Homomorphic Filtering for Improving Time Synchronization in Wireless Networks
View/ Open
Author
Castillo Secilla, José María
Palomares Muñoz, José Manuel
León, Fernando
Olivares Bueno, Joaquín
Publisher
MDPIDate
2017Subject
Clock skewWSN
Synchronization
Temperature
Oscillators
Tuning-fork
Homomorphic filtering
TelosB
802.15.4
TinyOS
METS:
Mostrar el registro METSPREMIS:
Mostrar el registro PREMISMetadata
Show full item recordAbstract
Wireless sensor networks are used to sample the environment in a distributed way.
Therefore, it is mandatory for all of the measurements to be tightly synchronized in order to guarantee
that every sensor is sampling the environment at the exact same instant of time. The synchronization
drift gets bigger in environments suffering from temperature variations. Thus, this work is focused
on improving time synchronization under deployments with temperature variations. The working
hypothesis demonstrated in this work is that the clock skew of two nodes (the ratio of the real
frequencies of the oscillators) is composed of a multiplicative combination of two main components:
the clock skew due to the variations between the cut of the crystal of each oscillator and the clock
skew due to the different temperatures affecting the nodes. By applying a nonlinear filtering,
the homomorphic filtering, both components are separated in an effective way. A correction factor
based on temperature, which can be applied to any synchronization protocol, is proposed. For testing
it, an improvement of the FTSP synchronization protocol has been developed and physically
tested under temperature variation scenarios using TelosB motes flashed with the IEEE 802.15.4
implementation supplied by TinyOS.