• Journal of applied mathematics & informatics
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• 제32권1_2호
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• pp.61-74
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• 2014

This paper describes an iterative method for orthogonal projections $AA^+$ and $A^+A$ of an arbitrary matrix A, where $A^+$ represents the Moore-Penrose inverse. Convergence analysis along with the first and second order error estimates of the method are investigated. Three numerical examples are worked out to show the efficacy of our work. The first example is on a full rank matrix, whereas the other two are on full rank and rank deficient randomly generated matrices. The results obtained by the method are compared with those obtained by another iterative method. The performance measures in terms of mean CPU time (MCT) and the error bounds for computing orthogonal projections are listed in tables. If $Z_k$, k = 0,1,2,... represents the k-th iterate obtained by our method then the sequence of the traces {trace($Z_k$)} is a monotonically increasing sequence converging to the rank of (A). Also, the sequence of traces {trace($I-Z_k$)} is a monotonically decreasing sequence converging to the nullity of $A^*$.

• 대한전자공학회논문지TC
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• 제46권3호
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• pp.15-18
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• 2009

본 논문에서는 수신기에서 채널 추정을 필요로 하지 않는 MWSK (M-ary orthogonal Walsh sequence keying)를 적용한 ST-MWSK (space-time MWSK)를 제안한다. ST-MWSK의 noncoherent ML (maximum-likelihood) 검출기의 계산 복잡도는 기존의 ST-FSK (ST frequency-shift keying) 방식에 비해 크게 줄어든다. 또한 ST-MWSK는 ST-FSK와 거의 동일한 성능을 나타낸다.

• East Asian mathematical journal
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• 제40권1호
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• pp.25-36
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• 2024

Full univariate moment problems have been studied using continued fractions, orthogonal polynomials, spectral measures, and so on. On the other hand, the truncated moment problem has been mainly studied through confirming the existence of the extension of the moment matrix. A few articles on the multivariate moment problem implicitly presented about some results of this note, but we would like to rearrange the important results for the existence of a representing measure of a moment sequence. In addition, new techniques with orthogonal polynomials will be introduced to expand the means of studying truncated moment problems.

• 대한전자공학회논문지TC
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• 제47권7호
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• pp.93-101
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• 2010

본 논문에서는 GF(2)에서의 두 생성다항식에 의해 생성된 M-sequence로 Gold-Sequence를 생성한 후, Permutation을 해줌으로써 Hadamard 행렬의 특성을 가지게 됨을 살펴보았다. M-sequence는 선형 귀환 천이 레지스터 부호 생성기(Linear feedback shift register code generator)에 의해 생성되었으며, 두 개의 M-sequence에 의해 생성된 Gold-sequence의 첫 열에 $8\times1$의 영행렬을 추가하고 Permutation을 시켜줌으로써 Hadamard 행렬의 주요 성질인 직교성(Orthogonal)과 한 행렬과 이 행렬의 Transpose시킨 행렬의 결과가 단위행렬이 되고, 역행렬은 element-wise Inverse가 되며, 고속 Jacket행렬의 성질을 만족한다. 또한 선형 귀환 축차 생성기를 통하여 생성된 M-sequence의 1행과 1열을 추가함으로써 위에서 언급한 Hadamard 행렬의 주요 성질을 만족하고 L-matrix 와 S-matrix 를 통하여 고속변환이 가능함을 보인다.

• Journal of Electrical Engineering and information Science
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• 제2권4호
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• pp.19-22
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• 1997

In this paper, we propose a new communciation scheme combining both MT modulation and DS-CDMA with a concatenated orthogonal/PN spreading sequence. This scheme incorporates the advantages of both DS-CDMA wit a concatenated sequence, and an MT modulation technique to combat the effect of a multipath fading channel. It is shown that he proposed system outperforms the MT-CDMA system with a convetional PN sequence.

• 한국전자파학회논문지
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• 제10권7호
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• pp.1033-1043
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• 1999

We consider an improved multicarrier(MC) CDMA system that combines both DS-CDMA with a concatenated orthogonal/PN spreading sequence and MC modulation. This system incorporates the advantages of DS-CDMA with a concatenated sequence to achieve large user capacity and MC modulation technique to combat the effects of a multipath fading channel and intersymbol interference(ISI). Considering voice activity and imperfect sectorization, the system performance is analysed for the maximal ratio combiner(MRC) under a multicell, multiuser, and multipath Rayleigh/Rician fading channels. The performance of the system is improved much more for the single path fading channel compared to the multipath fading channel. Also the system is shown to have the more improved average bit error rate(BER) over the orthogonal MC-CDMA with the conventional PN sequence.

