Time Synchronization with Extended Clock Model for Wireless Sensor Networks
30 Jul 2007-Vol. 2, pp 534-539
TL;DR: In the protocol, the clock offset is corrected continuously avoiding the time discontinuity which is a prevalent drawback of existing synchronization protocols and the bound-drift clock model is extended by considering both the absolute drift and the relative drift.
Abstract: Time synchronization is an essential problem for WSNs. The synchronization performance is mainly affected by two factors: the uncertainty in the message delay, and the clock drift. Most solutions on time synchronization in WSNs have concentrated on one of the two factors, and neglected the other. In this paper, we consider both of them and propose a novel time synchronization protocol for WSNs. In the protocol, we model the variation of the clock drift and develop algorithms to estimate and compensate the drift. Meanwhile, the clock offset is corrected continuously avoiding the time discontinuity which is a prevalent drawback of existing synchronization protocols. Additionally, we extend the bound-drift clock model by considering both the absolute drift and the relative drift. Mathematical analyses and simulations are presented in this paper, and verify the effectiveness of our synchronization protocol.
Citations
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TL;DR: This paper makes the first step toward the experimental characterization of a small-scale WSN implementing some of these protocols versus common wireless busses such as BT, Wi-Fi, and ZigBee.
Abstract: Nowadays, careful measurement applications are handed over to wireless sensor networks (WSNs). In most of these tasks, sensor nodes work together to recognize the data fusion process. Synchronization is a critical element in this scenario. Nodes have to be regulated to a common clock and regulated among them. Many synchronization algorithms can be found in literature, and some of them have been intentionally established for low-cost structural designing where efficient memory management and reduced computational burden are important constraints. The performance of these algorithms is usually evaluated either in simulation environments or by adopting ad hoc radio systems. Attention is rarely paid to the influence of factors, such as the following: clock stability, the dependence of the measurement application on the synchronization algorithm and vice versa, the effect of the limited bandwidth available on real radio systems, and the change of performance when common commercial wireless communication busses such as Wi-Fi, Bluetooth (BT), and ZigBee are adopted. This paper makes the first step toward this direction, proposing the experimental characterization of a small-scale WSN implementing some of these protocols versus common wireless busses such as BT, Wi-Fi, and ZigBee.
36 citations
14 Jul 2008
TL;DR: This paper makes a first step toward an experimental characterization of synchronization protocols that hold into account also influence factors which arise when commercial wireless communication busses as WiFi, BlueTooth (BT), ZigBee are adopted.
Abstract: Nowadays more and more measurement applications where sensor nodes cooperate to realize a data fusion process are entrusted to wireless sensor networks (WSN). Data fusion to be accurate requires that nodes be referred to a common clock and among themselves. In this scenario node synchronization got a crucial research topic and even sophisticated synchronization algorithms can be easily found in literature. Not a few others show to be especially designed for low cost, low memory and low power architectures. Their performance is usually evaluated either through analytical considerations or in simulation environments, but in some cases where ad hoc radio systems have been adopted. This paper makes a first step toward an experimental characterization of synchronization protocols that hold into account also influence factors which arise when commercial wireless communication busses as WiFi, BlueTooth (BT), ZigBee are adopted.
8 citations
13 May 2012
TL;DR: An experimental approach to the optimization of synchronization protocols for wireless sensor networks by proposing that the sensor node be synchronized with the master node on the basis of two suitable figures of merit: the former takes into account the past synchronizations, whilst the latter depends on the residual error after the last synchronization.
Abstract: The paper proposes an experimental approach to the optimization of synchronization protocols for wireless sensor networks. The authors' research is aimed in both minimizing the synchronization residual error and the wireless sensor node energy consumption. The approach has been thought to be applied to different synchronization protocols and to give the best results for small scale wireless sensor network. In particular, results concerning the well know Timing Synchronization Protocol for Sensor Networks (TPSN) are presented in the paper. The main idea is that the sensor node be synchronized with the master node on the basis of two suitable figures of merit: the former takes into account the past synchronizations, whilst the latter depends on the residual error after the last synchronization. On the basis of the on board and real time evaluation of these two indexes the number of synchronization events and the node energy consumption can be both reduced.
7 citations
01 Mar 2017
TL;DR: The proposed approach reduces synchronization error to that of less than 0.3 ms, which meets the accuracy requirement of VANET specification and can greatly reduce the frequency of handover performed by the high speed OBUs.
