An Efficient Flooding Method
in Ad-hoc Networks
for Reducing Power Consumption
Masato Noto
Kanagawa University, Japan
13, Oct., 2008
2
Contents







Introduction
Ad-hoc Networks and Protocol of RFC
Route Discovery in DSR
Proposed Flooding Method
Simulation
Result
Conclusion and Future Work
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Introduction

Ad-hoc Network


Temporary network for the exchange of
information among mobile wireless terminals.
Allows multi-hop communication via multiple
nodes without the need for base stations or
other fixed infrastructure.
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Protocol of RFC

DSR: The most typical of the protocols used in
ad-hoc networks

Route Discovery
①Route Request (RREQ)
②Route Reply (RREP)
①Route Request: phase to discover the
DEST (Destination node)
②Route Reply: phase that notifies to receive it from
DEST to SRC (Source node)
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Route Discovery in DSR
A
A
A
A
A
1. SRC sends the RREQ
packets.
A
A
A
A
A
A
A
A
A
S RREQ A
A
RREP D
A
2. RREQ packet has
already reached DEST.
3. The flooding for DEST is
done again and again,
and continues regardless
of the fact that RREQ has
already arrived at DEST.
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A Characteristic of the DSR
(RREP with Cache)
D
B
Destination
C
A Cache [A,B,C,D]
S
Source
RREP
E
When relay node A possesses cache leading to
D, A can return RREP instead of D.
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Proposed Flooding Method

Nodes wait a constant delay time after the
RREQ is received before flooding to neighboring
nodes rather than flooding immediately, up to
some fixed number of hops, hmax.
A
A
A
CP (Closing Packet):
The packet sent by SRC to end
the flooding
A
A
A
A
A
A
A
A
A
A
CP
A
S
RREP D
A
A
・Consumption power
⇒ decrease
・Delay
⇒ increase
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Example of Flooding in Proposed Method
D
S
4
1
2
3
5
Act
1
RREQ(S→1)
2
Wait(2:1)
4
RREQ(1→D,2,3)
5
RREP(D→1)
Wait(4:2,3)
6
RREP(1→S)
7
CP(S→1)
8
CP(1→2,3)
7
RREQ
RREP
Time
6
CP
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Simulation
1.
2.
3.
4.
5.
6.
Arrange nodes randomly.
Specify the SRC and DEST randomly and
begin flooding of RREQ from SRC.
Execute the route search while all nodes
are moving in a random walk.
Determine the route.
Return to step 2.
Stop the simulation when the processing
from step 2 to step 5 has been executed
10,000 times.
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Simulation Parameters

Random walking model on a square plane
Model size
100×100
1cycle:Time to need it so that a
Number of nodes
5 to 100
node transmits one time of packet
Communication range
20
Distance of motion
Number of trials
Transmission
power consumption
The number of hops to save
1/1 (cycle) in Packet：
Proposal (i) 1hop ahead
10000
Proposal (ii)1hop and 2hop ahead
1
Sending time of 1 hop
1
Time to live of cache
0,30, 50
h : Hop count
tstop: Wait time
t stop  2h
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Evaluation Method
Wall: total power consumption
(Average power consumption of the
entire network)
Wall
1 s1
  Wi
s1 i 1
Tall
1

s2
Tall: average delay
(Average of time before RREP returning
to SRC)
s2
T
i 1
i
S1: Number of trials
S2: Number of trials in which RREP was returned
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Result (Existing Method (DSR))
Average Delay Time (DSR)
Total Power Consumption (DSR)
6
life: 0
life: 30
life: 50
100
life: 0
life: 30
life: 50
5.5
Average delay time
Total power consumption
120
80
60
40
20
5
4.5
4
3.5
3
2.5
2
0
0
20
40
60
Number of nodes
Higher cache time to
live values
80
100
0
20
40
60
80
100
Number of nodes
Total power
I. (node=40～70) Decrease somewhat
consumption ： II.(node=0～40,70～100) No change
Average delay time ： Decrease
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Result (Proposed Method (Life: 0))
Total Power Consumption
(DSR and Proposed Method (Life: 0))
Average Delay Time
(DSR and Proposed Method (Life: 0))
8
DSR_life:0
Proposal (i)_life:0
Proposal (ii)_life:0
100
80
Average delay time
Total power consumption
120
60
40
20
0
DSR_life:0
Proposal (i)_life:0
Proposal (ii)_life:0
7
6
5
4
3
2
0
20
40
60
80
Number of nodes
Power :
Proposal (i) 8% decrease
Proposal (ii) 16% decrease
100
0
20
40
60
80
100
Number of nodes
Proposal (i) decreased,
Proposal (ii) was able to show the
effect more
Delay : Proposal (i) increased, Proposal (ii) increased more
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Result (Proposed Method (Life: 50))
Total Power Consumption
(DSR and Proposed Method (Life: 50))
Average Delay Time
(DSR and Proposed Method (Life: 50))
6
DSR_life:50
Proposal (i)_life:50
Proposal (ii)_life:50
100
80
Average delay time
Total power consumption
120
60
40
20
0
0
20
40
60
Number of nodes
80
100
DSR_life:50
Proposal (i)_life:50
Proposal (ii)_life:50
5
4
3
2
0
20
40
60
80
100
Number of nodes
As time to live becomes higher, a difference disappears to total
power consumption of proposal (i) and proposal (ii).
Time to live : high
Network with a little movement : Proposal (i)
Time to live : low
Network with much movement : Proposal (ii)
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Conclusion and Future Work

In our research, we reduced the power
consumption by incorporating proposed
method in existing DSR.

In the future, we need the flooding method
considering power consumption and delay.
SMC2008/WINGS12 in Singapore
Thank you for your
kind attention!