• 전자공학회논문지 IE
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• v.43 no.2
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• pp.80-86
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• 2006

The wireless communication based on LDPC and adaptive spatial-subcarrier coded modulation using MQAM for orthogonal frequency division multiplexing (OFDM) wireless transmission by using instantaneous channel state information and employing multiple antennas at both the transmitter and the receiver. Adaptive coded modulation is a promising idea for bandwidth-efficient transmission on time-varying, narrowband wireless channels. On power limited Additive White Gaussian Noise (AWGN) channels, low density parity check (LDPC) codes are a class of error control codes which have demonstrated impressive error correcting qualities, under some conditions performing even better than turbo codes. The paper demonstrates OFDM with LDPC and adaptive modulation applied to Multiple-Input Multiple-Output (MIMO) system. An optimization algorithm to obtain a bit and power allocation for each subcarrier assuming instantaneous channel knowledge is used. The experimental results are shown the potential of our proposed system.

• 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.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.5
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• pp.25-30
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• 2020

Recently, non-orthogonal multiple access (NOMA) have been received considerable attention to be involved in the next generation mobile system. However, there are inherent inter-user interferences caused by the multiplexing multiple users in the same communication resource in NOMA systems. Two representative methods, the approximate white noise and random variable methods, have been adapted for the analysis of interferences in NOMA systems. In this paper, we derive the outage probabilities of an uplink NOMA system with the two analysis methods and compare the results. The numerical results of the outage probabilities versus transmitted power, distances, and power allocation are compared. We noticed that the derived functions are different each other, but the numerical results are coincident. It is shown that the two interference analysis methods can be applied to the analysis of NOMA systems.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.6 s.360
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• pp.48-56
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• 2007

OFDMA (Orthogonal Frequency Division Multiple Access) is widely used as multiple access techniques for next generation mobile communication systems. However, OFDMA has a disadvantage of high peak-to-average power ratio and SC-FDMA (Single-Carrier Frequency Division Multiple Access) was proposed for uplink systems to overcome the drawback. SC-FDMA also has several demerits including degraded performance with high-order modulations or with multiple antenna techniques, and less flexibility in resource allocation and pilot patterns. In order to achieve the best performance over a wide range of environments, each mobile station should select either of OFDMA and SC-FDMA according to the given condition and a pilot structure for SC-FDMA systems should be similar to that of OFDMA to maintain the same frame structure. While conventional SC-FDMA schemes require an entire SC-FDMA symbol or a separate short symbol for pilots, this paper proposes a method which supports the pilots included in SC-FDMA data parts and enables a SC-FDMA frame to hold the same structure as an OFDMA frame.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.3
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• pp.520-526
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• 2018

In this paper, considering the superposition transmission-based wireless cooperative multicast communication system (ST-CMS) with multiple relays and destinations, we propose a relay selection scheme to improve the data rate of multicast communication. In addition, we adopt the optimal power allocation coefficient for the superposition transmission to maximize the data rate of the proposed relay selection scheme. To propose the relay selection scheme, we derive an approximate expression for the data rate of the ST-CMS, and present the relay selection scheme using only partial channel state information based on the approximate expression. Moreover, we derive an approximate average data rate of the proposed relay selection scheme. Through numerical investigation, comparing the average data rates of the proposed relay selection scheme and the optimal relay selection scheme using full channel state information, we show that the proposed scheme provides extremely similar performance to the optimal scheme in the high signal-to-noise power ratio region.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.33-41
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• 2018

The idea of the Internet of Things as a platform on the Smart Campus has become increasingly popular. It requires an infrastructure consisting of communication networks, sensor nodes and gateways to connect to the Internet. Each sensor node is responsible for gathering data from the environment. This document outlines a network of wireless sensors on the Internet for the application of Smart Campus monitoring. Wireless sensor network Monitoring have become a complete solution to using a low power implementation and integrated systems. The numerous restrictions however result from the low communication range, the limited computing power, the lack of availability of the network protocol, the lack of programming security and the security failures in the areas of confidentiality, integrity and availability. A new security technique and its functionality for WSNM nodes developed. Development in the research of a secure network and suggestions for avoiding denial of service (DOS) and complexity attacks. These systems if properly implemented can provide an energy efficiency mechanism through pre-allocation and a new key from key management models with a secure routine algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.10
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• pp.1279-1286
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• 2021

The electrocardiogram (ECG) signal is a good indicator for early diagnosis of heart abnormalities. The ECG signal has a different reference normal signal for each person. And it requires lots of data to diagnosis. In this paper, we propose an adaptive OpenCL-based FPGA-GPU hybrid-layer platform to efficiently accelerate ECG signal diagnosis. As a result of diagnosing 19870 number of ECG signals of MIT-BIH arrhythmia database on the platform, the FPGA accelerator takes 1.15s, that the execution time was reduced by 89.94% and the power consumption was reduced by 84.0% compared to the software execution. The GPU accelerator takes 1.87s, that the execution time was reduced by 83.56% and the power consumption was reduced by 62.3% compared to the software execution. Although the proposed FPGA-GPU hybrid platform has a slower diagnostic speed than the FPGA accelerator, it can operate a flexible algorithm according to the situation by using the GPU.

