• International Journal of Computer Science & Network Security
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• 제24권9호
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• pp.41-49
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• 2024

This paper proposes dual symbol superposition block carrier transmission with frequency domain equalization (DSS-FDE) system. This system is based upon χ-transform matrix, which is obtained by concatenation of discrete Hartley transform (DHT) matrix and discrete Fourier transform (DFT) matrices into single matrix that is remarkably sparse, so that, as it will be shown in this paper, it only has non-zero entries on its principal diagonal and one below the principle anti-diagonal, giving it shape of Latin alphabet χ. When multiplied with constellation mapped complex transmit vector, each entry of resultant vector is weighted superposition of only two entries of original vector, as opposed to all entries in conventional DFT based OFDM. Such a transmitter is close to single carrier block transmission with frequency domain equalization (SC-FDE), which is known to have no superposition. The DSS-FDE offers remarkable simplicity in transmitter design and yields great benefits in reduced complexity and low PAPR. At receiver-end, it offers the ability to harvest full diversity from multipath fading channel, full coding gain, with significant bit error rate (BER) improvement. These results will be demonstrated using both analytical expressions, as well as simulation results. As will be seen, this paper is Part III of three-paper series on alternative transforms for multicarrier communication (MC) systems.

• 대한전자공학회논문지
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• 제21권4호
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• pp.7-12
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• 1984

DFT로 대각선화 할 수 있는 circulant matrix가 대칭이고 실수인 경우에 이를 대각선화 할 수 있는 CDFT(composite DFT)를 유도했다. 일반적인 실수 신호의 대칭 covariance matrix에 대하여 DFT와 CDFT 변환했을 경우의 variance 분포를 분석했고, 이를 토대로 rate distortion 이론에 의하여 이들의 성능을 비교한 결과 CDFT가 DFT보다 bit rate면에서 효과적임을 볼 수 있었다. 그리고 f(q)=(0.95)q인 covariance matrix(64×64)에 대해 CDFT가 DFT에 비해. 계산결과, 평균적으로 0.0095bit가 감소될 수 있었다.

• 대한전기학회논문지:전력기술부문A
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• 제54권6호
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• pp.293-305
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• 2005

This paper describes an improved Prony method in its speed, accuracy and reliability by efficiently determining the optimal sampling interval with use of DFT (discrete Fourier transformation). In the Prony method the computation time is dominated by the size of the linear prediction matrix, which is given by the number of data times the modeling order The size of the matrix in a general Prony method becomes large because of large number of data and so does the computation time. It is found that the Prony method produces satisfactory results when SNR is greater than three. The maximum sampling interval resulting minimum computation time is determined using the fact that the spectrum in DFT is inversely proportional to sampling interval. Also the process of computing the modes is made efficient by applying Hessenberg method to the companion matrix with complex shift and computing selectively only the dominant modes of interest. The proposed method is tested against the 2003 KEPCO system and found to be efficient and reliable. The proposed method may play a key role in monitoring in real time low frequency oscillations of power systems .

• 대한전자공학회논문지
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• 제26권10호
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• pp.1617-1623
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• 1989

The introduction of the fast Fourier transform(FFT),an efficient computational algorithm for the discrete Fourier transform(DFT) by Cooley and Tukey(1965), has brought to the limelight various other discrete transforms. Some of the analog functions from which these transforms have been derived date back to the early 1920's, for example, Walsh functions (Walsh, 1923) and Hadamard Transform(Enomoto et al, 1965). Fast algorithms developed for the forward transform are equally applicable, exept for minor changes, to the inverse transform. In this paper, we present a simple pipelined Hadamard matrix(HM) which is used to develop a fast algorithm for the Hadamard Processor (HP). The Fast Hadamard Transform(FHT) can be derived using matrix partitioning techniques. The HP system is incorporated through a modular design which permits tailoring to meet a wide range of video data link applications. Emphasis has been placed on a low cost, a low power design suitable for airbone system and video codec.

• 방송공학회논문지
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• 제16권5호
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• pp.782-792
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• 2011

In this paper, we address a new fast DCT-II/DFT/HWT hybrid transform architecture for digital video and fusion mobile handsets based on Jacket-like sparse matrix decomposition. This fast hybrid architecture is consist of source coding standard as MPEG-4, JPEG 2000 and digital filtering discrete Fourier transform, and has two operations: one is block-wise inverse Jacket matrix (BIJM) for DCT-II, and the other is element-wise inverse Jacket matrix (EIJM) for DFT/HWT. They have similar recursive computational fashion, which mean all of them can be decomposed to Kronecker products of an identity Hadamard matrix and a successively lower order sparse matrix. Based on this trait, we can develop a single chip of fast hybrid algorithm architecture for intelligent mobile handsets.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권4호
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• pp.1292-1306
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• 2014

This paper proposes a space-polarization division multiple access (SPDMA) system that has limited feedback channels. The system simultaneously serves data streams to multiple mobile users through dual-polarized antenna arrays, by using pre-determined sets of precoding vectors that are orthogonal in both space and polarization domains. To this end, a codebook whose elements are sets of the precoding vectors is systematically designed based on the discrete Fourier transform (DFT) matrix and considering the power imbalance of polarized channels. Throughput of the SPDMA system is evaluated and compared to that of space division multiple access (SDMA) system, according to the various parameters including cross polarization discrimination (XPD). The results show that the throughput of SPDMA system outperforms that of SDMA in the environments of high XPD with many mobile users.

