Position Routing MANET

8/2/2019 Position Routing MANET

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A Survey on Position-Based

Routing in Mobile Ad-Hoc Networks

Alok Sabherwal


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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


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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


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Position-based routing

Position-based routing algorithms eliminate some ofthe limitations of topology-based routing by usingadditional information.

A location serviceis used by the sender of a packetto determine the position of the destination and toinclude it in the packets destination address.

Position-based routing thus does not require the

establishment or maintenance of routes.(Forwarding Strategy)


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Location Services

In order to learn the current position of a specificnode, 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 adhoc network.

Location services can be classified according tohow many nodes host the service Some-for-some Some-for-all All-for-some All-for-all


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Location Services

Distance Routing Effect Algorithm for Mobility (DREAM)

Quorum-Based Location Service

Grid Location Service (GLS)

Homezone


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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 mneighbors in thedirection of destination


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** All for all approach


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Quorum Based Location Services 1 of 3

Known from information

replication

Update and request

performed on different nodesubsets

If subsets intersect up todate information can always

be found


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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 nearestbackbone node

Backbone node contacts the nodes of a (usuallydifferent) quorum

Timestamps to choose most current information

Tradeoff: Quorum size

(communication cost and resilience against

unreachable backbone nodes)


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How to deal with the movement ofbackbone node?

The topology of the backbone will be

rearranged

If a backbone node has been disconnectedfrom the network for more than a threshold

amount of time, a new node will be chosenas the replacement


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Grid Location Service (GLS)

Geographic Forwarding

- Each node maintains its position usingGPS and broadcast HELLO packet to itsneighbors


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Geographic Forwarding more..

Each node maintains a routing table for allnodes within two hops

Forward a packet to the neighbor nodeclosest to the destination

** All for some approach


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An Example of Grid


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The Grid Location Service (Cont.)

Three main activities

Location server selection

Location query request Location server update

Handling Failures


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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 nodes ID

ID space is circular


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Location Server Organization


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Location Query Request

The query request packet is forwarded toa node that is closest to the destination,within the order-2 square

The packet is forwarded through thehigher order grid square until it reachesthe location server of the destination

The destination responds directly with itsdestination to the source node


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Location Server Update

Each node maintains two tables

- A location table

- A location cache

Update packet is sent to location servers

Update distance threshold


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Location Query Failures

Two types of failures

- A location server has out-of-date

informationSolution: use the old location information

- A node moves out of its current grid

Solution: forwarding pointers


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Homezone

A virtual homezone where position informationfor a node is stored

The position C of the homezone for a node can

be derived by applying a well-known hashfunction to the node identifier

All nodes within a disk with radius R centered atC have to maintain position information for the

node If the homezone is sparsely populated, R may

have to be increased


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Comparisons of Location Service


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Forwarding Strategies



Hierarchical Routing


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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


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Greedy Routing Strategies


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Greedy Routing Failure


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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 thetimestamp of the position information source has

about destination, and Vmax is the maximum speedthat a node may travel in the ad hoc network

The direction toward destination is defined by the linebetween source and destination and the angle


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DREAM


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Location-Aided Routing (LAR)

Each node knows its location in everymoment

Using location information for route

discoveryRouting is done using the last known

location + an assumption

Route discovery is initiated when: S doesnt know a route to D

Previous route from S to D is broken


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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 routerequest


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LAR


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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-reachabledestination


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Terminodes Routing


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Grid Routing

It is similar to Terminodes Routing

A proactive distance vector routing is usedat local level

Intermediate Node Forwarding (INF) isused for long-distance routing


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Comparisons of ForwardingStrategies


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Work done

How to discover the position of thedestination ?

How to forward the packets based onabove ?


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Results

All for some services like GLS incombination of greedy packet forwardingis the most promising in general position

based routing.

DREAM & LAR could be useful insituations where a small number of

packets need to be transmitted veryreliably.


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References

Martin Mauve, et al, A Survey on positionbased routing in ad-hoc networks , IEEENetwork Magazine 15 (6), pp. 30-39,

November 2001.


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Thank you!!

Position Routing MANET

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