Review: Analysis of Wireless Sensor

Networks for Habitat MonitoringPolastre, Szewczyk, Mainwaring, Culler

Review by Nate Ota

CS294

8/28/03

The Application: Great Duck Island

• Motivation: use a habitat monitoring application to deploy a long term network

• Problem– Human interaction impact w/ environment– Node interaction impact w/ environment

• “shadowing effect”

– Cost of equipment and personnel

• Approach– Use tiered architecture sensor network to address

problems and make data available locally and remotely (sensor patch, gateway, base station)

The Application: Great Duck Island

Dimension Spatial Temporal

scale - sampling cubic meter (size of burrow) seconds (70) and duration of events

scale - extent 10's (43) constant

scale - density sparsely located dense patches (<= 50 patches) 1 node: 1 burrow constant

variability - structure none  none

variability - task none low

variability - space none none

autonomy - modalities light, thermistor, humidity, thermopile subset of spatial

autonomy - complexity low - sends data to DB low

Packet Loss

• Expected 4.8M, Actual 1.1M readings• Pattern of packet loss despite expected CSMA

correction • Sources

– Packet collisions• Clock skew and capture effect• Not major source of loss• Use signal strength meter to avoid false “pkts”

– Environmental Conditions• Failed temp correlated to failed humidity sensors• High humidity correlated with significant voltage drop

– Battery state • Drain due to moisture, but not a cause of node failure• Related to high moisture

Power Management

• Only 5 nodes exhaust battery

• Non-graceful degradation– Battery not meant periodic use

Last Points

• Failure– Abnormally high moisture– Clock skew– Exposure to wildlife

• Battery matching to application

• Sensor readings can be used to predict node failure

Before the slaughter…

• Anyone need a partner for the assignment