Sensor Network Applications

Sensor Network Applications

IntroductionIntroduction

– Habitat and environmental monitoring represent essential class of sensor Habitat and environmental monitoring represent essential class of sensor network applications by placing numerous networked micro-sensors in an network applications by placing numerous networked micro-sensors in an environment where long-term data collection can be achievedenvironment where long-term data collection can be achieved

– The sensor nodes perform filtering and triggering functions as well as The sensor nodes perform filtering and triggering functions as well as application-specific or sensor-specific data compression algorithms thru application-specific or sensor-specific data compression algorithms thru the integration of local processing and storagethe integration of local processing and storage

– The ability to communicate allows nodes to cooperate in performing The ability to communicate allows nodes to cooperate in performing tasks such as statistical sampling, data aggregation, and system health tasks such as statistical sampling, data aggregation, and system health and status monitoringand status monitoring

– Increased power efficiency assists in resolving fundamental design Increased power efficiency assists in resolving fundamental design tradeoffs, e.g., between sampling rates and battery lifetimestradeoffs, e.g., between sampling rates and battery lifetimes

Wireless Sensor Networks for Habitat Monitoring [Mainwaring+ 2002]


– The sensor nodes can be reprogrammed or retasked after deployment in The sensor nodes can be reprogrammed or retasked after deployment in the field by the networking and computing capabilities providedthe field by the networking and computing capabilities provided

– Nodes can adapt their operation over time in response to changes in the Nodes can adapt their operation over time in response to changes in the environmentenvironment

– The application context helps to differentiate problems with simple and The application context helps to differentiate problems with simple and concrete solutions from open research areasconcrete solutions from open research areas

– An effective sensor network architecture and general solutions should be An effective sensor network architecture and general solutions should be developed for the domaindeveloped for the domain

– The impact of sensor networks for habitat and environmental monitoring The impact of sensor networks for habitat and environmental monitoring is measured by their ability to enable new applications and produce new is measured by their ability to enable new applications and produce new resultsresults



– This paper develops a specific habitat monitoring application, but yet a This paper develops a specific habitat monitoring application, but yet a representative of the domainrepresentative of the domain

– It presents a collection of requirements, constraints and guidelines that It presents a collection of requirements, constraints and guidelines that serve as a basis for general sensor network architectureserve as a basis for general sensor network architecture

– It describes the core components of the sensor network for this domain– It describes the core components of the sensor network for this domain– hardware and sensor platforms, the distinct networks involved, their hardware and sensor platforms, the distinct networks involved, their interconnection, and the data management facilitiesinterconnection, and the data management facilities

– The design and implementation of the essential network services – The design and implementation of the essential network services – power management, communications, re-tasking, and node management power management, communications, re-tasking, and node management can be evaluated in this contextcan be evaluated in this context


Habitat MonitoringHabitat Monitoring

– Researchers in the Life Sciences are concerned about the impacts of Researchers in the Life Sciences are concerned about the impacts of human presence in monitoring plants and animals in the field conditionshuman presence in monitoring plants and animals in the field conditions

– It is possible that chronic human disturbance may adversely effect results It is possible that chronic human disturbance may adversely effect results by changing behavioral patterns or distributionsby changing behavioral patterns or distributions

– Disturbance effects are of concern in small island situations where it may Disturbance effects are of concern in small island situations where it may be physically impossible for researchers to avoid some impact on an be physically impossible for researchers to avoid some impact on an entire populationentire population

– Seabird colonies are extreme sensitive to human disturbanceSeabird colonies are extreme sensitive to human disturbance

– Research in Maine [Anderson 1995], suggests that a 15 minute visit to a Research in Maine [Anderson 1995], suggests that a 15 minute visit to a cormorant colony can result in up to 20% mortality among eggs and cormorant colony can result in up to 20% mortality among eggs and chicks in a given breeding year. Repeated disturbance can lead to the chicks in a given breeding year. Repeated disturbance can lead to the end of the colonyend of the colony


Habitat MonitoringHabitat Monitoring

– On Kent Island, Nova Scotia, research learned that Leach’s Storm Petrels On Kent Island, Nova Scotia, research learned that Leach’s Storm Petrels are likely to desert their nesting burrows in case of disturbance during the are likely to desert their nesting burrows in case of disturbance during the first two weeks of incubationfirst two weeks of incubation

– Sensor networks advances the monitoring methods over the traditional Sensor networks advances the monitoring methods over the traditional invasive onesinvasive ones

– Sensors can be deployed prior to the breeding season or other sensitive Sensors can be deployed prior to the breeding season or other sensitive period or while plants are dormant or the ground is frozen on small islets period or while plants are dormant or the ground is frozen on small islets where it would be unsafe or unwise to repeatedly attempt field studieswhere it would be unsafe or unwise to repeatedly attempt field studies

