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

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

2. Topology-based Topology-based routing protocols use the information about the links that exist in the network to perform packet forwarding. Proactive approach, Reactive approach, Hybrid approach. Position-based routing.

3. Position-based routing Other than the destination’s position, each node need know only its own position and the position of its one-hop neighbors in order to forward packets. Since it is not necessary to maintain explicit routes, position-based routing does scale well even if the network is highly dynamic. Position-based routing algorithms require that information about the physical position of the participating nodes be available. GPS

5. Location Services Distance Routing Effect Algorithm for Mobility (Dream) Flooding The frequency at which it sends position updates (temporal resolution) Indicating how far a position update may travel before it is discarded (spatial resolution) All-for-all

6. Quorum-Based Location Service Information updates (write operations) are sent to a subset (quorum) of available nodes, and information requests (read operations) are referred to a potentially different subset.

7. A={1,6,2} B={6,5,4} C={1,2,4} Quorums A,B,C

8. Grid Location Service GLS divides the area that contains the ad hoc network into a hierarchy of squares. quadtree. GLS establishes a notion of near node IDs, defined as the least ID greater than a node’s own ID. Homezone

9. Forwarding Strategies Greedy Packet Forwarding

10. Greedy Packet Forwarding most forward within r (MFR) nearest with forward progress (NFP) Compass routing Randomly chosen

11. Greedy routing may fail to find a path between sender and destination, even though one does exist.

12. GPSR Algorithm Greedy Perimeter Stateless Routing algorithm consists of two methods: Greedy Forwarding: used if possible Perimeter Forwarding: second choice

13. Greedy Forwarding All data packet are marked initially at their originators as greedy mode. Upon receiving a greedy mode packet, forward the packet to the neighbor closest to D.

14. Trapped in local maximum:

15. Perimeters When no neighbor is closer, the node marks the packet into perimeter mode x seek to route around the void using right-hand rule

16. x may be adjacent to multiple faces

25. The underlying topology Relative neighborhood graph, RNG Gabriel graph, GG

26. RNG is a subgraph of GG When keeping fewer links Many MAC layer perform efficiently The contention in shared channel and hidden terminal problem can be reduced This paper uses RNG to control the underlying topology.

27. Location-Aided Routing LAR: in MobiCom 1998. Main Idea Using location information to reduce the number of nodes to whom route request is propagated. Location-aided route discovery based on “limited” flooding

28. Location Information Consider a node S that needs to find a route to node D. Assumption: each host in the ad hoc network knows its current location precisely (location error considered in one of their simulations) node S knows that node D was at location L at time t0, and that the current time is t1

29. Expected Zone

30. Request Zone LAR’s limited flooding A node forwards a route request only if it belongs to the request zone The request zone should include expected zone other regions around the expected zone No guarantee that a path can be found consisting only of the hosts in a chosen request zone. timeout expanded request zone

31. Membership of Request Zone How a node determines if it is in the request zone for a particular route request

32. LAR Scheme 1(Rectangular shape)

33. S includes their coordinates (S, A, B and C) with the route request message transmitted when initiating route discovery. Size of the request zone: the size of the rectangular request zone above is proportional to (i) average speed of movement v, and (ii) time elapsed since the last known location of the destination was recorded.

34. LAR Scheme 2

35. Telecommunication Systems, 2001. Hierarchical Routing:“GRID: A Fully Location-Aware Routing Protocol for Mobile Ad Hoc Networks”

36. Basic Idea Adopt Positioning Systems such as GPS receivers President Clinton ordered to discontinue SA (selective availability) in May 2000 will increase the accuracy by an order Fully utilize location information: route discovery data forwarding route maintenance We propose a new protocol called GRID.

37. How to Utilize Location Information:Observation 1 Determine route quality based on location information: passing B is better than passing A

38. How to Utilize Location Information:Observation 2 (“Route Handover”) Improving the vulnerability and quality of a route based on location information: When B moves away, E can work on behalf of B. When F roams in, using F is more reliable.

39. Comparison of Using Location Information

40. The GRID Routing Protocol Partition the physical area into d x d squares called grid.

41. Protocol Overview In each grid, a leader will be elected, called gateway. Routing is performed in a grid-by-grid manner. Responsibility of gateway: forward route discovery packets propagate data packets to neighbor grids maintain routes which passes the grid

42. Route Search We can adopt any existing route discovery protocol. Major features/differences: limit the search range by the locations of source and destination only gateway will help with the discovery process The more crowded the area is, the more saving. routing table is indicated by grid ID (instead of host address)

43. Route Search Example route search route reply

44. Route Search Range Options

45. Routing Table Format Next-hop routing: the next hop is identified by grid ID (not host ID)

46. Route Maintenance Two issues: how to maintain a gateway in each grid how to maintain a grid-by-grid route Special Feature: longer route lifetime: as long as there is a host in each gateway, a route will be alive more robust In existing protocols, once a node in the route roams away, the route will be broken.

47. Gateway Election in a Grid Any “leader election” protocol in distributed computing can be used. Weaker than leader election: It is acceptable that there are multiple leaders in a grid. But “without leader” is less acceptable. Preference in electing a gateway: near the physical center of the grid likely to remain in the grid for longer time once elected, a gateway will remain so until leaving the grid to avoid ping-pong effect

48. Gateway Election Details

49. How to Maintain a Grid-by-Grid Route Strength: more robust route mobility-resistant Problems: Gateway moves away: The gateway election will find the new gateway. So the route will remain alive. Source moves away: (see next page) getting closer getting farther away Destination move away: (similar)

51. Directions of Future Research Location services: To ensure that Homezone’s hashing works properly in the face of very dynamic networks. The problem of ensuring anonymity. Strategies for position-based packet forwarding: How to make greedy routing more tolerant of inaccurate position information