• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.10 s.89
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• pp.996-1004
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• 2004

1-Dimensional Cluster-Based Sequence Equalizer(1-D CBSE) lessens computational load, compared with the classic maximum likelihood sequence estimation(MLSE) equalizers, and has the superiority in the nonlinear channels. In this paper, we proposed an algorithm of searching for optimal training sequence that estimates the cluster centers instead of time-varying multipath fading channel estimation. The proposed equalizer not only resolved the problems in 1-D CBSE but also improved the bandwidth efficiency using the shorten length of taming sequence to improve bandwidth efficiency. In experiments, the superiority of the new method is demonstrated by comparing conventional 1-D CBSE and related analysis.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.3
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• pp.425-432
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• 2011

To increase the bit rate over than 1 Gb/s in LED visible light communications, we need to reduce the multipath effect of the light in indoor environment. In this paper, we propose a MAC protocol for LED visible light wireless LAN with beamforming technique. We assumed that spatial light modulator is used for beamforming function. We use polling method since detecting another uplink channel is difficult in visible light communication. We also estimated the performance of the proposed MAC protocol.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.774-777
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• 2005

In this paper, we propose performance improvement algorithm for high data rate wireless personal area network (HDR-WPAN) system using turbo code. Turbo code increase detection delay and computation according to iterate counts. However, turbo code has been shown to be very close th the Shanon limit, can be classified as a block-based error correction code. Turbo code has gain about E$_b$/N$_o$=5.8dB at 10$^{-4}$ in the multipath indoor channel. In the result, HDR-WPAN system adopted turbo code has reliable communication by low power.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.6A
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• pp.885-892
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• 2000

A multi-used detector(MUD) using a radial basis function(RBF) network is proposed in a multicarrier-code division multiple access (MC-CDMA) system. In the proposed scheme, a RBF network is connected to the frequency domain in order to effectively utilize the frequency diversity. Simulations have been performed over the frequency selective and multipath fading channel. From these simulations, the proposed receiver is verified to be used for making the performance improvement in combating near-far effects and increasing the number of active users. The system capacity is increaed about 1.8 times at a BER of $10^{-3}$ under a single cell when the proposed scheme is compared with MUD using a parallel interference canceller(PIC).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9A
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• pp.889-895
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• 2010

In this paper, we have studied the implementation and adaptation of a smart antenna system for mobile terminals. We have designed a smart antenna system with switching beam structure in order to reduce the hardware and computational complexity. Additionally we have analyzed the reduction of the effect of multipath fading due to beamforming using real measurement data from commercial CDMA cellular channel environments. After analyzing the measurement data, we found out that the effect of fading reduces by ~3dB due to the effect of $2{\times}2$ beamforming in mobile terminals with 6dB beamforming gain.

• Journal of Broadcast Engineering
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• v.8 no.2
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• pp.136-145
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• 2003

This paper proposes a DTV receiver using beamforming techniques to improve indoor and mobile reception. The proposed DTV receiver estimates the directions of arrival (DOAs) of incoming signals using Capon's DOA estimation method and generates an adaptive antenna beam pattern to the estimated DOA of the mainpath signal to Improve the channel condition. After beamforming, a following decision feedback equalizer (DFE) removes the remaining multipath components. The proposed receiver can be implemented with a conventional DTV receiver without anymodification. The performance of the proposed receiver is analyzed with modified Brazilian field test models, which include DOA information of Incoming signals. Simulation results show that the proposed receiver can satisfy the threshold of visibility (TOV) when input signal to noise ratio is slightly over 10 dB.

• Journal of Broadcast Engineering
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• v.8 no.2
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• pp.146-152
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• 2003

ATSC DTV receivers use repetitive data segment syncs or Gardner algorithm as a tuning recovery circuit. Many multipath signals can induce timing-offset in the symbol timing recovery circuit using Gardner algorithm and this timing-offset shifts sampling instant to the wrong points, causing the performance of the equalizer to become nr. When many echoes exist, the optimal sampling instant will be the Point at which the main-path has a peak value. In this paper, by using channel correlation techniques, we find the optimal sampling instant, thereby compensating the timing offset and improving DTV reception performance. We analyzed the Performance enhancement of DTV receivers using the timing offset compensator.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.5
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• pp.429-436
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• 2017

Since the telemetry performance using the time-delayed data dissipates the wireless channel resources, we propose the spectral efficient retransmission scheme in this paper. In the proposed scheme, the telemetry data is retransmitted based on triggered memory to improve the spectral efficiency. The proposed scheme minimizes the error caused by multipath fading, antenna pattern as well as the error caused by the flight events. In the flight simulation data, we show the proposed scheme improves the telemetry performance based on spectral efficient retransmission.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.583-586
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• 2004

In this paper, we have analyzed the performance of synchronization of CCK(Complementary Code Keying) modulation scheme used for IEEE 802.11g wireless LAM system supporting 54 Mbps of high speed data rate over 2.4 GHz. At receiver, the clock frequency offset is caused by noise or fading. This frequency error occurs the offset of clock timing and causes ISI. Therefore the tracking is required to reduce the clock timing offset. The DLL(Delay Lock Loop), asychronization mode, performing tacking the clock is used for the simulation. The simulation result shows jitter variance and BER performance in the AWGN and multipath fading channel environment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.3
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• pp.1416-1421
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• 2013

In this paper, the Euclidean distance between the probability density functions (PDFs) for biased errors and a Dirac-delta function located at zero on the error axis is proposed as a new performance criterion for adaptive systems in non-Gaussian noise environments. Also, based on the proposed performance criterion, a supervised adaptive algorithm is derived and applied to adaptive equalization in the shallow-water communication channel distorted by severe multipath fading, impulsive and DC-bias noise. The simulation results compared with the performance of the existing MEDE algorithm show that the proposed algorithm yields over 5 dB of MSE enhancement and the capability of relocating the mean of the error PDF to zero on the error axis.