Acoustic localization Acoustic localization

for real-life for real-life wireless sensor wireless sensor

network applicationsnetwork applicationsMichael AllenMichael Allen

Cogent Computing ARCCogent Computing ARCin collaboration with:

Centre for Embedded Networked Sensing, UCLA WaveScope project, CSAIL, MIT

Wireless networked sensingWireless networked sensing

Wirelessly networked, embedded, battery Wirelessly networked, embedded, battery powered, sensor enabled computerspowered, sensor enabled computers

Sample and process data about a physical Sample and process data about a physical phenomenaphenomena Temperature, light, sound, imageTemperature, light, sound, image

Aims/advantagesAims/advantages Cheap, pervasive, collaborativeCheap, pervasive, collaborative Distributed computationDistributed computation

My ResearchMy Research Physical phenomena is sound - Acoustic Physical phenomena is sound - Acoustic

localization:localization: For self/node-localization (locate nodes using For self/node-localization (locate nodes using

acoustics)acoustics) For source localization (locate acoustic event of For source localization (locate acoustic event of

interest)interest) Real-life aspectReal-life aspect

Real problems/questions, real environmentsReal problems/questions, real environments Systems research (reliability, robust behaviour)Systems research (reliability, robust behaviour) Field-usable toolsField-usable tools

Theoretical aspectTheoretical aspect Design principles, algorithmsDesign principles, algorithms ScalabilityScalability Data fusionData fusion

Motivating applicationsMotivating applications

Primary motivation: bioacousticsPrimary motivation: bioacoustics Acoustic source localization of animals/bird Acoustic source localization of animals/bird

callscalls Position estimation is helpful for behaviour Position estimation is helpful for behaviour

analysisanalysis ProblemsProblems

Exploratory systems development is often Exploratory systems development is often requiredrequired

Currently available platforms are not Currently available platforms are not suited to thissuited to this

Current work - VoxNetCurrent work - VoxNet

An Interactive platform for bioacoustics An Interactive platform for bioacoustics researchresearch Hardware and softwareHardware and software

Forms Forms real-life, systemsreal-life, systems aspect of thesis aspect of thesis researchresearch

Allow on-line and off-line operationAllow on-line and off-line operation React to events in-fieldReact to events in-field Full data set gathered at nodeFull data set gathered at node

Network consists of Network consists of xx nodes and 1 sink nodes and 1 sink Sink is endpoint for programsSink is endpoint for programs Nodes talk over multi-hop IP to sinkNodes talk over multi-hop IP to sink

Sink/control

Hardware – Acoustic Hardware – Acoustic ENSBoxENSBox

More capable than current WSN research More capable than current WSN research platforms: platforms: 32-bit ARM CPU, 64MB RAM32-bit ARM CPU, 64MB RAM Four channel 48KHz audioFour channel 48KHz audio wi-fi/802.11bwi-fi/802.11b internal battery (5-10hr)internal battery (5-10hr)

Rapidly deployable:Rapidly deployable: Attended, short-lived deploymentsAttended, short-lived deployments

Self-localization and time synchronisation:Self-localization and time synchronisation: cm accuracy acoustic based localization (up to 100m cm accuracy acoustic based localization (up to 100m

range)range) 10us time synchronisation across network10us time synchronisation across network

V2 (2007)

L. Girod, M. Lukac, V. Trifa, and D. Estrin. "The Design and Implementation of a Self-calibrating Acoustic Sensing Platform." in Proc. of SenSys 2006

Deployment in ColoradoDeployment in Colorado Acoustic localization application running on platformAcoustic localization application running on platform

In-situ, on-line operation (detecting marmots)In-situ, on-line operation (detecting marmots) Nodes run adaptive event detectorsNodes run adaptive event detectors

Signal energy in frequency bands of interestSignal energy in frequency bands of interest On detection, data is passed to sink (4 channels/node)On detection, data is passed to sink (4 channels/node)

Sink clusters together related eventsSink clusters together related events Makes DoA estimates based on each node’s detectionMakes DoA estimates based on each node’s detection Estimates position from crossing of DoAsEstimates position from crossing of DoAs

Allen, M., Girod, L., Newton, R., Madden, S., Blumstein, D., Estrin, D., “VoxNet: An Interactive, Rapidly-Deployable Acoustic Monitoring Platform”, International Conference on Information Processing in Sensor Networks (IPSN 2008)

Problems/ObservationsProblems/Observations

Latency problemsLatency problems Uncoordinated, interfering network trafficUncoordinated, interfering network traffic

Event grouping at sinkEvent grouping at sink Grouped by arrival time – BADGrouped by arrival time – BAD Events arrive out of order, lateEvents arrive out of order, late

Overall position estimate took far too Overall position estimate took far too longlong Link qualityLink quality Multi-hop data transfer latencyMulti-hop data transfer latency

ImprovementsImprovements

On-line clustering algorithmOn-line clustering algorithm Group events based on detection timeGroup events based on detection time

Smart event groupingSmart event grouping Nodes only send notification of detectionNodes only send notification of detection Sink requests dataSink requests data

Adaptive behaviour trade-offAdaptive behaviour trade-off Nodes monitor network linksNodes monitor network links Decide to process locally or pass raw Decide to process locally or pass raw

datadata

Future workFuture work

Scalability of acoustic localization Scalability of acoustic localization networksnetworks Coverage, density – they make sense?Coverage, density – they make sense? Bounds on performanceBounds on performance

Data fusion for position estimateData fusion for position estimate Quickest way to get data and fuse itQuickest way to get data and fuse it Information theory/Bayesian Information theory/Bayesian

approaches to data fusionapproaches to data fusion