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

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

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)

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, …)

Collaborative Sensing

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

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

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

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

Context Providers’ Index

1. Context Request(Event filters)

2. Sensor value

3. Context Response

Humidity = 7

Humidity = 7

Humidity < 10

The responses are aggregated

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

Smart Sensors

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, …

A IEEE 1451 smart sensor

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

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?!