efficient flooding techniques for mobile ad hoc networks
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Efficient Flooding Techniques for Mobile Ad Hoc Networks
Special Topic for CS587x
Department of Computer Science
Iowa State University
1. Introduction on MANET
2. Existing flooding techniques
3. Proposed techniques
4. Future Works
Outline
Mobile Ad Hoc Networks (MANET)
• Characteristics of MANET
– No fixed network infrastructure
– Hosts act as routers on demand
• Flooding is a communication primitive
– Frequently invoked for route discovery
Plain Flooding
• Each host needs to forward a
broadcast if the broadcast is received
at the first time
– Advantage : simple and reliable
– Drawback : broadcast storm
Probabilistic Broadcasting [Tseng99, Sasson01]
• Each host forwards only a certain
percentage of the flooding packets it
receives
– Advantage : reduced network traffic
– Drawback : not reliable
Multipoint Relaying [Laouite01, Peng02, etc.]
• Each host selects some
of its 1-hop neighbors to
forward
– Require 2-hop topology
– Intensive computation
B
A
2
1
3
4
C
D
E
Research Motivation
• Problems of the existing schemes
– Excessive network traffic
– Reduced flooding reachability
– Excessive control overhead
– Excessive computation cost
Edge Forwarding – Partition
• The broadcast coverage of each mobile host is divided into six partitions
A
P1
P2
P3
P4P5
P6
Edge Forwarding - Subpartition
• The location of a mobile host divides a given partition into six subpartitions P12
P11
P16
P13
P14 P15
B
A
Observation
• B does not need to forward A ’s broadcast if at least one forwarding occurs in each of A ’s subpartitions
P12P11
P16
P13
P14 P15
B
A
Forwarding Rule
• B must forward a broadcast
from A if any P1i (i = 1, …,
6) contains no hostsP12
P11
P16
P13
P14 P15
B
A
Proof of Reliability
• If B does not forward, then at least one host in
each P1i (i = 1, …, 6) will
forward
B
A
C
Advanced Forwarding
P12P11
P16
P13
P14 P15
B
A
• Push the forwarding responsibility to the hosts close to the broadcast perimeter
Edge Forwarding Protocol
Receive a new packet P
Forward ?
Overhearing
To time units
Forward P Done on P
Forward ?
Y N
Y N
Confirming
Tc time units
Why Wait ?
• Further deduction of
redundant transmission
• Make forwarding occur in
better order • Overhearing phase (To)
• Handle host uncertainty (eg.,
energy fading, movement,
etc.)• Confirming phase (Tc)
B
A
C
D
Scalability with Network Size
0
200
400
600
800
1000
1200
1400
1600
1800
2000
100 200 300 400 500 600 700 800 900 1000
Ave
rage
sen
ding
cos
t
Network Area (x1000 meter^2)
Plain Flooding
Edge Forwarding
Significant and Impact of Edge Forwarding
• Edge Forwarding is the first scalable and reliable 1-hop flooding technique
– Low control overhead
– Low computation cost
– Minimum forwarding delay
– Easy implementation
Reading Assignment 1
• Read one of these two papers (search on Google) Location-Aided Routing (LAR) in mobile ad hoc networks
(MOBICOM 2000)
Energy Efficient Indexing on Air (SIGMOD 1994)
Prepare presentation slides (due Feb 18) what is the problem
what is the state of the art and their limitation
how this is resolved
comments (originality, technical depth, drawback)
• Two students will be chosen to present the paper in the class (TBD)
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