Wireless Sensor Networks for Habitat Monitoring Alan Mainwaring1 Joseph Polastre2 Robert Szewczyk2 David Culler1,2 John Anderson3 1: Intel Research Laboratory at Berkeley 2: University of California, Berkeley 3: College of the Atlantic

Introduction Application Driven System Design, Research, and Implementation Parameterizes Systems Research: Localization Calibration Routing and Low-Power Communications Data Consistency, Storage, and Replication How Can All of these Services and Systems Be Integrated into a Complete Application?

Great Duck Island Breeding area for Leach’s Storm Petrel (pelagic seabird) Ecological models may use multiple parameters such as: Burrow (nest) occupancy during incubation Differences in the micro-climates of active vs. inactive burrows Environmental conditions during 7 month breeding season Clearly, such a model would consider multiple parameters. We’re focusing on ones in-and-around the underground nests (burrows) where eggs are laid. p.s. If anyone asks why they are called ‘petrels’, here’s the story: The birds are planktonic feeders and spend hours during the day hovering above the ocean’s surface picking bits of planton out with their feet. Sailors being a superstitious bunch likened this to walking on water, something for which St. Peter was famous.

Application > 1000 ft

Sensor Network Solution

Outline Application Requirements Habitat Monitoring Architecture Sensor Node Power Management Sensor Patch Transit Network Wide Area Network and Disconnected Operation Sensor Data System Analysis Real World Challenges

Application Requirements Sensor Network Longevity: 7-9 months Space: Must fit inside Small Burrow Quantity: Approximately 50 per patch Environmental Conditions Varying Geographic Distances Inconspicuous Operation Reduce the “observer effect” Data As Much as Possible in the Power Budget Iterative Process

Application Requirements Predictable System Behavior Reliable Meaningful Sensor Readings Multiple Levels of Connectivity Management at a Distance Intermittent Connectivity Operating Off the Grid Hierarchy of Networks / Data Archiving

Habitat Monitoring Architecture Transit Network Basestation Gateway Sensor Patch Patch Network Base-Remote Link Data Service Internet Client Data Browsing and Processing Sensor Node Pictorial outline

Sensor Node: Mica Hardware Software Atmel AVR w/ 512kB Flash 916MHz 40kbps Radio Range: max 100 ft Affected by obstacles, RF propogation 2 AA Batteries Operating: 15mA Sleep: 50mA Software TinyOS / C Applications Power Management Digital Sensor Drivers Remote Management & Diagnositcs

Sensor Node: Power Management AA Batteries have ~2500 mAh capacity Mica consumes 50mA in sleep = 1.2 mAh/day Mica Expected Lifetime Node Activity Days Years Mica Always On 7 0.1 Mica Always Sleeping 2081 5.7 Expected Lifetime (days) Number of Operating Hours per Day

Sensor Node: Power Management Operation nAh Transmitting a packet 20.000 Receiving a packet 8.000 Radio Listening for 1ms 1.250 Operating Sensor for 1s (analog) 1.080 Operating Sensor for 1s (digital) 0.347 Reading a Sample from the ADC 0.011 Flash Read Data 1.111 Flash Program/Erase Data 83.333 Target Lifetime: 7-8 months Power Budget: 6.9mAh/day Questions: What can be done? How often? What is the resulting sample rate? Operation Operating Time per Day Duty Cycle Sample Rate Always Sleep 24 hours 0% 0 samples/day + mCPU on 52 minutes 3.61% + Radio On (Listen) 28 minutes 1.94% + Sample All Sensors 21 minutes 1.45% 630 samples/day + Transmit Samples 20 minutes 1.38% 600 samples/day

Sensor Node: Mica Weather Board Digital Sensor Interface to Mica Onboard ADC 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 Meeting the guidelines for env monitoring system

Sensor Node: Mica Weather Board Accuracy Interchange Max Rate Startup Current Photo N/A 10% 2000 Hz 10 ms 1.235 mA I2C Temp 1 K 0.2 K 2 Hz 500 ms 0.150 mA Pressure 1.5 mbar 0.5% 10 Hz 0.010 mA Press Temp 0.8 K 0.24 K Humidity 2% 3% 500 Hz 0.775 mA Thermopile 3 K 5% 200 ms 0.170 mA Thermistor 5 K 0.126 mA Work through power budget Energy per sample vs current x sample Important to Biologists Affect Power Budget

Sensor Node: Packaging Parylene: Great but sucks for connectors or exposed sensors (non soldered connections) Acrylic Size matters Ventilation Parylene Sealant Acrylic Enclosures

Sensor Patch Network Nodes: Transmit Only Network Single Hop Repeaters Approximately 50 Half in burrows, Half outside RF unpredictable Burrows Obstacles Drop packets or retry? Transmit Only Network Single Hop Repeaters 2 hop initially Most Energy Challenged Adheres to Power Budget

Transit Network Two implementations Antennae Linux (CerfCube) Relay Mote Antennae No gain antenna (small) Omnidirectional Yagi (Directional) Implementation of transit network depends on: Distance Obstacles Power Budget Duty cycle of sensor nodes dictates transit network duty cycle Same power budget could apply here using sophisticated scheme using traffic for entire patch, or you can engineer around it… Provision node adequately

Transit Network Renewable Energy Sources CerfCube needs 60Wh/day Assuming an average peak of 1 direct sunlight hour per day: Panel must be 924 in2 or 30” x 30” for a 5” x 5” device! A mote only needs 2Wh per day, or a panel 6” x 6”

Base Station / Wide Area Network Disconnected Operation and Multiple Levels of State Laptop DirecWay Satellite WAN PostgreSQL 47% uptime Redundancy and Replication Increase number of points of failure Remote Access Physical Access Limited Keep state all areas of network Resiliency to Disconnection Network Failures Packet Loss Potential Solution: Keep Local Caches Synchronization Challenges and Accomplishments: CoLo analogy etc

Sensor Data Analysis Tell story about john anderson

Sensor Data Analysis Outside Burrow Inside Burrow

System Analysis Power Management Goals Calculated 7 months, expect 4 months Battery half-life at 1.2V Predictable Operation Observed per node constant throughput, % loss 739,846 samples as of 9/23, network is still running Battery Consumption at Node 57 Packet Throughput and Active Nodes

Real World Experiences System and Sensor Network Challenges Low Power Operation (low duty cycle) Affects hardware and software implementation Multihop Routing Allows bigger patches Route around physical obstacles Must have ~1% operating duty cycle In Situ Retasking/Reconfiguration Let biologists interactively change data collection patterns Not Implemented due to conservative energy implementation Lack of Physical Access Remote management Disconnected operation Fault tolerance Reliance on other people and their networks Physical Size of Device Affects microcontroller selection, radio, practical choice of power sources

Real World Experiences Failures Extended Loss of Wide Area Connectivity Unreliable Reboot Sequence in Windows Solderless Connections Fail (expansion/contraction cycles) Node Attrition (Petrels are not mote neutral) Environmental Conditions (50km/hr gale winds knock over equipment) Lack of post-mortem diagnositics

Conclusions First long term outdoor wireless sensor network application Application driven sensor network design Defines requirements and constraints on core system components (routing, retasking, fault tolerance, power management)

Backup Slides

Mote 18: Outside

Mote 26: Burrow 115a

Mote 53: Burrow 115b

Mote 47: Burrow 88a

Mote 40: Burrow 88b

Mote 39: Burrow 84