SLIDE 2 2 Phase III: Localization
Walking GPS
Installer wears GPS device Motes infer position based on beacons sent out by
wearable GPS device
VigilNet created prototype system Accurate up to 0.8 +/- 0.5 meters, studied to be
sufficient for routing, sensing, and tracking
Phase IV: Asymmetric Detection
Asymmetric links – Different reception rates along
different directions between same pair of motes
Link Symmetry Detection
Designed to reduce irregularity for upper network layers Local Beaconing
- Each node has an ID
- Beaconing node adds all discovered neighbors to beacon
- When node receives beacon, it adds the node to its list
- Checks to see whether its own ID is on the list, if so this is a
symmetric link, otherwise asymmetric
Phase V: Backbone Creation
Diffusion Tree
Time synchronization messages used to distribute
information needed to create routes back to basestation
Creates network from base station to leaf motes Updates to the tree allow for mote failure
detection
New routes updated during each execution
Phase VI: Sentry Selection
Sentry mote performs reconnaissance duty 2 conditions for sentry selection
Internal node of diffusion tree No neighboring sentries
Contention: Sentry declaration message with
delay on each mote
Energy balancing: Delay based on energy Sensing coverage: Declaration message
range smaller than magnetic sensor range
Phase VIII: Power Management
Proactive
Periodic sleep commands sent by sentry to each
neighboring mote with timer associated with data
Non-sentry motes receive the sleep commands,
and sleep the length of the timer
Reactive
Transition between sleep and wakeup controlled
by timer. Chosen for VigilNet
Phase VIII: Event Tracking and Reporting
Problem: Many motes are going to track the
vehicle as it passes through the mote path, creating increased traffic and energy consumption
Solution: Report Aggregation
Groups of motes formed dynamically in response
to an event, and migrate when an event moves
A group leader reports to the base station.
