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A Survey on Position-Based Routing in Mobile Ad-Hoc Networks

A Survey on Position-Based Routing in Mobile Ad-Hoc Networks. Alok Sabherwal. Overview. Introduction Location Services Distance Routing Effect Algorithm for Mobility Quorum-Based Location Service Grid location Service Homezone Forwarding Strategies Greedy Packet Forwarding

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A Survey on Position-Based Routing in Mobile Ad-Hoc Networks

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  1. A Survey on Position-Based Routing in Mobile Ad-Hoc Networks Alok Sabherwal ECE 5970 02/24/2005

  2. Overview • Introduction • Location Services • Distance Routing Effect Algorithm for Mobility • Quorum-Based Location Service • Grid location Service • Homezone • Forwarding Strategies • Greedy Packet Forwarding • Restricted Directional Flooding • DREAM • LAR • Hierarchical Routing • Terminodes Routing • Grid Routing • Comparisons ECE 5970 02/24/2005

  3. Routing in MANET • Static vs. Mobile • Flooding-based routing • Reactive vs. Proactive • Source routing vs. Table driven routing • Flat vs. Hierarchical routing • Non-location based vs. Location based routing ECE 5970 02/24/2005

  4. Position-based routing • Position-based routing algorithms eliminate some of the limitations of topology-based routing by using additional information. • A location serviceis used by the sender of a packet to determine the position of the destination and to include it in the packet’s destination address. • Position-based routing thus does not require the establishment or maintenance of routes. (Forwarding Strategy) ECE 5970 02/24/2005

  5. Location Services • In order to learn the current position of a specific node, the help of a location serviceis needed. • Difficult to get the position of location server! (Egg & Chicken) • No guarantee for one position server in each ad hoc network. • Location services can be classified according to how many nodes host the service • Some-for-some • Some-for-all • All-for-some • All-for-all ECE 5970 02/24/2005

  6. Location Services • Distance Routing Effect Algorithm for Mobility (DREAM) • Quorum-Based Location Service • Grid Location Service (GLS) • Homezone ECE 5970 02/24/2005

  7. Distance Routing EffectAlgorithm for Mobility (DREAM) • Proactively disseminate location information • Distance Effect : • Closer nodes are updated more frequently • “age” field in location update • Mobility Effect : • rate of location update controlled by mobility • No bandwidth wastage for no movement • Routing policy • If no entry for destination in table, flood • Otherwise forward data to m neighbors in the direction of destination ECE 5970 02/24/2005

  8. ** All for all approach ECE 5970 02/24/2005

  9. Quorum Based Location Services 1 of 3 • Known from information replication • – Update and request performed on different node subsets • – If subsets intersect up to date information can always be found ECE 5970 02/24/2005

  10. Quorum Based Location Services 2 of 3 • A some-for-some scheme – Node subset hosts position databases – Virtual backbone between those nodes (non-position-based routing algorithm) – Send position update and query to the nearest backbone node – Backbone node contacts the nodes of a (usually different) quorum – Timestamps to choose most current information – Tradeoff: Quorum size (communication cost and resilience against unreachable backbone nodes) ECE 5970 02/24/2005

  11. Quorum Based Location Services 3 of 3 • How to deal with the movement of backbone node? • The topology of the backbone will be rearranged • If a backbone node has been disconnected from the network for more than a threshold amount of time, a new node will be chosen as the replacement ECE 5970 02/24/2005

  12. Grid Location Service (GLS) • Geographic Forwarding - Each node maintains its position using GPS and broadcast HELLO packet to its neighbors ECE 5970 02/24/2005

  13. Geographic Forwarding more.. • Each node maintains a routing table for all nodes within two hops • Forward a packet to the neighbor node closest to the destination ** All for some approach ECE 5970 02/24/2005

  14. An Example of Grid ECE 5970 02/24/2005

  15. The Grid Location Service (Cont.) • Three main activities • Location server selection • Location query request • Location server update • Handling Failures ECE 5970 02/24/2005

  16. Selecting Location Servers • Unique ID using hash function • Select nodes with ID “closest” to its own ID • “Closest” means the least ID greater than the node’s ID • ID space is circular ECE 5970 02/24/2005

