• Journal of the Korea Society for Simulation
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• v.17 no.3
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• pp.27-34
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• 2008

Wireless sensor networks are comprised of sensor nodes with resource-constrained hardware. Nodes in the sensor network without adequate protection may be compromised by adversaries. Such compromised nodes are vulnerable to the attacks like false reports injection attacks and false data injection attacks on legitimate reports. In false report injection attacks, an adversary injects false report into the network with the goal of deceiving the sink or the depletion of the finite amount of energy in a battery powered network. In false data injection attacks on legitimate reports, the attacker may inject a false data for every legitimate report. To address such attacks, the probabilistic voting-based filtering scheme (PVFS) has been proposed by Li and Wu. However, each cluster head in PVFS needs additional transmission device. Therefore, this paper proposes a fuzzy logic-based false report detection method (FRD) to mitigate the threat of these attacks. FRD employs the statistical en-route filtering scheme as a basis and improves upon it. We demonstrate that FRD is efficient with respect to the security it provides, and allows a tradeoff between security and energy consumption, as shown in the simulation.

• Journal of KIISE
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• v.42 no.12
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• pp.1495-1502
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• 2015

Data compression involves a trade-off between delay time and data size. Greater delay times require smaller data sizes and vice versa. There have been many studies performed in the field of wireless sensor networks on increasing network life cycle durations by reducing data size to minimize energy consumption; however, reductions in data size result in increases of delay time due to the added processing time required for data compression. Meanwhile, as energy generation occurs periodically in solar energy-based wireless sensor networks, redundant energy is often generated in amounts sufficient to run a node. In this study, this excess energy is used to reduce the delay time between nodes in a sensor network consisting of solar energy-based nodes. The energy threshold value is determined by a formula based on the residual energy and charging speed. Nodes with residual energy below the threshold transfer data compressed to reduce energy consumption, and nodes with residual energy above the threshold transfer data without compression to reduce the delay time between nodes. Simulation based performance verifications show that the technique proposed in this study exhibits optimal performance in terms of both energy and delay time compared with traditional methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.175-182
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• 2018

As Internet of things with a large number of nodes emerges, wireless-power communication networks (WPCN) based on a random access protocol needs to be investigated. In the random access-based WPCN, a terminal accessing later in given random access (RA) slots can harvest more energy before transmission and thus can transmit data with higher power and achieve higher throughput if the access is successful. On the basis of this property, the proposed random access control protocol gives the terminals priority and distinguishes the RA slots according to the priority level, so that a near terminal with access point allows to access preferentially other than a remote terminal. This operation decreases the throughput of near terminal and increases the throughput of remote terminal, and then, the doubly near-far problem in WPCN is resolved and the user fairness is improved. Results show that the proposed random access control improves both channel throughput and user fairness according to the priority level.

• Annual Conference of KIPS
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• 2011.04a
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• pp.564-567
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• 2011

Preserving energy of sensor node in wireless sensor network is an effort to prolong the lifetime of network. Energy of sensor node is very crucial because battery powered and irreplaceable. Energy conservation of sensor node is an effort to reduce energy consumption in order to preserve resource for network lifetime. It can be achieved through efficient energy usage by reducing consumption of energy or decrease energy usage while achieving a similar outcome. In this paper, we propose optimization of energy efficient base station assisted hierarchical routing protocol in wireless sensor network, named BSAH, which use base station to controlled overhead of sensor node and create clustering to distribute energy dissipation and increase energy efficiency of all sensor node. Main idea of BSAH is based on the concept of BeamStar, which divide sensor node into group by base station uses directional antenna and maximize the computation energy in base station to reduce computational energy in sensor node for conservation of network lifetime. The performance of BSAH compared to PEGASIS and CHIRON based of hierarchical routing protocol. The simulation results show that BSAH achieve 25% and 30% of improvement on network lifetime.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.8
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• pp.725-732
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• 2013

Recently, various applications for LED lightings are growing continuously due to their better performances such as low power consumption, longer life time, operation speed, controllability, high quality color rendering, and sustainability. However, in developing the high-powered LEDs illumination system, heat-sink problem is one of the important obstacle. In this paper, a heat-sink design with multi-layered structure for high-powered LEDs is proposed, which is composed of metal core PCB, heat-pipes, heat-sink plates, and fans. And also, in this paper, a design for LED controls using DMX512 protocols through RS-485 communications is proposed, which is considered as de facto international standard in LEDs illumination control and is widely used in landscape lighting and stage lighting. In this paper, LED control and its application techniques are introduced and the method of wireless remote control for main controller is proposed.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.5
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• pp.360-370
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• 2009

Using solar power in wireless sensor networks requires a different approach to energy optimization from networks with battery-based nodes. Solar energy is an inexhaustible supply which can potentially allow a system to run forever, but there are several issues to be considered such as the uncertainty of energy supply and the constraint of rechargeable battery capacity. In this paper, we present SolarSS: a reliable storage system for solar-powered sensor networks, which provides a set of functions, in separate layers, such as sensory data collection, replication to prevent failure-induced data loss, and storage balancing to prevent depletion-induced data loss. SolarSS adapts the level of layers activated dynamically depending on solar energy availability, and provides an efficient resource allocation and data distribution scheme to minimize data loss.

