A Lean Approach for Evolving Heterogeneous Wireless Sensor Networks An Assisted Living Case Study Thomas Patzke Software Product Line Department Lórant Vajda, Attila Török Institute for Applied Telecommunication Technologies RCEAS 2007 Budapest, November 23

© Fraunhofer 2007 RCEAS 2007 Budapest, A Lean Approach for Evolving Heterogeneous Wireless Sensor Networks November 2007 Overview  Context & Problems  Consequences  Solution Ideas  Product Lines  Case Study  Lessons Learnt

© Fraunhofer 2007 RCEAS 2007 Budapest, A Lean Approach for Evolving Heterogeneous Wireless Sensor Networks November 2007 Context & Problems  Bilateral German-Hungarian Collaboration Project on Ambient Intelligence Systems ( )  Subproject: Ambient Assisted Living  Application problem: Supporting elderly people with AmI technology to live longer in their own home  Engineering problems: building and evolving („maintaining“) high-quality AmI systems in a cost-effective way

© Fraunhofer 2007 RCEAS 2007 Budapest, A Lean Approach for Evolving Heterogeneous Wireless Sensor Networks November 2007 Consequences  Evolution aspects: Space -heterogeneous systems Time -system extension or contraction  Quality & cost aspects: At runtime -Functionality, efficiency (little resources!), safety During construction -Minimal construction & evolution effort -Rapid response to changes

© Fraunhofer 2007 RCEAS 2007 Budapest, A Lean Approach for Evolving Heterogeneous Wireless Sensor Networks November 2007 Solution Ideas  Reuse: WSN systems as a product line (HW & SW) benefit from their similarities across the entire system engineering life-cycle -requirements, analysis, design, implementation  Simplicity by feature prioritization by removing arbitrary complexities goal: simple-enough systems  Vision: Self-generating autonomous systems

© Fraunhofer 2007 RCEAS 2007 Budapest, A Lean Approach for Evolving Heterogeneous Wireless Sensor Networks November 2007 Large-Scale-Reuse Approach: Product Lines  A (software) PL is a set of (SW) products that are developed and evolved together Product 1 Product 2 Product 3 Single systems Product line  Important PL concepts Commonality - what PL members have in common Variability - where PL members differ Variation points - where the variation occurs Defaults - what most (but not all) PL members share

© Fraunhofer 2007 RCEAS 2007 Budapest, A Lean Approach for Evolving Heterogeneous Wireless Sensor Networks November 2007 WSNs as a Product Line – The Feature Model WSN Sensor Nodes SendReceive Legend: Mandatory feature Optional feature Broadcast Unicast SenseActuate Adapter Nodes Sink Nodes

© Fraunhofer 2007 RCEAS 2007 Budapest, A Lean Approach for Evolving Heterogeneous Wireless Sensor Networks November 2007 Case Study – Heterogeneous Technologies  MicaZ and Particle Computer  Domain analysis results: similar kinds of sensors (acceleration, light, temperature, sound) similar transmission modality (send & receive, wirelessly) but: different communication modes (pull vs. push) different node programming language (nesC vs. C) same sink programming language (Java)

© Fraunhofer 2007 RCEAS 2007 Budapest, A Lean Approach for Evolving Heterogeneous Wireless Sensor Networks November 2007 Case Study – Integration  Experiment: Combine the „technology clusters“ in all different send/receive combinations, and in gathering redundant data  Possibilities: Direct hardware connection -combinatory explosion of connections Common adapter/gateway -localizes exchange -chosen because of simplest integration  Integration of Push (Event) & Pull (Poll) Approach

© Fraunhofer 2007 RCEAS 2007 Budapest, A Lean Approach for Evolving Heterogeneous Wireless Sensor Networks November 2007 Lessons Learnt  Even using the same programming language (Java) does not warrant seamless integration (version differences!)  Text (as opposed to binary data) is a simple, valuable format for distributing aggregated sensor data facilitates development and evolution -avoids data size & endianness problems -is human-readable promotes common metadata formats (CSV,…) -easily reusable across technology clusters  It is not wise to focus on efficiency first

© Fraunhofer 2007 RCEAS 2007 Budapest, A Lean Approach for Evolving Heterogeneous Wireless Sensor Networks November 2007 Further Information  BelAmI project  Product Lines  Institute for Applied Telecommunication Technologies