– Sensor network deployment may be more economical method for Sensor network deployment may be more economical method for conducting long-term studies than traditional personnel-rich methodsconducting long-term studies than traditional personnel-rich methods

– A “deploy ‘em and leave ‘em” strategy of wireless sensor usage would A “deploy ‘em and leave ‘em” strategy of wireless sensor usage would decrease the logistical needs to initial placement and occasional servicingdecrease the logistical needs to initial placement and occasional servicing


Great Duck IslandGreat Duck Island

– The College of Atlantic (COA) is field testing in-situ sensor networks for The College of Atlantic (COA) is field testing in-situ sensor networks for habitat monitoringhabitat monitoring

– Great Duck Island (GDI) is a 237 acre island located 15 km south of Great Duck Island (GDI) is a 237 acre island located 15 km south of Mount Desert Island, MaineMount Desert Island, Maine

– At GDI, three major questions in monitoring the Leach’s Storm Petrel At GDI, three major questions in monitoring the Leach’s Storm Petrel [Anderson 1995]:[Anderson 1995]:

1.1. What is the usage pattern of nesting burrows over the 24-72 hour What is the usage pattern of nesting burrows over the 24-72 hour cycle when one or both members of a breeding pair may alternate cycle when one or both members of a breeding pair may alternate incubation duties with feeding at sea?incubation duties with feeding at sea?

2.2. What changes can be observed in the burrow and surface What changes can be observed in the burrow and surface environmental parameters during the course of the approximately 7 environmental parameters during the course of the approximately 7 month breeding season (April-October)?month breeding season (April-October)?


Great Duck IslandGreat Duck Island

3.3. What are the differences in the micro-environments with and without What are the differences in the micro-environments with and without large numbers of nesting petrels?large numbers of nesting petrels?

– Presence/absence data is obtained through occupancy detection and Presence/absence data is obtained through occupancy detection and temperature differentials between burrows with adult birds and burrows temperature differentials between burrows with adult birds and burrows that contain eggs, chicks, or are emptythat contain eggs, chicks, or are empty

– Petrels will most likely enter or leave during the daytime; however, 5-10 Petrels will most likely enter or leave during the daytime; however, 5-10 minutes during late evening and early morning measurements are minutes during late evening and early morning measurements are needed to capture the entry and exit timingsneeded to capture the entry and exit timings

– More general environmental differentials between burrow and surface More general environmental differentials between burrow and surface conditions can be captured by records every 2-4 hours during the conditions can be captured by records every 2-4 hours during the extended breeding season; whereas, the differences between “popular” extended breeding season; whereas, the differences between “popular” and “unpopular” sites benefit from hourly samplingand “unpopular” sites benefit from hourly sampling


Great Duck Island RequirementsGreat Duck Island Requirements

1.1. Internet AccessInternet Access

– The sensor networks at GDI must be accessible via the Internet since the The sensor networks at GDI must be accessible via the Internet since the ability to support remote interactions with in-situ networks is essentialability to support remote interactions with in-situ networks is essential

2.2. Hierarchical NetworkHierarchical Network

– Habitats of interest are located up to several kilometers away. A second Habitats of interest are located up to several kilometers away. A second tier of wireless networking provides connectivity to multiple patches of tier of wireless networking provides connectivity to multiple patches of sensor networks deployed at each of the areas.sensor networks deployed at each of the areas.

3.3. Sensor Network LongevitySensor Network Longevity

– Sensor networks that runs for several month from non-rechargeable Sensor networks that runs for several month from non-rechargeable power sources would be desirable since studies at GDI can span multiple power sources would be desirable since studies at GDI can span multiple field seasonsfield seasons



4.4. Operating off-the gridOperating off-the grid

– Every level of the network must operate with bounded energy suppliesEvery level of the network must operate with bounded energy supplies

– Renewable energy such as solar power may be available some locations, Renewable energy such as solar power may be available some locations, disconnected operation is a possibilitydisconnected operation is a possibility

– GDI has enough solar power that run the application 24x7 with small GDI has enough solar power that run the application 24x7 with small probabilities of service interruptions due to power lossprobabilities of service interruptions due to power loss

5.5. Management at-a-distanceManagement at-a-distance

– Remoteness of the field sites requires the ability to monitor and manage Remoteness of the field sites requires the ability to monitor and manage sensor networks over the Internet. The goal is no on-site presence for sensor networks over the Internet. The goal is no on-site presence for maintenance and administration during the field season, except for maintenance and administration during the field season, except for installation and removal of nodesinstallation and removal of nodes



6.6. Inconspicuous operationInconspicuous operation

– It should not disrupt the natural processes or behaviors under studyIt should not disrupt the natural processes or behaviors under study

– Removing human presence from the study areas would eliminate a Removing human presence from the study areas would eliminate a source of error and variation in data collection and source of disturbancesource of error and variation in data collection and source of disturbance

