• 방송공학회논문지
• /
• 제17권5호
• /
• pp.781-788
• /
• 2012

HEVC에서는 움직임 예측 시, 복잡도를 줄이기 위해 고속 탐색 기법이 사용된다. 고속 탐색 기법에는 SAD 계산 복잡도를 줄인 부-화소 단위 SAD 계산 기법(sub-sampled SAD)과 양-예측시의 단-예측 반복횟수를 줄인 간소화된 양-예측 기법으로 이루어져 있다. 고속 탐색 기법으로 인해 복잡도는 크게 줄었지만 부호화 이득 역시 감소하였다. 본 논문에서는 감소된 부호화 효율을 보상하기 위해 간소화된 양-예측을 확장하였고 확장된 양-예측으로 증가된 복잡도를 줄이기 위해 예측 비용 기반의 복잡도 감소 기법들을 제안한다. 예측 비용 기반의 복잡도 감소 기법은 양-예측 조기 종료 기법과 양-예측 생략 기법으로 이루어져 있다. HM 6.0 참조 소프트웨어와 비교하여 확장된 양-예측 기법과 예측 비용 기반의 복잡도 감소 기법으로 복잡도의 증가 없이 평균 0.42%의 BD-bitrate을 감소시켰다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제13권6호
• /
• pp.2908-2924
• /
• 2019

Multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) is widely applied in wireless communication by virtue of its excellent properties in data transmission rate and transmission accuracy. However, as a major drawback of MIMO-OFDM systems, the high peak-to-average power ratio (PAPR) complicates the design of the power amplifier at the receiver end. Some available PAPR reduction methods such as selective mapping (SLM) suffer from high computational complexity. In this paper, a low-complexity SLM method based on active constellation extension (ACE) and joint space-time selective mapping (AST-SLM) for reducing PAPR in Alamouti STBC MIMO-OFDM systems is proposed. In SLM scheme, two IFFT operations are required for obtaining each transmission sequence pair, and the selected phase vector is transmitted as side information(SI). However, in the proposed AST-SLM method, only a few IFFT operations are required for generating all the transmission sequence pairs. The complexity of AST-SLM is at least 86% less than SLM. In addition, the SI needed in AST-SLM is at least 92.1% less than SLM by using the presented blind detection scheme to estimate SI. We show, analytically and with simulations, that AST-SLM can achieve significant performance of PAPR reduction and close performance of bit error rate (BER) compared to SLM scheme.

• 전자공학회논문지
• /
• 제52권8호
• /
• pp.40-48
• /
• 2015

본 논문에서는 다중 입력 다중 출력 시스템을 위한 전 처리 과정인 QR Decomposition (QRD) 과 Lattice Reduction (LR)에 대하여, 두 과정의 연산의 공유성을 바탕으로 이를 공동으로 처리하는 프로세서를 제안한다. 제안하는 전 처리 프로세서는 다중 사이클 아키텍처로 설계하여 하드웨어 복잡도를 낮추었고, 두 전 처리 과정을 채널 환경에 따라 선택적으로 수행한다. 제안하는 전 처리 프로세서는 $0.18-{\mu}m$ CMOS공정의 셀 라이브러리를 사용하여 139K의 논리 게이트로 구현되었고, 최대 117MHz의 동작주파수에서 $8{\times}8$ 행렬에 대한 QRD와 LR의 수행에 대하여 $5{\mu}s$의 latency를 갖는다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제9권6호
• /
• pp.2201-2216
• /
• 2015

Peak to average power ratio (PAPR) is one of the main imperfections in the broadband communication systems with multiple carriers. In this paper, a new crest factor reduction (CFR) scheme based on interleaved phase sequence called Dummy Sequence Insertion Enhanced Partial Transmit Sequence (DSI-EPTS) is proposed which effectively reduces the PAPR while at the same time keeps the total complexity low. Moreover, the prototype of the proposed scheme in field programmable gate array (FPGA) is demonstrated. In DSI-EPTS scheme, a new matrix of phase sequence is defined which leads to a significant reduction in hardware complexity due to its less searching operation to extract the optimum phase sequence. The obtained results show comparable performance with slight difference due to the FPGA constraints. The results show 5 dB reduction in PAPR by applying the DSI-EPTS scheme with low complexity and low power consumption.

