Self-Organizing Time Synchronization of Wireless Sensor Networks with Adaptive Value Trackers

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.

It is important and challenging to achieve secure time synchronization in wireless sensor networks, which may be deployed in a hostile environment under various malicious attacks. The recently developed average-consensus-based time synchronization protocol (ATS) is a promising alternative as it does not depend on any reference node or network topology, which makes it robust to different kinds of attacks, e.g., denial-of-service, node destruction, etc. However, the in-network information fusion nature of average consensus makes the ATS vulnerable to the well-known message manipulation attacks. In this paper, we focus on how to defend the ATS protocol in wireless sensor networks under message manipulation attacks. We first investigate the impact of message manipulation attacks over ATS, and derive a necessary condition for ATS to converge. Then based on the obtained insights, we propose a novel adjusting parameter checking mechanism which exploits the two-hop neighboring information to dynamically constrain the attackers. We further incorporate all checking processes into the traditional ATS protocol to form a secure average-consensus-based time synchronization protocol (SATS). We prove that SATS guarantees the network time synchronization with an exponentially converging speed.

Wireless Sensor Networks (WSNs) have extensively been worked upon due to their ability to monitor various physical phenomenon. Time synchronization is the most fundamental and most important challenge faced by WSNs. Time Synchronization in WSN can be achieved either by gaining consensus amongst all the nodes or by a reference node which broadcasts a single unit of time to the entire network. The paper describes a novel technique to achieve fully distributed cluster clock synchronization, which synchronizes all the nodes in the network to a common consensus value. The algorithm employs clustering and confidence weighted running average (CWA) method for offset and skew compensations. The efficiency of protocol is validated with simulation results presented in the paper.

Study of consensus-based time synchronization in wireless sensor networks

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.

Time Synchronization in WSNs with Random Communication Delays: A Constant Gain Design

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.

Firstly, we show that in the unified structural model of the consensus-based time synchronization (CBTS) algorithm, the offset estimate is divergent in general while the drift estimate converges in a rate of $1/k$ , where $k$ is the discrete time. Then, we propose an offset compensation approach to guaranteeing the boundedness of the offset estimate for wireless sensor networks (WSNs) with random bounded communication delays. Two numerical experiments are presented to illustrate the availability of this algorithm and the better synchronization performance.

Wireless sensor networks (WSNs) are quickly becoming an essential part of today's modern infrastructure, and it is becoming crucial to consider time synchronisation problems in WSNs. Furthermore, one of the main design issues in WSN time synchronisation is the efficient use of energy at each sensor node to prolong the lifespan of the network. This paper describes a new energy-efficient time protocol based on the spanning tree of the network model graph in a WSN. Three major cases are discussed: 1) time synchronisation using the energy-efficient spanning tree (EST) protocol in a WSN with approximately 300 sensors; 2) an improved EST protocol in large-scale WSNs; 3) an improved EST protocol under weighted graph. Additionally, a series of practical algorithms are proposed in this paper, where both energy and time efficient can be clearly shown through a number of simulated examples along with their comparative results.

Time synchronization for wireless sensor networks (WSNs) has been studied in recent years as a fundamental and significant research issue. Many applications based on these WSNs assume local clocks at each sensor node that need to be synchronized to a common notion of time. Time synchronization in a WSN is critical for accurate time stamping of events and fine-tuned coordination among the sensor nodes to reduce power consumption. This paper proposes a bidirectional, reference based, tree structured time synchronization service for WSNs along with network evaluation phase. This offers a push mechanism for (i) accurate and (ii) low overhead for global time synchronization. Analysis study of proposed approach shows that it is lightweight as the number of required broadcasting messages is constant in one broadcasting domain.

ABSTRACTReliability is a crucial aspect of time synchronization for industrial wireless applications in wireless sensor networks. Existing time synchronization algorithms often provide good synchronization in laboratory environments; however, outdoor environments with associated radio interference influence the performance of time synchronization. In this paper, we propose a random time source protocol for industrial wireless applications in wireless sensor network synchronization. Each synchronized node randomly selects its time source for each period in order to prevent reliance on a fixed time source because this may lead to resynchronization once the source fails. We have implemented the algorithm on the SIA2420 platform usingTinyOS, and the results show the reliability of our protocol. Copyright © 2011 John Wiley & Sons, Ltd.

Wireless Sensor Networks (WSNs) play a necessary position in todays actual world applications. WSNs are a team of autonomous sensor nodes that are geographically distributed to accumulate information and monitor events. WSNs are similarly sense that they rely on wireless connectivity and spontaneous formation of networks so that sensor information can be transported via wireless. Sometimes called dust network, minute sensors as small as dust referring to smart dust. WSNs are spatially distributed two to screen or bodily temperature, sound, pressure, etc. and to cooperatively ignore their data via the network to different locations. Each such sensor network node has typically various parts. Routing in WSNs in one of the important technique, because all node executes its battery power, if may be one node failure it collapse entire networks. Routing in WSNs is in reality difficult due to the intrinsic characteristics that differentiate these networks from different networks. The plan of routing protocols in WSN is affected via number of exigent factors. In this paper, a review on routing protocols for Wireless Sensor Networks (WSNs) and performance of its execution.

Impact of time synchronization error on the mode-shape identification and damage detection/localization in WSNs for structural health monitoring

Localization and synchronization are two important issues in communication systems and wireless sensor networks. These two problems are addressed in many applications, and share many aspects in common. However, these two problems are traditionally treated separately. In this paper, we present a unified framework to jointly solve these two problems at the same time. The maximum likelihood joint estimation of location and timing is firstly derived. Then, a more computationally efficient two-stage least square method is proposed. The Cramer-Rao lower bound for the joint localization and time synchronization is also derived. Simulation results show that the performances of the maximum likelihood and two-stage least square estimators can both achieve the Cramer-Rao lower bound.

Energy efficiency has received extensive attention in energy-constrained Wireless Sensor Networks (WSNs). As is known, radio communication accounts for major energy consumption of wireless device and the control of radio transmitter can make effective function with energy efficiency system. In this paper we test and analyse the relationship between precision and synchronization rate and we also give an initial model denote for the relationship among synchronous cycle, time error and energy consumption. The experiments and analysis in the paper show the feasibility of long cycle time synchronization for WSNs under certain limitation and the result will be helpful for the time synchronization method with low energy consumption.