Habitat monitoring on Great Duck Island

Robert SzewczykJoe Polastre

Alan MainwaringJohn Anderson

David CullerUniversity of California, Berkeley

June 3, 2004

Outline

• GDI application overview

• 2002 deployment

• 2003 deployment & analysis

• Lessons learned & conclusions

Design

Deployment

Analysis

Scientific motivation: Leach’s Storm Petrel• Questions

– What environmental factors make for a good nest? How much can they vary?

– What are the occupancy patterns during incubation?

– What environmental changes occurs in the burrows and their vicinity during the breeding season?

• Methodology – Characterize the climate inside and outsize the

burrow– Collect detailed occupancy data from a number

of occupied and empty nest– Spatial sampling of habitat – sampling rate

driven by biologically interesting phenomena, non-uniform patches

– Validate a sample of sensor data with a different sensing modality

– Augmented the sensor data with deployment notes (e.g. burrow depth, soil consistency, vegetation data)

– Try to answer the questions based on analysis of the entire data set

Computer science research

• Focus on problems that matter to users of the system!– Network architecture

» Can this application be easily recast in other scenarios– Long-distance management

• Node design tradeoffs– Mechanical – expose sensors, while protecting the electronics– Low power hardware vs. high quality sensing– Size matters!

• Real world testbed– How do the simulation and lab results translate into the deployed application– What are common failure modes?– What factors impact the the functionality and performance of the sensor

network? – How do they vary across different deployments?

Sensor Node GDI ’02

• Mica platform– Atmel AVR w/ 512kB Flash– 916MHz 40kbps RFM Radio

» Range: max 100 ft» Affected by obstacles, RF propogation

– 2 AA Batteries, boost converter

• Mica weather board – “one size fits all”– Digital Sensor Interface to Mica

» Onboard ADC sampling analog photo, humidity and passive IR sensors

» Digital temperature and pressure sensors

– Designed for Low Power Operation» Individual digital switch for each sensor

– Designed to Coexist with Other Sensor Boards» Hardware “enable” protocol to obtain exclusive access

to connector resources

• Packaging– Conformal sealant + acrylic tube

Application architecture

Base-Remote Link

Data Service

Internet

Client Data Browsingand Processing

Transit Network

Basestation

Gateway

Sensor Patch

Patch Network

Sensor Node

GDI 2002 deployment

GDI 2002 results: sensor data

Thermopile data

Often need ground truth to establish validity of data

Need to know what is being measured.

GDI ’02 population

• 43 distinct nodes reporting data between July 13 and November 18

• Heavy daily losses– Between 3 and 5% daily

Redesign directions

• Node-level issues that need resolving– Size – motes were too large to fit in many burrows

– Packaging – did not provide adequate protection for electronics or proper conditions for sensors

– Node reliability

– Power consumption

– Data interpretation challenges

» Sensor calibration

» Occupancy data interpretation – need more sophisticated processing of sensor data and/or ground truth data

» Better metadata – sensor location & conditions

Miniature weather station

• Sensor suite– Sensirion humidity + temperature

sensor

– Intersema pressure + temperature sensor

– TAOS total solar radiation sensor

– Hamamatsu PAR sensor

– Radiation sensors measure both direct and diffuse radiation

• Power supply– SAFT LiS02 battery, ~1 Ah @

2.8V

• Packaging– HDPE tube with coated sensor

boards on both ends of the tube

– Additional PVC skirt to provide extra shade and protection against the rain

Burrow occupancy detector

• Sensor suite– Sensirion humidity +

temperature sensor

– Melexis passive IR sensor + conditioning circuitry

• Power supply– GreatBatch lithium thionyl

chloride 1 Ah battery

– Maxim 5V boost converter for Melexis circuitry

• Packaging– Sealed HDPE tube, emphasis

on small size

Application architecture

Base-Remote Link

Data Service

Internet

Client Data Browsingand Processing

Transit Network

Basestation

Gateway

Sensor Patch

Patch Network

Sensor Node

Verification Network

Mica2-EPRB#2

IBM laptop #1DB

Web power strip

Axis 2130 PTZ South

Wireless bridge

4-port VPN router and

16-port Ethernet switch

Power over LAN midspan DB

IBM laptop #2

Mica2-EPRB#2

WWW power strip

Southern WAP

Satellite router

GDI ’03 patch network

• Single hop network deployed mid-June– Rationale: Build a simple, reliable network that allows

» HW platform evaluation» Low power system evaluation» Comparisons with the GDI ’02 deployment

