• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.11
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• pp.78-87
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• 1994

In this paper, we have addressed a new approach to encode the DCT coefficients efficiently by exploiting the structural differences among the probability distribution functions of them. We have proved analytically that if signals are separated according to their source models, the entropy of the separated signals decreases below that of the unseparated signals. And simulation results show that the average codelength decrease when each (runlength, level) symbol is encoded adaptively according to the index associated with the symbol.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.2
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• pp.10-17
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• 1989

The Berlekamp-Massey algorithm, the method of using the Euclid algorithm, and Fourier transforms over a finite field can be used for the decoding of Reed-Solomon codes (called RS codes). RS codes can also be decoded by the algorithm that was developed by Peterson and refined by the Gorenstein and Zierler. However, the decoding of RS codes using the Peterson-Gorenstein-Zieler algorithm offers sometimes computational or implementation advantages. The decoding procedure of the double-error correcting (31,27) Rs code over the symbol field GF ($2^5$) will be analyized in this paper. The complete analysis, gate array design, and implementation for encoder/decoder pair of (31.27)RS code are performed with a strong theoretical justification.

• Journal of IKEEE
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• v.22 no.3
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• pp.800-804
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• 2018

This paper presents a novel HF band differential quadrature phase-shift keying (DQPSK) orthogonal frequency-division multiplexing (OFDM) communication system. The system can deliver 3.6 kbps with a bandwidth of about 3 kHz. In a digital modem, OFDM with 32-point fast Fourier transform is used. In the system, each subcarrier uses DQPSK modulation. Hence, a demodulator does not require carrier phase recovery and symbol timing recovery. And, each subcarrier employs CRC error check code individually. By using CRC code for each subcarrier, bit error caused by multipath fading can be recovered simply.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.179-183
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• 2007

This paper is to implement a low power frequency Shift Keying(FSK) receiver using Xilinx System Generator. The receiver incorporates a 16 point Fast Fourier Transform(FFT) for symbol detection. The design units of the receiver are digital designs for better efficiency and reliability. The receiver functions on one bit data processing and supports data rates 10kbps. In addition CORDIC algorithm is used for avoiding complex multiplications while computing FFT, multiplication of twiddle factor is substituted by rotators. The design and simulation of the receiver is carried out in Simulink, then the simulink model is translated to a hardware model to implement FPGA using Xilinx System Generator and to verify performance.

• Journal of the Korea Society of Computer and Information
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• v.11 no.5 s.43
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• pp.195-201
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• 2006

In multicarrier code division multiple access(MC-CDMA), the total system bandwidth is divided into a number of sub-bands, where each subband may use direct-sequence(DS) spreading and each subband signal is transmitted using a subcarrier frequency. In this paper, the system performance analysis of MC-CDMA using to gain combining(EGC) and maximal ratio combining(MRC) method over frequency selective Nakagami-m fading channel is analyzed. In the proposed system, a data sequence is serial-to-parallel converted, and MC-CDMA is used on each of the parallel data streams. The data streams are spread at both the symbol fraction level and at the chip level by the transmitter. In this paper, the compare to analysis,two standard diversity combining techniques, EGC and MRC, The good performance of system using to MRC more than EGC

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2C
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• pp.209-216
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• 2009

The repeater for wireless broadband internet (Wibro) system using OFDM demands the short processing delay to eliminate inter-symbol interference resulted from the time delay greater than the guard time. Towards this, the total system delay of repeater is expected to be minimized as possible as it can without distorting signal quality. In general, the FIR-type of filter is commonly deployed as a channelization filter, but due to its large amount of coefficients for producing prerequisite filter response the excessive large time delay occurs. To withstand this problem, the paper proposes the method for designing IIR filter whose response almost identical to that of the original filter. Moreover, in order to linearize the phase response of the designed IIR filter, this paper also introduce the way of designing the all-pass filter to be cascaded works for linearizing phase response of the channelization as well as the de-channelization filter. To achieve the further improvement in linearization of the phase response and reduction of the overall complexity, this paper tries to transform the integrated IIR filter group into the structure in polyphase style. The computer simulation verifies that the integrated IIR filter group designed in this paper reveals the relatively short processing delay without harming the acceptible signal quality.

