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MotivationScopes in WSN

Conclusion and Perspectives

Scoping in Wireless Sensor NetworksA Position Paper

Jan Steffan, Ludger Fiege, Mariano Cilia,Alejandro Buchmann

Department of Computer ScienceDarmstadt University of Technology

2nd Workshop on Middleware for Pervasive

and Ad-Hoc Computing 2004

Steffan, Fiege, Cilia, Buchmann Scoping in Wireless Sensor Networks
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Outline

1 Motivation

Introduction

Motivating Example

Problem Statement

2 Scopes in WSN

Making Scoping Explicit

Architecture Overview

3 Conclusion and PerspectivesFurther Possibilities

Summary

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IntroductionMotivating ExampleProblem Statement

Wireless Sensor Networks: Common Assumptions

sink

Hardware:

1000s of inexpensive sensor nodes

Sensors: temperature, humidity, . . .

nodes have short range radio interfaces

Goal:nodes form multi-hop ad-hoc network

sink node(s) collects selected sensor data

resilience to node and link failures

Challenges:nodes have limited capabilities

(C, few kB of RAM and ROM)

battery power is scarce

ad-hoc and distributedSteffan, Fiege, Cilia, Buchmann Scoping in Wireless Sensor Networks
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Distinction from other Networks

Common Networks: Internet, Overlay networks,. . .

Nodes have unique IDs (e.g. IP addresses)

Nodes are addressed by unicast or

Nodes join multicast groups

Sensor Networks: Nodes are selected based on:

Collected data (type, accuracy, . . . )

Context (location, distance, density, . . . )

Capabilities and resources (sensor type,

battery level, . . . )

Scope

We call a group of nodes selected by a rule scope.

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Current WSN Software Development and Architecture

Software Development:

Optimized custom solutions based on low level

hardware or software interfaces

Trend: Generic high level interfaces

(declarative query languages)Architecture:

Tight integration of query processing, data collection,

aggregation, routing, medium access

No modularizationScoping is implicit

Usually only one type of scoping supported

Integration of new scope types is not provided for.


M i i I d i
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Example Scenario: Freight Container Monitoring

Sensors inside containers:

temperaturehumidity

door alarm. . .

Containers form ad-hoc network

Data Sinks at harbour, ship, fork lifters, . . .


M ti ti I t d ti
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Different Scopes for each Application

measure temperature

in containers in top row or facing south

measure temperaturein containers with dangerous goods

detect tampering

at doors of accessible containers

request inventory

of one owners containers

measure humidity

in containers with low temperature


Motivation Introduction
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measure temperature


measure temperature

in containers with dangerous goods

detect tampering


request inventory


measure humidity



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measure temperature


measure temperature


detect tampering


request inventory


measure humidity



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measure temperature


measure temperature


detect tampering


request inventory


measure humidity



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measure temperature


measure temperature


detect tampering


request inventory


measure humidity



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Scopes in WSNConclusion and Perspectives

Motivating ExampleProblem Statement

Multipurpose WSN Infrastructure

Requirements:Multiple concurrent applications

Different, maybe evolving requirements

Shared, heterogeneous infrastructure

Efficient, cost effective and future-proof

Our Approach:

Scopes as a means of customizing and

modularizing WSN functionalitySupport multiple scope types simultaneously

Enable the adaption and addition of scope types

Keep high level query interfaces


MotivationMaking Scoping Explicit
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Making Scoping ExplicitArchitecture Overview


Why scopes?

Scoping is one of the fundamental building blocks of WSNs

Implicit part of many WSN applications and algorithms

Scoping is orthogonal to data collection and processing

Factoring out scoping allows for:

Cleaner design

Efficient use of resourcesEfficient implementation of individual scope types




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Scope Representation

Scope creation requires only a few parameters:

Scope

Ascope consists of

Unique Scope-IDScope-type (determining selection of algorithms)

Scope-type dependent membership-condition

(e.g. geographic region, sensor type)

Optional:Scope life-time

optional annotations specifying communication semantics


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Integrating Scopes with WSN

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Networking, Neighbor Management, Localization, . . .

Application 1 Application 2Applications

Low-level Services


MotivationS i WSN

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Low-level Services

Membership policies

Nodefeature

Geographical

Networktopology

Implementation

modules


MotivationS i WSN

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g p g pArchitecture Overview


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Low-level Services

Membership policies

Nodefeature

Geographical

Networktopology

Implementation

modules

Scope ADescriptive Scopes

Instantiationof scopes



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g p g pArchitecture Overview


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Low-level Services

Membership policies

Nodefeature

Geographical

Networktopology

Implementation

modules

Scope ADescriptive Scopes

Instantiationof scopes

Scope B



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Examples of two Deployed Scopes

Forwarding

Member





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Application logic

Scopetype

Networking Output Queue

Medium Access

Implementations ID ...Forwarder?Member or



Making Scoping ExplicitA hi O i


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Scope Deployment and Maintenance

Deployment: Creating a new scope

Find scope member nodes according to rule

Establish routing paths between member

nodesMaintenance: Keep the scope functional

Handle node and network failures

Maintain connectivity

Scope-membership updates due to dynamic

conditions or mobility

We can use existing specialized algorithms for each scope-type.



Further PossibilitiesS
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pConclusion and Perspectives

Summary

Binding Communication Semantics to Scopes

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Low-level Services

of scopesInstantiation

modules

Implementation

Descriptive Scopes Scope A Scope B

Nodefeature

Geographical

Networktopology

Membership policies



Further PossibilitiesSummary


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pConclusion and Perspectives

Summary

Binding Communication Semantics to Scopes

.

.

.

.

.

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Low-level Services

of scopesInstantiation

modules

Implementation

Descriptive Scopes Scope A Scope B

Nodefeature

Geographical

Networktopology

Membership policies Communication policies

Security

Priority

Visibility



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Conclusion and PerspectivesSummary

Security: Restricting Visibility of Sensor Data

So far we have discussed:

Scopes as a means of restricting the visibility of

queries/subscriptions

Selecting a tight set of data sources

In order to enforce security policies we can:

Restrict the visibility of sensor data to scope members

Only selected sinks may see sensitive data

Only trusted nodes may act as forwarding nodesAny complex policy scheme can be implemented as special

scope type



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Summary

Addressing groups of nodes (scopes) is

a fundamental building block of WSN applications.

Applications and algorithms need

very distinct node selection rules.

Factoring out scoping leads to simplified andcleaner application development.

Concurrent scopes enable extensible

multipurpose sensor networks.

Scopes are useful beyond data source selection:e.g. selecting alternative communication semantics,

enforcing security policies, distributing keys,

deploying application components



C l i d P i

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Questions?

?Jan Steffan

http://localhost/var/www/apps/conversion/tmp/scratch_1/[email protected]://localhost/var/www/apps/conversion/tmp/scratch_1/[email protected]://find/

wsns in harbour -mpac23-steffan

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