– A set of readings from every mote every 5 minutes– 23 weather station motes, 26 burrow motes– Placement for connectivity– Network diameter 70 meters– Asymmetric, bi-directional communication with low power

listening – send data packets with short preambles, receive packets with long preambles

– Expected life time – 4+ months» Weather stations perform considerably better than

burrow motes – their battery rated for a higher discharge current

GDI ’03 Multihop network

• Motivation – Greater spatial reach– Better connectivity into burrows

• Implementation– Alec Woo’s generic multihop subsystem– Low power listening: tradeoff channel capacity for average power

consumption

• The network nodes– 44 weather motes deployed July 17– 48 burrow motes deployed August 6– Network diameter – 1/5 mile– Duty cycle – 2% to minimize the active time (compromise between

receive time and send time)– Reading sent to base station every 20 minutes, route updates every

20 minutes. Expected lifetime: 2.5 months– 2/3 of nodes join within 10 minutes of deployment, remainder within 6

hours. Paths stabilize within 24 hours

GDI ’03 deployment

10m

Single hop weatherSingle hop burrowMulti hop weatherMulti hop burrow

Multihop network over time

07/06 07/13 07/20 07/27 08/03 08/10 08/17 08/24 08/31 09/07 09/14 09/21 09/28 10/05 10/12 10/19 10/260

50

100Time-series characteristics of the mutlihop network

07/06 07/13 07/20 07/27 08/03 08/10 08/17 08/24 08/31 09/07 09/14 09/21 09/28 10/05 10/12 10/19 10/260

0.5

1

1.5

2

07/06 07/13 07/20 07/27 08/03 08/10 08/17 08/24 08/31 09/07 09/14 09/21 09/28 10/05 10/12 10/19 10/260

0.5

1

1.5PC uptime fraction

Parent change-network size ratio

Active nodesParent changes

GDI 2003: mote lifetimes

0 20 40 60 80 100 120 1400

0.1

0.2

0.3

0.4

0.5

Fra

ctio

n of

pop

ulat

ion

Distribution of lifetimes in the multi hop network

0 20 40 60 80 100 120 1400

0.1

0.2

0.3

0.4

0.5

Fra

ctio

n of

pop

ulat

ion

Days of activity

Burrow

Weather

0 20 40 60 80 100 120 1400

0.1

0.2

0.3

0.4

0.5

Fra

ctio

n of

pop

ulat

ion

Distribution of lifetimes in the single hop network

0 20 40 60 80 100 120 1400

0.1

0.2

0.3

0.4

0.5

Fra

ctio

n of

pop

ulat

ion

Days of activity

Burrow

Weather

Power management evaluation

0 20 40 60 80 100 120 140

2.4

2.6

2.8

3

Lifetime (days)

Vol

tage

dur

ing

last

3 h

rs (

V)

Weather motes

4 single hop, 13 multihop motes

17 single hop, 32 multihop motes

Clustering caused by base-station shutdown in Sep.

15 single hop motes stilloperate at the end of experimentat the end of Oct.

0 20 40 60 80 100 120 1402.5

3

3.5

4

Lifetime (days)

Vol

tage

dur

ing

last

3 h

rs (

V)

Burrow motes

8 single hop, 11 multihop motes

11 single hop, 33 multihop motes

Single hopMulti hop

Single hopMulti hop

First day of deployment

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1Packet delivery CDF

Fraction of packets delivered per mote per day

Fra

ctio

n of

mot

es

SH Weather, Mean: 204.00, Std Dev: 47.17, Median: 221SH Burrow, Mean: 210.97, Std Dev: 66.64, Median: 235MH Weather, Mean: 55.06, Std Dev: 10.77, Median: 57MH Burrow, Mean: 39.44, Std Dev: 15.26, Median: 42

Performance over time

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1Packet delivery CDF

Fraction of packets delivered per mote per day

Fra

ctio

n of

mot

es

SH Weather, Mean: 182.34, Std Dev: 82.69, Median: 219SH Burrow, Mean: 169.08, Std Dev: 90.24, Median: 206MH Weather, Mean: 41.20, Std Dev: 37.59, Median: 38MH Burrow, Mean: 25.49, Std Dev: 20.46, Median: 20

Packet delivery in the multihop network

0 1 2 3 4 5 6 7 80

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Average depth

Packet delivery vs. network depthF

ract

ion

of p

acke

ts d

eliv

ered

Weather: 0.57*0.90depth

Burrow: 0.46*0.88depth

WeatherBurrow

Multihop tree structure

0 5 10 15 20 250

5

10

15

20

25

30

Num

ber

of m

otes

Number of children

Properties of the routing tree

N=101 Median # children=2 Mean # children= 4.64

Multihop links characteristics

100

101

102

103

104

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1CDF of links and packets delivered through those links

