SensorIT Workshop Dynamic Sensor Networks

1
SensorIT WorkshopDynamic Sensor Networks

• Dr. Jack Wills
• Oct 7-8, 1999
• USC Information Sciences Institute

2
Dynamic Sensor Networks - Overview

• Low Power
• Power Aware Routing
• Minimum Energy Communications
• Power Aware Sensor Management
• Node Components
• WinCE PDA
• GPS/Radio
• Sensor Array

3
Dynamic Sensor NetworksNode Architecture
Processor Subsystem
Sensor Array Subsystem
Optional for Command Node
Long Range Radio

• Network
• Connection

PDA
Temp
Vibration
Other
Serial Port
Serial Port
TOD
Communications Subsystem
GPS
Radio
Comm Antenna
GPS Antenna
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Dynamic Sensor NetworksGPS/Radio

• TDMA Burst Communications synchronized by GPS
  Time of Day
• Tx and Rx are scheduled on for power savings
• Commercial 915 MHz ISM Band Chipset
• RFMD 9901/9902 - FSK - 100 kbps
• Commercial GPS
• Motorola Oncore UT
• Microcontroller - PLD - Power Supply

5
Dynamic Sensor NetworksGPS Performance

• Type - Motorola Oncore UT
• Channels - 5
• Power
• Active lt0.9 Watts at 5 volts
• Sleep 5?A typ. At 2.5 volts
• Position Accuracy
• 100 meter 2D RMS (selective availability on)
• Time Accuracy
• lt50 nS (1 sigma) with position hold on

6
Dynamic Sensor NetworksWakeup Problem

• A single sensor node (while in a low data rate,
  high latency communications mode) may identify an
  event which warrants high rate, low latency
  communications
• e.g. The Redcoats are coming Paul Revere
• Possible Solutions
• Low power receiver continuously on
• Out of band signaling

7
Distributed Sensor NodesAlarm Channel

• Very Low Bit Rate
• Micropower receiver
• Extra Low Frequency
• 160-190 kHz
• Simple Waveform
• AM FSK
• Tuned RF receiver - no local oscillator

8
Distributed Sensor NodesELF Radio

• Large Wavelength
• 1750 meters
• Near Field Propagation
• Antenna Efficiency Issues
• Tuned Ferrite Rods
• Q50
• Bandwidth 3kHz at 175 kHz
• Coupled Inductors
• Orientation Sensitive

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Dynamic Sensor Networks Future Extensions

• Micropower radio receiver architecture
• Super Heterodyne
• Tuned Radio Frequency
• Super Regenerative
• Low Bit Rate Control Channels
• Adaptive Waveform Control
• Quartz clock locked to GPS