Time synchronization algorithm for wireless sensor networks based on K-neighboring topology

This article proposes a delay compensation-based time synchronization (DCBTS) algorithm for wireless sensor networks (WSNs) with random bounded communication delays. First, we point out that in the framework of consensus-based time synchronization (CBTS) algorithms, the offset estimate is generally divergent in networks containing at least two root nodes due to immeasurable delays even if the drift estimate converges at a rate no slower than 1/k , where k is the discrete time. Second, we introduce a delay compensation mechanism in the offset estimation algorithm and utilize the first difference of the offset estimate to adaptively adjust the delay compensation. An upper bound of the adjusting gain is also provided, which ensures the boundedness of the offset estimate. Besides simulations under different clock, network, and delay settings, a series of physical experiments have been conducted on our autonomously designed test bed for comparing the DCBTS algorithm with some existing time synchronization algorithms, such as Average TimeSynch (ATS), Weighted-Maximum TimeSynch (WMTS), Least-Square estimation TimeSynch (LSTS), and PISync. Both numerical simulations and physical experiments validate the availability, effectiveness, and better performance of this novel time synchronization algorithm.

In a Wireless Sensor Network (WSN), time synchronization is highly desired because data collected from agglomerated sensors become truly meaningful when they are stamped with accurate time. Most of current studies on time synchronization continue to adapt algorithms from a general distributed system. Inspired by Optimal Foraging Theory (OFT) in ecology, we proposed a novel algorithm for time synchronization in wireless sensor networks in this paper. The new strategy reduces or avoids redundant message exchange in time synchronization and extends the lifetime of a sensor network by reducing energy expenditure of time synchronization.

Automatic localization is one of the major issues in Wireless Sensor Networks (WSN). DV-hop algorithm is a well-known localization algorithm in WSN but with limited localization accuracy. In this paper, an improved DV-hop localization algorithm in hybrid optical wireless sensor networks is proposed based on the optimization of the parameters in WSN. Various factors that affect the localization accuracy of the DV-hop algorithm in WSN are investigated, including the communication radius of the node, the number of beacon nodes and the number of the total nodes. As the DV-hop algorithm is applied into hybrid optical sensor and WSNs (O-WSN) with rectangular topology, different parameters have to be optimized accordingly. Simulation results show that the square topology outperforms the rectangle topology more than 45 % under the same network parameters using the improved DV-hop algorithm. Therefore another improved DV-hop called Sub-Square Weighted DV-hop (SSW DV-hop) is proposed for the rectangle topology. Both simulation and experiment results demonstrate that applying the SSW DV-hop algorithmin O-WSNs could significantly improve the localization accuracy.

Wireless Sensor Networks (WSNs) have received considerable attention in recent years because of its broad area of applications. In the same breadth, it also faces many challenges. Time synchronization is one of those fundamental challenges faced by WSN being a distributed system. Several approaches have been proposed in the last decade for time synchronization in WSNs. Recently, Consensus Time Synchronization (CTS) approaches are gaining popularity due its computational lightness, robustness and distributed nature. Though a rich set of CTS algorithms are proposed, their energy consumption has so far not been studied. Apart from synchronization precision, energy consumption should also be considered meticulously for time synchronization algorithms in energy-constraint WSNs. In this paper, a thorough energy consumption analysis is presented for some recent state-of-the-art CTS algorithms for WSN and tested by simulation. The simulation results will help in selecting an appropriate CTS algorithm that meets the requirements of synchronization accuracy and energy consumption for a specific WSN application.

