• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권2호
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• pp.485-499
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• 2021

Although non-binary low-density parity-check (NB-LDPC) codes have better error-correction capability than that of binary LDPC codes, their decoding complexity is significantly higher. Therefore, it is crucial to reduce the decoding complexity of NB-LDPC while maintaining their error-correction capability to adopt them for various applications. The extended min-sum (EMS) algorithm is widely used for decoding NB-LDPC codes, and it reduces the complexity of check node (CN) operations via message truncation. Herein, we propose a low-cost CN processing method to reduce the complexity of CN operations, which take most of the decoding time. Unlike existing studies on low complexity CN operations, the proposed method employs quick selection algorithm, thereby reducing the hardware complexity and CN operation time. The experimental results show that the proposed selection-based CN operation is more than three times faster and achieves better error-correction performance than the conventional EMS algorithm.

• The Journal of the Acoustical Society of Korea
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• 제17권3E호
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• pp.53-57
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• 1998

Spectral information at a speech coder should be quantized with sufficient accuracy to keep perceptually transparent output speech. Spectral information at a low bit rate speech coder is usually transformed into corresponding line spectrum pair parameters and is often quantized with a vector quantization algorithm. As the vector quantization algorithm generally has high complexity in the optimal code vector searching routine, the complexity reduction in that routine is investigated using the ordering property of the line spectrum pair. When the proposed complexity reduction algorithm is applied to the well-known split vector quantization algorithm, the 46% complexity reduction is achieved in the distortion measure compu-tation.

• 한국통신학회논문지
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• 제36권4C호
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• pp.217-225
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• 2011

본 논문에서는 영상의 지역 특성별로 보간 방법을 적응적으로 선택하여 적용하는 효과적인 디인터레이싱 알고리듬을 제안한다. 기존의 알고리듬들의 경우 각기 다른 방법으로 방향성을 구하기 때문에 영상의 지역 특성별로 성능이 다르게 나오는 경우가 있다. 또한, FDD(Fine Directional De-interlacing) 알고리듬의 경우 PSNR(Peak Signal-to-Noise Ratio)은 다른 알고리듬들에 비해 높게 나오지만 계산량이 많다는 단점이 있다. 이를 보안하기 위해 본 논문에서는 여러 영상들에서 계산량은 적으면서 화질 성능은 뛰어난 LA(Line Average), MELA(Modified Edge-based Line Average), LCID(Low-Complexity Interpolation Method for De-interlacing) 알고리듬들 중 지역복잡도 (DoLC, Degree of Local Complexity)별로 효과적인 알고리듬을 학습하여 이를 이용하여 보간을 수행하는 디인터레이싱 방법을 제안한다. 실험 결과 제안하는 방법은 좋은 성능에 비해 계산량이 적은 LCID 알고리듬과 비슷한 계산량을 보이면서 객관적 화질이 우수한 FDD, MELA 알고리듬보다 PSNR로 대표되는 객관적 화질과 주관적 화질 측면에서 우수한 결과를 나타내는 것을 알 수 있다.

• 대한임베디드공학회논문지
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• 제13권1호
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• pp.1-8
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• 2018

This paper proposes a low complexity super resolution algorithm for frequency modulated continuous wave (FMCW) radar systems for foreign object debris (FOD) detection. FOD radar has a requirement to detect foreign object in small units in a large area. However, The fast Fourier transform (FFT) method, which is most widely used in FMCW radar, has a disadvantage in that it can not distinguish between adjacent targets. Super resolution algorithms have a significantly higher resolution compared with the detection algorithm based on FFT. However, in the case of the large number of samples, the computational complexity of the super resolution algorithms is drastically high and thus super resolution algorithms are difficult to apply to real time systems. In order to overcome this disadvantage of super resolution algorithm, first, the proposed algorithm coarsely obtains the frequency of the beat signal by employing FFT. Instead of using all the samples of the beat signal, the number of samples is adjusted according to the frequency of the beat signal. By doing so, the proposed algorithm significantly reduces the computational complexity of multiple signal classifier (MUSIC) algorithm. Simulation results show that the proposed method achieves accurate location even though it has considerably lower complexity than the conventional super resolution algorithms.

• Journal of Computing Science and Engineering
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• 제6권4호
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• pp.310-319
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• 2012

Next generation wireless receivers demand low computational complexity algorithms with high computing power in order to perform fast signal detections and error estimations. Several signal detection and estimation algorithms have been proposed for next generation wireless receivers which are primarily designed to provide reasonable performance in terms of signal to noise ratio (SNR) and bit error rate (BER). However, none of them have been chosen for direct implementation as they offer high computational complexity with relatively lower computing power. This paper presents a low-complexity power-efficient algorithm that improves the computing power and provides relatively faster signal detection for next generation wireless multiuser receivers. Measurement results of the proposed algorithm are provided and the overall system performance is indicated by BER and the computational complexity. Finally, in order to verify the low-complexity of the proposed algorithm we also present a formal mathematical proof.