7.7. System behaviorSystem behavior

– Sensor networks should present stable, predictable, and repeatable Sensor networks should present stable, predictable, and repeatable behavior at all times since unpredictable system is difficult to debug and behavior at all times since unpredictable system is difficult to debug and maintainmaintain

– Predictability is essential in developing trust in these new technologies Predictability is essential in developing trust in these new technologies for life scientistsfor life scientists



8.8. In-situ interactionsIn-situ interactions

– Local interactions are required during initial development, maintenance Local interactions are required during initial development, maintenance and on-site visits and on-site visits

– PDAs can be useful in accomplishing these tasks – they may directly PDAs can be useful in accomplishing these tasks – they may directly query a sensor, adjust operational parameters and so onquery a sensor, adjust operational parameters and so on

9.9. Sensors and samplingSensors and sampling

– The ability to sense light, temperature, infrared, relative humidity, and The ability to sense light, temperature, infrared, relative humidity, and barometric pressure are essential set of measurementsbarometric pressure are essential set of measurements

– Additional measurements may include acceleration/vibration, weight, Additional measurements may include acceleration/vibration, weight, chemical vapors, gas concentrations, pH, and noise levelschemical vapors, gas concentrations, pH, and noise levels



10.10. Data archivingData archiving

– Sensor readings must be achieved for off-line data mining and analysisSensor readings must be achieved for off-line data mining and analysis

– The reliable offloading of sensor logs to databases in the wired, powered The reliable offloading of sensor logs to databases in the wired, powered infrastructure is essentialinfrastructure is essential

– It is desirable to interactively “drill-down” and explore sensors in near It is desirable to interactively “drill-down” and explore sensors in near real-time complement log-based studies. In this mode of operation, the real-time complement log-based studies. In this mode of operation, the timely delivery of sensor data is the keytimely delivery of sensor data is the key

– Nodal data summaries and periodic health-and-status monitoring also Nodal data summaries and periodic health-and-status monitoring also requires timely delivery of the datarequires timely delivery of the data


System ArchitectureSystem Architecture

– A tiered architecture is developedA tiered architecture is developed

– The lowest level consists of the The lowest level consists of the sensor nodessensor nodes that perform general that perform general purpose computing and networking as well as application-specific sensingpurpose computing and networking as well as application-specific sensing

– The sensor nodes may be deployed in dense patches and transmit their The sensor nodes may be deployed in dense patches and transmit their data through the sensor network to the sensor network data through the sensor network to the sensor network gatewaygateway

– Gateway is responsible for transmitting sensor data from the Gateway is responsible for transmitting sensor data from the sensor patchsensor patch through a local through a local transit networktransit network to the remote to the remote base stationbase station that provides that provides WAN connectivity and data loggingWAN connectivity and data logging

– The base station connects to database replicas across the internetThe base station connects to database replicas across the internet

– At last, the data is displayed to researchers through a user interfaceAt last, the data is displayed to researchers through a user interface




Figure 1: System architecture for habitat monitoringFigure 1: System architecture for habitat monitoring


– The autonomous sensor nodes are placed in the areas of interest where The autonomous sensor nodes are placed in the areas of interest where each sensor node collects environmental data about its immediate each sensor node collects environmental data about its immediate surroundingssurroundings

– Since these sensors are placed close to the area of interest, they can be Since these sensors are placed close to the area of interest, they can be built using small and inexpensive individual sensors – high spatial built using small and inexpensive individual sensors – high spatial resolution can be achieved through dense deployment of sensor nodesresolution can be achieved through dense deployment of sensor nodes

– This architecture offers higher robustness compared to traditional This architecture offers higher robustness compared to traditional approaches which use a few high quality sensors with complex signal approaches which use a few high quality sensors with complex signal processingprocessing

– The computational module is a programmable unit that provides The computational module is a programmable unit that provides computation, storage and bidirectional communication with other nodescomputation, storage and bidirectional communication with other nodes



– The computational module interfaces with the analog and digital sensors The computational module interfaces with the analog and digital sensors on the sensor module, performs basic signal processing and dispatches on the sensor module, performs basic signal processing and dispatches the data according to the needs of the applicationthe data according to the needs of the application

– Compared to traditional data logging systems, networked sensors offer Compared to traditional data logging systems, networked sensors offer two main advantages: they can be re-tasked in the field and they can two main advantages: they can be re-tasked in the field and they can communicate with the rest of the systemcommunicate with the rest of the system

– In-situ re-tasking gives researchers the ability to refocus their observations In-situ re-tasking gives researchers the ability to refocus their observations based on the analysis of the initial results – initially, absolute temperature based on the analysis of the initial results – initially, absolute temperature readings are desired, after a while, only significant temperature changes readings are desired, after a while, only significant temperature changes exceeding a threshold may become more usefulexceeding a threshold may become more useful



