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A Survey on Position-Based A Survey on Position-Based Routing in Mobile Ad-Hoc NetworksRouting in Mobile Ad-Hoc Networks
Alok SabherwalAlok Sabherwal
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OverviewOverview IntroductionIntroduction Location ServicesLocation Services
Distance Routing Effect Algorithm for MobilityDistance Routing Effect Algorithm for Mobility Quorum-Based Location ServiceQuorum-Based Location Service Grid location ServiceGrid location Service HomezoneHomezone
Forwarding StrategiesForwarding Strategies Greedy Packet ForwardingGreedy Packet Forwarding Restricted Directional FloodingRestricted Directional Flooding
• DREAMDREAM• LARLAR
Hierarchical RoutingHierarchical Routing• Terminodes RoutingTerminodes Routing• Grid RoutingGrid Routing
ComparisonsComparisons
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Routing in MANETRouting 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
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Position-based routingPosition-based routing
Position-based routing algorithms eliminate Position-based routing algorithms eliminate some of the limitations of topology-based some of the limitations of topology-based routing by using routing by using additional informationadditional information..
A A location servicelocation service is used by the sender of a is used by the sender of a packet to determine the packet to determine the position of the position of the destinationdestination and to include it in the packet’s and to include it in the packet’s destination address.destination address.
Position-based routing thus does Position-based routing thus does notnot require require the establishment or maintenance of routes. the establishment or maintenance of routes. ((Forwarding StrategyForwarding Strategy))
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Location ServicesLocation Services In order to learn the current position of a In order to learn the current position of a
specific node, the help of a specific node, the help of a location servicelocation service is is needed. needed. Difficult to get the position of location Difficult to get the position of location
server! (Egg & Chicken)server! (Egg & Chicken) No guarantee for one position server in No guarantee for one position server in
each ad hoc network.each ad hoc network. Location services can be classified according to Location services can be classified according to
how many nodes host the servicehow many nodes host the service Some-for-someSome-for-some Some-for-allSome-for-all All-for-someAll-for-some All-for-allAll-for-all
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Location ServicesLocation Services
Distance Routing Effect Algorithm for Mobility (DREAM)Distance Routing Effect Algorithm for Mobility (DREAM)
Quorum-Based Location ServiceQuorum-Based Location Service
Grid Location Service (GLS)Grid Location Service (GLS)
HomezoneHomezone
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Distance Routing EffectDistance Routing EffectAlgorithm for Mobility (DREAM)Algorithm for Mobility (DREAM)
Proactively disseminate location informationProactively disseminate location information Distance Effect Distance Effect ::
Closer nodes are updated more frequentlyCloser nodes are updated more frequently ““age” field in location updateage” field in location update
Mobility Effect Mobility Effect :: rate of location update controlled by mobilityrate of location update controlled by mobility No bandwidth wastage for no movement No bandwidth wastage for no movement
Routing policyRouting policy If no entry for destination in table, floodIf no entry for destination in table, flood Otherwise forward data to Otherwise forward data to m m neighbors in the neighbors in the
direction of destinationdirection of destination
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** All for all approach** All for all approach
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Quorum Based Location Services 1 of 3Quorum 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
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Quorum Based Location Services 2 of 3Quorum 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)
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Quorum Based Location Services 3 of 3Quorum Based Location Services 3 of 3
How to deal with the movement of How to deal with the movement of backbone node?backbone node? The topology of the backbone will be The topology of the backbone will be
rearrangedrearranged If a backbone node has been disconnected If a backbone node has been disconnected
from the network for more than a threshold from the network for more than a threshold amount of time, a new node will be chosen as amount of time, a new node will be chosen as the replacementthe replacement
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Grid Location Service (GLS)Grid Location Service (GLS)
Geographic ForwardingGeographic Forwarding
- Each node maintains its position using - Each node maintains its position using GPS and broadcast HELLO packet to its GPS and broadcast HELLO packet to its neighborsneighbors
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Geographic Forwarding more..Geographic Forwarding more..
Each node maintains a routing table for all Each node maintains a routing table for all nodes within two hopsnodes within two hops
Forward a packet to the neighbor node Forward a packet to the neighbor node closest to the destinationclosest to the destination
** All for some approach** All for some approach
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An Example of GridAn Example of Grid
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The Grid Location Service (Cont.)The Grid Location Service (Cont.)
