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OpenSense
OpenSense
Karl Aberer, EPFL Boi Fal6ngs, Alcherio Mar6noli,
Mar6n Ve<erli, EPFL Lothar Thiele, ETH Zürich
OpenSense
Overview
• Research challenges • Research progress and results • Deployments • Conclusion
OpenSense
Air Pollu6on • Air pollu6on in urban areas is a global concern – affects quality of life and health – urban popula6on is increasing
• Air pollu6on is highly loca6on-‐dependent – traffic chokepoints – urban canyons – industrial installa6ons
OpenSense
Air Pollu6on Monitoring • Precise loca6on-‐dependent and real-‐6me
informa6on on air pollu6on is needed • Officials
– environmental engineers: loca6on of pollu6on sources
– municipali6es: crea6ng incen6ves to reduce environmental footprint
– public health studies • Ci6zens
– advice for outside ac6vi6es – assessment of long-‐term exposure – pollu6on maps
OpenSense
Opportunity • Monitoring today – few sta6onary and expensive sta6ons – models that extrapolate from pollu6on sources
– data mostly inaccessible to the public • Opportuni6es – wireless communica.on: deploy larger numbers of sta6ons
– mobility: deploy mobile sta6ons – mobile devices: gather context informa6on and deploy applica6ons for ci6zens
Nabel sta6on Zürich
wireless fixed nodes mobile nodes
GPRS GPS
Nabel sta6on Zürich
OpenSense
Value of Dense Measurements • Tradi6onal approach
– Few sta6ons – Low resolu6on interpolated
es6mates of pollutant concentra6ons across massive regions
• Recent results – Massive deployment of
sta6ons (150) at street-‐level (2008/2009 New York City Community Air Quality Survey)
– Pollutants of interest heavily concentrated along roads with high traffic densi6es
OpenSense
Overview • Mo6va6on
• Research progress and results • Deployments • Conclusion
OpenSense
Research Challenge
• More data, more noise, but also more redundancy – Can we produce be<er quality data?
• Exemplary use case for other environmental phenomena – Radia6on, noise, energy
SENSING SYSTEM From many wireless, mobile, heterogeneous, unreliable raw measurements …
INFORMATION SYSTEM … to reliable, understandable and
Web-‐accessible real-‐Dme informaDon NAN
O TERA
Nabel sta6on Zürich wireless fixed nodes
mobile nodes
GPRS GPS
sensor network control opDmizaDon of data acquisiDon
informaDon disseminaDon
OpenSense
Technical Challenges • Wireless sensing devices
– energy efficiency, data transmission and compression, sensors control • Mobile sensors
– sampling under mobility, data collec6on and dissemina6on with mobile devices, freshness of data, stream data management
• Community sensing – privacy protec6on, trustworthiness of data, relevance of data gathered and
informa6on produced
• Modelling – behaviour and mobility of sensing devices è
sensor, device and mobility models – air quality informa6on from raw data è
air quality models – behaviour, interests and mobility of informa6on consumers è
privacy, trust and acDvity models
OpenSense
What is the problem? • A measurement system such
as OpenSense is a complex system – layers – dependencies – dynamicity
• Op6miza6on becomes a complex task – mul6ple op6miza6on
dimensions – many system components and
layers – feedback
• Illustra6on 1. Node decides individually
depending on its state, e.g. energy
2. Nodes communicate WSN and coordinate
3. Base sta6on schedules nodes 4. Mobility model: a third node
arrives, don’t measure! 5. Air quality model: don’t need
measurement! 6. Privacy model: node 1 should
measure! 7. Applica6on model (e.g.
health no6fica6on): no measurement needed! Two mobile nodes:
who should measure?
OpenSense
U6lity-‐based Control
Sensors: Individual state
Wireless sensor network: Local coordinaDon
Mobility model: PredicDon
Air quality model: Sampling and correlaDon
Trust and privacy model: Reliability and security
User acDvity model: Mobility and user state
ApplicaDon model: Relevance and cost
Control: translate high level u6lity to low level u6lity
Data: translate low level data to high level informa6on
OpenSense
Testbed Sensors • CO2, infrared based • CO electrochemical • NO2 electrochemical • SO2 electrochemical • O3 silicon based • Fine par6cles mechanical
Deployments • Lausanne: buses • Zürich: trams • Basel: sta6onary wireless
network
pDr1000: ultrafine par6cles (FH Nordwestschweiz)
Telaire T6613: C02 Langan T15n: CO
SHT75: air temp and humidity
Power suppliers
Sensorscope Smart Interfaces
Sensorscope DataLogger
OpenSense
Overview • Mo6va6on • Research challenges
• Deployments • Conclusion
OpenSense
Overview • Mo6va6on • Research challenges
• Deployments • Conclusion
OpenSense
Sensor Behavior Open sampling
Sensors directly exposed to environmental measurand Benefits: • simple & “slim” solu6on • con6nuous sampling Drawbacks: • no absolute concentra6on values • noisy signal Typical response:
Closed sampling
Sensors exposed to measurand inside controlled chamber Benefits: • absolute measurements • noise due to environment filtered Drawbacks: • complex & bulky • non-‐con6nuous sampling Typical response:
IDEA: Combine the two approaches and get the benefits of both.