– Individual sensor nodes communicate and coordinate with one another Individual sensor nodes communicate and coordinate with one another

– These nodes form a multi-hop network by forwarding each other’s These nodes form a multi-hop network by forwarding each other’s messages and if needed, the network can perform in-network aggregation messages and if needed, the network can perform in-network aggregation (e.g., relaying the average temperature across the region)(e.g., relaying the average temperature across the region)

– Eventually, data from each sensor needs to be propagated to the InternetEventually, data from each sensor needs to be propagated to the Internet

– The propagated data may be raw, filtered or processed dataThe propagated data may be raw, filtered or processed data

– Since direct wide area connectivity cannot be brought to each sensor path Since direct wide area connectivity cannot be brought to each sensor path due to several reasons (e.g., cost of equipment, power, disturbance due to several reasons (e.g., cost of equipment, power, disturbance created by the installation of the equipment in the environment), wide are created by the installation of the equipment in the environment), wide are connectivity is brought to a connectivity is brought to a base stationbase station instead instead



– The base station may communicate with the sensor patch using a wireless The base station may communicate with the sensor patch using a wireless LAN where each sensor patch is equipped with a LAN where each sensor patch is equipped with a gatewaygateway that can that can communicate with the sensor network and provides connectivity to the communicate with the sensor network and provides connectivity to the transit networktransit network

– The transit network may consist of a single hop link or series of networked The transit network may consist of a single hop link or series of networked wireless nodes and each transit network design has different wireless nodes and each transit network design has different characteristics with respect to expected robustness, bandwidth, energy characteristics with respect to expected robustness, bandwidth, energy efficiency, cost and manageabilityefficiency, cost and manageability

– To provide data to remote end-users, the To provide data to remote end-users, the base stationbase station includes WAN includes WAN connectivity and persistent data storage for the collection of sensor connectivity and persistent data storage for the collection of sensor patchespatches



– It is expected that WAN connection will be wirelessIt is expected that WAN connection will be wireless

– The architecture needs to address the disconnection possibilitiesThe architecture needs to address the disconnection possibilities

– Each layer (sensor nodes, gateways, base stations) has some persistent Each layer (sensor nodes, gateways, base stations) has some persistent storage to protect against data loss due to power outage as well as data storage to protect against data loss due to power outage as well as data management servicesmanagement services

– At the sensor level, these will be primitive, taking the form of data loggingAt the sensor level, these will be primitive, taking the form of data logging

– The base station may provide relational database service while the data The base station may provide relational database service while the data management at the gateways falls somewhere in betweenmanagement at the gateways falls somewhere in between

– When it comes to data collection, long-latency is preferable to data lossWhen it comes to data collection, long-latency is preferable to data loss

– Users interact with the sensor network in two waysUsers interact with the sensor network in two ways



– Remote users access the replica of the base station database Remote users access the replica of the base station database

– This approach assists on integration with data analysis and mining tools This approach assists on integration with data analysis and mining tools while masking the potential wide area disconnections with the base while masking the potential wide area disconnections with the base stationsstations

– On-site users may require direct interaction with the network and this can On-site users may require direct interaction with the network and this can be accomplished with a small, PDA-sized device, referred to as be accomplished with a small, PDA-sized device, referred to as gizmogizmo

– Gizmo allows the user to interactively control the network parameters by Gizmo allows the user to interactively control the network parameters by adjusting the sampling rates, power management parameters and other adjusting the sampling rates, power management parameters and other network parametersnetwork parameters

– The connectivity between any sensor node and gizmo may or may not rely The connectivity between any sensor node and gizmo may or may not rely on functioning on multi-hop sensor network routingon functioning on multi-hop sensor network routing


Implementation StrategiesImplementation Strategies

Sensor Network NodeSensor Network Node

– UC Berkeley motes are used as the sensor nodesUC Berkeley motes are used as the sensor nodes

– Mica uses a single channel, 916 MHz radio from RF Monolithics to Mica uses a single channel, 916 MHz radio from RF Monolithics to provide bi-directional communication at 40 Kbps, an Atmel Atmega 103 provide bi-directional communication at 40 Kbps, an Atmel Atmega 103 microcontroller running at 4 MHz and 512 KB nonvolatile storagemicrocontroller running at 4 MHz and 512 KB nonvolatile storage

– A pair of conventional AA batteries and a DC boost converter provide the A pair of conventional AA batteries and a DC boost converter provide the power source; however, other renewable energy sources can be usedpower source; however, other renewable energy sources can be used



Sensor BoardSensor Board

– The Mica Weather Board provides sensors that monitor changing The Mica Weather Board provides sensors that monitor changing environmental conditions with the same functionality as a traditional environmental conditions with the same functionality as a traditional weather stationweather station

