Cross-layer Design & Optimization for Wireless Sensor Networks
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Transcript of Cross-layer Design & Optimization for Wireless Sensor Networks
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Cross-layer Design & Optimization for Wireless Sensor Networks
Weilian Su and Tat L. LimDepartment of Electrical and Computer Engineering
Naval Postgraduate School
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Outline
Objectives Framework Approach Results & Findings Conclusions
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Objectives
Develop a framework for the cross-layer design and optimization study
Investigate & explore the various areas where performance gains can be achieved in the context of WSNs
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Cross-layer Design Framework
Physical
Network
Transport
Session
Presentation
ApplicationOp
timiz
atio
n A
gen
t (O
A)
OA
Top-downfeedback
Bottom-up feedback
Intra-layer interactionsInter-layer interactions
OSI Stack
Data Link (MAC/Link)
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Approach
-> Approach: Study the effects of the wireless channel and performance at PHY to develop insights that can be used to design the optimization agent (OA)
Tapped delay line implementation for wireless channel modeling
Performance measurements using the micaz motes from Crossbow, Inc.
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Tap Delay Line (TDL) Implementation
2-TDL channel model 12-taps TDL channel model from
GSM REC.05-05 model to validate the results
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TDL implementation
2-TDL Modelx(t)
Transmitted
signal
AWGN
Doppler
Filter(Jakes)
Doppler
Filter(Jakes)
τ1 τ1- τ2
y(t) : Received signal
Delay
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Results & Findings (1): TDL implementation
(a) BER of 2-TDL model (b) BER of 12-TDL model (GSM REC.05-05)
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Performance measurements of WSN using Micaz Motes
Interference / Co-existence problems
Transmission range & power transmit levels
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Interference Measurements:Frequency Spectrum
IEEE 802.11b channels
Overlap
Overlap
Overlap
IEEE 802.15.4 channels
Overlapping of frequency bands between IEEE802.15.4 and IEEE802.11b channels within 2.4
GHz ISM band
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Experimental Setup for Interference Measurements
Setup 2 networks: IEEE802.15.4 network (using 4 micaz motes) IEEE802.11b (via 2 laptops) – interference source
IEEE802.11b Ad-hoc Network channel 1
Micaz moteNode 1
MIB600
Micaz moteNode 2
Micaz moteNode 3
10 m
3 m5 m
IEEE802.15.4 Channel 11
Laptop 2
Laptop 1
Laptop 3
Micaz moteNode 0 (Base)
5 m
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Results & Findings (2): Interference Measurements
(a)Interference turned on (b) Interference turned off
73% 100%
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Results & Findings (2): Interference Measurements
Packets Received Rate for Micaz Motes
0
20
40
60
80
100
120
0 20 40 60Duration (mins)
Per
cent
age
Yie
ld
Node 3
Node 2
Node 1
Interference Period
Packets received rate
Node 3 (@ 10 m) more affected by interference
Node 1 & 2 (@ <5 m) unaffected
by interference
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Results & Findings (3): Transmission range and power levels
Maximum transmission range of 55-60m
Transmission Range of Micaz Motes (at 0dBm)
0
20
40
60
80
100
120
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70
Distance (meters)
Lin
k Q
ualit
y (%
)
Transmission range for micaz motes set at max power of 0
dBm
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Conclusions Increasing BER under mobility conditions Possible interference within ISM bands and can
affect the performance of WSN (especially for long links/hops)
Max range for micaz motes is around 60m and recommended operating range < 30m
Many factors need to be considered in the design of WSN
Insights gained can be used to design and develop the optimization agent, to enhance the performance of wireless sensor networks
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Q & A
Thank You