  17. Location Server Organization ECE 5970 02/24/2005

  18. Location Query Request • The query request packet is forwarded to a node that is closest to the destination, within the order-2 square • The packet is forwarded through the higher order grid square until it reaches the location server of the destination • The destination responds directly with its destination to the source node ECE 5970 02/24/2005

  19. Location Server Update • Each node maintains two tables - A location table - A location cache • Update packet is sent to location servers • Update distance threshold ECE 5970 02/24/2005

  20. Location Query Failures • Two types of failures - A location server has out-of-date information Solution: use the old location information - A node moves out of its current grid Solution: forwarding pointers ECE 5970 02/24/2005

  21. Homezone • A virtual homezone where position information for a node is stored • The position C of the homezone for a node can be derived by applying a well-known hash function to the node identifier • All nodes within a disk with radius R centered at C have to maintain position information for the node • If the homezone is sparsely populated, R may have to be increased ECE 5970 02/24/2005

  22. Comparisons of Location Service ECE 5970 02/24/2005

  23. Forwarding Strategies • Greedy Packet Forwarding • Restricted Directional Flooding • Hierarchical Routing ECE 5970 02/24/2005

  24. Greedy Packet Forwarding • MFR • Most Forward within R • It tries to minimize the number of hops a packet has to traverse in order to reach D • NFP • Nearest with Forward Progress • The packet is transmitted to the nearest neighbor of the sender which is closer to the destination • Better than MFR • Compass routing • It selects the neighbor closest to the straight line between sender and destination ECE 5970 02/24/2005

  25. Greedy Routing Strategies ECE 5970 02/24/2005

  26. Greedy Routing Failure ECE 5970 02/24/2005

  27. Restricted Directional Flooding • DREAM • Sender will forward the packet to all one-hop neighbors that lie in the direction of destination • Expected region is a circle around the position of destination as it is known to source • The radius r of the expected region is set to (t1-t0)*Vmax, where t1 is the current time, t0 is the timestamp of the position information source has about destination, and Vmax is the maximum speed that a node may travel in the ad hoc network • The direction toward destination is defined by the line between source and destination and the angle  ECE 5970 02/24/2005

  28. DREAM ECE 5970 02/24/2005

  29. Location-Aided Routing (LAR) • Each node knows its location in every moment • Using location information for route discovery • Routing is done using the last known location + an assumption • Route discovery is initiated when: • S doesn’t know a route to D • Previous route from S to D is broken ECE 5970 02/24/2005

  30. LAR - Definitions • Expected Zone • S knows the location L of D in t0 • Current time t1 • The location of D in t1 is the expected zone • Request Zone • Flood with a modification • Node S defines a request zone for the route request ECE 5970 02/24/2005

  31. LAR ECE 5970 02/24/2005

  32. Hierarchical Routing • Terminodes Routing • TLR (Terminode Local Routing) • It uses a proactive routing scheme if the destination is close to the source node. • TRR (Terminode Remote Routing) • TRR allows data to be sent to non-TLR-reachable destination ECE 5970 02/24/2005

  33. Terminodes Routing ECE 5970 02/24/2005

  34. Grid Routing • It is similar to Terminodes Routing • A proactive distance vector routing is used at local level • Intermediate Node Forwarding (INF) is used for long-distance routing ECE 5970 02/24/2005

  35. Comparisons of Forwarding Strategies ECE 5970 02/24/2005

  36. Work done • How to discover the position of the destination ? • How to forward the packets based on above ? ECE 5970 02/24/2005

  37. Results • All for some services like GLS in combination of greedy packet forwarding is the most promising in general position based routing. • DREAM & LAR could be useful in situations where a small number of packets need to be transmitted very reliably. ECE 5970 02/24/2005

  38. References • Martin Mauve, et al, “A Survey on position based routing in ad-hoc networks “, IEEE Network Magazine 15 (6), pp. 30-39, November 2001. ECE 5970 02/24/2005

  39. Thank you!! ECE 5970 02/24/2005

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