• 산업경영시스템학회지
• /
• 제43권3호
• /
• pp.41-52
• /
• 2020

This paper investigates the stress-reducing preventive maintenance model through numerical experiments. The preventive maintenance model is used to analyze the relationship between related conditions and variables to gain insight into the efficient operation of the system when performing preventive maintenance in real-world situations. Various preventive maintenance models have been developed over the past decades and their complexity has increased in recent years. Increasing complexity is essential to reflect reality, but recent models can only be interpreted through numerical experiments. The stress-reducing preventive maintenance is a newly introduced preventive maintenance concept and can only be interpreted numerically due to its complexity, and has received little attention because the concept is unfamiliar. Therefore, for information purposes, this paper investigates the characteristics of the stress-reducing preventive maintenance and the relationship between parameters and variables through numerical experiments. In particular, this paper is focusing on the economic feasibility of stress-reducing preventive maintenance by observing changes in the optimal preventive maintenance period in response to changes in environmental stress and the improvement factor. As a result, when either the environmental stress or the improve effect of stress-reducing preventive maintenance is low, it is not necessary to carry out the stress-reducing preventive maintenance at excessive cost. In addition, it was found that the age reduction model is more economical than the failure rate reduction model.

• 전자공학회논문지B
• /
• 제30B권1호
• /
• pp.10-17
• /
• 1993

This paper analyzes succinct graph descriptions and its complexity of connectivity problems on context free graph languages under various restrictions. It defines SNLC(Simple Context Free Node Label Controlled) grammar and presents reduction method that solves graph problems without expanding the hierarchical description. It exemplifies the method by giving efficient solutions to connectivity problems on graphs and presents parallel algorithm for reduction and analyzes the complexity. Its results will help application of desing for NETWORK. CAD. VLSI and other engineering problems.

• 한국음향학회:학술대회논문집
• /
• 한국음향학회 1998년도 학술발표대회 논문집 제17권 1호
• /
• pp.155-158
• /
• 1998

IMBE(Improved Multi-Band Excitation) vocoders exhibit good performance at low data rates. The major drawback to IMBE coders is their large computational requirements. In this paper, thus, we propose a new pitch search method that preserves the quality of the IMBE vocoder with reduced complexity. The basic idea is to reduce computation complexity of the pitch searching by using the SAMDF. Applying the proposed method to the IMBE vocoder, we can get approximately 52.02% searching time reduction in the pitch search. There is no difference in voice quality between conventional IMBE and proposed IMBE.

• 한국음향학회:학술대회논문집
• /
• 한국음향학회 1995년도 제12회 음성통신 및 신호처리 워크샵 논문집 (SCAS 12권 1호)
• /
• pp.141-145
• /
• 1995

Code excited linear prediction speech coders exhibit good performance at data rates as low as 4800 bps. The major drawback to CELP type coders is their large computational requirements. In this paper, we propose a new codebook search method that preserves the quality of the CELP vocoder with reduced complexity. The basic idea is to restrict the searching range of the random codebook by using a searching technique of the regular pulse excitation. Applying the proposed method to the CELP vocoder, we can get approximately 48% complexity reduction in the codebook search.

• 한국전자파학회논문지
• /
• 제18권10호
• /
• pp.1172-1180
• /
• 2007

Orthogonal Frequency Division Multiplexing(OFDM) 시스템은 주파수 선택적 페이딩에 강하고 높은 대역 효율을 갖는 통신 시스템이다. OFDM 신호는 높은 PAPR로 인하여 비선형 증폭기에서 왜곡이 생긴다. 그래서 비선형 왜곡 성분인 IMD(Inter-Modulation Distortion)를 저감하는 것이 중요하다. IMD 저감 방식은 비선형 왜곡에 대하여 PAPR(Peak-To-Average Power Ratio) 저감 방식보다 BER 성능을 좋게할 수 있지만, 송신기에 FFT(Fast Fourier Transform)가 추가되어 시스템 복잡도를 증가시킨다. 본 논문에서는 IMD 저감 방식을 기반으로 하는 OFDM 통신 시스템의 BER 분석과 복잡도를 저감하기 위한 연구를 하였다. SPW(Sub-Block Phase Weighting)을 적용한 IMD 저감 방식에서 계산량 감소를 위한 새로운 방식을 제안하고 기존의 방식과 계산 복잡도를 비교한다. SPW 방식은 입력 데이터를 여러 개의 서브 블록으로 나누고 위상 회전 벡터를 곱해줌으로써 PAPR을 감소하거나 IMD를 저감한다. 제안된 방식은 BER 성능 면에서 기존 방식과 비슷하지만, PAPR처럼 시간 영역에서 IMD의 전력량을 계산하므로 시스템의 계산 복잡도와 시스템 크기를 줄일 수 있는 장점이 있다.

• ETRI Journal
• /
• 제27권5호
• /
• pp.639-642
• /
• 2005

This paper proposes two kinds of complexity-reduced algorithms for a low density parity check (LDPC) decoder. First, sequential decoding using a partial group is proposed. It has the same hardware complexity and requires a fewer number of iterations with little performance loss. The amount of performance loss can be determined by the designer, based on a tradeoff with the desired reduction in complexity. Second, an early detection method for reducing the computational complexity is proposed. Using a confidence criterion, some bit nodes and check node edges are detected early on during decoding. Once the edges are detected, no further iteration is required; thus early detection reduces the computational complexity.