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)