• Journal of Korea Multimedia Society
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• v.15 no.10
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• pp.1196-1204
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• 2012

In this paper, a series of algorithms are proposed for controlling different kinds of multimedia contents and realizing interact between human and computer by using single input device. Human gesture recognition based on NUI is presented firstly in my paper. Since the image information we get it from camera is not sensitive for further processing, we transform it to YCbCr color space, and then morphological processing algorithm is used to delete unuseful noise. Boundary Energy and depth information is extracted for hand detection. After we receive the image of hand detection, PCA algorithm is used to recognize hand posture, difference image and moment method are used to detect hand centroid and extract trajectory of hand movement. 8 direction codes are defined for quantifying gesture trajectory, so the symbol value will be affirmed. Furthermore, HMM algorithm is used for hand gesture recognition based on the symbol value. According to series of methods we presented, we can control multimedia contents by using human gesture recognition. Through large numbers of experiments, the algorithms we presented have satisfying performance, hand detection rate is up to 94.25%, gesture recognition rate exceed 92.6%, hand posture recognition rate can achieve 85.86%, and face detection rate is up to 89.58%. According to these experiment results, we can control many kinds of multimedia contents on computer effectively, such as video player, MP3, e-book and so on.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.59-67
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• 2006

OFDM (Orthogonal frequency Division Multiplexing) systems convert serial data stream to N parallel data streams and modulate them to N orthogonal subcarriers. Thus spectrum utilization efficiency of the OFDM systems are high and high-speed data transmission is possible. However, with the OFDM systems using the same modulation method at all subcarriers, the error probability is dominated by the subcarriers which experience deep fades. Therefore, in order to enhance the performance of the system adaptive modulation is required, with which the modulation methods of the subcarriers are determined according to the estimated SNRs. The IEEE 802.11a system selects various transmission speed between 6 and 54 Mbps according to the modulation mode. There are three typical methods for SNR estimation: Direct estimation method uses the frequency domain symbols to estimate SNR directly by minimizing MSE (Mean Square Error), EVM method utilizes the distance between the demodulated constellation points and received complex values, and the method utilizing the Viterbi algorithm uses the cumulative minimum distance in decoding process to estimate the SNR indirectly. Through comparison analyses of three methods we propose a new SNR estimation method, which employs both the EVM method and the Viterbi algorithm. Finally, we perform extensive computer simulations to confirm the performance improvement of the proposed adaptive OFDM systems on the basis of IEEE 802.11a.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.4
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• pp.442-450
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• 2008

In this paper, the phase diverisity in a direct-conversion receiver for a UHF RFID reader is analyzed and the optimal I/Q signal combining methods is presented with respect to tag modulation. At first, fading characteristics of a single channel receiver is shown to prove the importance of phase diversity due to the phase relationship between the backscattered signal and the local oscillator. And the optimal signal combining methods are presented in order to overcome the signal power reduction due to phase diversity. In case of ASK, the power combining method is presented for the optimal I/Q combining. And the arctangent and principal component combining methods using covariance matrix of I and Q channels are presented for the optimal I/Q combining in case of PSK. In order to analyze the performance of suggested methods, the selection diversity and the optimal combining methods are compared. According to analysis and simulation results, the optimal combining methods have a maximum 3 dB SNR enhancement than selection diversity.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.4
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• pp.15-23
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• 2011

An interleaver rearranges a channel-encoded data in the symbol unit to spread burst errors occurred in channels into random errors. Thus, the interleaving process makes it difficult for a receiver, who does not have information of the interleaver parameters used in the transmitter, to de-interleave an unknown interleaved signal. Recently, various researches on the reconstruction of an unknown interleaved signal have been studied in many places of literature by estimating the interleaver parameters. They, however, have been mainly focused on the estimation of the block interleaver parameters required to reconstruct the de-interleaver. In this paper, as an extension of the previous researches, we estimate the convolutional interleaver parameters, e.g., the number of shift registers, a shift register depth, and a codeword length, required to de-interleave the unknown data stream, and propose the de-interleaving procedure by reconstructing the de-interleaver.