Ultra-Low Power Time Synchronization Using Passive Radio

Ultra-Low Power Time
Synchronization Using Passive
Radio Receivers
Yin Cheny, Qiang Wangz, Marcus Changy, Andreas Terzisy
Johns Hopkins University, Harbin Institute of Technology
IPSN 2011
Presenter: SY
Time Synchronization Protocols
• GPS, RBS, FTSP, PulseSync, Power line, etc.
• Desired properties
– Low-power consumption GPS, RBS, FTSP, PulseSync
– Support for large scale networks
– Accuracy that is independent of network size
– Access to UTC time
– Support for disconnected operation
– Low latency
– Operate in both indoors and outdoors Power line
Their accuracy is in ms
Time Signal Radio Stations
Universal Time Signal Receiver
Applications And Conclusion
Time Signal Radio Stations
• Broadcast time signal periodically
• Some of the time signal radio stations
WWVB Radio Station
• Location: Fort Collins, Colorado
• National Institute of Standards
and Technology (NIST)
• Coverage Area
• Location: Mainflingen, Germany
• German national meteorology institute (PTB)
• Coverage area
LF Radio Waves
• Two components
– Ground wave
• follows the Earth’s curvature
– Sky wave
• Earth’s ionosphere
• For 50 kW DCF77 transmitter
– within 600 km  ground wave dominates
– 600-1100 km  ground wave and sky wave equal magnitude
– beyond 1100 km  only the refracted sky wave
WWVB Data Frame
• One-bit-per-second time code
• Each frame contains 60 bits
• Data frames transmitted back-to-back
– 60 frames per hour
• Start-of-a-second time stamps
06:11 UTC on the 144th day (May 24) of 2010
DST bits indicate that the daylight saving time is active
Time Signal Radio Stations
Universal Time Signal Receiver
Applications And Conclusion
Universal Time Signal Receiver
25 mm
one-pulse-persecond (1PPS)
CME6005 radio chip
33 mm
analog time signals
digital outputs
timer value
Power Consumption: 90uA
Record timer value
Calculate interval
Power Consumption:
0.6uA (sleep)
800uA (Active)
UART output
Power Consumption
Compare Power Consumption
• Universal Time Signal Receiver
• Compare
Synchronization Error
Signal Availability
• Hourly decoded ratio
Signal Availability
Some Notes
• Interference
– Steel frame buildings completely shield
– Brick buildings allow signal reception
– CRT screens can interfere from 5-10 meters
– Laptops can interfere within one meter
• Local Time Signal Generators
– Up to 50 meters radius
Synchronous MAC Protocols
• Implemented a time-scheduled version of LPL
• running CTP on top
• Duty cycles
Other Applications
Latency Reduction
Sparse Networks
Drop-in Replacement for GPS
Network-Wide Wakeup
Failure-Prone Sensor Networks
• Implemented universal time signal receiver
– Very low power
– Millisecond accuracy
– Wide availability

similar documents