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

Wireless sensor networks (WSNs) have received much attention in recent years because of its broad area of applications. In the same breadth, it also faces many challenges. Time synchronisation is one of those fundamental and important challenges faced by WSN. Several approaches have been proposed in recent years for time synchronisation. Most of the approaches are based on synchronising to a reference (root) node's time by considering a hierarchical backbone for the network. However, this approach seems to be not purely distributed, higher accumulated synchronisation error for farthest node from the root and subjected to the root node failure problem. In this study, a fully distributed time synchronisation algorithm is proposed which synchronises all nodes’ time to a consensus value, that is, an average of all nodes’ initial clock values. The algorithm exploits a selective pairwise averaging approach with a linear message complexity of O (n), to achieve faster convergence and better synchronisation accuracy than the existing random pairwise average time synchronisation protocol. Simulation results show that almost 50% improvement is achieved in convergence speed, measured in terms of number of iterations, and nearly 30% improvement in total synchronisation error.

In this paper, we investigated the data fusion routing algorithm and the time synchronization algorithm for the wireless sensor networks. First, we proposed a new data fusion routing algorithm - Low Energy Consumption Cluster-Based Routing Algorithm (LECCBRA). Simulation results show that the total energy can be effectively saved, and the balance in energy consumption between clusters can be achieved with LECCBRA, thus the network lifetime is extended. Second, we proposed a time synchronization algorithm - Clustering-based Time Synchronization (CBTS), which is suitable for LECCBRA. Performance analysis and simulation results show that the total energy can be effectively saved, and the accuracy can be improved.

Based on the study of RBS algorithm in wireless sensor network, an improved algorithm named RBRS is presented, to solve the time synchronization problem of multi hop networks. On the basis of RBS, the broadcast group and least square linear regression methods were used to realize entire network time synchronization in the algorithm. Synchronization error and overhead with the existing improved BRS are compared in the article. The result shows that the algorithm has certain superiority in many algorithms, which is suitable for light and low power consumption network load. Through an emulation with the matlab software, the result indicates that error accumulation is lower in the optimized algorithm, the synchronization overhead is significantly reduced and can realize the time synchronization of the whole network. A time synchronization algorithm based on RBRS algorithm is proposed for multi-hop and the low power consumption. A variable period synchronization method is introduces in the algorithm: in line with Bias maximum a posterior estimation principle, the maximum phase offset is estimated to determine the synchronization period, which can reduce the number of node synchronization, and with the least square linear regression method, the periodic fitting clock offset. The Simulation in matlab indicate that RBRS algorithm can improve the synchronization accuracy and reduce energy consumption significantly, which is conducive to extend the life of the network.

With the expansion of the scale of wireless sensor network (WSN), the network node number is increasing. Because of the huge network overhead and low precision, the reference broadcast time synchronization algorithm can not meet the actual demand. In this paper, a novel time synchronization algorithm for high precision energy efficient wireless sensor networks is proposed. Through a Markov random field-based maximum a posteriori estimation method of wireless sensor network in two nonadjacent nodes in receiving multiple reference broadcast messages, the algorithm estimated the clock drift under the condition of phase error estimation, tracked in real time by the Gardner loop, and then realized the time synchronization process. Finally, the MATLAB simulation showed the proposed algorithm not only has a further improvement in the time synchronization accuracy, but also effectively reduces the overall energy consumption level of the whole WSN.

Time synchronization is an indispensable requirement for wireless sensor network (WSN) applications. But, the traditional, centralized time synchronization algorithms are not suitable for WSN. Nowadays, consensus-based time synchronization (CTS) algorithms are becoming popular due to its distributed nature. In this context, various consensus-based time synchronization algorithms have been proposed, but their performance vary depending on various factors. This paper presents a thorough performance analysis of some state-of-the-art CTS algorithms in terms of random network topology, synchronization period, convergence speed, and synchronization error. This analysis will give an insight into the behavior of different CTS algorithms which will help the research community to understand the intrinsic property of this class of synchronization algorithms.KeywordsWireless sensor network (WSN)Consensus-based time synchronization (CTS)Clock skewClock offset