– The Mica Weather Board includes temperature, photoresistor, barometric The Mica Weather Board includes temperature, photoresistor, barometric pressure, humidity, and passive infrared (thermopile) sensorspressure, humidity, and passive infrared (thermopile) sensors


Table 1: Mica Weather BoardTable 1: Mica Weather Board


Sensor BoardSensor Board


Figure 2: Mica Hardware Platform: The Mica sensor node (left) with the MicaFigure 2: Mica Hardware Platform: The Mica sensor node (left) with the MicaWeather Board developed for environmental monitoring applicationsWeather Board developed for environmental monitoring applications


Energy BudgetEnergy Budget

– Typical habitat monitoring applications need to run for nine monthsTypical habitat monitoring applications need to run for nine months

– The application chooses how to allocate the energy budget between The application chooses how to allocate the energy budget between sleep modes, sensing, local calculations and communicationssleep modes, sensing, local calculations and communications

– Since different nodes have different functions, they also have different Since different nodes have different functions, they also have different power requirements, for instance, the nodes near the gateway may need power requirements, for instance, the nodes near the gateway may need to forward all messages from a patch while a node in a nest may only to forward all messages from a patch while a node in a nest may only need to report its own readingsneed to report its own readings

– When a set of power limited nodes exhaust their power supplies, the When a set of power limited nodes exhaust their power supplies, the network can become disconnected and inoperablenetwork can become disconnected and inoperable

– There is a need to budget the power with respect to the energy There is a need to budget the power with respect to the energy bottlenecks of the networkbottlenecks of the network



Energy BudgetEnergy Budget

– The baseline life time of the node is determined by the current draw in The baseline life time of the node is determined by the current draw in the sleep statethe sleep state

– Minimizing power in sleep mode means turning off the sensors, the radio Minimizing power in sleep mode means turning off the sensors, the radio and putting the processor into a deep sleep modeand putting the processor into a deep sleep mode


Table 2: Power required by various Mica operationsTable 2: Power required by various Mica operations


Sensor DeploymentSensor Deployment

– A wireless sensor network using Mica motes with Mica Weather Board A wireless sensor network using Mica motes with Mica Weather Board has been deployed in July 2002has been deployed in July 2002

– Environmental protective packaging has been designed which minimally Environmental protective packaging has been designed which minimally obstruct sensing functionalityobstruct sensing functionality


Figure 3: Acrylic enclosure used for deploying the Mica moteFigure 3: Acrylic enclosure used for deploying the Mica mote


Patch GatewaysPatch Gateways

– Usage of different gateway nodes directly affects the underlying available Usage of different gateway nodes directly affects the underlying available transit networktransit network

– Two designs implemented: an 802.11b single hop with an embedded Two designs implemented: an 802.11b single hop with an embedded Linux system and a single hop mote-to-mote networkLinux system and a single hop mote-to-mote network

– Initially, CerfCube [Cerfcube] which is a small StrongARM-based Initially, CerfCube [Cerfcube] which is a small StrongARM-based embedded system to act as a sensor patch gateway, is chosenembedded system to act as a sensor patch gateway, is chosen

– Each gateway is equipped with a CompactFlash 802.11b adapterEach gateway is equipped with a CompactFlash 802.11b adapter

– Gateway use permanent storage of up to 1GBGateway use permanent storage of up to 1GB

– The mote-to-mote solution consisted of a mote connected to the base The mote-to-mote solution consisted of a mote connected to the base station and a mote in the sensor patchstation and a mote in the sensor patch



Patch GatewaysPatch Gateways

– The differences between the mote and CerfCube include differentThe differences between the mote and CerfCube include different

o communication frequencycommunication frequency

o power requirements power requirements

o software componentssoftware components

– The mote’s MAC layer does not require bi-directional link like 802.11bThe mote’s MAC layer does not require bi-directional link like 802.11b

– In addition, the mote sends raw data with a small packet header (4 bytes) In addition, the mote sends raw data with a small packet header (4 bytes) directly over the radio as opposed to overheads imposed by 802.11b and directly over the radio as opposed to overheads imposed by 802.11b and TCP/IP connectionsTCP/IP connections



Base-station installationBase-station installation

– For achieve remote access, collection of sensor patches is connected to For achieve remote access, collection of sensor patches is connected to the Internet through a wide-area linkthe Internet through a wide-area link

– On GDI, Internet connectivity is accomplished through a two-way satellite On GDI, Internet connectivity is accomplished through a two-way satellite connection provided by Hughes and similar to DirecTV systemconnection provided by Hughes and similar to DirecTV system

– The satellite system is connected to a laptop which coordinates the The satellite system is connected to a laptop which coordinates the sensor patches and provides a relational database servicesensor patches and provides a relational database service

