• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.11
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• pp.2062-2068
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• 2006

In his paper, embedded system implementation for IEEE802.l1p based OFDM-DSRC is presented. After the IEEE802.11p physical layer specification is introduced and BER performance of the modem is evaluated by simulation, implementation aspects of the system such as system architecture, design method and implementation results are addressed. Implemented embedded system for the OFDM-DSRC communication consists of FPGA, flash memory, ARM9 CPU Core, peripherals, etc. from the results, it is shown that the implemented system operates well according to IEEE802.11p specification. It is expected that implemented embedded system shall be used for wireless communication system such as ITS application by enhancing system optimizing.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.4
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• pp.89-95
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• 2008

In the maritime communication, Orthogonal Frequency Division Multiplexing (OFDM) communication terminal should be operated with low power consumption, because the communication should be accomplished in the circumstance of disaster. Therefore, Low power FFT processor is required to be designed with current mode signal processing technique than digital signal processing. Current- to-Voltage Converter (IVC) is a device that converts the output current signal of FFT processor into the voltage signal. In order to lessen the power consumption of OFDM terminal, IVC should be designed with low power design technique and IVC should have wide linear region for avoiding distortion of signal voltage. To design of one-chip of the FFT LSI and IVC, IVC should have a small chip size. In this paper, we proposed the new IVC with wide linear region. We confirmed that the proposed IVC operates linearly within 0.85V to 1.4V as a function of current-mode FFT output range of -100~100[uA]. Designed IVC will contribute to realization of low-power maritime data communication using OFDM system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.141-150
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• 2010

In this paper, performance of a turbo-coded OFDM system is analyzed and simulated in a power line communication channel. Since the power line communication system typically operates in a hostile environment, turbo code has been employed to enhance reliability of transmitted data. The performance is evaluated in terms of bit error probability. As turbo decoding algorithms, MAP (maximum a posteriori), Max-Log-MAP, and SOVA (soft decision viterbi output) algorithms are chosen and their performances are compared. From simulation results, it is demonstrated that Max-Log-MAP algorithm is promising in terms of performance and complexity. It is shown that performance is improved 3dB by increasing the number of iterations, 2 to 8, and interleaver length of a turbo encoder, 100 to 5000. The results in this paper can be applied to OFDM-based high-speed power line communication systems.

• The Journal of the Acoustical Society of Korea
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• v.40 no.3
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• pp.219-227
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• 2021

This paper proposed an Orthogonal Frequency Division Multiplexing (OFDM) based biomimetic communication method using a dolphin whistle which covertly transmits communication signals to allies. The proposed method divides the dolphin whistle into several time slots corresponding to a number of OFDM symbols, and modulates the communication signal by mapping differential phase shift keying (DPSK) symbols into subcarriers that have the frequency bands of the dolphin whistle in each slot. The advantages of the proposed method are as follows: In the conventional Chirp Spread Spectrum (CSS) and Frequency Shift Keying (FSK) based biomimetic communication methods, the discontinuity of the frequency contour is large, but the proposed method can reduce the discontinuity. Even if the modulation order is increased, the degradation of the mimicking performance is small. The computer simulations demonstrate that the Bit Error Rate (BER) and mimicking performance of the proposed method are better performance than those of the conventional CSS and FSK.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.11
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• pp.1026-1033
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• 2004

Clipping is a simple and convenient PAPR reduction method to prevent the high-speed OFDM communication system from the nonlinear distortion. However, it inherently produces clip noise so that BER performance can be degraded. Clipping noise can be divided into in-band and out-of-band clipping noise. In this paper, we study the clipping effect on the forward link of the OFDM-FDMA system. BER performance of OFDM-FDMA system using clipping method is theoretically analyzed. We also investigate the BER performance of the clipped OFDM-FDMA signal through the HPA. From the simulation results it can be quantified how much the BER performance of OFDM-FDMA system is degraded by the clipping method. From the study results, we can choose the appropriate IBO value and CR(clip ratio) to get the desired BER performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.10
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• pp.1863-1868
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• 2006

In this paper we propose the communication system model which improve the performance of OFDM based DSRC system by adopting selective pilot overlay channel estimation scheme. Assuming AWGN and fading channel environment, the performance of OFDM system according to IEEE802.11p physical layer being standardized for OFDM based DSRC is obtained, and the performance of proposed OFDM based DSRC system adopting selective pilot overlay channel estimation scheme is compared with the conventional system. from the simulation results, it is shown that proposed system is superior to conventional one due to reducing channel estimation error.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.6
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• pp.949-954
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• 2017

Multiple input, multiple output orthogonal frequency division multiplexing (MIMO OFDM) systems are the candidate for the future wireless communications. However, the main drawback of MIMO OFDM systems is their sensitivity to carrier frequency offset (CFO) similar to the single input, single output OFDM (SISO OFDM) systems. The demodulation of a signal with CFO causes large bit error rate and degrade the performance of a symbol synchronizer. It is important to estimate the frequency offset and minimize or eliminate its impact. In this paper, we propose a technique based on observation training symbols for estimating CFO by employing block-by-block estimation for SISO OFDM systems. The technique of SISO OFDM is extended to the MIMO OFDM systems. Simulation results show that the proposed techniques have a superior performance and better accuracy compared to the conventional techniques in the sense of mean square error.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.190-196
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• 2009

In this paper, performance of a turbo-coded OFDM system is analyzed and simulated in a power line communication channel. Since the power line communication system typically operates in a hostile environment, turbo code has been employed to enhance reliability of transmitted data. The performance is evaluated in terms of bit error probability. As turbo decoding algorithms, MAP (maximum a posteriori), Max-Log-MAP, and SOVA (soft decision Viterbi output) algorithms are chosen and their performances are compared. From simulation results, it is demonstrated that Max-Log-MAP algorithm is promising in terms of performance and complexity. It is shown that performance is substantially improved by increasing the number of iterations and interleaver length of a turbo encoder. The results in this paper can be applied to OFDM-based high-speed power line communication systems.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.6
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• pp.263-268
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• 2010

As the demand of high quality service in next generation wireless communication systems, a high performance of data transmission requires an increase of spectrum efficiency and an improvement of error performance in wireless communication systems. In this paper, we propose a multi-user multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system with cyclic delay diversity and block diagonalization procoding method to improve bit error rate (BER) performance with wireless local area network (WLAN) channel model C and D for 802.11n WLAN system. The results of mathlab simulation show the improvement of BER performance in 802.11n wireless indoor channel environment.

• ETRI Journal
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• v.37 no.3
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• pp.460-470
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• 2015

Orthogonal frequency-division multiplexing (OFDM) is one of the most widely used technologies in current wireless communication systems and standards. Cognitive radio (CR) provides a robust solution to the problem of spectrum congestion as it offers opportunistic usage of frequency bands that are not occupied by primary users. Due to the underlying sensing, spectrum shaping, scaling, and interoperable capabilities of OFDM, it has been adapted as a best transmission technology for CR wireless systems. However, the performance of an OFDM-based CR wireless system is affected by the existence of narrowband interference (NBI) from other users. Further, due to carrier frequency offset in NBI sources, NBI energy may spread over all subcarriers of an OFDM signal. In this paper, a fixed Amplify-and-Forward (AF) relay that operates at a frequency band that is different from that of direct mode is introduced to suppress the effect of NBI. Analytical expressions are derived for outage probability in direct, AF-relay, and incremental relaying modes. The outage performance of the proposed AF relay-based CR network is proven to be better than that of direct mode.