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

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Presentation on theme: "ECE 5970 02/24/2005 A Survey on Position-Based Routing in Mobile Ad-Hoc Networks Alok Sabherwal."— Presentation transcript:

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

2 ECE /24/2005 Overview Introduction Introduction Location Services Location Services Distance Routing Effect Algorithm for Mobility Distance Routing Effect Algorithm for Mobility Quorum-Based Location Service Quorum-Based Location Service Grid location Service Grid location Service Homezone Homezone Forwarding Strategies Forwarding Strategies Greedy Packet Forwarding Greedy Packet Forwarding Restricted Directional Flooding Restricted Directional Flooding DREAMDREAM LARLAR Hierarchical Routing Hierarchical Routing Terminodes RoutingTerminodes Routing Grid RoutingGrid Routing Comparisons Comparisons

3 ECE /24/2005 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

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

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

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

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

8 ECE /24/2005 ** All for all approach

9 ECE /24/2005 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

10 ECE /24/2005 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)

11 ECE /24/2005 Quorum Based Location Services 3 of 3 How to deal with the movement of backbone node? How to deal with the movement of backbone node? The topology of the backbone will be rearranged 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 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

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

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

14 ECE /24/2005 An Example of Grid

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

16 ECE /24/2005 Selecting Location Servers Unique ID using hash function Unique ID using hash function Select nodes with ID closest to its own ID Select nodes with ID closest to its own ID Closest means the least ID greater than the nodes ID Closest means the least ID greater than the nodes ID ID space is circular ID space is circular

17 ECE /24/2005 Location Server Organization

18 ECE /24/2005 Location Query Request The query request packet is forwarded to a node that is closest to the destination, within the order-2 square 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 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 The destination responds directly with its destination to the source node

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

20 ECE /24/2005 Location Query Failures Two types of 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

21 ECE /24/2005 Homezone A virtual homezone where position information for a node is stored 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 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 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 If the homezone is sparsely populated, R may have to be increased

22 ECE /24/2005 Comparisons of Location Service

23 ECE /24/2005 Forwarding Strategies Greedy Packet Forwarding Greedy Packet Forwarding Restricted Directional Flooding Restricted Directional Flooding Hierarchical Routing Hierarchical Routing

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

25 ECE /24/2005 Greedy Routing Strategies

26 ECE /24/2005 Greedy Routing Failure

27 ECE /24/2005 Restricted Directional Flooding DREAM DREAM Sender will forward the packet to all one-hop neighbors that lie in the direction of destination 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 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 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 The direction toward destination is defined by the line between source and destination and the angle

28 ECE /24/2005 DREAM

29 Location-Aided Routing (LAR) Each node knows its location in every moment Each node knows its location in every moment Using location information for route discovery Using location information for route discovery Routing is done using the last known location + an assumption Routing is done using the last known location + an assumption Route discovery is initiated when: Route discovery is initiated when: S doesnt know a route to D S doesnt know a route to D Previous route from S to D is broken Previous route from S to D is broken

30 ECE /24/2005 LAR - Definitions Expected Zone Expected Zone S knows the location L of D in t 0 S knows the location L of D in t 0 Current time t 1 Current time t 1 The location of D in t 1 is the expected zone The location of D in t 1 is the expected zone Request Zone Request Zone Flood with a modification Flood with a modification Node S defines a request zone for the route request Node S defines a request zone for the route request

31 ECE /24/2005 LAR

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

33 ECE /24/2005 Terminodes Routing

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

35 ECE /24/2005 Comparisons of Forwarding Strategies

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

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

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

39 ECE /24/2005 Thank you!! Thank you!!


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