Database Management SystemDatabase Management System

– The base station uses Postgres SQL database which stores time-The base station uses Postgres SQL database which stores time-stamped readings from the sensors, health status of the individual stamped readings from the sensors, health status of the individual sensors, and metadata (e.g., sensor locations)sensors, and metadata (e.g., sensor locations)



Database Management SystemDatabase Management System

– The GDI database is replicated every fifteen minutes over the wide-area The GDI database is replicated every fifteen minutes over the wide-area satellite link to Postgres database in Berkeleysatellite link to Postgres database in Berkeley

User InterfacesUser Interfaces

– Many user interfaces can be implemented on top of the sensor databaseMany user interfaces can be implemented on top of the sensor database

– GIS systems provide a widely used standard for analyzing geographical GIS systems provide a widely used standard for analyzing geographical data and most statistics and data analysis packages implement data and most statistics and data analysis packages implement interfaces to relational databasesinterfaces to relational databases

– Number of web interfaces can be implemented to provide the ubiquitous Number of web interfaces can be implemented to provide the ubiquitous interfaces to the habitat datainterfaces to the habitat data



– Focus is on issues related to dynamic sensor networks with mobile Focus is on issues related to dynamic sensor networks with mobile nodes and wireless communication between themnodes and wireless communication between them

– In this system, the sensor nodes collars carried by the animals under In this system, the sensor nodes collars carried by the animals under study; wireless ad hoc networking techniques are used to swap and store study; wireless ad hoc networking techniques are used to swap and store data in a peer-to-peer manner and to pass it towards a mobile base data in a peer-to-peer manner and to pass it towards a mobile base station that sporadically traverses the area to upload datastation that sporadically traverses the area to upload data

– Biology and biocomplexity research has been focused on gathering data Biology and biocomplexity research has been focused on gathering data and observations on a range of species to understand their interactions and observations on a range of species to understand their interactions and influences on each otherand influences on each other

– For example, how human development into wilderness areas affects For example, how human development into wilderness areas affects indigenous species there; understand the migration patterns of wild indigenous species there; understand the migration patterns of wild animals and how they may be affected by changes in weather patterns or animals and how they may be affected by changes in weather patterns or plant life, by introduction of non-native species, and by other influencesplant life, by introduction of non-native species, and by other influences

Energy-Efficient Computing for Wildlife Tracking: Design Tradeoffs and Early Experiences with ZebraNet [Juang+ 2002]


– Finding and learning these details require long-term position logs and Finding and learning these details require long-term position logs and other biometric data such as heart rate, body temperature, and frequency other biometric data such as heart rate, body temperature, and frequency feedingfeeding

– Current wildlife tracking studies rely on simple technology, for example, Current wildlife tracking studies rely on simple technology, for example, many studies rely on collaring a sample subset of animals with simple many studies rely on collaring a sample subset of animals with simple VHF transmittersVHF transmitters

– Researchers periodically drive through and/or fly over an area with a Researchers periodically drive through and/or fly over an area with a receiver antenna, and listen for pings from previously collared animalsreceiver antenna, and listen for pings from previously collared animals

– Once animal is found, its behavior can be observed and its observed Once animal is found, its behavior can be observed and its observed position can be logged; however, there are limits to such studiesposition can be logged; however, there are limits to such studies

– First, data collection is infrequent and can miss many “First, data collection is infrequent and can miss many “interesting eventsinteresting events””



– Second, data collection is mostly limited to daylight hours, but animal Second, data collection is mostly limited to daylight hours, but animal behavior and movements in night hours can be differentbehavior and movements in night hours can be different

– Third, data collection is impossible or very limited for secluded species Third, data collection is impossible or very limited for secluded species that avoid human contactthat avoid human contact

– The most elegant trackers commercially available use GPS to track The most elegant trackers commercially available use GPS to track position and use satellite uploads to transfer data to a base stationposition and use satellite uploads to transfer data to a base station

– These systems also suffer from several limitationsThese systems also suffer from several limitations

– First, at most a log of 3000 position samples can be logged and no First, at most a log of 3000 position samples can be logged and no biometric databiometric data

– Second, since satellite uploads are slow and uses high power Second, since satellite uploads are slow and uses high power consumption, they are done infrequently – this limits how often position consumption, they are done infrequently – this limits how often position samples can be gathered without overflowing 3000-entry log storagesamples can be gathered without overflowing 3000-entry log storage



– Third, downloads of data from the satellite to the researchers are both Third, downloads of data from the satellite to the researchers are both slow and expensive, therefore, constraining the amount of data collectedslow and expensive, therefore, constraining the amount of data collected

– Finally, these systems operate on batteries without recharge – when Finally, these systems operate on batteries without recharge – when power is drained, the system become unusable unless it is retrieved, power is drained, the system become unusable unless it is retrieved, recharged and re-deployedrecharged and re-deployed

