Tarun Banka Department of Computer Science Colorado State University

1. PSFQ: A Reliable Transport Protocol for Wireless Sensor Networks Chieh-Yih Wan, Andrew T. Campbell, Lakshman Krishnamurthy Tarun Banka Department of Computer Science Colorado State University

2. Motivation ? • Most Sensor Network applications don’t need reliable transport • New applications like re-tasking of sensors need reliable transport • Current sensor networks are application specific and optimized for that only • Future Sensor networks may be general purpose to some extent – ability to reprogram the functionality

3. Probability of successful delivery using End to End Model 1 (1-p) 2 n-1 (1-p)n-1 n (1-p)n p is the error rate of wireless link between two hops

4. Goals of PSFQ: Pump Slowly and Fetch Quickly • Recover from losses locally • Minimum signaling involved for Loss Detection and Recovery • To operate correctly in high error prone environment • Independent of the underlying routing infrastructure

5. 1 2 3 4 1 1 1 2 2 2 3 3 3 Multi-Hop Packet Forwarding When No Link Loss – Multi-Hop Forwarding takes place

6. 1 3 4 2 1 1 1 2 lost 3 3 Recover 2 3 Recover 2 Recover 2 Recovering from Errors Error Recovery Control Messages are wasted

7. 1 3 4 2 1 1 2 2 lost 1 3 Recover 2 2 2 2 3 3 How PSFQ Recovers from Errors“Store and Forward” No wastage of the Error Recovery control messages

8. 1 2 1 t Tmin 1 Tmax Tmin 1 Tmax PSFQ Pump Schedule If not duplicate and in-order and TTL not 0 Cache and Schedule for Forwarding at time t (Tmin<t<Tmax)

9. 1 2 1 1 2 2 lost 3 Tr Tr Recover 2 2 Tmin 2 Tmax “Fetch Quickly” Operation

10. 1 2 last-1 last Tproc last “Proactive Fetch”

11. Performance Evaluation • Compare with SRM (Scalable Reliable Multicast) • Performance Metrics • Average Delivery Ratio • Average Latency • Average Delivery Overhead

12. Experimental Setup 2 Mbps CSMA/CA Channel Access Tmax = 100ms Tmin = 50ms Tr = 20ms

13. Error Tolerance

14. Average Latency

15. Communication Cost for Reliability

16. Conclusion - PSFQ • Light weight and Energy efficient • Simple mechanism • Scalable and robust • Need to be tested for high bandwidth applications • Cache size limitation

17. CODA: Congestion Detection and Avoidance in Sensor Networks Chieh-Yih Wan, Shane B. Eisenman, Andrew T. Campbell Tarun Banka Department of Computer Science Colorado State University

18. What is CODA ? • Energy efficient congestion control scheme • Three mechanisms are involved • Congestion Detection • Open-loop hop-by-hop backpressure • Closed-loop multi-source regulation

19. Congestion Detection • Accurate and efficient congestion detection is important • Buffer queue length or Buffer occupancy – not a good measure of the congestion. • Channel loading – sample channel at appropriate time to detect congestion. • Report rate/Fidelity measurement – slow, observed over a longer period

20. 1 3 2 4 Congestion detected 5 6 Open-Loop Hop-by-Hop Backpressure

21. 1 2 Regulate bit is set 1,2,3 ACK 4,5,6 Congestion detected 7,8 ACK Closed Loop Multi-Source Regulation

22. CODA Performance – Cost Metrics • Average Energy Tax = Total Packets dropped in sensor NW / Total Packets received at Sink • Average Fidelity Penalty = Measures difference between average number of packets delivered at a sink using CODA and using ideal congestion scheme

23. Simulation Setup • Random Network Topologies with network size from 30 to 120 nodes • 2Mbps IEEE 802.11 MAC (RTS/CTS are disabled) • Directed Diffusion is used as routing core • Fixed Work load, 6 Sources and 3 Sinks • Source generate data at different rates. • Event Packet is 64 bytes and an interest packet is 36 bytes

24. Simulation Results(Case 1: Dense Source , High Rate)

25. Simulation Results(Case 2: Sparse Sources, Low Rate)

26. Simulation ResultsCase 2: Sparse Source, Low Rate

27. Simulation Results (Case 3: Sparse Sources, High Rate) Network Size (#no of nodes)

28. Conclusion • CODA is a energy efficient protocol • Can deal with Persistent and Transient Hotspots

29. Thank youQuestions!