• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.6
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• pp.147-152
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• 2016

Wireless sensor networks that are easy to deploy and install are ideal for building a system that monitors the condition of the equipment in a factory environment where wiring is difficult. The ZigBee has characteristics of low price and low power compared with other wireless communication protocols and is suitable for a monitoring system requiring a plurality of nodes. ZigBee communication requires encryption security between devices because all protocol layers are based on OTM trusted by each other. In the communication between nodes, node authentication must be guaranteed and exposure of confidential information managed by each node should be minimized. The facilities of the factory are regular and stationary in distribution location. In order to protect the information gathered from the sensor in the factory environment and the actuator control information connected to the sensor node, we propose a cryptosystem based on the two - dimensional grid - based key distribution method similar to the distribution environment of the facility.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4A
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• pp.345-355
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• 2011

This paper introduces the coded cooperation protocol in wireless relay network. We propose a two relay based coded cooperation protocol with RCPC codes for wireless networks. The proposed two-relay based system can achieve a diversity of order 4 under slow fading environment. Under fast fading, the diversity order is 2 times of the free distance of the convolutional code. We develop upper bounds on BER and FER for the system under both slow and fast fading with Rayleigh distribution. The effect of various channel conditions on the cooperation is also examined in this work.

• Journal of electromagnetic engineering and science
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• v.15 no.1
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• pp.14-19
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• 2015

In multicellular wireless networks, intercell interference limits system performance, especially cell edge user performance. One promising approach to solve this problem is the intercell interference coordination (ICIC) scheme. In this paper, we propose a new ICIC scheme based on a resource partitioning approach to enhance cell edge user performance in a wireless multicellular system. The most important feature of the proposed scheme is that the algorithm is performed at each base station in a distributed manner and therefore minimizes the required information exchange between neighboring base stations. The proposed scheme has benefits in a practical environment where the traffic load distribution is not uniform among base stations and the backhaul capacity between the base stations is limited.

• Journal of the Korean Society for Railway
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• v.16 no.6
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• pp.540-550
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• 2013

The Future Wireless Railway Communication System(FWRCS) has attracted attention for the various advantages of such a system like efficient management, precise periodicity of operation and speedy travel. Related to it, the area of bandwidth requirement estimation for the FWRCS is being researched actively because there is a great need for accurate bandwidth distribution. In this paper, sophisticated bandwidth requirement estimation method for FWRCS is proposed by modifying ITU-R M.1390. With this method, the expected frequency requirements for the present, for five years from now, and for 10 years from now can be calculated by applying the data gathered from the actual field.

• Journal of the Korean Magnetics Society
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• v.22 no.3
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• pp.97-102
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• 2012

In this paper, a non-contact power transferring has been performed. Power Transferring by using an electromagnetic inductive coupling is more suitable for high power transmission than by using a magnetic resonance method. Power transferring system has been designed with Loading Distribution Method to divide the electric and magnetic loading for designing the magnetic core and electric coil. To design optimum shapes of magnetic yoke, 3D finite element analysis has been performed. Experimental results show good agreement with numerical ones. So, it could be adopted in the electric power transferring system for a short-distance wireless electric power transferring machine.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2899-2902
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• 2003

Mobile communication is one of the fastest growing industries in the world and especially in Korea, where we have well over 30 million voice subscribers. Mobile communication now offers variety of data communication services such as wireless internet, multimedia messages, and color graphic displays. Handsets also have grown to accommodate such services, thus with functionalities such as programmable virtual machines that users can download and execute their own programs. In this paper, we have demonstrated a PCS handset monitoring system which can monitor biometry signals - in this case ECG over wireless internet and wireless data network (IS95C) based on programmable virtual machine architecture. The remote client handset receives data signals from a centralized server and processes and displays them in human friendly form in real time. Since every single handset on sales in Korea has programmable virtual machine and more than 10 million handsets are in distribution already, proper applications may have substantial impact on the related fields.

• Journal of Internet Computing and Services
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• v.18 no.6
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• pp.15-23
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• 2017

Wireless power transmission (WPT) for wireless charging is currently attracting much attention as a promising approach to miniaturize batteries and increase the maximum total range of an electric vehicle. The main advantage of the laser power beam (LPB) approach is its high power transmission efficiency (PTE) over long distance. In this paper, we present the design of a laser power beam based WPT system, which has a best WPT channel selection technique at the receiver end when multiple power transmitters and single power receiver are operated simultaneously. The transmitters send their transmission channel information via optically modulated laser pulses. The receiver uses the received signal strength indicator and digitized data to choose an optimum power transmission path. We modeled a vertical multi-junction photovoltaic cell array, and conducted an experiment and simulation to test the feasibility of this system. From the experimental result, the standard deviation between the mathematical model and the measured values of normalized energy distribution is 0.0052. The error between the mathematical model and measured values are acceptable, thus the validity of the model is verified.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.4
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• pp.886-892
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• 2010

It is possible to use wireless communication any time in every place because of well-developed wireless networks and mobile devices. The AVL(Automatic Vehicle Location) system, therefore, has made practical use in situation control, distribution industry, home delivery service, and ITS(Intelligent Transportation System) area. In this paper, we design and implement an AVL system in order to use for fire fighting activities such as emergency rescue and relief. To do this, first, we investigate and analyze the existing researches and systems related to AVL system. In details, we develop an AVL server and clients to support stable communication each other using wireless networks. Using AVL system, calling cars find the position of accidents quickly and the fire defense headquarters control unforeseen accidents efficiently because the state of calling cars are confirmed in real time by their GPS data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6A
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• pp.438-449
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• 2012

This paper presents new CRC-p codes for VHF band maritime wireless communication system based on performance analysis of various CRC codes. For this purpose, we firstly describe the method of determination of undetected error probability and minimum Hamming distance according to variation of CRC codeword length. By using the fact that the dual code of cyclic Hamming code and primitive BCH code become maximum length codes, we present an algorithm for computation of undetected error probability and minimum Hamming distance where the concept of simple hardware that is consisted of linear feedback shift register is utilized to compute the weight distribution of CRC codes. We also present construction of transmit data frame of VHF band maritime wireless communication system and specification of major communication parameters. Finally, new optimal CRC-p codes are presented based on the simulation results of undetected error probability and minimum Hamming distance using the various generator polynomials of CRC codes, and their performances are evaluated with simulation results of bit error rate based on the Rician maritime channel model and ${\pi}$/4-DQPSK modulator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5A
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• pp.561-570
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• 2008

Time synchronization is essential for a number of network applications such as high speed communication and parallel/distribution processing systems. As the era of ubiquitous computing is ushered in, the high precise time synchronization in wireless networks have been required in. This paper presents the design ana the implementation of the high precision time synchronization in wireless networks using ZigBee. To achieve high precision requirements, we have tried to analyze and reduce error factors such as the latency and jitters of a protocol stack on wireless environments. In addition, this paper includes some experiments and performance evaluations of our system. The result is that we established for nodes in a network to maintain their elects to within a 50 nanosecond offset from the reference clock.