– ZebraNetZebraNet project is building tracking nodes that include a low-power project is building tracking nodes that include a low-power miniature GPS system with user-programmable CPU, non-volatile miniature GPS system with user-programmable CPU, non-volatile storage for data logs, and radio transceivers for communicating either storage for data logs, and radio transceivers for communicating either with other nodes or with a base stationwith other nodes or with a base station



– One of the key principles of ZebraNet is that the system should work in One of the key principles of ZebraNet is that the system should work in arbitrary wilderness locations; no assumptions are made about the arbitrary wilderness locations; no assumptions are made about the presence of of fixed antenna towers or cellular phone servicepresence of of fixed antenna towers or cellular phone service

– The system uses peer-to-peer data swaps to move the data around; The system uses peer-to-peer data swaps to move the data around; periodic researcher drives bys and/or fly-overs can collect logged data periodic researcher drives bys and/or fly-overs can collect logged data from several animals despite encountering relatively few within rangefrom several animals despite encountering relatively few within range

– Even though ad hoc sensor networks have been heavily studied, not Even though ad hoc sensor networks have been heavily studied, not much has been published about the characteristics of mobile sensor much has been published about the characteristics of mobile sensor networks with mobile base stations and very few studies focus on networks with mobile base stations and very few studies focus on building real systemsbuilding real systems



– This paper has the following unique contributions:This paper has the following unique contributions:

o To the best knowledge of authors, this is the first study of mobile To the best knowledge of authors, this is the first study of mobile sensor networks protocols in which the base station is also sensor networks protocols in which the base station is also mobilemobile. It . It is presumed that researchers will upload data while driving or flying is presumed that researchers will upload data while driving or flying by the regionby the region

o Zebra-tracking is a domain in which the node mobility models are Zebra-tracking is a domain in which the node mobility models are unknown which makes it a research goal. Understanding how, when unknown which makes it a research goal. Understanding how, when and why zebras undertake long-term migrations is the most essential and why zebras undertake long-term migrations is the most essential biological question of this work. biological question of this work.

o ZebraNet’s data collection has communication patterns in which data ZebraNet’s data collection has communication patterns in which data can be cooperatively passed towards a base stationcan be cooperatively passed towards a base station

o Energy tradeoffs are examined in detail using real system energy Energy tradeoffs are examined in detail using real system energy measurements for ZebraNet prototype hardware in operationmeasurements for ZebraNet prototype hardware in operation



– Some of the interesting research questions to be explored are:Some of the interesting research questions to be explored are:

o How to make the communications protocol both effective and power-How to make the communications protocol both effective and power-efficient?efficient?

o To what extent can we rely on ad hoc, peer-to-peer transfers in a To what extent can we rely on ad hoc, peer-to-peer transfers in a sparsely-connected spatially-huge sensor network?sparsely-connected spatially-huge sensor network?

o How can we provide comprehensive tracking of a collection of How can we provide comprehensive tracking of a collection of animals, even if some of the animals are reclusive and rarely are animals, even if some of the animals are reclusive and rarely are close enough to humans to have their data logs updated directly?close enough to humans to have their data logs updated directly?

– This research work gives quantitative explorations of the design This research work gives quantitative explorations of the design decisions behind some of these questionsdecisions behind some of these questions


ZebraNet Design GoalsZebraNet Design Goals

– The ZebraNet project is a direct and ongoing collaboration between The ZebraNet project is a direct and ongoing collaboration between researchers in experimental computer systems and in wildlife biologyresearchers in experimental computer systems and in wildlife biology

– The wildlife biologists have determined the tracker’s overall design goals:The wildlife biologists have determined the tracker’s overall design goals:

o GPS position samples are taken every three minutesGPS position samples are taken every three minutes

o Detailed activity logs taken for three minutes every hourDetailed activity logs taken for three minutes every hour

o One year of operation without direct human intervention – that is, not One year of operation without direct human intervention – that is, not counting on tranquilizing and re-collaring an animal more than once counting on tranquilizing and re-collaring an animal more than once per yearper year

o No fixed base stations, antennas, or cellular service No fixed base stations, antennas, or cellular service

o A high success rate for A high success rate for eventuallyeventually delivering all logged data is delivering all logged data is essential while latency is not as criticalessential while latency is not as critical

o For a zebra collar, a weight limit of 3-5 lbs is recommendedFor a zebra collar, a weight limit of 3-5 lbs is recommended


ZebraNet Design GoalsZebraNet Design Goals

– Ultimately, this detailed information may include several position Ultimately, this detailed information may include several position estimates, temperature information, weather data, environmental data, estimates, temperature information, weather data, environmental data, and body movements that will serve as signatures of behavior; however, and body movements that will serve as signatures of behavior; however, in this initial system, the focus is only on position datain this initial system, the focus is only on position data

– Overall, the key goal is to deliver to researchers a very high fraction of the Overall, the key goal is to deliver to researchers a very high fraction of the data collected over the months or years that the system is in operationdata collected over the months or years that the system is in operation

