A Survey on Position-Based
Routing in Mobile Ad-Hoc Networks
Alok Sabherwal
ECE 5970 02/24/2005
Overview
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Introduction
Location Services

Distance Routing Effect Algorithm for Mobility

Quorum-Based Location Service
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Grid location Service

Homezone
Forwarding Strategies

Greedy Packet Forwarding

Restricted Directional Flooding
• DREAM
• LAR
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Hierarchical Routing
• Terminodes Routing
• Grid Routing
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Comparisons
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Routing in MANET
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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
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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 packet’s destination address.
Position-based routing thus does not require the
establishment or maintenance of routes.
(Forwarding Strategy)
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Location Services
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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)
 No guarantee for one position server in each ad
hoc network.
Location services can be classified according to
how many nodes host the service
 Some-for-some
 Some-for-all
 All-for-some
 All-for-all
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Location Services
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Distance Routing Effect Algorithm for Mobility (DREAM)
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Quorum-Based Location Service
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Grid Location Service (GLS)
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Homezone
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Distance Routing Effect
Algorithm for Mobility (DREAM)
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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 m neighbors in the
direction of destination
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** All for all approach
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Quorum Based Location Services 1 of 3
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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 3
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A some-for-some scheme
– Node subset hosts position databases
– Virtual backbone between those nodes (nonposition-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 3
 How
to deal with the movement of
backbone node?

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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
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Grid Location Service (GLS)
 Geographic
Forwarding
- Each node maintains its position using
GPS and broadcast HELLO packet to its
neighbors
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Geographic Forwarding more..
 Each
node maintains a routing table for all
nodes within two hops
 Forward a packet to the neighbor node
closest 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
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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 node’s 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 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 destination responds directly with its
destination 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
information
Solution: use the old location information
- A node moves out of its current grid
Solution: forwarding pointers
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Homezone
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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
 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
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Comparisons of Location Service
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Forwarding Strategies
 Greedy
Packet Forwarding
 Restricted
Directional Flooding
 Hierarchical
Routing
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Greedy Packet Forwarding
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MFR
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NFP
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Most Forward within R
It tries to minimize the number of hops a packet has
to traverse in order to reach D
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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Restricted Directional Flooding
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DREAM
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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 (t1t0)*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 
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DREAM
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Location-Aided Routing (LAR)
 Each
node knows its location in every
moment
 Using location information for route
discovery
 Routing is done using the last known
location + an assumption
 Route discovery is initiated when:
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S doesn’t know a route to D
Previous route from S to D is broken
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LAR - Definitions
 Expected
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S knows the location L of D in t0
Current time t1
The location of D in t1 is the expected zone
 Request
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Zone
Zone
Flood with a modification
Node S defines a request zone for the route
request
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LAR
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Hierarchical Routing
 Terminodes
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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-reachable
destination
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Terminodes Routing
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Grid Routing
 It
is similar to Terminodes Routing
 A proactive distance vector routing is used
at local level
 Intermediate Node Forwarding (INF) is
used for long-distance routing
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Comparisons of Forwarding
Strategies
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Work done
 How
to discover the position of the
destination ?
 How to forward the packets based on
above ?
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Results
 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.
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References

Martin Mauve, et al, “A Survey on position
based routing in ad-hoc networks “, IEEE
Network Magazine 15 (6), pp. 30-39,
November 2001.
ECE 5970 02/24/2005
Thank you!!
ECE 5970 02/24/2005