Abstract
Time synchronization is one of the key technologies in Industrial Wireless Sensor Networks (IWSNs), and clustering is widely used in WSNs for data fusion and information collection to reduce redundant data and communication overhead. Considering IWSNs’ demand for low energy consumption, fast convergence, and robustness, this paper presents a novel Cluster-based Maximum consensus Time Synchronization (CMTS) method. It consists of two parts: intra-cluster time synchronization and inter-cluster time synchronization. Based on the theory of distributed consensus, the proposed method utilizes the maximum consensus approach to realize the intra-cluster time synchronization, and adjacent clusters exchange the time messages via overlapping nodes to synchronize with each other. A Revised-CMTS is further proposed to counteract the impact of bounded communication delays between two connected nodes, because the traditional stochastic models of the communication delays would distort in a dynamic environment. The simulation results show that our method reduces the communication overhead and improves the convergence rate in comparison to existing works, as well as adapting to the uncertain bounded communication delays.
Highlights
Industrial Wireless Sensor Networks (IWSNs) utilize wireless communication to transmit data between industrial measurement and control equipment, which can effectively increase the coverage area of the network, reduce the layout cost, and improve the speed of the network construction [1,2,3].In IWSNs, many applications rely heavily on a common notion of time, such as nodes sleep scheduling, transmission scheduling, Time Division Multiple Access (TDMA)-based communication, sensed data fusion, etc
Some special applications have put forward special requirements for time synchronization in IWSNs: (1) low-power, because most of the nodes in IWSNs are battery powered, which is similar to wireless sensor networks; (2) high-precision, which is the primary demand to meet the high real-time in industrial production control process; (3) fast convergence: it should meet the requirements of rapid detection and control when equipment is on-line, and fast-recovery after node failure [6]
As shown in Algorithm 1, we develop the CMTS algorithm based on the IWSNs structure, communication mechanisms, and the pre-described clock model
Summary
Industrial Wireless Sensor Networks (IWSNs) utilize wireless communication to transmit data between industrial measurement and control equipment, which can effectively increase the coverage area of the network, reduce the layout cost, and improve the speed of the network construction [1,2,3].In IWSNs, many applications rely heavily on a common notion of time, such as nodes sleep scheduling, transmission scheduling, Time Division Multiple Access (TDMA)-based communication, sensed data fusion, etc. Most of the time synchronization methods in wireless sensor networks mainly aim to improve the precision and reduce the energy consumption [6,7,8,9,10,11], but they seldom consider the synchronization convergence time [12] and take the influence of network structure into account, which is important for industrial applications. Many methods suppose that the communication delays among two nodes are symmetric or obey a particular distribution, such as exponential distribution, Gaussian distribution, and so on [12,13,14,15] They neglect the fact that the predefined delay model would change with the influence of external environment, which results in a negative effect on synchronization performance, such as accuracy and convergence time of sync methods. A cluster-head can bear more calculation and communication in sync methods to prolong the network lifetime
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