• Journal of KIISE
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• v.41 no.10
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• pp.745-761
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• 2014

To address the problems of existing traffic information acquisition systems such as high cost and low scalability, wireless sensor networks (WSN)-based traffic information acquisition systems have been studied. WSN-based systems have many benefits including high scalability and low maintenance cost. Recently, various sensors are studied for traffic surveillance based on WSN, such as magnetic, acoustic, and accelerometer sensors. However, ultrasonic sensor based systems have not been studied. There are many issues for WSN-based systems, such as battery driven operation and low computing power. Thus, power saving methods and specific algorithms with low complexity are necessary. In this paper, we introduce optimal methodologies for power saving of ultrasonic sensors based on the modeling and analysis in detail. Moreover, a new vehicle detection algorithm for low complexity using ultrasonic data is presented. The proposed methodologies are implemented in a tiny microprocessor. The evaluation results show that our algorithm has high detection accuracy.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.9
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• pp.2442-2454
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• 2012

To ensure the security of wireless sensor networks, it is important to have a robust key management scheme. In this paper, we propose a Quorum-based key management scheme. A specific sensor, called as key distribution server (KDS), generates a key matrix and establishes a quorum system from the key matrix. The quorum system is a set system of subsets that the intersection of any two subsets is non-empty. In our scheme, each sensor is assigned a subset of the quorum system as its pre-distributed keys. Whenever any two sensors need a shared key, they exchange their IDs, and then each sensor by itself finds a common key from its assigned subset. A shared key is then generated by the two sensors individually based on the common key. By our scheme, no key is needed to be refreshed as a sensor leaves the network. Upon a sensor joining the network, the KDS broadcasts a message containing the joining sensor ID. After receiving the broadcast message, each sensor updates the key which is in common with the new joining one. Only XOR and hash operations are required to be executed during key update process, and each sensor needs to update one key only. Furthermore, if multiple sensors would like to have a secure group communication, the KDS broadcasts a message containing the partial information of a group key, and then each sensor in the group by itself is able to restore the group key by using the secret sharing technique without cooperating with other sensors in the group.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.2
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• pp.151-157
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• 2010

Rapid technological advances in the area of micro electro-mechanical systems (MEMS) have spurred the development of small inexpensive sensors capable of intelligent sensing. A significant amount of research has been done in the area of connecting large numbers of these sensors to create robust and scalable Wireless Sensor Networks (WSNs). The resource scarcity, ad-hoc deployment, and immense scale of WSNs make secure communication a particularly challenging problem. Since the primary consideration for sensor networks is energy efficiency, security schemes must balance their security features against the communication and computational overhead required to implement them. In this paper, we combine location information and probability to create a new security aware multipath geographic routing protocol. The implemented result in network simulator (ns-2) showed that our protocol has a better performance under attacks.

• Smart Structures and Systems
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• v.6 no.3
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• pp.183-196
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• 2010

Monitoring and economical design of alternative energy generators such as wind turbines is becoming increasingly critical; however acquisition of the dynamic output data can be a time-consuming and costly process. In recent years, low-cost wireless sensors have emerged as an enabling technology for structural monitoring applications. In this study, wireless sensor networks are installed in three operational turbines in order to demonstrate their efficacy in this unique operational environment. The objectives of the first installation are to verify that vibrational (acceleration) data can be collected and transmitted within a turbine tower and that it is comparable to data collected using a traditional tethered system. In the second instrumentation, the wireless network includes strain gauges at the base of the structure. Also, data is collected regarding the performance of the wireless communication channels within the tower. In both turbines, collected wireless sensor data is used for off-line, output-only modal analysis of the ambiently (wind) excited turbine towers. The final installation is on a turbine with embedded braking capabilities within the nacelle to generate an "impulse-like" load at the top of the tower. This ability to apply such a load improves the modal analysis results obtained in cases where ambient excitation fails to be sufficiently broad-band or white. The improved loading allows for computation of true mode shapes, a necessary precursor to many conditional monitoring techniques.

• International Journal of Advanced Culture Technology
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• v.2 no.2
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• pp.15-18
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• 2014

This paper presents a sensor location decision making method respect to Container-Grown Seedlings in view of precision agriculture (PA) when sensors involved in tree container measure received signal strength (RSS) or time-of-arrival (TOA) between themselves and neighboring sensors. A small fraction of sensors in the container-grown seedlings system have a known location, whereas the remaining locations must be estimated. We derive Rao-Cramer bounds and maximum-likelihood estimators under Gaussian and log-normal models for the TOA and RSS measurements, respectively.