Three main activitiesThree main activities Location server selectionLocation server selection Location query requestLocation query request Location server updateLocation server update
Handling FailuresHandling Failures
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Selecting Location ServersSelecting Location Servers
Unique ID using hash functionUnique ID using hash function Select nodes with ID “closest” to its own IDSelect nodes with ID “closest” to its own ID ““Closest” means the least ID greater than Closest” means the least ID greater than
the node’s IDthe node’s ID ID space is circularID space is circular
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Location Server OrganizationLocation Server Organization
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Location Query RequestLocation Query Request
The query request packet is forwarded to The query request packet is forwarded to a node that is closest to the destination, a node that is closest to the destination, within the order-2 squarewithin the order-2 square
The packet is forwarded through the The packet is forwarded through the higher order grid square until it reaches higher order grid square until it reaches the location server of the destinationthe location server of the destination
The destination responds directly with its The destination responds directly with its destination to the source nodedestination to the source node
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Location Server UpdateLocation Server Update
Each node maintains two tablesEach node maintains two tables
- A location table- A location table
- A location cache- A location cache Update packet is sent to location serversUpdate packet is sent to location servers Update distance thresholdUpdate distance threshold
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Location Query FailuresLocation Query Failures
Two types of failuresTwo types of failures
- A location server has out-of-date - A location server has out-of-date informationinformation
Solution: use the old location informationSolution: use the old location information
- A node moves out of its current grid- A node moves out of its current grid
Solution: forwarding pointers Solution: forwarding pointers
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HomezoneHomezone
A virtual homezone where position information A virtual homezone where position information for a node is storedfor a node is stored
The position C of the homezone for a node can The position C of the homezone for a node can be derived by applying a well-known hash be derived by applying a well-known hash function to the node identifierfunction to the node identifier
All nodes within a disk with radius R centered at All nodes within a disk with radius R centered at C have to maintain position information for the C have to maintain position information for the nodenode
If the homezone is sparsely populated, R may If the homezone is sparsely populated, R may have to be increasedhave to be increased
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Comparisons of Location ServiceComparisons of Location Service
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Forwarding StrategiesForwarding Strategies
Greedy Packet ForwardingGreedy Packet Forwarding
Restricted Directional FloodingRestricted Directional Flooding
Hierarchical RoutingHierarchical Routing
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Greedy Packet ForwardingGreedy Packet Forwarding MFRMFR
Most Forward within RMost Forward within R It tries to minimize the number of hops a packet has It tries to minimize the number of hops a packet has
to traverse in order to reach Dto traverse in order to reach D NFPNFP
Nearest with Forward ProgressNearest with Forward Progress The packet is transmitted to the nearest neighbor of The packet is transmitted to the nearest neighbor of
the sender which is closer to the destinationthe sender which is closer to the destination Better than MFRBetter than MFR
Compass routingCompass routing It selects the neighbor closest to the straight line It selects the neighbor closest to the straight line
between sender and destinationbetween sender and destination
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Greedy Routing StrategiesGreedy Routing Strategies
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Greedy Routing FailureGreedy Routing Failure
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Restricted Directional FloodingRestricted Directional Flooding
DREAMDREAM Sender will forward the packet to all one-hop Sender will forward the packet to all one-hop
neighbors that lie in the direction of destination neighbors that lie in the direction of destination Expected region is a circle around the position of Expected region is a circle around the position of
destination as it is known to sourcedestination as it is known to source The radius r of the expected region is set to (t1-The radius r of the expected region is set to (t1-
t0)*Vmax, where t1 is the current time, t0 is the t0)*Vmax, where t1 is the current time, t0 is the timestamp of the position information source has timestamp of the position information source has about destination, and Vmax is the maximum speed about destination, and Vmax is the maximum speed that a node may travel in the ad hoc networkthat a node may travel in the ad hoc network
The direction toward destination is defined by the line The direction toward destination is defined by the line between source and destination and the angle between source and destination and the angle
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DREAMDREAM
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Location-Aided Routing (LAR)Location-Aided Routing (LAR)
Each node knows its location in every Each node knows its location in every momentmoment
Using location information for route Using location information for route discoverydiscovery
Routing is done using the last known Routing is done using the last known location + an assumptionlocation + an assumption
Route discovery is initiated when:Route discovery is initiated when: S doesn’t know a route to DS doesn’t know a route to D Previous route from S to D is brokenPrevious route from S to D is broken
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LAR - DefinitionsLAR - Definitions
Expected Zone Expected Zone S knows the location L of D in tS knows the location L of D in t00
Current time tCurrent time t11
The location of D in tThe location of D in t1 1 is the expected zoneis the expected zone
Request ZoneRequest Zone Flood with a modificationFlood with a modification Node S defines a request zone for the route Node S defines a request zone for the route
requestrequest
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LARLAR
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Hierarchical RoutingHierarchical Routing
Terminodes RoutingTerminodes Routing TLR (Terminode Local Routing)TLR (Terminode Local Routing)
• It uses a proactive routing scheme if the It uses a proactive routing scheme if the destination is close to the source node.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 TRR allows data to be sent to non-TLR-reachable
destinationdestination
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Terminodes RoutingTerminodes Routing
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Grid RoutingGrid Routing
It is similar to Terminodes RoutingIt is similar to Terminodes Routing A proactive distance vector routing is used A proactive distance vector routing is used
at local levelat local level Intermediate Node Forwarding (INF) is Intermediate Node Forwarding (INF) is
used for long-distance routingused for long-distance routing
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Comparisons of Forwarding Comparisons of Forwarding StrategiesStrategies
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Work doneWork done
How to discover the position of the How to discover the position of the destination ?destination ?
How to forward the packets based on How to forward the packets based on above ?above ?
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ResultsResults
All for some services like GLS in All for some services like GLS in combination of greedy packet forwarding combination of greedy packet forwarding is the most promising in general position is the most promising in general position based routing.based routing.
DREAM & LAR could be useful in DREAM & LAR could be useful in situations where a small number of situations where a small number of packets need to be transmitted very packets need to be transmitted very reliably.reliably.
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ReferencesReferences
Martin Mauve, et al, Martin Mauve, et al, “A Survey on position “A Survey on position based routing in ad-hoc networks “, IEEE based routing in ad-hoc networks “, IEEE Network Magazine 15 (6), pp. 30-39, Network Magazine 15 (6), pp. 30-39, November 2001.November 2001.
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Thank you!!Thank you!!
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