Wireless Sensor Network Health Diagnostic

1. Wireless Sensor Network Health Diagnostic David Rogers, Stu Andrzejewski, Kelly Desmond, Brad Garrod

2. Sensors outnumber people

3. But how do we know they are working correctly? • Receiving correct data • Communicating across network nodes accurately • Proper operation EKG graphs

4. How can a sensor fail? Insufficient Node Power Environmental Factors Malicious Nodes

5. Implications of Sensor Failure • Can destroy… • Health/Lives • Air Pollution • Equipment • Automobile • Environment • Forest Fire Overall failing sensors can lead to millions of dollars in damage!

6. Steps for solving the problem • Configure a sensor network • Collect metrics about the network • Create human/network interface • Analyze correlations between metrics and node failure • Validate metrics and test for accuracy

7. Steps for solving the problem • Configure a sensor network • Define network topology • Identify vital components of sensor hardware • Select sensor network hardware • Collect metrics about the network • Create human/network interface • Analyze correlations between metrics and node failure • Validate metrics for accuracy

8. 1A. Network topology • Advantages • Better performance • Benefits from centralization • Isolation of nodes • Simple • Disadvantages • Centralization dependency • Expensive • Central hub failure = network failure • Advantages • Self- healing • Less traffic load • Isolation of node faults • Disadvantages • Complexity • Installation • Price • Mesh Topology • Nodes communicate directly to other nodes without the need of a cluster head • Star Topology • Cluster head controls data communication between nodes

9. 1B. Criteria for sensor nodes • What kinds of information from the sensor would be useful to understand how well they are functioning? • Battery life • Current draw • RF transmission power • Received signal strength • Processor load • Memory utilization

10. 1C. Proposed Sensor Network Kits • Powercast P2110-EVAL • Features • Low-power • Battery-free (RF Power) • Pre-loaded, custom firmware • Temperature, Humidity, and Light Sensors • External Sensor Port • RSSI Calculation • USB interface for power and data • SunSPOT • Features • Embedded Development Platform • Extremely flexible hardware and software package • Easy to program - Java top to bottom • Connected – Wireless Communication • Mobile & Secure • Built in Lithium Ion battery charged through USB • Able to sense and affect surroundings • Built-in high grade ECC public key cryptography

11. Steps for solving the problem • Configure a sensor network • Collect metrics about the network • What to monitor? • Create human/network interface • Analyze correlations between metrics and node failure • Validate metrics for accuracy

12. 2A. What to monitor? • Internal • Current Draw • Battery Life • Voltage Reported • RF Transmission • Received Signal Strength • Channel Availability • Processor Load • Memory Utilization (RAM) • External • Humidity • Temperature • Light • Sound • Motion • Pressure • Vibration • Electrical Fields

13. Steps for solving the problem • Configure a sensor network • Collect metrics about the network • Create human/network interface • Identify ideal communication protocol • Create graphical user interface • Analyze correlations between metrics and node failure • Validate metrics for accuracy

14. 3A. Identify proper communication protocols • Must be able to communicate with sensors remotely • IEEE 802.15.4 • Includes ZigBee, Bluetooth, Wifi • Uses CSMA/CA for secure communications • Nodes only transmit when the channel is idle • Devices also include power management functions such as link quality and energy detection.

15. 3B. Create graphical user interface • Create user-friendly display • Handles all incoming data packets from sensor nodes behind the scenes • The data will be displayed in a way for easy evaluation of the sensor data stream and network health • Alerts the operator when failures have occurred or are occurring

16. Steps for solving the problem • Configure a sensor network • Collect metrics about the network • Create human/network interface • Analyze correlations between metrics and node failure • Validate metrics for accuracy

17. 4. Analyze correlations between metrics and node failure • Determine the most important metrics that identify node failure • Algorithms for detecting malfunctioning nodes • Majority Voting • Thresholding • Weighted average • Understanding associations between multiple metrics • Attempting to measure current draw while the sensor is transmitting back to the cluster head

18. Steps for solving the problem • Configure a sensor network • Collect metrics about the network • Create human/network interface • Analyze correlations between metrics and node failure • Validate metrics for accuracy

19. 5. Validate metrics for accuracy • Design a test plan to ensure a high quality health diagnostic • Series of controlled experiments • Statistically validate chosen algorithms • Reduce false positives and false negatives

20. Conclusion • Monitoring sensor health is vital for proper function of a wireless sensor network • Many external and internal factors attribute to sensor node failure • By designing algorithms and a test plan to systematically validate failures, important metrics relating to the health of a wireless sensor network can be determined