• Journal of IKEEE
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• v.21 no.1
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• pp.66-69
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• 2017

In recent year, energy harvesting technologies from the ambient environments such as light, motion, wireless waves, and temperature again a lot of attraction form research community [1-5] due to its efficient solution in order to substitute for conventional power delivery methods, especially in wearable together with on-body applications. The drawbacks of battery-powered characteristic used in commodity applications lead to self-powered, long-lifetime circuit design. Thermoelectric generator, a solid-state sensor, is useful compared to the harvesting devices in order to enable self-sustained low-power applications. TEG based on the Seebeck effect is utilized to transfer thermal energy which is available with a temperature gradient into useful electrical energy. Depending on the temperature difference between two sides, amount of output power will be proportionally delivered. In this work, we illustrated a low-input voltage energy harvesting circuit applied discontinuous conduction mode (DCM) method for getting an adequate amount of energy from thermoelectric generator (TEG) for a specific wearable application. With a small temperature gradient harvested from human skin, the input voltage from the transducer is as low as 60mV, the proposed circuit, fabricated in a $0.6{\mu}m$ CMOS process, is capable of generating a regulated output voltage of 4.2V with an output power reaching to $40{\mu}W$. The proposed circuit is useful for powering energy to battery-less systems, such as wearable application devices.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.501-512
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• 2018

Radio frequency identification (RFID) sensor tag provides several advantages including battery-less operation and low cost, which are suitable for long-term monitoring. This paper presents a self-powered RFID temperature sensor tag for online temperature monitoring in substation. The proposed sensor tag is used to measure and process the temperature of high voltage equipments in substation, and then wireless deliver the data. The proposed temperature sensor employs a novel phased-locked loop (PLL)-based architecture and can convert the temperature sensor in frequency domain without a reference clock, which can significantly improve the temperature accuracy. A two-stage rectifier adopts a series of auxiliary floating rectifier to boost its gate voltage for higher power conversion efficiency. The sensor tag chip was fabricated in TSMC $0.18{\mu}m$ 1P6M CMOS process. The measurement results show that the proposed temperature sensor tag achieve a resolution of $0.15^{\circ}C$/LSB and a temperature error of $-0.6/0.7^{\circ}C$ within the range from $-30^{\circ}C$ to $70^{\circ}C$. The proposed sensor tag achieves maximum communication distance of 11.8 m.

• Annual Conference of KIPS
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• 2011.04a
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• pp.576-579
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• 2011

Wireless sensor network are widely all over different fields. Because of its distinguished characteristics, we must take account of the factor of energy consumed when designing routing protocol. Wireless sensor networks consist of small battery powered devices with limited energy resources. Once deployed, the small sensor nodes are usually inaccessible to the user, and thus replacement of the energy source is not feasible. Hence, energy efficiency is a key design issue that needs to be enhanced in order to improve the life span of the network. In BCDCP, all sensors sends data from the CH (Cluster Head) and then to the BS (Base Station). BCDCP works well in a smallscale network however is not preferred in a large scale network since it uses much energy for long distance wireless communication. TBRP can be used for large scale network, but it weakness lies on the fact that the nodedry out of energy easily since it uses multi-hops transmission data to the Base Station. Here, we proposed a routing protocol. A Cluster Based Energy Efficient Tree Routing Protocol (CETRP) in Wireless Sensor Networks (WSNs) to prolong network life time through the balanced energy consumption. CETRP selects Cluster Head of cluster tree shape and uses maximum two hops data transmission to the Cluster Head in every level. We show CETRP outperforms BCDCP and TBRP with several experiments.

• Journal of Digital Convergence
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• v.12 no.11
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• pp.289-298
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• 2014

Recently, the traditional paradigm in railroad technology is changing as more efficient and cost-effective electric vehicle (EV) technologies have emerged. The original concept of PRT (Personal Rapid Transit) proposed in the past has come to be regarded as unrealistic, but its feasibility is improving through the utilization of an EV platform. In particular, battery-powered vehicles pose difficult technical challenges in attempts to achieve reliable and efficient operation. However, based on the inductive power transfer (IPT) technology, the fast charging of supercapacitors with high energy density can contribute to overcoming this technical challenge and promote the transition to electric-powered ground transportation by improving the appearance of cities. This study discusses the development process of a power supply system for PRT, including concept design, numerical analysis, and device manufacturing, along with performance predictions and evaluations. In terms of results, the system was found to meet the performance requirements for power supply modules on a test-bed.