1. A Lean Approach for Evolving Heterogeneous Wireless Sensor Networks An Assisted Living Case Study Thomas Patzke thomas.patzke@iese.fraunhofer.de Software Product Line Department Lórant Vajda, Attila Török {vajda,torok}@ikti.hu Institute for Applied Telecommunication Technologies RCEAS 2007 Budapest, November 23

2. © 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

3. © 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 (2005-08)  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

4. © 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

5. © 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

6. © 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 1 2 3 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

7. © 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

8. © 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)

9. © 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

10. © 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

11. © Fraunhofer 2007 RCEAS 2007 Budapest, A Lean Approach for Evolving Heterogeneous Wireless Sensor Networks November 2007 Further Information  BelAmI project www.belami-project.org  Product Lines www.iese.fhg.de/fhg/iese/research/development/pla www.softwareproductlines.com  Institute for Applied Telecommunication Technologies www.ikti.hu