Abstract: Vehicular Ad hoc Network (VANET) is still a very attractive technology by which the construction of an Intelligent Transportation System (ITS) will be realized. The communication devices of VANET, i.e., OBUs and RSUs, are only allowed to transmit data in an assigned channel time and the channel switch will take place in about every 50 ms according to the standards of IEEE 802.11p and IEEE 1609.4. On the other hand, in the case of a large scale VANET, e.g., in the scenario of a traffic rush hour, available transmission time interval would be a few of milliseconds or even much less. Therefore, it is essential to achieve a precise time synchronization among the embedded devices. In this paper, we put forward a new specific time synchronization method among VANET devices. In our method, OBU can synchronize to other OBU or RSU initiatively. In the case that there is no center node in BSS (Basic Service Set), the proposed approach reduces synchronization error to that of less than 0.3 ms, which meets the accuracy requirement of VANET specification. In addition, we achieved time synchronization among RSUs. This can greatly reduce the frequency of handover performed by the high speed OBUs.
3 citations
References
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01 Jan 2003
TL;DR: It is argued that time synchronization schemes developed for traditional networks such as NTP are ill-suited for WSNs and suggest more appropriate approaches.
Abstract: Wireless sensor networks (WSNs) consist of large populations of wirelessly connected nodes, capable of computation, communication, and sensing. Sensor nodes cooperate in order to merge individual sensor readings into a high-level sensing result, such as integrating a time series of position measurements into a velocity estimate. The physical time of sensor readings is a key element in this process called data fusion. Hence, time synchronization is a crucial component of WSNs. We argue that time synchronization schemes developed for traditional networks such as NTP [23] are ill-suited for WSNs and suggest more appropriate approaches.
591 citations
"Time Synchronization with Extended ..." refers background in this paper
...However, time synchronization in WSNs has to meet challenges that are substantially different from those in traditional networks [2]....
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...More appropriate approaches designed specifically for WSNs are needed [2]....
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01 Oct 2001
TL;DR: This work presents a time synchronization scheme that is appropriate for sparse ad hoc networks and explains how the data sensed by various smart things can be combined to derive knowledge about the environment, which enables the smart things to "react" intelligently to their environment.
Abstract: Ubiquitous computing environments are typically based upon ad hoc networks of mobile computing devices. These devices may be equipped with sensor hardware to sense the physical environment and may be attached to real world artifacts to form so-called smart things. The data sensed by various smart things can then be combined to derive knowledge about the environment, which in turn enables the smart things to "react" intelligently to their environment. For this so-called sensor fusion, temporal relationships (X happened before Y) and real-time issues (X and Y happended within a certain time interval) play an important role. Thus physical time and clock synchronization are crucial in such environments. However, due to the characteristics of sparse ad hoc networks, classical clock synchronization algorithms are not applicable in this setting. We present a time synchronization scheme that is appropriate for sparse ad hoc networks
532 citations
20 Mar 2003
TL;DR: The proposed solution features minimal complexity in network bandwidth, storage and processing and can achieve good accuracy, and also provides tight, deterministic bounds on both the offsets and clock drifts.
Abstract: Time synchronization is important for any distributed system. In particular, wireless sensor networks make extensive use of synchronized time in many contexts (e.g. for data fusion, TDMA schedules, synchronized sleep periods, etc.). Existing time synchronization methods were not designed with wireless sensors in mind, and need to be extended or redesigned. Our solution centers around the development of a deterministic time synchronization method relevant for wireless sensor networks. The proposed solution features minimal complexity in network bandwidth, storage and processing and can achieve good accuracy. Highly relevant for sensor networks, it also provides tight, deterministic bounds on both the offsets and clock drifts. A method to synchronize the entire network in preparation for data fusion is presented. A real implementation of a wireless ad-hoc network is used to evaluate the performance of the proposed approach.
522 citations
01 Aug 2000
TL;DR: Two new leader election algorithms for mobile ad hoc networks that ensure that eventually each connected component of the topology graph has exactly one leader are presented.
Abstract: We present two new leader election algorithms for mobile ad hoc networks. The algorithms ensure that eventually each connected component of the topology graph has exactly one leader. The algorithms are based on a routing algorithm called TORA [5], which in turn is based on an algorithm by Gafni and Bertsekas [3]. The algorithm require nodes to communicate with only their current neighbors, making it well suited to the ad hoc environment. The first algorithm is for a single topology change and is provided with a proof of correctness. The second algorithm tolerates multiple concurrent topology changes.
369 citations
01 Sep 1999
TL;DR: Current work in stakeholder identification is discussed, an approach to identifying relevant stakeholders for a specific system is proposed, and future directions for the work are proposed.
Abstract: Adequate, timely and effective consultation of relevant stakeholders is of paramount importance in the requirements engineering process. However, the thorny issue of making sure that all relevant stakeholders are consulted has received less attention than other areas which depend on it, such as scenario-based requirements, involving users in development, negotiating between different viewpoints and so on. The literature suggests examples of stakeholders, and categories of stakeholder, but does not provide help in identifying stakeholders for a specific system. In this paper, we discuss current work in stakeholder identification, propose an approach to identifying relevant stakeholders for a specific system, and propose future directions for the work.
354 citations