Time Synchronization In Sensor Networks Research Articles

Design and development of a wireless sensor network time synchronization system for photovoltaic module monitoring

Since the working situation of photovoltaic modules cannot be tracked in the real time and defective components cannot be located and controlled specifically, a remote monitoring system of photovoltaic modules based on wireless sensor networks is designed to improve the management efficiency of photovoltaic power plants. The monitoring data (current, voltage, and illumination, etc.) of photovoltaic modules are collected by the wireless sensor network nodes in real time, and then, there are orderly transmitted to the coordinator and server by the ZigBee communication protocol with the time synchronization algorithm. Time synchronization algorithm based on Gaussian delay model performs best in synchronization accuracy and energy-efficient reference broadcast synchronization algorithm is the most advantageous in synchronization energy consumption. Adaptive energy–efficient reference broadcasting synchronization algorithm is proposed with a balance between energy consumption and accuracy, which is applicable to large networks and thus conducive to the application of wireless sensor network in large-scale photovoltaic module monitoring. With the analysis and processing of the received data, the situation of the photovoltaic modules can be accordingly judged and thus the information management of photovoltaic power plant can be realized. For a photovoltaic power plant with a total power output of 100 kW and with 400 photovoltaic modules, experimental results show that the overall efficiency of the photovoltaic power plant can be increased by a wide margin.

A hierarchical time synchronization algorithm for WSN

Wireless sensor networks generally require large-scale deployment. Each node in the network is solely responsible for data sensing in a certain area. In order to determine the sequence in which sensing data is generated, time synchronization between nodes is necessary. Due to the delay of multi-hop transmission and the influence of the frequency shift of the node crystal frequencies, the error of time synchronization between the nodes is larger. In order to reduce the error of time synchronization, it is common practice to increase the number of synchronizations. But this method will cause the node energy consumption to increase, affecting the network survival time. In order to solve this problem, a layered wireless sensor network time synchronization algorithm is proposed with reference to the unidirectional broadcast mechanism and bidirectional pairing mechanism. The algorithm uses a hierarchical strategy for time synchronization, while introducing a synchronization error compensation mechanism and clock compensation mechanism. Under the premise of ensuring the accuracy of time synchronization, the algorithm reduces the energy consumption of nodes and prolongs the network lifetime.

SRTS : A Self-Recoverable Time Synchronization for sensor networks of healthcare IoT

Sensor networks for healthcare IoT (Internet of Things) have advanced rapidly in recent years, which has made it possible to integrate real-time health data by connecting bodies and sensors. Body sensors require accurate time synchronization in order to collaboratively monitor health conditions and medication usage. Self-recovery and high accuracy are crucial for time synchronization protocols in sensor networks for healthcare IoT. Because body sensors are generally deployed with unstable energy sources, nodes can fail because of inadequate power supply. This influences the efficiency and robustness of time synchronization protocols. Tree-based protocols require stable root nodes as time references. The time synchronization process cannot be completed if a root node fails. To address this problem, we present a Self-Recoverable Time Synchronization (SRTS) scheme for healthcare IoT sensor networks. A recovery timer is set up for candidate nodes, which are dynamically elected. The candidate node whose timer expires first takes charge of selecting a new root node. Meanwhile, SRTS combines the two-points least-squares method and the MAC layer timestamp to significantly improve the accuracy of PBS. Furthermore, SRP and RRP models are used in SRTS. Thus, our approach provides higher accuracy than PBS, while consuming a similar amount of energy. We use NS2 network tools to evaluate our approach. The simulation results show that SRTS exhibits better self-recovery than time synchronization protocols STETS and GPA under different network scales. Moreover, accuracy and clock drift compensation are better than those of PBS and TPSN.

