Influence of Transmission Power on the Performance of Ad Hoc

Networks

Crystal Jackson

SURE 2004

Outline

Intro Overview of major protocols Model Results Conclusion and Future Work

What is an Ad Hoc Wireless Network?

Collection of self configuring wireless nodes

No infrastructure Simple example:

How They Work

Multi-hop environment

sourcedestination

Signal vs. Interference

Signal vs. Interference

EINR (energy to interference plus noise ratio)

EINR = N PO TC

PITc + No

where PO = PTL(d) and PI = ΣPRL(di)

L(d) = λ (path loss formula) 4πd

Received energy

NoiseInterference

i

α

Major Protocols

Slotted time system Channel access protocol

RTS/CTS/DATA/ACK rules

BRTSA CTSACK

•Exactly one RTS received•EINR > threshold

•CTS received•EINR > threshold

•Packet received•EINR > threshold

•Check for ACK

RTS CTS DATA ACK

1 Time Slot

Major Protocols Network Layer

Queue First in First Out Maximum limit of 50 packets

Routing Dijkstra’s algorithm to calculate routes with fewest

relays Radius calculated using EINR threshold

Packet Generation Each node generates a packet in a slot with probability p Randomly selected destination for packet

Model

Input Fileo Number of nodeso Size of the fieldo Duration of simulationo Spreading factor (value N in EINR

calculation) o Generation rate ando Transmission power of a node

Model

Nodes placed at random locations Simulation averaged for 10 trials Performance measures

o Completion Rate – packets received/packets generated

o Throughput – packets received/sloto Delay – slots/packet receivedo Throughput Efficiency- packets received/unit of

energy

Results

Modelo Number of nodes: 100 o Area: 14638m x 14638mo Duration: 30000 time slotso Spreading factor: 128o Generation rate: 0.001 to 0.030 packets/sloto Frequency: 1 GHzo Transmission power: vary

Transmission Powers Used

Power Average Diameter

1.0W 9.9 hops

1.4W 8.5 hops

2.2W 7.2 hops

7.1W 4.9 hops

41.5W 3.0 hops

Diameter = 2Diameter = 3

Completion Rate According to Variations in Transmission Power

70

75

80

85

90

95

100

0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.011 0.012 0.013 0.014 0.015Packets Generated/Slot

Va

lue

(%

)

1.0W

1.4W

2.2W

7.1W

41.5W

Throughput According to Variations in Transmission Power

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.011 0.012 0.013 0.014 0.015Packets Generated/Slot

Pa

ck

ets

/Slo

t

1.0W

1.4W

2.2W7.1W

41.5W

Delay According to Variation in Transmission Power

0

2

4

6

8

10

12

14

0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.011 0.012 0.013 0.014 0.015Packets Generated/Slot

Slo

ts/P

ac

ke

ts

1.0W1.4W2.2W7.1W41.5W

Throughput Efficiency According to Variations in Transmission Power

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.011 0.012 0.013 0.014 0.015Packets Generated/Slot

Pa

ck

ets

/Un

it o

f E

ne

rgy

1.0W1.4W2.2W7.1W41.5W

Conclusion

Higher transmission powers preferredo Advantages

o Higher completion rateo Higher throughputo Lower delay

o Disadvantageo Lower energy efficiencyo Lack of enough power for small devices

Future Work

Short-term Varying spreading factor Packets requiring multiple slots for delivery

Long-term Model with adaptive transmission powers

o Low transmission powers for lower generation rateso High transmission powers for higher generation rates

Acknowledgements

Dr. Russell

SURE Coordinators Dr. Noneaker Dr. Xu

NSF