• Journal of Broadcast Engineering
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• v.23 no.2
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• pp.293-301
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• 2018

In ISDB-T, which is Japanese digital terrestrial TV specification based on OFDM technology, 6MHz bandwidth is divided into 13 segments. Twelve segments (full-seg) are used for high definition broadcasting for fixed receivers and one segment (one-seg) for mobile receivers. Though one-seg supports high speed mobility by using QPSK modulation, it is not suitable for large display mobile devices because of its low data rate. Full-seg using 64QAM modulation also suffers from its low mobile performance. In this paper, mobile performance of ISDB-T full-seg receiver is evaluated by applying sub-carrier interference removing scheme, high speed mobile channel estimation scheme and antenna diversity scheme.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.225-230
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• 2005

The proposed Triple-band Compact Chip Antenna using Coupled Meander line and stacked meander Structure for Mobile RFID/PCS/WiBro. The proposed antenna is designed to operate at 900, 1800, and 2350 MHz, and is realized by parasitic coupled and stacked a meander line. Meander lines are using extend length of effective current path more than monopole and contribute miniaturization. The coupled meander line controls the excitations of the Mobile RFID and PCS, stacked meander line controls the excitation of the WiBro. The proposed antenna size is $11mm\times22.5mm\times1mm$. The antenna supports 900MHz, 1800MHz and 2350MHz operations simultaneously with bandwidths of 33MHz, 230MHz and 100MHz, respectively. The proposed antenna gains are result of simulation to be -0.8dBi, 3dBi and 3.8dBi, respectively.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.119-124
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• 2010

디지털 제작, 압축 기술의 발전, 유무선 인터넷 보급 확산, 다양한 전송 및 서비스 플랫폼의 등장, 전송 기술의 광대역화, 단말 기술의 발전, 라이프스타일 변화와 킬러 서비스 등장으로 미디어 시장은 급속도로 발전하고 있다. 지상파 방송은 아날로그에서 디지털로 전환하고 있으며, 고화질, 다채널, 모바일, 3D 서비스를 제공하거나 제공할 예정에 있다. 현재 디지털 TV는 아날로그 TV와 동시 방송 형태로 제공되고 있지만 2012년말 디지털 TV로 완전한 전환을 앞두고 있으며, 모바일 TV인 DMB는 2005년말 본방송을 시작하여 전국 서비스를 제공하고 방송 커버리지를 확장하고 있다. FM과 AM의 디지털화를 위한 디지털 오디오 방송도 방식 선정을 위한 절차가 진행 중이다. 전파는 송신소에서 단말까지 전송되는 도중 신호레벨 감쇠, 페이딩, 왜곡, 잡음 유입 등을 겪게 된다. 양질의 지상파 방송을 제공하기 위해서는 전파가 수신 가능한 상태 이상의 양호한 상태로 시청자에게 전달되어야 한다. 이를 위해 방송사는 방송 수신 품질을 측정하고 수신이 불량한 지역에 대해서는 송신기 설치, 송신 출력 증강, 중계기 설치 등을 통해 양질의 서비스 제공이 가능한 방송 서비스 영역을 확대한다. 다양한 지상파 방송 매체에서 수신 품질 평가를 위해 가장 많이 측정하는 항목은 전계강도이다. 대부분의 경우 어떤 지역의 전계강도가 해당 매체가 요구하는 기준 레벨 이상이면 해당 지역을 양호 지역으로 평가한다. 본 논문에서는 다양한 지상파 방송 매체에 대한 전계강도를 측정하고 이를 분석할 수 있는 시스템을 제안하고자 한다. 제안 시스템을 이용하면 자동화된 절차에 의해 최단 시간에 다양한 지역에 대한 방송 수신 품질을 측정하고, 그 결과를 분석하여 방송 서비스 영역에 대한 평가를 내릴 수 있으며, 측정결과를 DB로 관리하여 동일 채널에 대한 이전 측정결과와 비교 분석, 다른 채널과 전계강도 비교 분석을 통해 특정 송신기 출력이 감소되거나 특정 안테나 출력에 문제가 발생한 경우에도 이를 쉽게 감지하여 최적의 방송망 구축 및 관리가 가능하다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.11
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• pp.902-915
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• 2017

