Lightweight and energy efficient time synchronization for sensor network

Time synchronization has received a great attention as its crucial parts in wireless sensor networks. To minimize the number of transmission packets and achieve energy efficiency, a time synchronization scheme based on ant colony algorithm (TSAC) is presented in this paper. By exploiting the principle of ant colony algorithm adjusting the pheromone dynamically and automatically, an optimum pair selection theme is designed to select the nodes synchronized by performing the pairwise synchronization, and all the other nodes could be synchronized by listening. The simulation results show that TSAC needs less message exchanges and provides more accuracy than other time synchronization algorithms.

Attack-resilient time synchronization for wireless sensor networks

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.

The paper studies the basic characteristics and the definition of the wireless sensor networks, the time synchronization of wireless sensor network and the algorithm of time synchronization in wireless sensor networks. This paper studies the RBS algorithm and its improved algorithm. The research results have practical significance to the rapid development of network and the future network.

Study of consensus-based time synchronization in wireless sensor networks

A wireless sensor network (WSN) of distribution bus protection and fault location of distribution lines are presented. Architecture of the WSN and principles of bus protection are described in this paper. Traveling-waves will generate when a fault occurs in power transmission line. Based on the traveling-wave, a novel time synchronization scheme is proposed. Simulation results illustrate that precision of the synchronization scheme is less than 3 microseconds/km and can reduce the energy consumption.

Wireless Sensor Networks (WSN) based Structural Health Monitoring (SHM) is becoming popular in analyzing the life of critical infrastructure such as bridges on a continuous basis. For most of the applications, data aggregation requires high sampling rate. A need for accurate time synchronization in the order of 0.6 − 9 μs every few minutes is necessary for data collection and analysis. Two-stage energy-efficient time synchronization is proposed in this paper. Firstly, the network is divided into clusters and a head node is elected using Low-Energy Adaptive Clustering Hierarchy based algorithm. Later, multiple packets of different lengths are used to estimate the delay between the elected head and the entire network hierarchically at different levels. Algorithmic scheme limits error to 3-hop worst case synchronization error. Unlike earlier energy-efficient time synchronization schemes, the achieved results increase the lifetime of the network.

Time synchronization provides the basis for several applications in wireless sensor networks but the limited memory and computational power, and the use of low precision oscillators make the task of time synchronization non-trivial. In this demonstration, we present a novel time synchronization scheme that is based on time series analysis. To provide a general model for the practical behavior of low precision oscillators, autoregressive integrated moving average models are explored. Based on the analysis of experimental data, an autoregressive integrated model (ARI (1,1)) is derived. Unlike the resource hungry Kalman filter based formulations, the proposed scheme is resource efficient as it results in simple linear regression processing. Experiments are performed on real sensor devices including Zolertia and TelosB, where an accuracy below 1 clock tick1 is achieved.

Time synchronization provides the basis for several applications in wireless sensor networks but the limited memory and computational power, and the use of low precision oscillators make the task of time synchronization non-trivial. In this demonstration, we present a novel time synchronization scheme that is based on time series analysis. To provide a general model for the practical behavior of low precision oscillators, autoregressive integrated moving average models are explored. Based on the analysis of experimental data, an autoregressive integrated model (ARI (1,1)) is derived. Unlike the resource hungry Kalman filter based formulations, the proposed scheme is resource efficient as it results in simple linear regression processing. Experiments are performed on real sensor devices including Zolertia and TelosB, where an accuracy below 1 clock tick 1 is achieved.

The ever-increasing number of WSN deployments based on a large number of battery-powered, low-cost sensor nodes, which are limited in their computing and power resources, puts the focus of WSN time synchronization research on three major aspects, i.e., accuracy, energy consumption and computational complexity. In the literature, the latter two aspects have not received much attention compared to the accuracy of WSN time synchronization. Especially in multi-hop WSNs, intermediate gateway nodes are overloaded with tasks for not only relaying messages but also a variety of computations for their offspring nodes as well as themselves. Therefore, not only minimizing the energy consumption but also lowering the computational complexity while maintaining the synchronization accuracy is crucial to the design of time synchronization schemes for resource-constrained sensor nodes. In this paper, focusing on the three aspects of WSN time synchronization, we introduce a framework of reverse asymmetric time synchronization for resource-constrained multi-hop WSNs and propose a beaconless energy-efficient time synchronization scheme based on reverse one-way message dissemination. Experimental results with a WSN testbed based on TelosB motes running TinyOS demonstrate that the proposed scheme conserves up to 95% energy consumption compared to the flooding time synchronization protocol while achieving microsecond-level synchronization accuracy.

