• Journal of Satellite, Information and Communications
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• v.4 no.2
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• pp.28-33
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• 2009

In this paper, we evaluate the performance of various diversity techniques which can contribute to provide efficient multimedia broadcasting services via hybrid/integrated satellite and terrestrial network. Space-time coding can achieve the diversity gain in a multi-path environment without additional bandwidth requirement. Recent study results reported that satellite systems can achieve high diversity gains by appropriate utilization of STC and/or forward error correction. Based on these previous study results, we present various cooperative diversity techniques by combing STC and rate compatible turbo codes in order to realize the transmit diversity for the mobile satellite system. The satellite and several terrestrial repeaters operate in unison to send the encoded signals, so that receiver may realize diversity gain. The results demonstrated in this paper can be utilized in future system implementation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.5
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• pp.451-458
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• 2013

This paper proposes a cross-tier interference avoidance scheme to improve femtocell performance in single frequency heterogeneous cellular networks (SFHCN). The scheduled macrocell users located close femtocell base stations cause serious interference to those femtocells so that the performance of femtocell is dramatically deteriorated. To solve this problem, this paper proposes an interference avoidance scheme by reversing the uplink and downlink frames of such femtocells. After reversing the uplink and downlink frames, femtocell base station relays the macrocell user data as well as transmitting its own data. In the 1st relaying link, femtocell and macrocell users transmit their data respectively divided uplink frames and in the 2nd relaying link, femtocell base station transmit macrocell and femtocell data using a simultaneously superposition coding scheme. Computer simulation results confirm performance improvement of proposed scheme.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.177-183
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• 2015

The purpose of ICT Healing platform is the prevention of chronic disease. It is intended to early warning of the disease through the information such as the bio-signals and lifestyle. In this paper, we provide a 2-Step open system(TOS) for personalized health data access. TOS is connected between the personal health related data providers and service providers of individuals ICT Healing platform, a software engine for relaying personalized health data. The proposed system, to operate in isolation to 2 step in personal health document repository Inbound module and Outbound module to provide an inquiry service to external organizations. Therefore, we propose a personalized editable Manifest concept for defining data exchange between Step. This can be used as a reference model to collect the personal health information is scattered in many health related service institutions (Hospitals, Fitness Centers, Health Examination Centers, Personal Health Device, etc.) and under private-led liberalization.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.11
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• pp.763-770
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• 2014

In traditional routing protocols including LEACH for wireless sensor networks, nodes suffer from unbalanced energy consumption because the nodes require large transmission energy as the distance to the sink node increase. Multi-hop based routing protocols have been studied to address this problem. In existing protocols, each cluster head usually chooses the closest head as a relay node. We propose LEACH-CHT, in which cluster heads choose the path with least energy consumption to send data to the sink node. In our research, each hop, a cluster head selects the least cost path to the sink node. This method solves the looping problem efficiently as well as make it possible that a cluster head excludes other cluster heads placed farther than its location from the path, without additional energy consumption. By balancing the energy consumption among the nodes, our proposed scheme outperforms existing multi-hop schemes by up to 36% in terms of average network lifetime.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.4
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• pp.635-641
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• 1998

This paper presents development of a small size LNA operating at 824 ∼ 849 MHz used for a receiver of a CELLULAR CDMA Base station and a transponder. Using resistive decoupling circuits, a signal at low frequency is dissipated by a resistor. This design method increases the stability of the LNA and is suitable for input stage matching. The LNA consists of low noise GaAs FET ATF-10136 and internally matched VNA-25. The LNA is fabricated with both the RF circuit and the self-bias circuits in aluminum housing. As a result, the characteristics of the LNA implemented here shows above 35dB in gain and below 0.9dB in noise figure, 18.6dBm P1dB power, a typical two tone IM3, -31.17dB with single carrier backed off 10dB from P1dB.

