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Collaborative Sensing over Smart Sensors
Vassileios Tsetsos, Nikolaos Silvestros & Stathes Hadjiefthymiades
Pervasive Computing Research GroupDept of Informatics and Telecommunications
National and Kapodistrian University of Athens
October 2009 @ 2nd Student Workshop on Wireless Sensor Networks
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IPAC Platform Integrated Platform for Autonomic Computing
(EU FP7) Middleware, service execution and creation
environment Collaborative sensing, plug short range
communications Probabilistic broadcasting and epidemic
information dissemination Applications/Trials:
Autonomic networked objects in industryIntelligent TransportationCrisis Situations / Peace Keeping Military Operations
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Introduction & Motivation Nomadic computing
Embedded devices with limited resourcesFrequent node relocation / ad hoc communicationsBroadcast-based data disseminationContext-aware applications
Real-world problems: Not all nodes have sensorsEach node’s sensors are of different technology
and not interoperable (at all levels)
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Proposed Solutions (in brief) Collaborative Sensing
Nodes exchange sensor information (on demand)…
…in an efficient way Smart Sensors
Sensors that adopt standard interfaces are used
Sensor plug ‘n’ play is supported○ Plug in new sensors of the same or different
platform (Sun SPOT, Xbow Mica2, …)
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Collaborative Sensing
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Context Modeling
EnvironmentalSituation User Situation
InsideBuilding Happy
Situation
is-a
Fire
Action Rules: Fire BroadcastAlert (100)
Situation Classification Rules (SCR): Temperature>80 ^ Humidity<10 Fire (100, 10)
Spatial Validity
EnvironmentalContext
Temperature
User Context
Location Mood
Context
is-a
Temporal Validity
Declarative context description
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Overall Architecture
Context-aware Nomadic Applications
Short Range Communications
Context Foraging
Context Modeling & Reasoning
Node ArchitectureS
enso
rs
CR
CRel
CP
CR: Context RequestorCP: Context ProviderCRel: Context Relay
CRel
CP
Nodes are moving in random trajectories Nodes have location sensors Short range communications: WiFi, WiseMac, DSRC,
IEEE 1609 WAVE, ZigBee Not all nodes have sensors Nodes are willing to cooperate
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Context Request Formation & Dissemination
CR
CRel
CP
CRelCP
SVCReq = 100
Temperature>80 ^ Humidity<10 Fire (100, 10)
Spatial ValidityTemporal Validity
Local condition Remote condition
Humidity<10 (100, 10)CReq:
SCR:
CReq is retransmitted every 10 time unitsand within a range of 100 space units
1
1
2
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Context Providers Nodes with sensors They have an index structure that is used:
as a registry of all event filters received through context requests,
as a mechanism that matches incoming sensor values with event filters (context request conditions)
Index resembles a message forwarding engine of content-based network routers
Context Response CRes := vali = V Spatial validity: equal to the request’s value
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Context Providers’ Index
1. Context Request(Event filters)
2. Sensor value
3. Context Response
Humidity = 7
Humidity = 7
Humidity < 10
The responses are aggregated
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Performance Results
0
100000
200000
300000
400000
500000
600000
700000
0 1 2 4 10 20max speed
#Msg
CFor10 CFor5 CPol1 CPol2
0.00
0.20
0.40
0.60
0.80
1.00
0 1 2 4 10 20max speed
AS
DR
CFor10 CFor5 CPol1 CPol2
# of CR 40
# of CP 40
Comparison with a polling scheme (CPol)
# of nodes 100
Mobility model
Random waypoint
# of SCR per CR
2
SV of SCRs 110
Comm. range 50
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The IEEE 1451 Standards
A Family of standards that define all aspects of smart transducers (sensors, actuators)
The only available standard …but still evolving
Specifies:Transducer Electronic DataSheets (TEDS)Hardware/Software interfacesCommands, Messages, States, …
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A IEEE 1451 smart sensor
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Smart Sensors in IPAC
TCPHTTP
IPAC HW
OS
IPAC MW
SEC Proxy
TIMIPAC APPLICATION
IPAC node
USB
NCAP
Sun SPOTJava Virtual Machine
IEEE 1451.2
IEEE 1451.0
IEEE 1451.2
IEEE 1451.0
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Conclusions & Future Work IPAC adopts a novel and pragmatic
approach to context-aware computing Many applications can benefit: VANETs
and ITS, Crisis Management, … Interoperability at the sensor level is still
a challenge Hardware implementations of IEEE
1451 are required…any volunteers?!