OpenSense
On-‐the-‐Fly Calibra6on • Challenge:
– Supplied calibra6on may not match project requirements – Baseline driq due to sensor aging
• Approach: – Ini6al calibra6on using sta6onary, high quality instruments – When deployed periodic recalibra6on using mobile sensor nodes
Original calibra6on performs with an average error of
30ppb
Aqer recalibra6on the average error drops below 3ppb
OpenSense
High-‐resolu6on measurement Interpola6ng measurements of two Opensense sta6onary sta6ons • A difference of 10m from road is
considerable
Planned work • Measurements obtained along
the road network + anisotropic diffusion on lines, tuned by traffic and popula6on density (from mobile sensors)
Sta6on 1058
Sta6on 1059
OpenSense
Mobility Modeling Goal • Simulate realisDc trajectories of
vehicles Tes6ng different control strategies before deployment • What is the marginal benefit of
adding an addi6onal vehicle/line to the system
• Knowing the traffic pa<erns, is the system coverage “suitable” for regions with fluctua6ng traffic (emissions)?
• What is the effect of a traffic event on the coverage of the system?
3D view of traffic simulaDon run in front of Lausanne Train StaDon, using SimLo model (LAVOC, EPFL)
Appropriate tool: microscopic traffic simulators (SUMO, AIMSUN)
OpenSense
Route Scheduling • Given
– Area of interest Ω (Zurich) – N measurement instruments
• Each has a limited budget E – M tram and bus tracks
• Ques6ons – Which subset of tracks (and trams)
gives the best coverage of the city? – Which tram should measure over
shared track pieces? • The program is NP-‐Complete
OpenSense
Air Pollu6on Models • Forward Reasoning
– Spa6al and temporal interpola6on of pollu6on levels – Advanced warning for dangerous levels
• Backward Reasoning – Crea6ng an emission inventory – Iden6fying previously unknown sources
• Meta-‐Reasoning – Op6mal sensor placement – Sparse sampling
OpenSense
A Region-‐Based Model • Exis6ng grid-‐based models
– computa6onally expensive for fine grids
– do not dis6nguish streets • Pollu6on dispersion is not uniform
within a grid – Ground-‐level air pollu6on is heavily
influenced by streetscape and land use – A region-‐based model may be more
appropriate for OpenSense
ADMS-‐Urban, London 2010
OpenSense Mul6-‐model Query Processing in Mobile Geosensor Networks
• Approach – Middle layer produces a model
cover from a set of regression models on an area
– Con6nuous sensor updates – Con6nuous and ad-‐hoc queries
• Advantages – Handling spurious updates to the
data base – Minimizes data storage – Query results useful from
applica6on perspec6ve
Mobile Sensor Data (Pollu.on Values)
Model-‐based middle layer
Mobile Sensor Data (Pollu.on Values)
Con$nuous Moving Queries Give a (in car) pollu6on update every 30 mins Aggregate Queries
COX emi<ed yesterday in Lausanne center
DBMS (storage of raw sensor values)
OpenSense Model-‐Based Query Processing
Over Uncertain Data
what is the probability that Bob is at room 4 at $me 1?
original data stream ↓ inference of Dme-‐varying probability distribuDon (dynamic density metrics) ↓ creaDng probabilisDc views (Ω-‐View builder)
OpenSense
Model-‐based Anomaly Detec6on
original data stream ↓
approximaDon using user-‐selected models ↓
detecDng anomalies ↓
user confirmaDon: anomaly is an actual error?
OpenSense
Cloud-‐based Time Series Management
• TimeCloud: A Cloud System for Massive Time Series Management
• Key features – manages large-‐scale 6me series in the cloud – scalable, fault-‐tolerant – built upon Hadoop and Hbase – adap6ve data storage through par66on-‐and-‐
cluster – model-‐based cache for fast model-‐based
views – model-‐coding join for fast distributed join
based on bitmap representa6on of 6me series.
