Synchronizing low-cost energy aware sensors in a short-range wireless cell

Time management and synchronization in distributed systems has been studied thoroughly for many years. Basically the goal has bene to close the gap between local clocks of distributed devices. In systems that need to be both low cost and low power the devices sleep most of the time making standard CMOS timers impractical to use. Instead, imprecise RC oscillators are used to manage the wake up cycles. However, there is also a need to provide time management and synchronization in these systems. This is difficult with RC oscillators being the main device clock references. In this paper we propose a method that uses event timestamps to synchronize low cost, low power sensors with RC oscillators. The method relies on the cooperation of sensors in a wireless cell and a boundary node, which collects data from the sensors. Initial evaluation of the method shows that it is promising and possible can provide good synchronization with greater flexibility, lower costs and less energy than standard CMOS timers