• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.1 s.343
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• pp.89-94
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• 2006

We present a generalized version of principal ratio combining (PRC)[1], which is a near-optimum decoding scheme for space-time trellis codes in quasi-static flat fading environments. In [1], the performance penalty increases as the number of receive antennas increases. In the proposed scheme, receive antennas are divided into K groups, and the PRC decoding method is applied to each group. This shows a flexible tradeoff between performance and decoding complexity by choosing the appropriate K. Moreover, we also propose the performance index(PI) to easily predict the decoding performance among the possible different(receive antenna) configurations.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.11
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• pp.21-27
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• 2002

When decision-directed channel estimation is used for QAM-OFDM systems, the optimal shape of the two-dimensional filter depends on the amplitudes of the modulated symbols as well as the channel characteristics such as delay spread, Doppler frequency, and signal-to-noise ratio. While most conventional channel estimation methods did not consider the amplitudes of the modulated symbols because of the large computational complexity, we propose a simple channel estimation method for multi-level-amplitude-modulated systems. The proposed method can effectively reduce the noise variance of the estimates with small-sized filtering and there is a possibility of reducing the implementation cost and producing better results by avoiding the bias due to large filter sizes.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.12
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• pp.117-124
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• 2009

In this paper, we have developed communication modules for ubiquitous transportation sensor network (u-TSN). The developed module can be used for intelligent transportation services. The developed systems are based on IEEE 802.11a and IEEE 802.11g technologies for vehicle and infrastructure systems, respectively. We have found that the throughput for the developed systems is at maximum around 15 Mbps. It is reduced to 10 Mbps at a long distance and high speed condition. The performance is enough to support traffic control services in dense traffic condition.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.3-10
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• 2012

The visible light communication takes advantages of LED and PD for communication and is considered as a next generation wireless communication technology. It can support variety indoor applications. Especially, Visible LAN service has drawn much attention due to high data rate and no interference with existing WPAN system as well as high efficiency in illumination. However, existing MAC protocol occurs a high communication delay due to uplink collision and backoff time. In this paper, to reduce packet delay, we propose an enhanced MAC protocol based on FDD where the time difference between uplink frame and downlink frame transmission is utilized. Through computer simulations, we verified that the proposed MAC protocol outperforms the existing MAC protocol in terms of average packet delay.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1416-1426
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• 2008

In this paper, we present a small size and multiband directional dipole antenna for mobile communication repeaters. In the omni-directional dipole antenna, a planar reflector under the dipole provides improved directivity in front-direction with wide beamwidth. In order to miniaturize the directive dipole, the size of the reflector is reduced. A vertical stub on the reflector is proposed to enhance the front-directivity of the radiation pattern and mitigate the backward radiation due to the reduced reflector. Furthermore, we use horizontal stubs on edge of vertical stub to obtain additional reduction of the antenna size. To meet the current demand of wireless communication service, the designed antenna shows wideband characteristic by employing electromagnetic coupled two-dipoles with dual-resonance frequencies.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.1
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• pp.122-130
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• 2012

In this paper, we propose a broadband vehicle antenna that can operate at the WiBro band(2.3~2.4 GHz) for a wireless internet service. The feeding of the proposed antenna consists of two T-matching networks on both side of the polyarcylate substrate, and the two T-matching networks are connected through via holes. The designed antenna was built and installed on a rear window of a commercial sedan, and the antenna performances, such as the reflection coefficients and the radiation gain are measured in the open-sight area. The received signal strength of the designed antenna was also tested in a strong field area as well as in a weak field area. The measurement results show the matching bandwidth($S_{11}$ <10 dB) of about 300 MHz in the WiBro band and the average gain of about -5.13 dBi along the azimuth direction.

• Journal of Advanced Navigation Technology
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• v.15 no.4
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• pp.585-590
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• 2011

In the past few years, M2M (Machine-to-Machine) applications have become a hot topic in the wireless industry. While M2M applications can be used for many purposes (smart homes, smart metering/electricity meter reading, fleet management, mobile workforce, automobile insurance, vending machines, etc), and in many sectors (healthcare, agriculture, commercial, industrial, retail, utility, etc.), smart metering applications or smart grids present the biggest growth potential in the M2M market today. M2M platform is the future ubiquitous network technologies which provide the integrated service with the networks and devices. The promising technologies to tackle these problems are the Semantic technologies, for interoperability, and the Agent technologies for management of complex systems. In this paper the information communication technique based on the disaster prevention system's for the M2M, concepts and its requirement technology and application are studied.

• The Journal of Society for e-Business Studies
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• v.12 no.3
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• pp.75-93
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• 2007

This paper presents real-time online early fire warning systems developed for preserving cultural properties of Bulguksa which is a world heritage designated by UNESCO. The system is based on the ubiquitous sensor network employing 900MHz and 2.4GHz bands. In this paper, we analyze requirements that should be considered in building effective management systems of cultural heritages by using wireless sensor network. Finally, we introduce the architecture, sensor and network design, and software design of the fire warning systems which is an initial version of U-Bulguksa. The current version of systems has been operating in Bukguksa for a few months. U-Bukguksa project sponsored by National Information Society Agency is ultimately aimed at developing an integrated system of U-cultural heritage management and U-tourism. The former aims to conserve and manage intangible cultural properties by providing a variety of environmental information such as erosion, crack, and gradient as well as fire which are important causes of loss and damage in real-time and online. The latter refers to the intelligent tourism information and guidance systems allowing tourists to get the personalized content on cultural heritages and help guidance with mobile devices in Bulguksa.

• Journal of Advanced Navigation Technology
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• v.18 no.6
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• pp.541-545
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• 2014

Rec. ITU-R M.1842-1 is international recommendation for VHF band communication guideline in maritime mobile service RR Appendix 18 channels. In this paper, we simulate 28.8 kbps VHF ${\pi}$/4-DQPSK digital baseband modem compatible with the recommendation, then it is designed and implemented with FPGA. Cazac sequence is used as a preamble since packet format is not defined untill now in the recommendation. Baseband modem is designed by VHDL language and implemented on NEXYS4 development platform having Atrix7 FPGA chip from Xilinx. For wireless communication test of total prototype system, ADC/DAC board is implemented and EV9730 RF module is utilized. From the experimental results, implemented FPGA modem shows spectral bandwidth of 25 kHz and successful data exchanges between tx and rx communication platform.

• Journal of Advanced Navigation Technology
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• v.22 no.3
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• pp.213-219
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• 2018

In this paper, we propose a design method and process for hardware and software of hybrid V2X communication module that supports both C-ITS communication protocol designed for vehicle environment and Legacy LTE communication technology. C-ITS is suitable for safety service applications due to its low latency characteristics, and Legacy LTE is a technology suitable for non-safety applications such as traffic information and infotainment due to high latency and high capacity. The hybrid V2X communication module supports multiple communication technologies of WAVE and LTE, in which WAVE supports multiple channels, so that it is designed to transmit road information such as LDM and positioning correction information to an autonomous vehicle in real time. The main design results presented in this paper will be applied to the implementation of future hybrid V2X communication terminals for vehicles.