ECE 5970 02/24/2005ECE 5970 02/24/2005

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

Alok SabherwalAlok Sabherwal

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

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))

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

** All for all approach** All for all approach

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

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)

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

An Example of GridAn Example of Grid

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

Location Server OrganizationLocation Server Organization

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

Comparisons of Location ServiceComparisons of Location Service

ECE 5970 02/24/2005ECE 5970 02/24/2005

Forwarding StrategiesForwarding Strategies

Greedy Packet ForwardingGreedy Packet Forwarding

Restricted Directional FloodingRestricted Directional Flooding

Hierarchical RoutingHierarchical Routing

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

Greedy Routing StrategiesGreedy Routing Strategies

ECE 5970 02/24/2005ECE 5970 02/24/2005

Greedy Routing FailureGreedy Routing Failure

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

DREAMDREAM

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

LARLAR

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

Terminodes RoutingTerminodes Routing

ECE 5970 02/24/2005ECE 5970 02/24/2005

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

ECE 5970 02/24/2005ECE 5970 02/24/2005

Comparisons of Forwarding Comparisons of Forwarding StrategiesStrategies

ECE 5970 02/24/2005ECE 5970 02/24/2005

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 ?

ECE 5970 02/24/2005ECE 5970 02/24/2005

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.

ECE 5970 02/24/2005ECE 5970 02/24/2005

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.

ECE 5970 02/24/2005ECE 5970 02/24/2005

Thank you!!Thank you!!