• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5A
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• pp.382-388
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• 2005

An OFDM system may be a good candidate for a next-generation wireless communication system which requires high-speed and high-rate data transmission. In OFDM systems, guard intervals are inserted to mitigate the effects of ISI (Inter-Symbol Interference). But guard interval insertion degrades the system performance from the standpoint of data rate and bandwidth efficiency. In this paper, a new method to improve the performance of an OFDM system without guard interval. First, PIC (Parallel Interference Cancellation) scheme which can reduce ISI by subtracting the estimated multi-path components from the received signal will be considered. And the proposed system with Pseudo-Decorrelator estimates transmitted signals by using the inverse matrix of cross-correlation matrix relating to interference components. The performance of the proposed system is evaluated through computer simulations and compared with that of the PIC system and an OFDM system without guard interval.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12A
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• pp.925-932
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• 2009

Precise temperature monitoring is the major preconditioning to supervise quality losses within the transport chain for fresh products. ISO/IEC18000-6REV1 defines new protocols supporting BAP(Battery Assisted Passive) RFID tag which is completely compatible with EPCglobal Class1 Generation2 specification. In this paper, we designed a modem supporting BAP RFID tag with FPGA(Field Programmable Gate Array) and implemented sensor data processing function defined in ISO/IEC18000-6REV1. The transmit block of the modem supports pulse shaping filter and the output signal of the implemented RFID reader is satisfied with the spectrum mask defined in the standard. The receive block of the modem uses Gardner TED to synchronize timing of symbol. In this paper, we designed a modem supporting ISO/IEC18000-6REV1 standard and developed a RFID reader sndard. The developed RFID reader sndard can recognize sensor tag and passive tag in the wireless environment and supports real-time processing of the sensor data in the embedded linux platform.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12A
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• pp.991-997
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• 2009

Transmit beamforming is simple method to achieve the full diversity gain that is available in multiple antenna(MIMO) wireless systems. Unfortunately, the prior condition to achieve this gain requires perfect channel knowledge at both transmitter and receiver, which is impractical on account of limited feedback link. Therefore, for the practical system, codebook based feedback scheme is often employed, where the beamforming vector is selected from the codebook to maximize the output signal-to-noise ratio (SNR) at receiver, and the receiver only sends back the index of the best beamforming vector to the transmitter. In this paper we derive analytical expression of average bit error rate (BER) for the codebook based transmit beamforming MISO system over the feedback error channel. Using this analytical result, we present optimum codebook indexing scheme to improve the performance of this system. From some selected numerical examples we show that our proposed codebook indexing scheme can provide nonnegligible performance improvements in terms of average BER over the severe feedback error channel.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.29-35
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• 2006

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference(ISI) or Multiple Access Interference(MAI) to degrade the performance of CDMA(Code Division Multiple Access) system. Constant Modulus Algorithm which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye-pattern obtained from algorithm are compared.

• Journal of Sensor Science and Technology
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• v.22 no.1
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• pp.54-64
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• 2013

In this study, we developed a falling recognition system to transmit SMS data through CDMA communication using a three axises acceleration sensor and a two axises gyro sensor. 5 healthy men were selected into a control group, and the fall recognition system using the three axises acceleration sensor and the two axises gyro sensor was devised to conduct an experiment. The system was attached to the upper of their sternum. According to the experiment protocol, the experiment was carried out 3 times repeatedly divided into 3 specific protocols: falling during gait, falling in stopped state, and falling in everyday life. Data obtained in the falling recognition system and LabVIEW 8.5 were used to decide if falling corresponds to that regulated in an analysis program applying an algorithm proposed in this study. In addition, results from falling recognition were transmitted to designated cellular phone in a SMS (Shot Message Service) form. These research results show that an erroneous detection rate of falling reached 19% in applying an acceleration signal only; 6% in applying an angular velocity; and 2% in applying a proposed algorithm. Such finding suggests that an erroneous detection rate of falling is improved when the proposed algorithm is applied incorporated with acceleration and angular velocity. In this study therefore, we proposed that a falling recognition system implemented in this study can make a contribution to the recognition of falling of the aged or the disabled.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11C
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• pp.682-693
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• 2011