• 방송공학회논문지
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• 제24권7호
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• pp.1221-1227
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• 2019

This paper describes a low-density parity-check (LDPC) coded index modulated orthogonal frequency division multiplexing with quasi-orthogonal sequence (IM-OFDM-QOS) and provides performance evaluations of the proposed system. By using QOS as the spreading code, IM-OFDM-QOS scheme can improve the reception performance than IM-OFDM-SS scheme for a given data rate. On the other hand, LDPC code is widely used to the latest wireless communication systems as forward error correction (FEC) scheme and has Shannon-limit approaching performance. Therefore, by applying LDPC code to IM-OFDM-QOS system as FEC scheme, the reception performance can be further improved. Simulation results show that significant signal-to-noise ratio (SNR) gains can be obtained for LDPC coded IM-OFDM-QOS system compared to the LDPC coded IM-OFDM-SS system and the SNR gain increases with the higher code rate.

• 한국통신학회논문지
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• 제29권3A호
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• pp.248-256
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• 2004

Woerner는 비동기 트레리스 부호화 DS/COMA (asynchronous treilis-coded DS/CDMA systems, A-TC-CDMA) 시스템에 낮은 상관도의 다중 시퀀스 시그날링인 배직교 시퀀스 (biorthogonal sequence)를 이용함으로써 단일 시퀀스 시그날링인 M-ary PSK에 비해 보다 개선된 시스템 성능을 얻을 수 있음을 보여주었다. 본 논문에서는 최근 기 제안된 다중 시퀀스 시그날링 방식인 OPSM (orthogonal plane sequence modulation)과 배직교 시퀀스를 이용한 비동기 트레리스 부호화 CDMA 시스템 성능을 상호 비교 분석한다. 가입자 수신신호의 상호간섭 랜덤변수의 모멘트를 유도하고 그 결과 배직교 시퀀스 시그날링 방식에 비해 적은 수의 심볼당 시퀀스를 갖는 OPSM(orthogonal plane sequence modulation)이 시퀀스간 낮은 상호상관도 특성을 가짐을 보여준다. 또한 컴퓨터 시뮬레이션을 통하여 다중 시퀀스 시그날링 비동기 트레리스 시스템의 전력 효율 및 스펙트럼 효율을 비교 검증한다.

• 한국통신학회논문지
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• 제23권7호
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• pp.1824-1830
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• 1998

이 논문에서는 한 직교수열의 고유 성질을 바탕으로 한 잡음 줄임 기법을 생각한다. 이 변조 직교부호는 N 정보 심볼로부터 (information symbol) 길이가 $N^2$인 수열을 만든다. 먼저, 받은 심볼의 진폭을 써서 가장 작은 신호의 위치를 추정한 다음, 제안한 방법으로 잡음을 줄인다. 컴퓨터 모의 실험을 써서 제안한 방법의 성능을 확인한다.

• ETRI Journal
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• 제40권6호
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• pp.699-713
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• 2018

Orthogonal frequency division multiplexing (OFDM) has been the overwhelmingly prevalent choice for high-data-rate systems due to its superior advantages compared with other modulation techniques. In contrast, a high peak-to-average-power ratio (PAPR) is considered the fundamental obstacle in OFDM systems since it drives the system to suffer from in-band distortion and out-of-band radiation. The partial transmit sequence (PTS) technique is viewed as one of several strategies that have been suggested to diminish the high PAPR trend. The PTS relies upon dividing an input data sequence into a number of subblocks. Hence, three common types of the subblock segmentation methods have been adopted - interleaving (IL-PTS), adjacent (Ad-PTS), and pseudorandom (PR-PTS). In this study, a new type of subblock division scheme is proposed to improve the PAPR reduction capacity with a low computational complexity. The results indicate that the proposed scheme can enhance the PAPR reduction performance better than the IL-PTS and Ad-PTS schemes. Additionally, the computational complexity of the proposed scheme is lower than that of the PR-PTS and Ad-PTS schemes.