Proportional-Integral Clock Synchronization in Wireless Sensor Networks
  In this article, we present a new control theoretic distributed time synchronization algorithm, named PISync, in order to synchronize sensor nodes in Wireless Sensor Networks (WSNs). PISync algorithm is based on a Proportional-Integral (PI) controller. It applies a proportional feedback (P) and an integral feedback (I) on the local measured synchronization errors to compensate the differences between the clock offsets and clock speeds. We present practical flooding-based and fully distributed protocol implementations of the PISync algorithm, and we provide theoretical analysis to highlight the benefits of this approach in terms of improved steady state error and scalability as compared to existing synchronization algorithms. We show through real-world experiments and simulations that PISync protocols have several advantages over existing protocols in the WSN literature, namely no need for memory allocation, minimal CPU overhead and code size independent of network size and topology, and graceful performance degradation in terms of network size. 
Kas{\i}m Sinan Y{\i}ld{\i}r{\i}m and Ruggero Carli and Luca Schenato
cs.DC