• 한국음향학회지
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• 제38권5호
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• pp.522-533
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• 2019

거리-도플러 추정을 위한 압축센싱(Compressive Sensing,CS) 모델은 과소결정계인 y = Ax 선형시스템으로 표현할 수 있다. 압축센싱 기법으로 위 선형시스템의 해를 찾으려면 행렬 A가 충분히 비간섭적이고 x가 희소해야 한다. 본 연구는 행렬 A가 비간섭적이도록 행렬 A의 상호간섭성을 낮추는 동시에 소나시스템에서 요구하는 대역폭을 유지하는 송신파형 설계 방법을 제안하였다. 제안한 방법은 행렬사영으로 센싱행렬을 최적화하는 방법과 DFT(Discrete Fourier Transform) 행렬을 이용하여 원하지 않은 주파수밴드를 억압하는 두 가지 방법을 결합한 것이다. 정합필터와 압축센싱 기법을 이용하여 기존파형 LFM(Linear Frequency Modulated)과 설계한 파형의 거리-도플러 추정 성능을 비교하였다. 시뮬레이션을 통해 설계한 송신파형이 기존파형(LFM)보다 탐지성능이 우수함을 보인다.

• Journal of Communications and Networks
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• 제12권3호
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• pp.240-245
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• 2010

Jacket matrices, motivated by the complex Hadamard matrix, have played important roles in signal processing, communications, image compression, cryptography, etc. In this paper, we suggest a novel approach to design a simple class of space-time block codes (STBCs) to reduce its peak-to-average power ratio. The proposed code provides coding gain due to the characteristics of the complex Hadamard matrix, which is a special case of Jacket matrices. Also, it can achieve full rate and full diversity with the simple decoding. Simulations show the good performance of the proposed codes in terms of symbol error rate. For generality, a kind of quasi-orthogonal STBC may be similarly designed with the improved performance.

• 한국통신학회논문지
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• 제41권7호
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• pp.723-731
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• 2016

5G 이동무선통신에서 요구되는 증가된 데이터 속도를 제공하기 위한 핵심적인 기술 축은 대규모 어레이를 활용하는 MIMO 전송을 통한 주파수 효율의 향상이다. MIMO 전송을 위해서는 CSI-RS (channel state information-reference signaling)를 이용하는 채널 추정 및 추정 결과에 적합한 빔포밍이 필요하며, 따라서 빔포밍 벡터를 정의하는 코드북의 설계는 매우 중요한 이슈이다. 본 논문에서는 공간채널모델을 이용하여 생성된 채널의 통계적인 특성을 활용하여 DFT (discrete Fourier transform) 행렬 기반 다중 랭크 코드북의 설계 방안을 제안하였다. 제안 방식은 인접한 안테나 원소 간 위상차의 분포와 전송 레이어 별 선택되는 코드벡터의 특징을 고려하여 PMI (precoding matrix indicator)의 구조 변경을 하였으며, LTE (long-term evolution) 시스템에서 사용 중인 3GPP 표준 코드북과의 성능 비교를 통하여 제안 방식의 이득을 산출하고 검증하였다.

• 정보교육학회논문지
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• 제15권3호
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• pp.517-524
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• 2011

어떠한 현상 혹은 사물의 이미지를 학생들에게 제공하는데 있어서 여러 가지 원인에 의해 초점이 흐리거나 혹은 흔들린 이미지들이 등장하여 학생들에게 보여주기가 힘든 경우가 빈번하게 발생한다. 특히, 이미지에 대한 구체적인 정보가 없는 경우에는 그 이미지는 쓸모가 없는 것이 된다. 본 연구는 무정보 블러링 이미지를 아주 빠른 시간 내에 복구할 수 있는 2차원 DFT 기반의 하나의 블러링 제거 알고리즘을 제안하는데 있다. 제안된 방법의 빠른 처리 속도는 이산 푸리에 변환, 변환의 필터링과 회선 관계 및 Moore-Penrose 역행렬의 효과적인 계산 방식을 바탕으로 한다. 특히, 필터의 주파수 응답에 관한 처리는 유용한 회선 공식을 유도한다. 제안된 방법의 구현은 보통 크기의 블러링 이미지에 적용했을 때, 아주 빠른 시간 내에 블러링 효과를 제거시킬 수 있고, 보다 선명한 이미지를 제공할 수 있음을 보인다.