Link Longevity (packets received)

Fra

ctio

n

LinksPackets

Multihop network over time

07/06 07/13 07/20 07/27 08/03 08/10 08/17 08/24 08/31 09/07 09/14 09/21 09/28 10/05 10/12 10/19 10/260

50

100Time-series characteristics of the mutlihop network

07/06 07/13 07/20 07/27 08/03 08/10 08/17 08/24 08/31 09/07 09/14 09/21 09/28 10/05 10/12 10/19 10/260

0.5

1

1.5

2

07/06 07/13 07/20 07/27 08/03 08/10 08/17 08/24 08/31 09/07 09/14 09/21 09/28 10/05 10/12 10/19 10/260

0.5

1

1.5PC uptime fraction

Parent change-network size ratio

Active nodesParent changes

Multihop network dynamics

-0.5 0 0.5 1 1.5 2 2.50

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Parent changes/network size

Fra

ctio

n o

f ti

me

inte

rval

s

Parent change rate distribution, weighted by network size, 6 hrs interval

Biological analysis

Occupancy measurements GDI ‘03

• Calibrated ASIC for conditioning and processing the passive IR signal

– 0 to 40 deg C range

• Corroboration of data– Multiple sensor nodes in occupied

burrows

• Verification of data– Co-locate a completely different

sensing network with motes– IR-illuminated cameras– Ethernet video servers– Wireless connection to the

base station– Verification network mimics

the architecture of the sensornet

– Sample a 15 sec video/audio clipevery 5 minutes

– ~6 GB worth of data so far…

Sensor Patch

Power over LAN Midspan

IR Burrow Camera #1

IR Burrow Camera #2

IR Burrow Camera #3

)IR Burrow Camera #4

IR Burrow Camera #5

IR Burrow Camera #6

IR Burrow Camera #7

IR Burrow Camera #8

Axis 2401 Video Server

12VDC, 0.9Anetwork

Burrow Camera Configuration

Northern WAPEthernet switchWireless bridge

12V PoLActive Splitter

110VAC service

Occupancy data evaluation status

12:00 13:00 14:00 15:00 16:00 17:0039

39.5

40

40.5

41

Time

PIR

Tem

per

atu

re (

C)

PIR and ambient temperature, Burrow 3, Aug. 4

12

13

14

15

16

Am

bie

nt

Tem

per

atu

re (

C)

00:00 01:00 02:00 03:00 04:00 05:00 06:0010

15

20

25PIR and ambient temperature, Burrow 3, Jul 13

PIR

Tem

per

atu

re (

C)

10

15

20

25

Am

bie

nt

Tem

per

atu

re (

C)

Conclusions• Habitat monitoring networks

– Smaller, longer lasting, more robust nodes– Integration with more general purpose software services – multihop routing,

power management– So far, only mild challenges: low data rate, not really extreme environment

» But considerably different and harder than the lab

• Lessons learned– Experimental discipline in the deployment

» Calibration, sensor characterization» What is collected? All relevant information must be recorded as soon as

possible» Ground truth and building of trust in the experimental method

– Importance of packaging– Importance of infrastructure

» Redundancy» Remote access» Data verification

• Starting to produce biological results!– Characterization of different chabitats– Occupancy data

Thank you!

Energy cost of multihop forwarding

0 50 100 150 200 2501

10

100

1000

10000

Estimated load of the routed traffic

Mote ID (10..100 - burrow, 150..200 - weather)

Rou

ted

pack

ets

Packaging evaluation

• We observed what happens to motes when packaging fails– Battery venting, H2SO3 corroding the entire mote

– Need to assemble the package correctly – we failed to create proper indication of a good seal

– Majority of packages survived severe weather!

Ecological Conclusions to date

• Microhabitat variations exist, are measurable, and may not be fully captured by Macrohabitat classification schemes

• Burrows play a dramatic role in buffering occupants from variation in temperature and humidity

• There is no evidence that presence of motes per se constitutes a disturbance, but frequent visitation for maintenance may have been responsible for some abandonment

• Temperature and humidity sensors appear robust and give results within expected values and trends

• Some evidence for presence based on ambient temperature measurements, but needs verification with video and/or playback

Conclusions to date,Ecological/Technical:

• Voltage filtering removes many but not all spurious signals

• High variability in mote “talkback” rates may make precise pairing of data points difficult

• We are over-sampling, but that is probably good