Energy spreading transform (EST) based modulation is an effective technique to combat frequency-selective fading in broadband wireless communication. It performs close to the inter-symbol interference (ISI)-free matched filter bound (MFB) only at the complexity of a linear detector. Originally, EST-based modulation has been proposed for QPSK. However, to fully utilize the capacity of multipath fading channels, higher-order modulations are also necessary. In this paper, we review the EST based modulation that has originally been proposed for QPSK and discuss its extension to 8 PSK and 16 QAM. The performance of the extended system is verified through simulation in Proakis B and 8-tap fading channel. The EST based modulation for 8 PSK shows the performance which is very close to MFB and the EST based modulation for 16 QAM shows the performance gap between its receiver and MFB.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.42 no.2 s.302
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• pp.39-48
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• 2005

In this paper, we implement the multimedia remote control system by using existing internet service or wired online. We also provide user-friendly convenient environment with developed application program named EzPlay and PC-EPG. The multimedia remote control system consists of integrated wireless transceiver of PC and TV connected USB type and the users can easily use lots of contents because EzPlay program provides appropriate UI mode on the PC and TV screen. The unposed system can operate real-time playing, reserved video receding and data storing function using internet mesh based on signal detecting control theory. The PC-EPG system is implemented by server/client web program and the client program based on visual C++/MFC processes data storing in client computer through TCP/IP. It also provides intelligent function that constructs database according to user's preference.

• Journal of IKEEE
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• v.15 no.1
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• pp.29-36
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• 2011

Dithering scheme has been widely used to improve the resolution of DCO(Digitally Controlled Oscillator) in conventional ADPLLs(All Digital Phase Locked Loop). In this paper a new resolution improvement scheme is proposed where a simple DAC is employed to overcome the problems of dithering scheme. A 2.4GHz LC-based DCO has been designed in a $0.13{\mu}m$ CMOS process with an enhanced frequency resolution for wireless local area network applications. It has a frequency tuning range of 900MHz and a resolution of 58.8Hz. The frequencies are controled by varactors in coarse, fine, and DAC bank. The DAC bank consists of an inversion mode NMOS varactor. The other varactor banks consist of PMOS varactors. Each varactor bank is controlled by 8bit digital signal. The designed DCO exhibits a phase noise of -123.8dBc/Hz at 1MHz frequency offset. The DCO core consumes 4.2mA from 1.2V supply.

• The Journal of the Acoustical Society of Korea
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• v.39 no.6
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• pp.600-605
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• 2020

In this paper, we propose a sound event detection method using a multi-channel multi-scale neural networks for sound sensing home monitoring for the hearing impaired. In the proposed system, two channels with high signal quality are selected from several wireless microphone sensors in home. The three features (time difference of arrival, pitch range, and outputs obtained by applying multi-scale convolutional neural network to log mel spectrogram) extracted from the sensor signals are applied to a classifier based on a bidirectional gated recurrent neural network to further improve the performance of sound event detection. The detected sound event result is converted into text along with the sensor position of the selected channel and provided to the hearing impaired. The experimental results show that the sound event detection method of the proposed system is superior to the existing method and can effectively deliver sound information to the hearing impaired.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.3 no.1 s.4
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• pp.75-83
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• 2004

This paper describes the design, fabrication, and measurement of a low side lobe antenna for RSE base station of the ETCS which is one of the ITS services. The antenna is installed on the gantry of road side and provides the wireless communication lint between vehicles and RSE. The required characteristics of ETCS base station antenna are low sidelobe and specific beam pattern by the road and install environment and installed place of OBU. To minimize the affects of multipath signal by reflection, Circular polarization is required. To get low sidelobe of antenna, array configuration and weighting factor by Taylor distribution in radiator elements are applied. The measured results of fabricated antenna are as follows; return loss of 130MHz by -10dB, an axial ratio of 2.6dB, and a gain of 17dBi. It is found that the measured beam patterns are similar to design results.