• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.1
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• pp.182-187
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• 2009

In this paper, the power management module of wireless sensor node is designed and fabricated utilizing RF energy from reader antenna of commercial RFID system, which is mainly categorized in the energy harvesting. For this, the rectenna and the high efficient boost converter is designed to get the DC power from RF power for the charging the battery. When the RF power from RFID reader antenna is 1.2[W], the DC power of 3.1[mW] at the distance of 1[m] and 1[mW] at 5.5[m] are obtained. Considering the connection to the battery, the boost converter for enhancing the conversion efficiency is designed. The conversion efficiency at the distance of 4[m] is 79.3[%] and the harvested power is 1.36[mW] which is actually used for the charging the battery. This value is available in the wireless sensor networking.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.1
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• pp.1-6
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• 2017

Recent researches on radio frequency energy harvesting networks(RF-EHNs) with limited energy resource like battery have been focusing on the development of a new scheme that can effectively extend the whole lifetime of a network to semipermanent. In order for considerable increase both in the amount of energy obtained from radio frequency energy harvesting and its charging effectiveness, it is very important to design a network that supports energy harvesting and data transfer simultaneously with the full consideration of various characteristics affecting the performance of a RF-EHN. In this paper, we proposes an interference-based charging aware routing protocol(ICARP) that utilizes interference information and charging time to maximize the amount of energy harvesting and to minimize the end-to-end delay from a source to the given destination node. To accomplish the research objectives, this paper gives a design of ICARP adopting new network metrics such as interference information and charging time to minimize end-to-end delay in energy harvesting wireless networks. The proposed method enables a RF-EHN to reduce the number of packet losses and retransmissions significantly for better energy consumption. Finally, simulation results show that the network performance in the aspects of packet transmission rate and end-to-end delay has enhanced with the comparison of existing routing protocols.

• ETRI Journal
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• v.44 no.3
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• pp.389-399
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• 2022

Wireless sensor networks (WSNs) are one of the basic building blocks of Internet of Things (IoT) systems. However, the wireless sensing nodes in WSNs suffer from energy constraint issues because the replacement/recharging of the batteries of the nodes tends to be difficult. Furthermore, a number of realistic IoT scenarios, such as habitat and battlefield monitoring, contain mobile sensing elements, which makes the energy issues more critical. This research paper focuses on realistic WSN scenarios that involve mobile sensing elements with the aim of mitigating the attendant energy constraint issues using the concept of radio-frequency (RF) energy extraction. The proposed technique incorporates a cluster head election workflow for WSNs that includes mobile sensing elements capable of RF energy harvesting. The extensive simulation analysis demonstrated the higher efficacy of the proposed technique compared with the existing techniques in terms of residual energy, number of functional nodes, and network lifetime, with approximately 50% of the nodes found to be functional at the 4000th, 5000th, and 6000th rounds for the proposed technique with initial energies of 0.25, 0.5 and 1 J, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.11
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• pp.2022-2028
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• 2017

Recently, the energy shortage of sensors and the leakage of private information are considered as serious problems as the number of sensors is increasing due to the technological advance in Internet-of-Things. RF energy harvesting, in which sensors collect energy from external RF signals, and physical layer security become increasingly important to solve these problems. In this paper, we propose a time switching-based network analog coding for improving information security in wireless networks where the relay can harvest energy from source signals. We formulate 2-hop relay networks where an eavesdropper tries to overhear source signals, and find an optimal time switching ratio for maximizing the minimum required secrecy capacity using mathematical analysis. Through simulations under various environments, it is shown that the proposed scheme improves the minimum required secrecy capacity significantly, compared to the conventional scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.10
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• pp.1849-1854
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• 2017

Recently, RF energy harvesting, in which energy is collected from the external RF signals, is considered as a promising technology to resolve the energy shortage problem of wireless sensors. In addition, it is important to guarantee secure communication between sensors for implementing Internet-of-Things. In this paper, we propose a power splitting-based network analog coding for maximizing a physical layer security in 2-hop networks where the wireless-powered relay can harvest energy from the signals transmitted by two sources. We formulate systems where two sources, relay, and eavesdropper exist, and find an optimal power splitting ratio for maximizing the minimum required secrecy capacity using an exhaustive search. Through simulations under various environments, it is demonstrated that the proposed scheme improves the minimum required secrecy capacity by preventing the eavesdropper from overhearing source signals, compared to the conventional scheme.

