Time synchronization is a key requirement in distributed systems. Algorithms to synchronize computers date back to the dawn of net- worked system. Among these, the most famous that are still in use for general purpose networks are NTP (Network Time Protocol) and PTP (Precise Time Protocol). Recently, Wireless Sensor Net- work (WSN) have appeared, which are distributed systems with pe- culiar requirements, especially in terms of energy efficiency. Their main application is distributed sensing of some physical quantities over a medium to large area, and collect this information through a gateway in order to be stored and processed. Example applications include environmental sensing, including landslides, earthquakes, fires, or building monitoring. Energy efficency is a key require- ment for WSNs, as the individual nodes are almost always battery powered, or have limited energy harvesting capabilities. Clock syn- chronization in WSN is a necessity for two main reasons: first, ap- plication requirements often impose to add timestamps to measured data, in order to correlate the data sensed by the individual nodes. Second, the need to extend the battery life of nodes to several years can only be accomplished by having them go in a low power sleep state most of the time. In this state, also the radio transceiver is off, which means that nodes need synchronization to wake up together and exchange information. Different solutions have been proposed in the literature to achieve good clock synchronization in WSN, but the research topic remains to date open. This work is dedicated to detailing the integration of the FLOPSYNC clock synchronization scheme with the VHT (Virtual High-resolution Timer), which is a solution to have a high resolution and low power local clock time- base. This integration has uncovered a clock jitter problem, to which an innovative solution has been proposed. In addition, this work also deals with the integration of the clock synchronization scheme in the Miosix operating system, in order to for the kernel itself and its timing services exposed to the applications to benefit from the synchronized time.
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OS-level synchronization service for WSN node
RICCARDI, FABIANO
2015/2016
Abstract
Time synchronization is a key requirement in distributed systems. Algorithms to synchronize computers date back to the dawn of net- worked system. Among these, the most famous that are still in use for general purpose networks are NTP (Network Time Protocol) and PTP (Precise Time Protocol). Recently, Wireless Sensor Net- work (WSN) have appeared, which are distributed systems with pe- culiar requirements, especially in terms of energy efficiency. Their main application is distributed sensing of some physical quantities over a medium to large area, and collect this information through a gateway in order to be stored and processed. Example applications include environmental sensing, including landslides, earthquakes, fires, or building monitoring. Energy efficency is a key require- ment for WSNs, as the individual nodes are almost always battery powered, or have limited energy harvesting capabilities. Clock syn- chronization in WSN is a necessity for two main reasons: first, ap- plication requirements often impose to add timestamps to measured data, in order to correlate the data sensed by the individual nodes. Second, the need to extend the battery life of nodes to several years can only be accomplished by having them go in a low power sleep state most of the time. In this state, also the radio transceiver is off, which means that nodes need synchronization to wake up together and exchange information. Different solutions have been proposed in the literature to achieve good clock synchronization in WSN, but the research topic remains to date open. This work is dedicated to detailing the integration of the FLOPSYNC clock synchronization scheme with the VHT (Virtual High-resolution Timer), which is a solution to have a high resolution and low power local clock time- base. This integration has uncovered a clock jitter problem, to which an innovative solution has been proposed. In addition, this work also deals with the integration of the clock synchronization scheme in the Miosix operating system, in order to for the kernel itself and its timing services exposed to the applications to benefit from the synchronized time.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/133873