1. QoS-Assured In-Network Processing in Wireless Cyber-Physical Systems: A Survey Qiao Xiang Advisor: Hongwei Zhang

2. Outlines Introduction In-Network Processing Methods QoS-Assured INP in WCPS Open Issues Conclusion

3. Outlines Introduction In-Network Processing Methods QoS-Assured INP in WCPS Open Issues Conclusion

4. Introduction Wireless Sensor Networks: Highly Resource- (Energy-) and Environment- Constrained In-Network Processing: Reduce Traffic Flow → Resource (Energy) Efficient Category: Application IndependentApplication Dependent Data Aggregation Packet Packing Network Coding Data Fusion Query Processing

5. From WSN to WCPS Wireless Cyber-Physical Systems: Close-Loop vs. Open-Loop INP in WCPS: More emphasis on Quality of Service e.g., latency and reliability

6. Outlines Introduction In-Network Processing Methods QoS-Assured INP in WCPS Open Issues Conclusion

7. In-Network Processing Methods Data Aggregation Packet Packing Network Coding Data Fusion Query Processing

8. Data Aggregation Aggregate/Compress Correlated Data Most common INP mechanism Different Design Goals: Energy Efficiency Collision Reduction Scalability Network Lifetime

9. Data Aggregation Current Research: How to build efficient aggregation structure Representative approaches: Chain structure Cluster structure Tree structure Structure free

10. Packet Packing Assemble small packets into larger ones (No aggregation) Data correlation is not important Current Research: Schedule small packets to transmit or wait. Approaches: Opportunistic, Pre-defined waiting time Greedy Drawbacks : No hard latency guarantee

11. Network Coding Make use of the broadcast nature of wireless communication Main Goal: improve throughput Current Research: Cooperation of random linear network coding and routing

12. Network Coding Inter-flow coding: COPE Only packets with different destinations can be coded together Intra-flow coding: MORE, Pacifier Only packets with the same destination get coded together Hybrid coding: First do inter-flow coding, then do intra-flow coding

13. Examples of Inter and Intra Flow Coding

14. Data Fusion Main Goal: Assure data accuracy More complex than aggregation/compression Data is processed by sensors before the transmission Data can be further processed at intermediate sensors during the transmission Sensors’ roles are more flexible. Representative works: DFuse

15. Query Processing Main Goal: Data Accuracy and energy efficient Data is only collected when there is a query request. Requests are optimized before being sent to sensors. Depending on different query requests, data is processed during the transmission. Not every sensor need to response to a query request. Representative works: TAG, CAG, TinyDB

16. Outlines Introduction In-Network Processing Methods QoS-Assured INP in WCPS Open Issues Conclusion

17. QoS-Assured INP in WCPS Mission-Critical Real-Time WCPS Latency-Guaranteed INP Reliability-Guaranteed INP

18. Latency-Guaranteed INP Data Aggregation: Only Soft-Latency guarantee is provided End-to-End LatencyOne-hop Latency Feedback controlDefine rewards function Evenly divide the spare timeSemi-Markov chain Define new metric

19. Latency-Guaranteed INP Packet Packing Only Soft-Latency guarantee is provided End-to-End LatencyOne-hop Latency Grouping packetsPre-defined packet size Opportunistic Feedback control

20. Latency-Guaranteed INP Network Coding Network Coding can improve average end-to-end delay Individual delay of each packet is still an unexplored area Data Fusion Latency constraints can be achieved by adjusting network density

21. Reliability-Guaranteed INP Data Aggregation, Data Fusion, and Query Processing Traffic load reduced → Collision and Interferences reduced → Reliability is assured Packet Packing Packet size is controlled to ensure the reliability Network Coding Similar to packet packing, coding degree can be controlled to ensure the reliability

22. Outlines Introduction In-Network Processing Methods QoS-Assured INP in WCPS Open Issues Conclusion

23. Open Issues Systematic Modeling and Complexity Analysis Joint Optimization of QoS and WCPS-specific INP Cooperation of Different INP Methods in WCPS Theoretical Foundations of Algorithm

24. Outlines Introduction In-Network Processing Methods QoS-Assured INP in WCPS Open Issues Conclusion