• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9C
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• pp.846-852
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• 2006

The ${\kappa}$-error linear complexity is a ky measure of the stability of the sequences used in the areas of communication systems, stream ciphers in cryptology and so on. This paper introduces an efficient algorithm to determine the ${\kappa}$-error linear complexity and the corresponding error vectors of $p^m$-periodic binary sequences, where : is a prime and 2 is a primitive root modulo $p^2$. We also give a new sense about the ${\kappa}$-error linear complexity in viewpoint of coding theory instead of cryptographic results. We present an efficient algorithm for decoding binary cyclic codes of length $p^m$ and derive key properties of the minimum distance of these codes.

• The Journal of the Acoustical Society of Korea
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• v.23 no.4
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• pp.333-339
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• 2004

This Paper proposes the vector quantizer-pyramid vector quantizer(VQ-PVQ) structure. Also both predictive structure and safety-net concept are combined into the VQ-PVQ to quantize the IPC parameter of wideband speech codec. The Performance is compared to the LPC vector quantizer used in the AMR-WB(ITU-T G.722.2). demonstrating reduction in both spectral distortion and encoding memory.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6B
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• pp.610-615
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• 2002

This paper considers a communication system consisting of a vector quantizer with selected code vectors with mapped into points in the modulated signal space. The modulated signal is transmitted over a Rayleigh flat fading channel. We optimize the modulated signal constellation to minimize the overall distortion of the system with the fixed vector quantization codebook. The optimization is obtained by partitioning the modulated signal space. Simulation results show that the signal constellation based on the proposed optimization scheme outperforms the conventional methods.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10b
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• pp.259-261
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• 1999

본 논문은 MPEG-2 TM 5 video 부호기의 전체구조 및 처리과정을 기술한다. MPEG-2는 저장 매체, 통신, 방송 매체 등을 위한 동영상 압축이 표준이다. MPEG-2 압축 방법에는 공간적 압축과 시간적 압축 방법이 있다. 공간적 압축 방법에는 화면에서의 중복성을 줄이기 위한 표본화 주파수(4:4:4, 4:2:2, 4:2:0, format), DCT, scanning(zigzag 혹은 alternate scanning)과 quantization이 있고 시간적 압축 방법에는 움직임 예측(motion estimation)과 I, P, B-picture를 사용하는 방법이 있다. 본 논문에서는 MPEG-2 부호기의 핵심을 전체 구조, DPCM, MPEG bitstream syntax, MPEG-2 부호화 알고리즘, 움직임 예측, 움직임 벡터, rate control 그리고 가변길이 코딩(variable length coding)으로 구분하여 소개한다.

• The Journal of the Acoustical Society of Korea
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• v.19 no.7
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• pp.42-47
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• 2000

This paper describes a real-time implementation of a GSM-EFR (Global System for Mobil communications Enhanced Full Rate) speech coder using OakDSP core; a 16bit fixed-point Digital Signal Processor (DSP) by DSP Group, Inc. The real-time implemented speech coder required about 24MIPS for computation and 7.06K words and 12.19K words for code and data memory, respectively. The implemented GSM-EFR speech coder passes all of test vectors provided by ETSI (European Telecommunication Standard Institute), and perceptual speech quality measurement using MNB algorithm shows that the quality of the GSM-EFR speech coder is similar to the one of 32kbps ADPCM. The real-time implemented GSM-EFR speech coder which is the highest bit-rate mode of the GSM-AMR speech coder will be used as the basic structure of the GSM-AMR speech coder which is embedded in MODEM ASIC of IMT2000 asynchronous mode mobile station.

• The Journal of the Acoustical Society of Korea
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• v.20 no.5
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• pp.35-47
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• 2001

This paper describes an efficient harmonic-CELP speech coder by taking advantages of harmonic and CELP coders into account. According to frame voicing decision, the proposed harmonic-CELP coder adopts the RP-VSELP coder as a fast CELP in case of an unvoiced frame, or an improved harmonic coder in case of a voiced frame. The proposed coder has main features as follows: simple pitch detection, fast harmonic estimation, variable dimension harmonic vector quantization, perceptual weighting reflecting frequency resolution, fast harmonic synthesis, naturalness control using band voicing, and multi-mode. These features make the proposed coder require very low complexity, compared with HVXC coder To demonstrate the performance of the proposed coder, a 2.4 kbps coder has been implemented and compared with reference coders. From results of informal listening tests, the proposed coder showed good quality while requiring low delay and complexity.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.129-131
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• 2010