• 한국통신학회논문지
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• 제31권4C호
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• pp.303-309
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• 2006

By combining the space-time diversity technique and iterative turbo codes, space-time turbo codes(STTCS) are able to provide powerful error correction capability. However, the multi-path transmission and iterative decoding structure of STTCS make the decoder very complex. In this paper, we propose a low complexity decoder, which can be used to decode STTCS as well as general iterative codes such as turbo codes. The efficient implementation of the backward recursion and the log-likelihood ratio(LLR) update in the proposed algorithm improves the computational efficiency. In addition, if we approximate the calculation of the joint LLR by using the approximate ratio(AR) algorithm, the computational complexity can be reduced even further. A complexity analysis and computer simulations over the Rayleigh fading channel show that the proposed algorithm necessitates less than 40% of the additions required by the conventional Max-Log-MAP algorithm, while providing the same overall performance.

• The Journal of the Acoustical Society of Korea
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• 제28권3E호
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• pp.93-98
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• 2009

In this paper, we propose a new VSS-NLMS algorithm through a simple modification of the conventional NLMS algorithm, which leads to a low complexity algorithm with enhanced performance. The step size of the proposed algorithm becomes smaller as the error signal is getting orthogonal to the input vector. We also show that the proposed algorithm is an approximated normalized version of the KZ-algorithm and requires less computation than the KZ-algorithm. We carried out a performance comparison of the proposed algorithm with the conventional NLMS and other VSS algorithms using an adaptive channel equalization model. It is shown that the proposed algorithm presents good convergence characteristics under both stationary and non-stationary environments despites its low complexity.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권8호
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• pp.3772-3790
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• 2016

It is well known that the constant modulus algorithm (CMA) presents a large steady-state mean-square error (MSE) for high-order quadrature amplitude modulation (QAM) signals. In this paper, we propose a low-complexity hybrid adaptive blind equalization algorithm, which augments the CMA error function with a novel constellation matched error (CME) term. The most attractive advantage of the proposed algorithm is that it is computationally simpler than concurrent CMA and soft decision-directed (SDD) scheme (CMA+SDD), and modified CMA (MCMA), while the approximation of steady-state MSE of the proposed algorithm is same with CMA+SDD, and lower than MCMA. Extensive simulations demonstrate the performance of the proposed algorithm.

• 한국전자파학회논문지
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• 제22권7호
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• pp.705-710
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• 2011

본 논문에서는 Chase 알고리즘 기반의 연판정 e-BCH 복호시 계산량을 감소하는 알고리즘을 제시하였다. Chase 알고리즘 기반의 연판정 e-BCH 복호 방식은 test pattern을 만들기 위해 수신 데이터 중 신뢰성이 낮은 데이터를 순서대로 찾기 위해 ordering을 한다. 데이터를 ordering하는 과정과 test pattern 수 만큼을 수신 데이터와 비교함으로써 최적의 복호 열을 찾는 과정에서 높은 복잡도가 요구되며, 본 논문에서는 이러한 복잡도를 줄이는 방안을 제시하여 계산량 및 성능 관점에서 비교 분석하였다.

• 한국통신학회논문지
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• 제35권11A호
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• pp.1027-1037
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• 2010

본 논문에서는 블록 대각화 프리코딩 기법을 사용하는 다중 사용자 MIMO-OFDM 하향링크 시스템에서 전체시스템의 복잡도와 계산양을 감소시키기 위한 선형 보간법 기반 블록 대각화 프리코딩 근사화 기법을 제안한다. 일반적인 블록 대각화 프리코팅 기법을 다중 사용자 MIMO-OFDM 시스템에 그대로 적용할 경우 계산양이 부반송파의 수에 비례하여 증가하는 단점이 존재한다. 제안하는 선형 보간법 기반 블록 대각화 프리코딩 근사화 기법은 시스템의 복잡도와 계산양을 감소시키기 위하여 선형 보간법을 프리코딩 행렬의 근사화에 사용하여 성능을 최대한 유지하면서 계산양을 매우 크게 감소시킬 수 있다. 본 논문에서 제안된 선형 보간법 기반 블록 다각화 프리코딩 근사화 기법을 이용하여 시스템의 계산양을 매우 감소시킬 수 있음을 모의실험을 통해 증명했다.