– Therefore, ZebraNet must be power-efficient, designed with appropriate Therefore, ZebraNet must be power-efficient, designed with appropriate data log storage, and must be rugged to ensure reliability under tough data log storage, and must be rugged to ensure reliability under tough environmental conditionsenvironmental conditions


ZebraNet Problem StatementZebraNet Problem Statement

– The biologists design goals need to be translated into the engineering The biologists design goals need to be translated into the engineering task at handtask at hand

– Success rate at delivering position data to the researchers –data homing Success rate at delivering position data to the researchers –data homing rate– should approach 100%rate– should approach 100%

– Weight limits on each node translate almost directly to computational Weight limits on each node translate almost directly to computational energy limits since weight of the battery and solar panel takes bulk of the energy limits since weight of the battery and solar panel takes bulk of the total weight of a ZebraNet node; therefore, collar and protocol design total weight of a ZebraNet node; therefore, collar and protocol design decisions must manage the number and size of data transmissions decisions must manage the number and size of data transmissions requiredrequired

– System design choices must be made that limit the range of System design choices must be made that limit the range of transmissions since the required transmitter energy increases transmissions since the required transmitter energy increases dramatically with the distance transmitteddramatically with the distance transmitted



– The amount of storage needed to hold position logs must be limited – if The amount of storage needed to hold position logs must be limited – if many redundant copies are stored and swapped, the storage many redundant copies are stored and swapped, the storage requirements can scale as requirements can scale as O(nO(n22))

– Although the energy cost of storage is small compared to that of Although the energy cost of storage is small compared to that of transmissions, it is still necessary to develop storage-efficient designtransmissions, it is still necessary to develop storage-efficient design

– Due to limited transceiver, coverage and a base station only sporadically Due to limited transceiver, coverage and a base station only sporadically available, ZebraNet must forward data through other nodes in peer-to-available, ZebraNet must forward data through other nodes in peer-to-peer manner and store redundant copies of position logs in other tracking peer manner and store redundant copies of position logs in other tracking nodesnodes

– Some of the key challenges in ZebraNet come from the spatial and Some of the key challenges in ZebraNet come from the spatial and temporal scale of the systemtemporal scale of the system



– In terms of temporal scale, keeping a system running autonomously In terms of temporal scale, keeping a system running autonomously months at a time is challenging; it requires tremendous design-time months at a time is challenging; it requires tremendous design-time attention to both hardware and software reliabilityattention to both hardware and software reliability

– In terms of spatial scale, ZebraNet is also aggressive; it is the specific In terms of spatial scale, ZebraNet is also aggressive; it is the specific intent of the system to operate over an area of hundreds or thousands of intent of the system to operate over an area of hundreds or thousands of square square kilometerssquare square kilometers

– Due to the large distances involved and sparse sensor coverage, Due to the large distances involved and sparse sensor coverage, energy/connectivity tradeoffs become keyenergy/connectivity tradeoffs become key



– These challenges mentioned here tackles several open problems:These challenges mentioned here tackles several open problems:

– ZebraNet protocol promises good communication behavior on mobile ZebraNet protocol promises good communication behavior on mobile sensors forwarding data towards a mobile base stationsensors forwarding data towards a mobile base station

– ZebraNet explores design issues for sensors that are more coarse-ZebraNet explores design issues for sensors that are more coarse-grained than many prior sensor proposals. Larger the weight limits grained than many prior sensor proposals. Larger the weight limits and storage budgets allow researchers to consider different protocols and storage budgets allow researchers to consider different protocols with improved leverage for sparsely-connected, physically-with improved leverage for sparsely-connected, physically-widespread sensorswidespread sensors


[Anderson 1995] J.G.T. Anderson, Pilot survey of mid-coast Maine seabird colonies: an evaluation of techniques, Bangor, ME, 1995. Report to the State of Maine Dept. of Inland Fisheries and Wildlife.

[Cerfcube] Cerfcube embedded StrongARM system, http://www.intrinsys.com/products/cerfcube

[Juang+ 2002] P. Juang, H. Oki, Y. Wang, M. Martonosi, L-S Peh, and D. Rubenstein, Energy-Efficient Computing for Wildlife Tracking: Design Tradeoffs and Early Experiences with ZebraNet, ACM SIGARCH Computer Architecture News, vol. 30, no. 5, December 2002 .

[Mainwaring+ 2002] A. Mainwaring, J. Polastre, R. Szewczyk, D. Culler, and J. Anderson, Wireless Sensor Networks for Habitat Monitoring, 1st ACM International Workshop on Wireless Sensor Networks and Applications (WSNA 2002), Atlanta, Georgia, September 28, 2002.

References

http://www.intrinsys.com/products/cerfcube

Documents

Sensor Network Applications