OTSA: Optimized Time Synchronization Approach for Delay-based Energy Efficient Routing in WSN

Time Synchronization is one of the problems and still ignored problem in area of wireless sensor network (WSN). After reviewing the existing literatures, it is found that there are few studies that combinely address the problem of energy conservation, clustering, routing along with minimizing the errors due to time synchronization in sensor network. Therefore, this manuscript presents a delay-based routing which considers the propagation delay to formulate a mechanism for delay compensation in large scale wireless sensor network. The prime goal of this technique is to jointly address energy problems, time synchronization, and routing in wireless sensor network. The outcome of the proposed study was found to posse’s minimized communication overhead, minimized synchronization errors, lower energy consumption, and reduced processing time when compared with the existing standards of time synchronization techniques.

Time Synchronization Algorithms in Low-Cost Wireless Sensor Network Systems

Time synchronization is an essential building block of sensor network systems. In this paper, we present a comprehensive study of least squares algorithms for time synchronization in sensor networks, with a focus on continuous monitoring and data collection applications. We propose a set of algorithms to address a number of issues in practical implementation on typical low-cost sensor network platforms, including a scaled signal model to achieve numerical stability in an ill-conditioned problem, sequential estimators for the scaled signal model to reduce computational complexity, a fast initialization scheme to improve energy efficiency, and outlier detection algorithms to improve robustness in long-term autonomous operations. The proposed algorithms are implemented and a measurement-based simulation method is employed to study the performance.

Nonidentical Linear Pulse-Coupled Oscillators Model With Application to Time Synchronization in Wireless Sensor Networks

Similar to other cyber infrastructure systems, as wireless sensor networks become larger and more complex, many classic algorithms may no longer work efficiently. This paper presents a wireless sensor network time synchronization model that was initially inspired by synchronous flashing of fireflies. Synchronous flashing of fireflies is an interesting phenomenon that has been studied for decades. A variety of models have been proposed to explain this phenomenon, among which is the pulse-coupled oscillators model that models fireflies as oscillators. The oscillators in such a model interact only through discrete pulses, similar to the flashing of fireflies. In this paper, we propose a new nonidentical linear pulse-coupled oscillators model and use the model to analyze synchronization of pulse-coupled oscillators with different frequencies. The conditions to achieve and maintain synchronization are derived, and then, the results are used to prove that the oscillators in the model can achieve synchronization eventually, except for a set of frequencies with zero Lebesgue measure. Furthermore, through simulations and implementation on a wireless sensor network testbed, we demonstrate that the proposed nonidentical linear pulse-coupled oscillators model can be used in designing lightweight scalable time synchronization protocols for distributed systems.

Research on a Real-Time Fault Tolerant Time Synchronization Algorithm for GSM-R Wireless Sensor Networks Based on Network Materials

Time synchronization is a key technology in wireless sensor networks. In this paper, aim at high-speed railway GSM-R network require higher real time, fault tolerance and band coverage way, presents a real-time fault-tolerant wireless sensor network time synchronization algorithm, using direct forwarding strategy, regression analysis and abnormal data filtering methods to meet the requirements of GSM-R network. Analysis and simulation show that the algorithm has good real-time and fault tolerance to meet the requirements of GSM-R network applications.

Towards a unified view on space and time in sensor networks

In wireless sensor networks, many applications rely on the ability of sensor nodes to estimate their physical location and time with respect to a common reference scale. This necessity is reflected by the development of a significant number of algorithms for localization and time synchronization for sensor networks in the recent past. However, research on location estimation on the one hand and on time synchronization on the other hand has been largely separated. Despite this, models, requirements, techniques, and algorithms of the two domains are rather similar and in some respects closely related. The purpose of this paper is to make this affinity explicit, with the hope of stimulating a mutual fertilization and enabling a better understanding of both domains.

Time synchronization in sensor networks: a survey

Time synchronization is an important issue in multihop ad hoc wireless networks such as sensor networks. Many applications of sensor networks need local clocks of sensor nodes to be synchronized, requiring various degrees of precision. Some intrinsic properties of sensor networks, such as limited resources of energy, storage, computation, and bandwidth, combined with potentially high density of nodes make traditional synchronization methods unsuitable for these networks. Hence, there has been an increasing research focus on designing synchronization algorithms specifically for sensor networks. This article reviews the time synchronization problem and the need for synchronization in sensor networks, then presents in detail the basic synchronization methods explicitly designed and proposed for sensor networks.