• Journal of Internet Computing and Services
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• v.9 no.3
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• pp.51-58
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• 2008

Wireless sensor networks are used by various application areas to implement smart data processing and ubiquitous system. In the recent research of parking management system based on wireless sensor networks, adaptive sensing and efficient data processing are not considered. The effectiveness of implementing these distributed computing devices affects the performance of the applications in parking management. This paper proposes an adaptive sensing using fuzzy wireless sensor for the ubiquitous networks of parking management system. The fuzzy inference system is encoded in the sensor for efficient car presence detection. Moreover, a rule base adaptive module is proposed which wirelessly transmit the new values to each sensor for adapting the environment of car park area. The result of experiments shows that the fuzzy wireless sensor provides more throughputs and less time delays compared to a normal method of data gathering by wireless sensors.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.2014-2025
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• 2015

Wireless Sensor Networks (WSNs) are special network which has purpose of usage for gathering information of certain area and observing situation. WSNs consist of small nodes with sensing event such as temperature, movement or certain objects. The sensor has the capabilities to collect data and route data back to the sink. The sensors route data either to other sensors or back to a sink in one direction. That is, traditional WSNs communicate asymmetrically. However, under the new paradigm of the Internet of Things (IoTs) or Cyber Physical system (CPS), WSNs have potential to be used as important area. So, more research is necessary to communicate with each moving objects symmetrically in WSNs. In this paper, we proposed symmetric communication scheme among mobile objects in wireless sensor network. Simulation results show that our scheme is superior th the existing ones in terms of energy consumption and transmission success ratio.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.7
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• pp.3412-3432
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• 2019

Recent advances in radio frequency (RF) power transfer provide a promising technology to power sensor nodes. Adoption of mobile chargers to replenish the nodes' energy has recently attracted a lot of attention and the mobility assisted energy replenishment provides predictable and sustained power service. In this paper, we study the joint optimization of mobile charging and data gathering in sensor networks. A wireless multi-functional vehicle (WMV) is employed and periodically moves along specified trajectories, charge the sensors and gather the sensed data via one-hop communication. The objective of this paper is to maximize the uplink throughput by optimally allocating the time for the downlink wireless energy transfer by the WMV and the uplink transmissions of different sensors. We consider two scenarios where the WMV moves in a straight line and around a circle. By time discretization, the optimization problem is formulated as a 0-1 programming problem. We obtain the upper and lower bounds of the problem by converting the original 0-1 programming problem into a linear programming problem and then obtain the optimal solution by using branch and bound algorithm. We further prove that the network throughput is independent of the WMV's velocity under certain conditions. Performance of our proposed algorithm is evaluated through extensive simulations. The results validate the correctness of our proposed theorems and demonstrate that our algorithm outperforms two baseline algorithms in achieved throughput under different settings.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.1961-1972
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• 2014

Recently, with the increasing of the interest in the integration of medical technology and information communication technology, researches on WBAN (Wireless Body Area Networks) that try to apply sensor network to the human body have been processed actively. The existing sensor network technology has the potential to be used in WBAN, but it has some limitations also. In particular, because the sensors are likely to communicate through each part of the body, it has a very different network environment from the sensor network that uses a free space. Therefore, researches on WBAN have a variety area of study that slightly different from the conventional sensor networks and take into account the characteristics of the body. In this study, we investigate the environmental characteristics of WBAN that are separated from the conventional sensor network, and the research trends of WBAN systematically by using the technique of SLR (Systematic Literature Review) from 2001 around when the concept of WBAN has been introduced. The investigation includes the classification of research and the researcher's features. And the survey results and the outlook for further study are summarized.

• Industrial Engineering and Management Systems
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• v.10 no.3
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• pp.221-231
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• 2011

One of the critical issues in wireless sensor network is the design of a proper routing protocol. One possible approach is utilizing a virtual infrastructure, which is a subset of sensors to connect all the sensors in the network. Among the many virtual infrastructures, the connected dominating set is widely used. Since a small connected dominating set can help to decrease the protocol overhead and energy consumption, it is preferable to find a small sized connected dominating set. Although many algorithms have been suggested to construct a minimum connected dominating set, there have been few exact approaches. In this paper, we suggest an improved optimal algorithm for the minimum connected dominating set problem, and extensive computational results showed that our algorithm outperformed the previous exact algorithms. Also, we suggest a new heuristic algorithm to find the connected dominating set and computational results show that our algorithm is capable of finding good quality solutions quite fast.