In recent years, mobile devices have become increasingly multi-functional and high performance, resulting in a dramatical increase in processing speed. On the other hand, the size of device is reduced, circuits inside the device are more easily exposed to electromagnetic interference radiated from antenna or adjacent circuits, degrading the system performance. To prevent this, it is necessary to design the device considering the electromagnetic characteristics with EM simulation at the design stage of product. However, the EM simulation takes a long analysis time and require high-level system resources for fast analysis. In this paper, an equivalent circuit modeling method for a round wire is proposed using a PEEC method and the electromagnetic coupling from a dipole antenna to a transmission line is analyzed in frequency domain. And compared with the result of electromagnetic simulator. As a result, PEEC method shows good agreement with those of electromagnetic simulation, in a much more short time.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.5
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• pp.44-51
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• 2015

The deployment of high capacity backhaul is required due to explosive growth in mobile data services. For rapid backhaul deployment, point to point microwave is a much easier and cheaper technology. The space diversity scheme is used in point to point microwave links. The purpose of space diversity is to overcome fading by combining signals from two separate receiver antennas. For signal combining algorithm, maximum power and minimum distortion methods were used and these algorithms were reported not to be good enough for robustness in selective fading. In this paper, a more practically efficient signal combining scheme from the main and diversity branch is proposed and evaluated in selective fading channel. The proposed algorithm has shown significant performance improvement in terms of signal spectrum.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.6
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• pp.535-544
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• 2013

This paper considers an uplink power control scheme for a virtual multi-input multi-output (MIMO) multi-cell system where multiple mobile stations with single transmit antenna form a virtual MIMO link. Unlike the conventional approach of the game theoretic formulation to add a power penalty term to improve the performance, a constraint on the total effective interference power is introduced to the maximization of the utility function of the transmission rate with linear receive beamforming. Introducing inertia, we show that the proposed power control is guaranteed to converge. The simulation results verify that the proposed power allocation can significantly improve the performance in an interference limited multi-cell system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4A
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• pp.401-407
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• 2010

As according to utilizing mobile devices, the real time locating system to provide high quality service is required. RTLS based on wireless communication can be damaged from radio shadow areas which guarantee the line of sight. To cope with the radio shadow area, this paper proposes the performance improvement method using assistant tags and a directional antenna based reader. In addition, this paper also provides the design and implementation of RTLS and experiments for performance evaluation. The result shows that a success rate is increased up to 38% and accuracy is a CEP of 1.13 meters.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.5
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• pp.902-910
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• 2016

Recently, the volume of mobile data traffic increases exponentially due to the emergence of various mobile services. In order to resolve the problem of mobile traffic increase, various new technologies have been devised. Especially, two-way relay communication in which two nodes can transfer data simultaneously through relay node, has gained lots of interests due to its capability to improve spectral efficiency. In this paper, we analyze the SM-PNC which combines Physical-layer Network Coding (PNC) and Spatial Modulation (SM) under two-way relay communication environment. Log-Likelihood Ratio (LLR) is considered and both separate decoding and direct decoding have been taken into account in performance analysis. Through performance evaluation, we have found that the bit error rate of the proposed scheme is improved compared to that of the conventional PNC scheme, especially when SNR is high and the number of antennas is large.

• Journal of Advanced Navigation Technology
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• v.18 no.1
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• pp.84-89
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• 2014

Worldwide Interoperability for Microwave Access (WiMAX) is an efficient technology for 20th century communication system. The technology provides broadband speed without the need for cables and is based on the IEEE 802.16 standard(also called Wireless MAN). Mobile WiMAX is defined as IEEE802.16e which is advanced and efficient technology for mobile telecommunication rather than GSM, CDMA technology. In this work link budget calculation for WiMAX have been done. Cell range have been calculated over digital modulations and they are BPSK, QPSK and QAM. Here different types of models like Cost 231 model have been used for different types of areas like open, rural and urban areas and Erceg-Greenstein model for sub-urban areas. Effect of various parameters like frequency, base station antenna height, transmission power and SNR over cell range have been studied. Analysis have done for both uplink and downlink.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.12
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• pp.66-72
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• 2011

In Japan, the specification for digital terrestrial television broadcasting systems has been approved for employing a transmission scheme for ISDB-T, which can accommodate HDTV service and portable mobile reception by adapting segmentation of frequency. In this paper, we have developed 3.5 inch mobile TV according to One-Seg system and presented the results of our development. In addition, we introduce two diversity schemes to compensate the defect that signal is interrupted when the portable TV is moving fast. In order to achieve a reliable communication in One-Seg system, we introduce STD(space time diversity) which uses more than 2 antennas at TX and cooperative reception diversity which utilizes signal-exchanging between different mobile terminals. And, its performance enhancements to reception reliability of previous system are evaluated by computer simulations.