Node localization is significant importance for supporting many critical applications in wireless sensor networks. However, traditional Amorphous localization algorithm and its variants still cannot provide sufficient localization accuracy. We propose an improved amorphous algorithm in wireless sensor network based on approximate equilateral triangle beacon selection(AET-Amorphous), which first employs hops threshold design and approximate equilateral triangle function to select the three beacons as reference nodes, and then two-dimensional hyperbolic calculation method is adopted instead the classic trilateration/least square method to determine the locations of unknown nodes, which can eliminate error and improve the node location accuracy. Simulations are conducted to validate the accuracy of our proposed localization algorithm in wireless sensor networks. Remarkably, the average localization error of our proposed localization algorithm is lower than those of Amorphous and its improved algorithms, under both Square-shaped and C-shaped random uniformly node distributions.

Data transmission is a critical function in wireless sensor network (WSN). Due to the limited resource of energy, processing ability, memory, etc, how to extend the lifetime of WSN faces a great challenge. Therefore, it has recently become a hotspot. In this paper, we propose a novel time synchronization algorithm for wireless sensor networks. Using the proposed time synchronization algorithm, we present an energy efficient data transmission protocol. Sensor nodes can weak up and sleep at accurate time. Therefore the listening time can be reduced. The proposed algorithm and protocol are implemented on the Mica2 motes and their performance is evaluated. Experimental result shows that the proposed time synchronization technique can greatly extend the lifetime of wireless sensor network.

In this work we will develop an extension of one of existing routing algorithm in wireless sensor network. This new adaptation will permit the sensor node to save more energy and transmit images in wireless mode. This situation will be strategic and helpful especially in disaster scenario, where groups of rescuers must be on site to accomplish emergency tasks; therefore it's very important and necessary to establish a wireless communication in real time between individuals or groups. The nature of wireless video sensor network makes it suitable to be used in the context of emergencies because introducing a video give more information in precise time and this is very advantageous when the existing infrastructure is down or severely overloaded. In emergencies the network topology may change rapidly and randomly. The increasing mobility of terminals makes them progressively dependent on their autonomy from the power source. This is illustrated by introducing many mobility models and using many scenarios of mobility in emergency situation, where image transmission via sensor node is used. Low complexity algorithm in image processing in order to reduce time transfer of selected data by this way allows saving energy. Efficiency in emergency scenario is the main objective of this work, achieved by the combination of three strategies: low-power mode algorithm, a power-aware routing strategy and compression technique in image processing used in sensor node. A selected set of simulations studies and real test bed on sensor node platform (Telos-B) indicate a reduction in energy consumption and a significant increase in node lifetime whereas network performance is not affected significantly. This is the big interest of our work in emergency situation, by increasing life time of node, individual can communicate longer and give more chance to rescuers to find them.

Time synchronization is critical for wireless sensor networks (WSNs). However, due to environmental harshness and node mobility, time synchronization is hard for underwater WSNs (UWSNs). In this paper, we predict the velocity of unsynchronized nodes by the mobility pattern and spatial correlation, and propose a time synchronization algorithm based on the clock parameters estimated by the relative speed of nodes. Simulation results show that the proposed algorithm significantly outperforms existing algorithms and mitigates the detrimental effect of node mobility on time synchronization.

In most wireless sensor network time synchronization algorithms in the past, common nodes typically synchronize the clock with a reference node (or root node), which is easily disturbed by unexpected events. This paper mainly studies a time-synchronized protocol for batch-calibrated sensor networks (BC-TPSN) algorithm. The algorithm is based on the TPSN algorithm and is mainly corrected for the time-frequency offset of TPSN. In the inter-level synchronization phase, synchronization between the levels is accomplished using a synchronization mechanism of two-way message exchange. In the intra-level synchronization phase, the improved two-way message exchange synchronization mechanism is used to complete the synchronization of the internal nodes of the hierarchy. In this paper, the time-base synchronous batch calibration method based on wireless sensor network nodes is applied to highway infrastructure condition monitoring, which can simultaneously calibrate and unify the time base of nodes and improve the performance of precise synchronous networking.