분산 비디오 부호화(distributed video coding)는 분산 소스 부호화의 대표적인 응용분야로서 부호화 복잡도가 부호화기에서 복호화기로 이동되어 저전력 부호화 환경에 매우 적합하다. 본 논문에서는 분산 비디오 부호화의 성능 향상에 있어 가장 중요한 보조 정보의 효과적인 생성 방법을 제안한다. 우선 보조 정보 생성을 위한 키 프레임들 간의 블록 움직임 추정에 있어 기존 방법들이 대체적으로 가정하고 있는 선형적인 움직임 이동에 따른 잘못된 예측을 해결하기 위해 두 장 이상의 키 프레임을 사용하여 블록 움직임을 추정한 후, 선형 회귀(linear regression)를 이용하여 보조 정보 상의 블록 움직임 궤적을 추정한다. 이때 움직임 추정을 위한 키 프레임 번호를 증가하며 선입선출(FIFO)형 버퍼에 저장 및 삭제하여 동일한 보조정보에 해당하는 여러 움직임 벡터 필드와, 기존의 선형적인 움직임이 가정된 움직임 벡터 필드를 동시에 생성한다. 다음으로 보간(interpolation)하려는 보조 정보 프레임 내의 임의의 블록에 가장 가깝게 통과하는 움직임 벡터 필드를 선택하여 해당하는 블록의 최종 움직임 벡터로 선택한다. 실험결과 제안하는 보조 정보 생성 방법은 기존의 방법과 비교했을 때 비대칭성 움직임 벡터 사용만으로 평균 PSNR이 0.216dB 만큼 증가하는 것을 확인할 수 있었다.

• Journal of Broadcast Engineering
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• v.10 no.4 s.29
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• pp.621-631
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• 2005

To enhance the performance of multi-view sequence CODEC, an efficient disparity vector coding method fur multiview sequences is proposed herein. For higher coding efficiency, we encode the differential vectors acquired by subtracting the original vectors from the predicted ones. To enhance the performance of disparity vector coding, it is essential to predict the disparity vectors accurately. The prediction by this proposed method utilizes the correlation among the multiview images, while conventional methods exploit the correlation among the causal blocks. Experiments were performed fur three different 5 view sequences. We were able to confirm that the proposed method predicts disparity vectors accurately by comparing the entropy and the mean absolute values for differential vectors with conventional methods. Its performance is superior to vector coding methods used in MPEG-4 which uses only a spatial correlation. The proposed method increases the coding efficiency by a factor of $30{\~}45\%$ while preserving image quality.

• The Journal of the Acoustical Society of Korea
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• v.15 no.6
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• pp.59-65
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• 1996

This paper proposes a 4 kbps PSI-VSELP(Pitch Synchronous Innovation-Vector Sum Excited Linear Prediction) speech coder which produces speech equivalent to that of the conventional 4.8 kbps VSELP. Since the 'half-rate' is differently defined from country to country, there may be a need to reduce the bit rate of conventional half-rate coder. To minimize the degradation of speech quality caused by bit-rate reduction, it is desirable to perform bit-allocation based on the carefull consideration of the effect of various transmission parameters. This paper adopts this analytical approach for bit-allocation at 4 kbps. To improve the quality of the VSELP coder at 4 kbps, basis vectors which play the most important role in the performance, are optimized by an iterative closed-loop training process and the PSI technique is employed in the VSELP performance, are optimized by an iterative closed-loop training process and the PSI technique is employed in the VSELP coder. To demonstrate the performance of the proposed speech coder, we peformed experiments under the noiseless and error free conditions. From experimental results, even though the proposed 4 kbps PSI-VSELP coder showed lower scores in the objective measure, higher scores in subjective measure was obtained compared with those of the conventional 4.8 kbps VSELp.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6C
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• pp.632-639
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• 2002

To reduce the area and power consumption in constant coefficient multiplications, the constant coefficient can be encoded using canonic signed digit(CSD) representation. When the partial product terms are added depending on the nonzero bit(1 or -1) positions in the CSD-encoded multiplier, all sign bits are properly extended before the addition takes place. In this paper, to reduce the overhead due to sign extension, a new method is proposed based on the fact that carry propagation in the sign extension part can be controlled such that a desired input bit can be propagated as a carry. Also, a fixed-width multiplier design method suitable for CSD multiplication is proposed. As an application, 43-tap filbert transformer for SSB/BPSK-DS/CDMA is implemented. It is shown that, about 16∼28% adders can be saved by the proposed method compared with the conventional methods.