• Journal of Internet Computing and Services
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• v.6 no.3
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• pp.71-84
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• 2005

Recently, the expert call center solution has become the center of interest, since finance and tele-marketing system, which is focused on a communication industry, have been increasing, Specially, the call center market is growing up with a supporting Caller-ID for a cellular phone in Korea, In the present, although large size companies are developing expensive solutions and instruments to service only for the big companies, there little solutions for SOHO markets, Therefore, in this paper we have shown a design and an implementation of a CTI system which is capable of in/outbound call processing by using CTI, and providing stable services by linking the customer's DB. And these functionalities have become possible by integrating functions of PBX and the computer control of the PBX. First, we have constructed call flows and analyzed packets for the standard communication through the PBX in call. Then, we have designed and implemented a middleware which linked a call between a client and a customer. Finally, we have constructed a database module for applying the CRM technology to the management of customer's contents.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.5
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• pp.1013-1019
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• 2016

This paper describes a novel Context-awareness Markov Chain Prediction (CMCP) algorithm based on movement prediction using Markov chain in Delay Tolerant Network (DTN). The existing prediction models require additional information such as a node's schedule and delivery predictability. However, network reliability is lowered when additional information is unknown. To solve this problem, we propose a CMCP model based on node behaviour movement that can predict the mobility without requiring additional information such as a node's schedule or connectivity between nodes in periodic interval node behavior. The main contribution of this paper is the definition of approximate speed and direction for prediction scheme. The prediction of node movement forwarding path is made by manipulating the transition probability matrix based on Markov chain models including buffer availability and given interval time. We present simulation results indicating that such a scheme can be beneficial effects that increased the delivery ratio and decreased the transmission delay time of predicting movement path of the node in DTN.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.980-992
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• 2011

WSN gateway which runs transmission between WSN (Wireless Sensor Network) based on IEEE 802.15.4 and PN (Public Network) based on TCP/IP belongs to core technology of application based on two network. Because WSN Gateway receives various kinds of packet from many sensor nodes in an uncertain time as well as uses hardware's performance enough, it has high level of complexity about software and it is hard to be implemented. To solve these problems, this paper suggests both efficient event detection scheme for identify packet and implementation unit of protocol called 'Transaction'. The results of applying the proposed network framework, complexity of software reduces. And we provide software development environments of reflect various performance requirements.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.2
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• pp.473-480
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• 2013

In this paper, location recognition algorithm is developed to improve the accuracy using improve Trilateration. The location recognition algorithm is first calculate the location refer to the measured signal power. Error can be occurred when measure distance with arranged node in specific location. If the distance data is received from node (receiver, coordinator), Node selected for location calculation is defined through section. If the distance data is received from node (receiver, coordinator), Node selected for location calculation is defined through section. Second, we apply algorithm of section filtering. If there are 4 sections in node, we consider 1 section to 6 location recognition coordinates. A special characteristic drawback of RF is that the actual distance is actually farther than the calculated received distance data. This is error is incurred when the signal strength increases. We reduce the location recognition error by applying an improved algorithm as secondary after filtering primary through section filtering.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.408-414
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• 2005

The VCDRO(Voltage Controlled Dielectric Resonate. Oscillator) with low phase noise is designed using nonlinear analysis, and its phase noise characteristics are compared with that of Lesson's equation. The microstripline coupled with dielectric resonator is realized as a high impedance inverter to improve the phase noise performance, and the quality factor of resonator circuit can be transferred to active device with the enhanced the loaded quality factor. The worst case and part stress analyses are achieved to obtain the high reliability of VCDRO and the reliability analysis is accomplished to estimate the probability of operation at the end of life. The developed VCDRO has the oscillating tuning factor of 0.56MHZ1V for the control voltage range of 0-l2V. This VCDRO requires the DC power of 136mW. The phase noise characteristics exhibit good performances of -94.18dBc/Hz (a)10KHz and -116.3dBc/Hz (a)100KHz. And, the output power over 7.33dBm is measured.