drop the REPLY if having forwarded/overhead one from the node closer to destination • Multiple replies: select the node closer to destination E F S B M C L J Reply message D H I G K

25. Position Update and Route Optimization • Update next hop position when overhearing packet forwarding by next hop (carrying sending node position) • Validate next hop • Estimate next hop • If both old and new positions are fresh • If only new position is available, it will be used as the estimated position • Search for new route • If both old and new positions are outdated • If estimated position is out of transmission range or no longer closer to destination than current forwarding node • Optimize routing path: three cases

26. Move CORRECT A Case 1: A is the destination • As A is the destination, B should send packet directly to A, so A sends CORRECT to B A B C • B sets its next hop to A Old path Old position Current position New path

27. Move A CORRECT Case 2: Greedy Mode Forwarding A F • If A is closer to F than C is to F, A sends CORRECT to B B C • B compares A’s and C’s positions to F, and sets its next hop to A if it is closer to F Greedy Old position Current position Old path New path

28. Move A CORRECT Case 3: Recovery Forwarding F • If A is closer to F than that from B and C, A sends CORRECT to B • If B is the first hop of recovery, if A is closer to F than B is to F, then A is closer to F than both B and C • If B is the last hop of recovery, if A is closer to F than C is to F, then A is closer to F than both B and C A D B C Recovery mode Greedy • B compares A and C’s positions relative to F, if A is closer to F, B sets its next hop to A Old position • If B is the first hop of recovery, change mode togreedy Current position Old path New path

29. Proposed Geographic Routing Protocols • BIGR: Beaconless Interactive Geographic Routing • BTGR: Beacon-on-Trigger Geographic Routing

30. BTGR: Beacon-on-Trigger Geographic Routing • Position distribution: through beacons • Packet forwarding • Send packet through greedy forwarding in general. • Use perimeter forwarding in recovery mode. • Beacon generation: triggered by data traffic and route optimization • Adaptive to traffic • Send beacon periodically when overhearing data forwarding or requested by neighbor • Stop beaconing if there is no traffic • Route optimization • Broadcast a beacon upon detecting non-optimal path • Topology maintenance • Only maintain positions of neighbors when there is traffic

31. Beacon Triggering by Non-optimal Path • Route validation • Delete invalid neighbors • Update the positions of other members based on estimation • Route optimization: also three cases • The first two cases are similar to those of BIGR • Case 3: When A overhears forwarding from B to C using perimeter mode • If A is closer to the destination than that of the node position where the perimeter mode started, B should resume greedy forwarding earlier • A broadcasts a beacon to refresh its position, B will send future packets to A

32. Performance Studies • Setup: • Tool: GlomoSim • Network size: 3000 m x 1000 m, 300 nodes • Traffic: 30 CBR with rate 8kbps each • Mobility model: Random Waypoint • Measures: • Packet delivery ratio • The ratio of packets delivered to those originated by the source • Control overhead • The number of control messages over the number of packets received • Average number of data packet transmissions • The total number of packet transmissions accumulated from each hop over the total number of packets received • Average end-to-end delay • Average time interval for packets to traverse from source to destination

33. BIGR and BTGR delivery ratios are not impacted by speed BIGR more actively updates the position as speed increases Performance: Impact of Mobility Delivery ratio Control overhead

34. Performance: Impact of Mobility (cont) Total transmissions Average end-to-end delay Our protocols have significantly lower transmission redundancy and end-to-end delay than GPSR due to more updated topology.

35. Summary of Part I • Propose two self-adaptive on-demand geographic routing protocols • Alleviate unnecessary overhead due to proactive beacons • More efficient position distribution and very robust to topology change: packet transmission delay is reduced more than three times at high mobility as compared to GPSR • Outperform existing geographic protocols in all test scenarios, including mobility, node density and traffic load

36. Talk Overview • Background and motivation • Part I: Self-adaptive geographic unicast routing • Part II: Scalable geographic multicast routing • On-going and future work

37. Existing Multicast Routing Protocols • Tree-based (AMRIS, MAODV, LAM) • Utilize network resources efficiently • Mesh-based (FGMP, CAMP, ODMRP) • Robust Difficult to scale due to overhead for route searching, group membership management, and tree/mesh maintenance over dynamic topology • Geographic multicast (LGT, DSM, PBM) • Only consider packet forwarding scheme • Reduce topology maintenance overhead, but not scalable

38. Why Is Geographic Multicast Difficult to Scale? • Putting the information of all group members into packet header creates excessive overhead for large group • Relying on location service to obtain positions for all group members adds more overhead

39. Our Contributions • Design an efficient on-demand hierarchical group membership management scheme • Use geographic forwarding to avoid building and maintaining tree/mesh structure • Introduce the home zone to avoid periodical network-range flooding of source information • Combine group membership management with location service to avoid location searches for group members

40. Source Group member Member Zone Zone leader Home zone Track the addresses and Zone IDs of sources Terms Used in SGMP

41. SGMP: Basic Principles Join Join (RERESH) (REPORT) Member Zone Leader Source Data Data Member Member Zone Source Packet sending: geographic unicasting, and the packet for a zone is sent towards the zone center.

42. Source Announcements • A source • At session initiation time, floods an ANNOUNCE, with address, position, and group ID • Later piggybacks its information with the multicast packets • A node interested in being a member • Records source information

43. Home Zone Management • Home zone information update • Home zone searching • Home zone election • A source sends its zone ID to home zone when moving to new zone • The first home zone node floods source info to whole zone • Other nodes: search home zone with ring of increasing size. • Source: announces its current zone as home zone, and sets sequence number to 0; Sequence number increases by one each time home zone changes. • Will be triggered when a node receives a message addressed to home zone with ID different from record (due to zone update or zone announcement from a new source)

44. Sends REFRESH to leader periodically and when joining /leaving group, carrying its membership and position • Floods LEADER periodically within the zone to announce its leadership, carrying its own position and the positions and group IDs of the multicast members Membership Management within Zone • A member • A leader

45. Membership Management at Upper Tier Source: records the member zones Leader knows source location Membership report SOURCE message Home Zone Leader does not know source location or Source information is outdated

46. Moving between Zones • When a node moves into a new zone • Clears old zone’s information • If the node is a group member • Will continue receiving packets forwarded by old zone • Sends REFRESH to new zone leader • When a leader is moving out of a zone • Hands leadership to other nodes

47. Empty Zone Problem

48. Empty Zone Handling • Member zone • The departing leader notifies the source • Home zone • The last node announces the new zone it is moving to as the home zone; floods source information within new home zone; sends ANNOUNCE to network with sequence number of home zone increased by one

49. Multicast Packet Delivery • Source • Sends packets to all member zones and members in its zone • Aggregates transmissions and sends one copy if several members share next hop • Intermediate nodes • Take similar action • If the message includes their current zone, replace zone ID in the message with the information of the members in the zone. Source Zone leader Group member Other nodes

50. SGMP has up to 35% higher delivery ratio and 20 % lower overhead at high mobility Performance: Impact of mobility Delivery ratio Control overhead