• Journal of the Korea Safety Management & Science
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• v.16 no.2
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• pp.111-119
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• 2014

This paper describes the design and implementation of a electromagnetic energy harvesting mechanism and electronic circuit for autonomous emergency call system. This analysis results show the power output of the proposed harvesting mechanism and circuit up to max power output 5V and it can hold up to 65 msec of the power generation and 10msec of the RF transmission. Based on the these testing results, the implementation of autonomous emergency call device without battery power or any external power source is feasible.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.9
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• pp.1044-1053
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• 2016

In this paper, we consider the secondary users (SUs) who are capable of harvesting energy from ambient radio frequency (RF) signals and are allowed to sequentially sense up to 2 different channels to find out idle channels not occupied by the primary users (PUs). The EH SUs are permitted to transmit data packets only if both idle channels and sufficient energy are available. Compared with traditional SUs, the EH SUs consume energy with data transmission and also harvest energy without additional energy supply. Consequently, the battery state is expected to be fluctuated due to energy consumption and harvesting, and therefore we develop a Markov battery model to provide energy variations at the 2-channel sensing EH SUs. With the proposed battery model, we derive the steady-state probability that the EH SUs completely run out of energy, and the achievable throughput of EH SUs is derived accordingly. To evaluate the proposed Markov battery model, the Monte-Carlo simulation was performed to validate the accuracy of energy outage probability and achievable throughput at the 2-channel sensing EH SUs.

• Journal of Satellite, Information and Communications
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• v.12 no.4
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• pp.141-145
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• 2017

Spectrum sensing is a critical functionality of Cognitive Radio(CR) systems and the CR systems can be applied to RF energy harvesting systems to improve an energy harvesting rate. There are number of spectrum sensing techniques. One of techniques is energy detection. Energy detection is the simplest detection method and is the most commonly used. But, energy detection has a hidden terminal problem in real wireless communication, because of secondary user (SU) can be affected by frequency fading and shadowing. Cooperative spectrum sensing can solve this problem using spatial diversity of SUs. But it has a problem of increasing data by processing multiple secondary. So, we propose the system model using adaptive spectrum sensing algorithm and system model is simulated. This algorithm chooses sensing method between single energy sensing and cooperative energy according to the received signal's Signal to Noise Ratio (SNR) from Primary User (PU). The simulation result shows that adaptive spectrum sensing has an efficiency and improvement in CR systems.

• Proceedings of the Korea Contents Association Conference
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• 2017.05a
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• pp.45-46
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• 2017

본 논문에서는 간섭신호가 존재하는 무선 에너지 중계 네트워크 환경에서 중계 노드의 에너지 수확률을 결정하는 TSR 기반 에너지 하베스팅 기법의 성능을 향상시키기 위하여 간섭을 고려한 전송채널 분석 모델과 에너지 하베스팅 최적화 기법을 제안한다. 특히, 간섭 신호를 고려한 최적의 수신기 모드 스위칭 메커니즘 설계를 위한 최적의 에너지 수확률(energy harvesting ratio) 결정 기법을 제안하여 RF 에너지 하베시팅 시스템의 처리율을 최대화 할 수 있도록 하였다.

• Journal of Sensor Science and Technology
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• v.29 no.5
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• pp.293-302
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• 2020

Food safety has emerged as a growing concern for human health in recent times. Consuming contaminated food may lead to serious health problems, and therefore, a system for monitoring food freshness that is both non-detrimental to the quality of food and highly accurate is required to ensure that only high-quality fresh food packages are provided to the customers. This paper proposes a method to monitor and detect food quality using a compact smart sensor tag. The smart tag is composed of three ultra-low-power sensors, which monitor four major indicators of food freshness: temperature, humidity, and the concentrations of ammonia and hydrogen sulfide gases. An RF energy scavenging circuit is integrated into the smart sensor tag to harvest energy from radio waves at a high frequency of 13.56 MHz to supply sufficient power to the tag. Experimental results show that the proposed energy harvester can efficiently obtain energy at a distance of approximately 40 cm from a 4 W reader. In addition, the proposed smart sensor tag can operate without any battery, thereby eliminating the requirement of frequent battery replacement and consequently decreasing the cost. Meanwhile, the freshness of preserved pork is continuously monitored under two conditions--room temperature and refrigerator temperature--both of which are the most common temperatures under which food is generally stored. The food-monitoring experiments are conducted over a period of one week using the proposed battery-less tag. Based on the experimental results, the food assessment is classified into four categories: fresh, normal, low, and spoiled.