Wireless Sensor Network Health

DiagnosticDavid Rogers, Stu Andrzejewski,

Kelly Desmond, Brad Garrod

Sensors outnumber people

Receiving correct data Communicating across network nodes

accurately Proper operation

But how do we know they are working correctly?

EKG graphs

How can a sensor fail?

Malicious Nodes

Environmental FactorsInsufficient Node Power

Can destroy…◦ Health/Lives

Air Pollution◦ Equipment

Automobile◦ Environment

Forest Fire

Implications of Sensor Failure

Overall failing sensors can lead to millions of dollars in damage!

1. Configure a sensor network2. Collect metrics about the network3. Create human/network interface 4. Analyze correlations between metrics and

node failure5. Validate metrics and test for accuracy

Steps for solving the problem

1. Configure a sensor networkA. Define network topologyB. Identify vital components of sensor

hardwareC. Select sensor network hardware

2. Collect metrics about the network3. Create human/network interface 4. Analyze correlations between metrics and

node failure5. Validate metrics for accuracy

Steps for solving the problem

Mesh Topology

◦ Nodes communicate directly to other nodes without the need of a cluster head

1A. Network topology Star Topology

◦ Cluster head controls data communication between nodes

• 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

What kinds of information from the sensor would be useful to understand how well they are functioning?

1B. Criteria for sensor nodes

◦ Battery life◦ Current draw◦ RF transmission power◦ Received signal strength◦ Processor load◦ Memory utilization

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

1. Configure a sensor network2. Collect metrics about the network

A. What to monitor?

3. Create human/network interface 4. Analyze correlations between metrics and

node failure5. Validate metrics for accuracy

Steps for solving the problem

2A. What to monitor?

External◦ Humidity◦ Temperature◦ Light◦ Sound◦ Motion◦ Pressure◦ Vibration◦ Electrical Fields

Internal◦ Current Draw◦ Battery Life◦ Voltage Reported◦ RF Transmission◦ Received Signal

Strength◦ Channel Availability◦ Processor Load◦ Memory Utilization

(RAM)

1. Configure a sensor network2. Collect metrics about the network3. Create human/network interface

A. Identify ideal communication protocolB. Create graphical user interface

4. Analyze correlations between metrics and node failure

5. Validate metrics for accuracy

Steps for solving the problem

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.

3A. Identify proper communication protocols

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

3B. Create graphical user interface

1. Configure a sensor network2. Collect metrics about the network3. Create human/network interface 4. Analyze correlations between metrics

and node failure5. Validate metrics for accuracy

Steps for solving the problem

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

4. Analyze correlations between metrics and node failure

1. Configure a sensor network2. Collect metrics about the network3. Create human/network interface 4. Analyze correlations between metrics and

node failure5. Validate metrics for accuracy

Steps for solving the problem

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

5. Validate metrics for accuracy

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

Conclusion