1. Real-Time and Reliable WSNsfor Smart Wireless Automation Applications Maurizio Bocca, M.Sc. Department of Automation and Systems Technology Aalto University School of Electrical Engineering www.wsn.tkk.fi

2. 1 WSNs Applications Maurizio Bocca - Automaatio XIX, Helsinki, 16.3.2011

3. Wireless Automation Challenges Energy efficiency: Guarantee an extended lifetime of the system Scalability: Cope with a large and varying number of nodes Reliability: Packets must arrive at destination Timeliness: Fulfill the deadlines of the monitored industrial processes 2 Maurizio Bocca - Automaatio XIX, Helsinki, 16.3.2011

4. Outline 3 TSMP-Lite Initialization RNP Protocol Device-Free Tracking Maurizio Bocca - Automaatio XIX, Helsinki, 16.3.2011

5. TSMP-Lite Initialization TSMP-Lite: Time Synchronized Mesh Protocol for WSNs applications Network initialization procedure: Neighbors discovery and connectivity graph Useful to adjust the routes in case of nodes failures Link quality evaluation and topology definition High-accuracy time synchronization For energy-efficient multi-channel time-slotted communications 4 Maurizio Bocca - Automaatio XIX, Helsinki, 16.3.2011

6. Case Study: Industrial Environment 5 Maurizio Bocca - Automaatio XIX, Helsinki, 16.3.2011

7. Case Study: Greenhouse 6 Maurizio Bocca - Automaatio XIX, Helsinki, 16.3.2011

8. Real-Time Networking Protocol Mesh networking based on nodes cooperation: Transmission in broadcast mode based on network status Packet forwarding over multiple hops by pyggybacking Redundant paths to be utilized when required Base for reliable wireless data transfer 7 Network status related information Maurizio Bocca - Automaatio XIX, Helsinki, 16.3.2011

9. RNP MAC and PHY Layers TDMA and CSMA hybrid channel access: TDMA to control delays and introduce determinism CSMA for avoiding collisions and improving coexistance with other systems Antenna diversity: Additional redundancy at the physical layer Reduces link failures and need for retransmissions Improves reliability and decreases latency 8 Maurizio Bocca - Automaatio XIX, Helsinki, 16.3.2011

10. Case Study: Industrial Environment 9 NO antenna diversity WITH antenna diversity Maurizio Bocca - Automaatio XIX, Helsinki, 16.3.2011

11. Device-Free Tracking A person crossing a LoS link between two nodes causes shadowing of the radio signal Movement in the close proximity of the nodes causes multipath fading Distributed processing of the RSSI: RSSI signals are processed locally in the nodes to detect significant changes The nodes transmit to the sink only information concerning significant events High-accuracy time synchronization 10 Maurizio Bocca - Automaatio XIX, Helsinki, 16.3.2011

12. DF Tracking Performance (1/2) Alarm notifications received from the network processed at the sink Tracking performance improved by applying a Kalman filter Experimental setup: 12 nodes covering 36 m2 Average error: 0.17 m 11 Maurizio Bocca - Automaatio XIX, Helsinki, 16.3.2011

13. DF Tracking Performance (2/2) Distributed RSSI processing reduces the communication overhead Alarm notifications account only for 7.18 % of the total number of broadcasts Through time synchronization, the radio is enabled for: TX slot: 2.30 ms RX slot: 4.05 ms Extended system lifetime 12 Maurizio Bocca - Automaatio XIX, Helsinki, 16.3.2011

14. Conclusions The use of WSNs in industrial environment brings several advantages: Possibility to deploy a high number of sensors/actuators at a reduced cost Improved screening capability Reduction of installation time and costs Ease of maintenance Industrial applications are expected to increase significantly in number over the next years 13 Maurizio Bocca - Automaatio XIX, Helsinki, 16.3.2011

15. A Look at the Future 14 “The Economist” December 2010 Maurizio Bocca - Automaatio XIX, Helsinki, 16.3.2011

16. Thank You! 15 Questions? maurizio.bocca@tkk.fi http://autsys.tkk.fi/MaurizioBocca