• 한국정보통신학회논문지
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• 제5권1호
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• pp.183-191
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• 2001

본 논문은 데이터 슬라이스에서의 정보 흐름을 모델링하기 위해서 데이터 값 흐름 그래프(VFG: data Value Flow Graph)라고 하는 새로운 데이터 슬라이스(data slice) 표현을 개발한다. 다음으로, VFG에서의 정보 흐름의 복잡도를 측정하기 위해 기존의 흐름 복잡도를 이용하여 슬라이스 복잡도 척도를 정의한다. 본 연구에서는 각 슬라이스에 대한 슬라이스 복잡도와 전체 슬라이스 복잡도 간의 관계를 보여주고, VFG에서의 극소 수정(atomic modification)과 합성 연산자(concatenation operator)를 통해서 슬라이스 복잡도 척도의 스케일(scale) 인자들을 증명한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권9호
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• pp.4372-4389
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• 2019

Spectrum sensing has attracted much attention due to its significant contribution to idle spectrum detection in Cognitive Radio Networks. However, specialized discussion is on complexity-based sensing strategy for spectrum sensing seldom considered. Motivated by this, this paper is devoted to complexity-based sensing strategy for spectrum sensing. Firstly, three efficiency functions are defined to estimate sensing efficiency of a spectrum scheme. Then a novel sensing strategy is proposed given sensing performance and computational complexity. After that, the proposed sensing strategy is extended to energy detector, Cyclostationary feature detector, covariance matrix detector and cooperative spectrum detector. The proposed sensing strategy provides a novel insight into sensing performance estimation for its consideration of both sensing capacity and sensing complexity. Simulations analyze three efficiency functions and optimal sensing strategy of energy detector, Cyclostationary feature detector and covariance matrix detector.

• Journal of Positioning, Navigation, and Timing
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• 제13권3호
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• pp.277-287
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• 2024

In satellite systems, efficient communication and observation require identifying of specific signal arrival points using onboard antenna systems. When utilizing massive array antennas to estimate the angle of arrival (AOA) of signals, traditional high-performance AOA estimation algorithms such as Multiple Signal Classification (MUSIC) encounter extremely high complexity due to the numerous individual antenna elements. Although, in order to improve this computational complexity problem, the cascade AOA estimation algorithm with CAPON and beamspace-MUSIC was recently proposed, the comparison of the computational complexity of the proposed algorithm across different massive array antenna configurations has not yet been conducted. In this paper, we provide the analyzed results of the computational complexity of the proposed cascade algorithm based on various massive array antennas, and determine an optimal antenna configuration for the efficient AOA estimation in satellite systems.

• Journal of information and communication convergence engineering
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• 제3권2호
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• pp.72-75
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• 2005

In this work, we first present our study on the decoding schemes for space-time block code as well as our comments on their complexity. Then, we propose a new modified complex sphere decoding scheme, which has lower computational load than that of conventional complex sphere decoders. In the proposed scheme, the boundary for searching is aided with the intersection of approximate polygon of searching circle and disk of constellation. Therefore, the proposed scheme can reduce the searching boundary while can avoid missing searching points. The performance of the proposed scheme is verified by computer simulation that consolidates our scheme.

• 한국정보과학회논문지:정보통신
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• 제28권4호
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• pp.455-462
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• 2001

본 논문에서는 네트웍으로 연결된 일련의 장치들이 서로를 발견하는 문제인 자원 발견 (Resource Discovery)문제를 해결하는 알고리즘을 제안한다. 최근 Harchol등은, 장치의 수를 n이라 할 때, O($nlog^2\;n$) 연결 통신복잡도와 O($n^2log^2\;n$) 포인터 통신복잡도를 가지고 O($log^2\;n$) 시간복잡도에 이문제를 해결하는 알고리즘을 제안하였는데, 이는 임의(randomized) 알고리즘이며 종료시점(convergence)을 식별할 방법이 없다는 단점을 가진다. 본 논문에서 우리는 이러한 단점을 없앤 더욱 효율적인 결정(deterministic) 알고리즘을 제안한다 .제안 알고리즘은, 총 링크 수를 m이라 할 때，O(mlog n) 연결 통신 복잡도와 O($n^2log\;n$) 포인터 통신복잡도를 가지고 O(log n) 시간복잡도에 자원발견 문제를 해결한다.

