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Due to the oceanic climate and frequent earthquakes in Japan, bridge health diagnosis is a problem of greater complexity. In bridge diagnosis system, we develop a wireless sensor network to sample and gather the vibration data of bridge. Time synchronization is a crucial component for the wireless sensor network (WSN), because large populations of sensor nodes will collaborate in order to complete...
The demand for economical wireless sensor nodes have been increased due to advancement in processor, memory and wireless communication techniques. To give the on time and fast response for different actions, wireless sensor nodes work together in cooperation with each other. The most important requirement to maintain the co-ordination among different nodes during execution of an application is perfect...
Power saving is a very critical issue in energy-constrained wireless sensor networks. Many schemes can be found in the literature, which have significant contributions in energy conservation. The aim of this study is to propose a distributed technique able to guarantee communications over all sensors and reducing in a considerable rate the energy consumed. The originality of the solution is the use...
Low duty cycle operation is a well-known mechanism used for achieving energy efficiency in wireless sensor networks (WSNs). Nodes under this concept work only for a small percentage of time and remain largely inactive to conserve energy. S-MAC, is a popular protocol designed specifically for WSNs with low duty cycle operation. At its inception, S-MAC has been designed for low traffic loads. In this...
Reliability and predictability of the timing behavior have shown to be major issues for wireless sensor network deployments. Real-time requirements presented by several applications can be fulfilled by implementing communication schemes that lower possible sources of non-determinism of the timing behavior, assuming that the nodes are synchronized. The predictability of current synchronization protocols,...
Wireless Sensor Network is application specific data centric networks, having application span ranging from house hold application to mission critical applications. Applications like fire detection require immediate attention from the base station. Further these networks are resource constrain networks which require efficient utilization of scare resources. IEEE 802.15.4 is one of the low power, low...
This article presents wireless personal area networks with low transmission rate, utilized more and more often in industrial or alarm systems, as well as in sensor networks. The structure of these systems and available ways of transmission are defined by the IEEE 802.15.4 standard. The second part of the paper contains the description of simulation tests that have been realized. Their results make...
Wireless sensor networks require shared medium access management to prevent collisions, message corruption and other unhelpful effects. Cellular sensornets require minimal energy consumption to maximise network lifetime, and management of interaction with base stations and other cells. We present a protocol which dynamically generates a near-optimal duty schedule within a cell such that communication...
Time synchronization is important for wireless sensor networks because it facilitates cooperation among nodes and helps raise power efficiency. Time synchronization protocols like TPSN, RBS and FTSP have provided great schemes to fulfill fast synchronization with efficiency. In some applications, nodes might hope to sleep for a long time without timestamp exchanges with other nodes. In that case,...
Energy efficiency in wireless sensor networks is one of the most crucial technologies. In this paper, we propose a simple and feasible synchronous sleep and wake mechanisms for wireless sensor networks in a small scale. Sensor nodes are divided into forwarding nodes and listening nodes. Beacon frame containing sleep command from coordinator can be forwarded to listening nodes by forwarding nodes....
Time synchronization is a crucial component of wireless sensor networks, many applications require uniform clock information. In order to avoid network congestion and reduce the overhead of transmitting data packets , a spanning subtree based multi-channel time synchronization algorithm (SSMTS) is presented . The scheme is composed of two phases: spanning tree construction phase and time synchronization...
In this paper, the problem of clock synchronization is analyzed based on the two-way message exchange mechanism. In order to estimate the clock offset and the clock skew with unknown fixed delay, the maximum likelihood estimator (MLE) and a low-complexity estimator are proposed. Furthermore, their corresponding performance limits and complexities are analyzed. It is found that the MLE achieves the...
Cooperative transmission using space time codes can be used to reduce transmission energy consumption for long range communication in wireless sensor networks (WSN). However, differing from traditional (multi-input-multi-output) MIMO systems, distributed cooperative communication systems in WSN usually lack of perfect synchronization. For the cooperative systems using Alamouti code, the effect of...
Although localization and synchronization share many aspects in common, they are traditionally treated separately. In this paper, we present a unified framework to jointly solve these two problems at the same time. The joint approach is attractive because it can solve both localization and synchronization using the same set of message exchanges. This is extremely important for energy saving, especially...
Wireless sensor networks (WSN) are characterized by stringent power constraints. Researchers focus on improving their power efficiency in order to allow building up networks that survive for long periods of time on limited battery resources without any human intervention. Improvements have been proposed for every hardware and software component, including every networking layer of the sensor nodes...
This paper studies the impact of crystal clock drift on the ranging accuracy. A novel technique in which a group of sensor devices, each having a different clock drift, can reduce this adverse effect by a 2-phase round robin fashion is presented. In comparison to the conventional way of point-to-point group ranging scheme, this technique has the desirable advantage of low energy consumption, which...
The duty cycle of a wireless sensor node is a key factor that determines the life time of a wireless sensor network. In general, sensor medium access control protocols reduce the duty cycle to achieve longer lifetime. However, we found out that their performance improvements substantially decrease under extremely low duty cycles (<0.1%). Our proposed W-MAC protocol targets achieving low energy...
There have been many time synchronization protocols proposed for sensor networks. However, the security problems related to time synchronization have not been fully solved yet. If malicious entities manipulate time synchronization, failures of many functionalities in the sensor networks would occur. In this paper, we identify various attacks against time synchronization and then develop a detection...
Achieving secure time-synchronization in wireless sensor networks (WSNs) is a challenging, but very important problem that has not yet been addressed effectively. This paper proposes an attack-tolerant time-synchronization protocol (ATSP) in which sensor nodes cooperate to safeguard the time- synchronization service against malicious attacks. ATSP exploits the high temporal correlation existing among...
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