Synchronization of data measurements in wireless sensor networks for IoT applications

Abstract

Time synchronization is a challenging problem for wireless sensor networks, as clocks deviate and sensor measurements need to be associated with the reference clock time they took place. In Internet of Things (IoT) environments, crucial factors like energy, robustness, limited capabilities and extreme ambient conditions (e.g., when nodes are deployed in soil) lead researchers to consider various schemes of relaxing the synchronization requirements. In this paper, a lightweight synchronization algorithm is proposed for wireless sensor networks, focusing on synchronizing the particular measurements in a per hop basis as they are transmitted encapsulated in data packets towards the sink node. The aim is to synchronize data measurements instead of node clocks, and thereby, induce negligible extra overhead, since extra messages and re-synchronization periods are not required. The analysis of the proposed algorithm regarding time deviation and the corresponding variance shows a dependency on residual time (i.e., the particular time period a data packet remains within a node), distance (i.e., the number of hops between the sink node and the sensor node that sensed the data in the first place) and the average skew deviation value. Various simulations were carried out aiming to exhibit thoroughly the effectiveness of the proposed algorithm, as well as the validation of the analytical results. Findings from a comparison between the proposed algorithm and a traditional synchronization algorithm along with their simulation results show that the proposed algorithm can be a suitable solution for demanding environments like IoT systems.