• Journal of Communications and Networks
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• 제13권3호
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• pp.232-239
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• 2011

This paper investigates the user selection problem of successive zero-forcing precoded multiuser multiple-input multiple-output (MU-MIMO) downlink systems, in which the base station and mobile receivers are equipped with multiple antennas. Assuming full knowledge of the channel state information at the transmitter, dirty paper coding (DPC) is an optimal precoding strategy, but practical implementation is difficult because of its excessive complexity. As a suboptimal DPC solution, successive zero-forcing DPC (SZF-DPC) was recently proposed; it employs partial interference cancellation at the transmitter with dirty paper encoding. Because of a dimensionality constraint, the base station may select a subset of users to serve in order to maximize the total throughput. The exhaustive search algorithm is optimal; however, its computational complexity is prohibitive. In this paper, we develop two low-complexity user scheduling algorithms to maximize the sum rate capacity of MU-MIMO systems with SZF-DPC. Both algorithms add one user at a time. The first algorithm selects the user with the maximum product of the maximum column norm and maximum eigenvalue. The second algorithm selects the user with the maximum product of the minimum column norm and minimum eigenvalue. Simulation results demonstrate that the second algorithm achieves a performance similar to that of a previously proposed capacity-based selection algorithm at a high signal-to-noise (SNR), and the first algorithm achieves performance very similar to that of a capacity-based algorithm at a low SNR, but both do so with much lower complexity.

• 한국전자통신학회논문지
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• 제7권3호
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• pp.545-551
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• 2012

본 논문에서는 류수 계산의 복잡성과 소인수분해의 어려움을 덫으로 하는 IQC(Imaginary Quadratic Cryptosystem)에 기반을 둔 새로운 암호계를 제안한 다음, 그의 암호화와 복호화 시간을 줄이는 효율적인 알고리즘을 제시하기로 한다. 또한 제안하는 암호계의 안전성을 쉽게 알 수 있도록, 그 암호계의 가장 간단한 예를 들어 그 암호계에 사용되는 공개키 또는 비밀키의 복잡도와 안전성을 분석하고 제안된 암호계의 작동과정을 소개하기로 한다.

• Journal of information and communication convergence engineering
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• 제16권3호
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• pp.142-147
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• 2018

We present a practical design algorithm for quantizers at nodes in distributed systems in which each local measurement is quantized without communication between nodes and transmitted to a fusion node that conducts estimation of the parameter of interest. The benefits of vector quantization (VQ) motivate us to incorporate the VQ strategy into our design and we propose a low-complexity design technique that seeks to assign vector codewords into sets such that each codeword in the sets should be closest to its associated local codeword. In doing so, we introduce new distance metrics to measure the distance between vector codewords and local ones and construct the sets of vector codewords at each node to minimize the average distance, resulting in an efficient and independent encoding of the vector codewords. Through extensive experiments, we show that the proposed algorithm can maintain comparable performance with a substantially reduced design complexity.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권1호
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• pp.118-125
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• 2016

This paper presents a new high-efficient algorithm and architecture for an elliptic curve cryptographic processor. To reduce the computational complexity, novel modified Lopez-Dahab scalar point multiplication and left-to-right algorithms are proposed for point multiplication operation. Moreover, bit-serial Galois-field multiplication is used in order to decrease hardware complexity. The field multiplication operations are performed in parallel to improve system latency. As a result, our approach can reduce hardware costs, while the total time required for point multiplication is kept to a reasonable amount. The results on a Xilinx Virtex-5, Virtex-7 FPGAs and VLSI implementation show that the proposed architecture has less hardware complexity, number of clock cycles and higher efficiency than the previous works.

• 한국전자통신학회논문지
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• 제6권1호
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• pp.20-26
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• 2011

본 논문에서는 NM(node monitoring) 알고리듬과 NP(Piecewise Linear Function Approximation)를 사용해서 LDPC 코드 복호의 복잡도를 감소시키기 위한 효율적인 알고리듬을 제안한다. 이 NM 알고리듬은 새로운 node-threshold 방법과 message passing 알고리듬에 근거해서 제안되었는데, 이에 NP 방법을 사용해서 알고리듬의 복잡도를 더 줄일 수 있었다. 이 알고리듬의 효율성을 입증하기 위해서 모의 실험을 하였다. 모의실험결과, 기존에 잘 알려진 방법에 비해서 20% 정도 더 효율적이었다.