• Korean Journal of Social Welfare
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• v.69 no.4
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• pp.99-125
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• 2017

Recent social studies on space have focused on changing the social relations that activate in space. In general, these studies have been based on the concept of social space on which is grounded the power-relation analysis such as power, oppression, resource allocation, and so on. Social work practice has traditionally recognized the importance of the environment surrounding human beings. Nonetheless, social work practice has tended to comprehend space in a neutral and abstract way because it has insufficiently considered modern spatial theories. For this reason, this study focusing on Lefebvre's social space theory reviewed the contemporary discourses on space in the area of social work practice. Following the review, this study attempted to establish the concept of "Space-based Social Work Practice". Specifically, this study analyzed the actual cases in social work field and explored the applicability of "SSWP". According to the results, this study delivered the implications of Space-based Social Work Practice as an alternative method and suggested the practical direction of SSWP.

• Journal of National Security and Military Science
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• s.7
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• pp.271-303
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• 2009

"Ubiquitous sensor network" definition is this-Someone attaches electro-magnetic tag everything which needs communication between man to man, man to material and material to material(Ubiquitous). By using attached every electro-magnetic tag, someone detects it's native information as well as environmental information such as temperature, humidity, pollution and infiltration information(Sensor). someone connects it realtime network and manage generated information(Network). 21st century's war is joint combined operation connecting with ground, sea and air smoothly in digitalized war field, and is systematic war provided realtime information from sensor to shooter. So, it needs dramatic development on watch reconnaissance, command and control, pinpoint strike etc. Ubiquitous computing and network technologies are essential in national defense to operate 21st century style war. It is possible to use many parts such as USN combined smart dust and sensor network to protect friend unit as well as to watch enemy's deep area by unmanned reconnaissance, wearable computer upgrading soldier's operational ability and combat power dramatically, RFID which can be used material management as well as on time support. Especially, unmanned watch system using USN is core part to transit network centric military service and to get national defense efficiency which overcome the dilemma of national defense person resource reducing, and upgrade guard quality level, and improve combat power by normalizing guardian's bio rhythm. According to the test result of sensor network unmanned watch system, it needs more effort and time to stabilize because of low USN technology maturity and using maturity. In the future, USN unmanned watch system project must be decided the application scope such as application area and starting point by evaluating technology maturity and using maturity. And when you decide application scope, you must consider not only short period goal as cost reduction, soldier decrease and guard power upgrade but also long period goal as advanced defense ability strength. You must build basic infra in advance such as light cable network, frequency allocation and power facility etc. First of all, it must get budget guarantee and driving force for USN unmanned watch system project related to defense policy. You must forwarded the USN project assuming posses of operation skill as procedure, system, standard, training in advance. Operational skill posses is come from step by step application strategy such as test phase, introduction phase, spread phase, stabilization phase and also repeated test application taking example project.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.1
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• pp.75-80
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• 2009

Bum-in test is one for eliminating semiconductor devices that are subject to early failures and other operational problems; it is usually carried out on the devices by imposing severe test conditions such as elevated voltages, temperatures, and time. In order for such a test to be performed, each burn-in board having devices to be tested, needs to be inserted into a corresponding slot. A set of such slots is called a zone. The slots comprising a zone can only have the burn-in boards with the devices of the same type. In order to test many different types of semiconductor devices, it is desirable to build a burn-in test system to have as many zones as possible. A zone controller controlling a zone, is a device that performs a burn-in test and collects test results. In case of existing systems, each zone controller takes care of a zone that consists of a fixed number of slots. Since a zone controller is, in most cases, embedded into a workstation that controls the overall testing process, adding new zone controllers is restricted by the spaces for them. As a way to solve or alleviate these problems, a dynamic zone system in which the number of slots in a zone can be dynamically allocated, is presented. This system maximizes the efficiency of system utilization, by altering the number of slots and hence minimizing the idle slots of a zone. In addition, all the test operations being performed must be aborted for maintenance in existing systems. In dynamic zone systems, however, a separate and independent maintenance is allowed for each slot, as long as the main power supply system has no problem.