Scheduling Method for Solving Successive Contentions of Heterogeneous Periodic Flows Based on Mathematical Formulation in Multi-Hop WSNs

Recently, the number of wireless sensor networks has been increasing. In these networks, sensors usually collect data every period. This leads to an increase in the number periodic flows and interferences among them. Most related studies only focus on a single type of periodic flow systems, which are not suitable for practical applications. The others are based on time division multiple access, which requires global synchronization and cannot thus be scaled. In this paper, we propose and prove a formula for determining interferences between heterogeneous periodic flows. By using this formula, we propose a scheduling method to improve the performance of heterogeneous periodic multi-hop sensors networks. The proposed method uses the naive and popular distributed coordination function for the MAC layer, which is low cost and highly feasible because of the wide diffusion of IEEE 802.11 and does not require global synchronization. Furthermore, because all calculations are done by the sink, the hardware requirement for sensor nodes is reduced. Therefore, this method is scalable and easy to implement. We further demonstrate the performance of the proposed method by extensive simulations. The results show the final proposal reduces the packet loss rate by 91% and 95% comparison with the delta shifting method and binary division method, respectively.