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Wireless Sensor Networking for “Hot” Applications: Effects of Temperature on Signal Strength, Data

Collection and Localization

Kenneth Bannister, Gianni Giorgetti, Sandeep K.S. Gupta

HotEmnets’08 – Charlottesville – 3 June 2008

IMPACT LABhttp://IMPACT.ASU.EDU


Outline

• Signal Strength Observations• Lab Experiments• Effect of Temperature on:

• Link Budget and Communication Range• Network Connectivity and Data Collection• Localization

• Conclusions and Future Work


Environmental MonitoringDaily Variations in RSS

The “SMART” Container

“SMART” Container Project Daily Variations in RSS

Botanical Garden, Phoenix, AZ


Correlation With Temperature

The “SMART” Container

“SMART” Container Project

Botanical Garden, Phoenix, AZRSS

TEMP

RSS

TEMP


Outline





25 30 35 40 45 50 55 60 65

-62

-60

-58

-56

-54

Heated Transmitter

Temperature [C]

RS

S [

dBm

]

25 30 35 40 45 50 55 60 65

-62

-60

-58

-56

-54

Heated Transmitter

Temperature [C]

RS

S [

dBm

]

25 30 35 40 45 50 55 60 65

-62

-60

-58

-56

-54

Heated Transmitter

Temperature [C]

RS

S [

dBm

]

Experimental Setup & Results

Temperature at the Transmitter/RSS

Effects of temperature on the transmitter

AttenuatorsThermal Chamber

POWER AMPLIFIER

RX Section of the CC2420


25 30 35 40 45 50 55 60 65

-62

-60

-58

-56

-54

Heated Receiver

Temperature [C]

RS

S [

dBm

]

Temperature Effects on the ReceiverEffects of temperature on the receiver

25 30 35 40 45 50 55 60 65

-62

-60

-58

-56

-54

Heated Receiver

Temperature [C]

RS

S [

dBm

]

25 30 35 40 45 50 55 60 65

-62

-60

-58

-56

-54

Heated Receiver

Temperature [C]

RS

S [

dBm

]

RX Section of the CC2420

Amplifies the RF signal from the antenna

LNA

Measures RSS

DEMODULATOR

AttenuatorsThermal Chamber


Sensitivity

~ 3 dB


Loss due to Temperature

-3.3 dB

-3.7 dB

-2.0 dB

-1.6 dB

TI CC2400 and CC2520 DatasheetsOutput Power vs Temperature

Sensitivity vs Temperature

Output Power vs Temperature

Sensitivity vs Temperature

Temperature (°C) Temperature (°C)

Temperature (°C) Temperature (°C)

Ou

tpu

t P

ow

er (

dB

m)

Ou

tpu

t P

ow

er (

dB

m)

Sen

siti

vity

(d

Bm

)

Sens

itivi

ty (d

Bm)

CC2400 and CC2520 DATASHEETS

CC2400

CC2400

CC2520

CC2520


Outline





Link Budget Analysis

PRX(d) = P0 + 10nplog10(d0/d)

0 25 50 75 100 125 150-100

-90

-80

-70

-60

-50

-40

RS

S [d

Bm

]

Distance [m]

+ LTX(T) + LRX(T)

np =2.3


Communication Range

Depending on the path loss model, losses due temperature cause reduction in range comprised between 40% and 60% the max. value


Outline





Network Connectivity @ 25°C

Avg. Connectivity = 8.94; Connected nodes = 100%; Avg. Path Length = 2.95.

SINK NODE



Avg. Connectivity = 4.57; Connected nodes = 98%. Avg. Path Length = 4.93.

Few nodes are disconnected.

SINK NODE



Avg. Connectivity = 1.88; Connected nodes = 0%. The sink is disconnected from the rest of the network!

SINK NODE


Data Collection: Summary

• Temperature steadily decreases connectivity• Failure of Critical Links can cause the sink to

become disconnected


Outline





Effect of Temperature on Localization

Anchors (GPS) Blind Nodes

Location awareness:• Enable Context-Aware Apps• Resource & Services Discovery• Tracking (People, Equipment,...)• Navigation Support• Security (Location-based access)

Two Approaches:• Range-Based Localization (e.g. triangulation)• Range-Free Localization (e.g connectivity)

Both Range Estimates and Connectivity can be obtained from

radio communication.


Ranging Errors

-90-85-80-75-70-650

0.1

0.2

RSS [dBm]

pdf

d = 10 md*=11.6m

• Received power modeled by the log-normal shadowing model:• PRX(d) = PLOG-D(d) + ∆; ∆~N(0, σdB);

• Maximum Likelihood Estimate:

• Errors increase with the temperature

d* = 21.5m

-95

σdB


Ranging Errors

Case 1Case 2Temperature will cause to over-estimate the node distances


Effect of Connectivity on Localization


Effect of Connectivity on Localization

1

11

1 1

1

132

2

3

4

2

2


Range-Based Connectivity-Based


Outline





Conclusions and Future Work• Actual measurements only available for the

CC2420 radio. Simple model to account for temperature effects on RSS.

• Tests with other platforms in progress• Importance of including temperature sensors in

node design.• Importance of proper insulation and placement.


Impact of Temperature on WSN Design

MCU

OS / HAL

Networking

Services

Applications

Sensors

Radio

Battery

Soft

war

eH

ardw

are

WSN Architecture

Link Budget RSS

Energy Capacity

Physical Models

Connectivity

Life-time

Networking Models

Design & Implementation

Routing / Scheduling

Data Collection

Localization

TEM

PERA

TURESource: CR2330 Datasheet

Panasonic


Don’t forget the sunscreen! Thanks

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