OpenSense
Sensor Context Extrac6on Objec6ve: Automa6cally annota6ng trajectories of different types of moving objects (cars, people)
Seman$c Annota$on Middleware
Map Matching
Hidden Markov Model
Spatial Join
region road network point of interest
e1 e3 e5 e2 e6 e4 e7 GPS
episodes
home office market home
bus metro walking Seman$c trajectory
OpenSense
User Privacy vs. Data Reliability • Mobile devices with sensing
capabili6es – ParDcipatory sensing – E.g. environmental sensing,
health-‐care monitoring, etc. • Incen6ves for par6cipa6on
– Privacy concerns • Iden6ty • Loca6on
– Trustworthiness
• Privacy protec6on mechanisms try to break the link between data and its source
• Thus, there is a clear trade-‐off between privacy and trustworthiness of data sources
Sensor, air polluDon, mobility, behavior models used to esDmate reliability of data
OpenSense
Privacy Protec6on Approach • Trust authority (e.g. telco)
knows iden6ty and trustworthiness of users
• Aggrega6on server receives trust-‐rated but privacy-‐preserving data – Anonymize data sources – Obfuscate data, loca6on-‐ or
6me-‐stamps – Hide/add events
Aggregation Server
Trust Authority
Ratings Trust
Scores
Honest and malicious measurements clearly dis6nguished
Entropy as measure for uncertainty about user data remains high
OpenSense
Overview • Mo6va6on • Research challenges • Research progress and results
• Conclusion
OpenSense
Deployment Status Basel/Sapaldia Status • Calibra6on tests performed in
2010 • Sta6onary sta6ons will be
delivered on May 18
Sapaldia study • Swiss Tropical and Public Health
Ins6tute of Basel University • Es6mate individual exposure
indoors and outdoors Sapaldia will use sta6ons for indoor air quality monitoring
OpenSense
Deployment Status Lausanne 2 prototype sta6onary sta6ons and 1 prototype mobile sta6on • Currently under tes6ng at EPFL • Mobile sta6on will be mounted on a
bus on May 23 Measured parameters • NO2, CO (2 sensors), Humidity,
Temperature, CO2 (only mobile sta6on)
Power • Solar panel (sta6onary sta6ons) • Bus power (mobile sta6on) Data • Transmission via GPRS to a central
server Sta6on 1058
Sta6on 1059
OpenSense
Deployment Status Zürich • 1 node @NABEL sta6on in Dübendorf
(for reference measurements): – Communica6on: GSM, WLAN – Sensors: 2 x O3, CO, temperature/humidity – GPS
• 1 node on top of Tram in Zürich is in prepara6on (mid. July 2011): – Communica6on: GSM, WLAN – Sensors: O3, temperature/humidity – GPS – Accelerometer
• 2 further nodes in construc6on (July)
14
OpenSense
GSM
Processor
GPS
USB-‐Hub
WLAN
Ozone-‐Sensor CO-‐Sensor
OpenSense
Calibra6on of CO Sensor @EMPA Lab
Ini6ally not calibrated
calibrated
gas bo<le empty
OpenSense
Installa6on @NABEL Dübendorf
Originally calibrated O3 sensor: correct trend, but wrong absolute value.
Calibra6on required.
OpenSense
OpenSense Visualiza6on Portal
sensordata cache
Image grid cache
Visualiza6on Server
Significant Change Condi6on
GSN
Interpola6on
OpenSense
OpenSense CrowdMap
The data from NABEL sta6ons are already integrated. It is possible to add data via SMS, Email or online Form. Based on open source plaworm.
OpenSense CrowdMap is not yet publicly available.
OpenSense
Overview • Mo6va6on • Research challenges • Research progress and results • Deployments
OpenSense
Conclusion • End-‐to-‐end system view crucial – Inves6gate all system layers: sensor – user interfaces – U6lity-‐based framework as integra6ve approach
• Results applicable beyond air pollu6on – Complex, distributed, par6cipatory measurement
• Involvement of Nokia – Personalized health applica6on
• For more informa6on: opensense.epfl.ch
OpenSense
Team • Karl Aberer, EPFL-‐LSIR, project leader
– Thanasis Papaioannou, postdoc – Dipanjan Chakraborty, (on leave from
IBM Research India), visi6ng researcher – Hoyoung Jeung, postdoc – Rammohan Narendula, PhD – Mehdi Riahi, PhD – Zhixian Yan, PhD – Sofiane Sarni, engineer – Alex Arion, PhD – Saket Sathe, PhD
• Mar6n Rajman, EPFL-‐LIA, coordinator • Boi Fal6ngs, EPFL-‐LIA, PI
– Jason Jingshi Li, postdoc • Mar6n Ve<erli, EPFL-‐LCAV, PI
– Guillermo Barrenetxea, postdoc – Andrea Ridolfi, postdoc – Heather Miller, PhD
• Alcherio Mar6noli, EPFL-‐DISAL, PI – Chris Evans, PhD – Emanuel Droz, engineer – Adrian Arfire, PhD
• Lothar Thiele, ETH Zürich, PI – Olga Saukh, postdoc – Jan Beutel, postdoc – Jayashree Ajay-‐Candadai, PhD