Wireless sensor networks require time synchronization, which is the coordination of events or actions to make a system operate in unison. In this work, real experiments and a theoretical analysis of the behavior of the clock sources, most used in wireless sensor networks, have been carried out. The experiments have been performed on two real platforms from two different manufacturers in real environments with sudden changes in temperature. Complementary metal-oxide-semiconductor oscillators have a low accuracy, bigger than 500 ppm, and a high dependency with temperature. External crystal oscillators have good accuracy, around 20 ppm, and are stable with temperature. Temperature-compensated crystal oscillators are very accurate, around 5 ppm, and the temperature has no influence in their drift. The use of phase-locked loop circuits minimizes the impact of temperature and stabilizes oscillators. We highlight and demonstrate the importance of the early stages of design, especially the selection of the clock source, because that decision has a great impact on the performance of the time synchronization in wireless sensor networks.

The need for distribution of accurate and reliable time synchronization is more and more urgent, especially with the development of the fifth-generation (5G) network and the rise of high precision communication. However, the vast majority of the current packet networks is the best effort and cannot offer precision time synchronization. To enable the precise time feature in packet networks, a novel time synchronization scheme is proposed based on software-defined networking/network functions virtualization enabled network architecture, exploring the programmability of network time synchronization as a fundamental concept to define the function model for core components. Time synchronization is built as a virtual network function (VNF), and a synchronization controller is designed to manage the synchronization processing and precision compensation together with the network controller and the proposed VNF. More specifically, the time synchronization model and compensation algorithms are introduced to reveal the mechanism of the synchronization process. To thoroughly study the performance of the proposed scheme, an analytical model is developed that covers the primary influencing factors of synchronization accuracy, including the link length, delay coefficient, timestamping granularity, and local oscillator's characteristic of the network element. Further, experimental and analytical results are presented to demonstrate the effectiveness of the proposed scheme.

Time synchronization, aiming to provide a common timescale among distributed sensor nodes, is a key enabling technology for many applications, such as collaborative condition monitoring and localization detection. Due to the complexity of time synchronization in wireless sensor networks, the Discrete Event Simulator is recommended to adopt resulting from the feature that the behavior of a complex is represented as an order sequence of well-defined event in time. In this paper, the PCO clock is firstly implemented into the open-source software simulator OMNeT++ by using desynchronization mechanism under a realistic scenario, and it can also be simulated at an adjustable and higher resolution. The developed relay node, can either be a Full Function Device or a Reduced Function Device, enables the high scalability for multi-node and multi-hop simulation. In addition, the shared code of this project on the GitHub directly benefits the researchers and engineers in communication.

In wireless sensor networks, energy efficiency is an important standard for evaluating the effectiveness of the time synchronization protocols. Hence, energy should be conserved as much as possible provided that algorithm can achieve a certain accuracy. In this paper, we propose an energy efficient time synchronization algorithm in which each layer of the network can be synchronized merely by receiving broadcast messages rather than relying on two-way message exchange. Simulation results show that our improved strategy reduced the energy consumption and prolonged the lifetime of network compared with TPSN.

In this paper, we propose a gradual time synchronization scheme for wireless mesh networks (WMNs) based on orthogonal frequency division multiple access (OFDMA). For distributed time synchronization in WMNs, each node controls its transmission time and fast Fourier transform (FFT) starting time within the possible range according to the requests of neighbor nodes. The possible range is determined by the cyclic prefix (CP) and the guard interval (GI) between transmitted sub frames and received sub frames. Simulation results show that this process leads to gradual synchronization of all nodes in the network.