modelling and handling seams in wide-area sensor networks...newman, schall, schmalstieg universities...

Modelling and Handling Seams in Wide-AreaSensor Networks

Joseph Newman12 Gerhard Schall2 Dieter Schmalstieg2

1Computer LaboratoryUniversity of Cambridge

2Insitute for Computer Graphics and VisionTechnical University of Graz

Thursday Oct 12th, 2006

Newman, Schall, Schmalstieg Universities of Cambridge and Graz

Modelling and Handling Seams in Wide-Area Sensor Networks

Introduction

Disciplines of Wearable Computing, Augmented Reality andUbiquitous Computing highly inter-related

Barriers to cross-fertilisation and collaboration

cultural, financial and technical

Technological choices introduce assumptions later reflected indesign patterns

Propose design patterns that match technical constraints, notconstrained by semi-arbitrary technological choices.

We are going to buy tracker X and display Y in order to do ZCould we do A, B, . . . ?Could we cooperate/interoperate with F, G, . . . ?



Comparison of Sensor Characteristics

VR AR UbicompUpdate rate 15 — 500 Hz ∼1 Hz

Latency < 30 ms ∼1 s

Cost Expensive Cheap

Working volume Small (< 5m3) Large

Granularity Fine Coarse

Quantity Scarce Abundant



Tracking versus Location

VR AR UbicompTracking X X 7

Location 7 X X



Event Bandwidth

Event Description BandwidthTracker Pose At timestamp T, locatable A has

pose P measured by tracker B.High15 – 50 Hz

Tracker Scope Locatable A is either being tracked by tracker B, or is no longer tracked by tracker B

Medium1 – 0.1 Hz

Data Flow Reconfiguration

The flow of data from trackers to clients is reconfigured.

Low0.2 – 0.01 Hz

Measurement Measurement of an environmen-tal property, e.g. points C and D,are separated by distance d.

Very low < 0.01 Hz



Design Patterns

AR/VR applications run as sessions

few participants and tracked implements usually defined a priorilow latency & high throughput

Ubicomp applications run as services 24/7 focussing onscalability and stability

Network protocols: various TCP/IP or multicast, e.g. VRPN

Federated data model: Nexus, QoSDream, SPIRIT, otherproprietary middlwares

Dwarf expresses needs and abilities of clients and services aspredicates, which are then matched in a distributed fashion

Pipes-and-filter: OpenTracker — sources, sinks and filters



Ubitquitous Tracking Architecture

sensor S1

UbitrackServerSpatialRelationshipGraph Server

ClientTier Client #1

Query/Response(OT configuration)

sensor S0

Client #n

sensor SN

Query/Response(spatial search)

Query/Response(OT configuration)



Example Deployment

VAIO U70

UbitrackServer

UTS

SpatialRelationshipGraphServer SRGS

sources

sinks

Desktop

sources

sinksfilters

OpenTracker

sources

sinks

filters

OpenTracker

Network source/sink

StbSink

Tracking sources: ARToolkitSource,InertiaCube3, UbiSource

Ubitrack sink



Usage Case

(a) Mobile platform (b) Mobile user



Client visualisation

(c) World-in-miniature (d) Omniscient observer



Conclusions

Develop design patterns that exploit inter-disciplinary natureof our fields

Not advocating pointless integration exercises

Proposed design pattern meeting needs of AR/Ubicompinterface

Queries expressed by clients

continuously reviewedbest effort

Ubicomp, AR and legacy apps can be better integrated



Acknowledgements

People:

Gerhard Schall

Dieter Schmalstieg

Robert Harle

Projects:

Austrian Science Fund FWF

PRESENCCIA Integrated Project



Questions?



modelling and handling seams in wide-area sensor networks...newman, schall, schmalstieg universities...

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