• 한국통신학회논문지
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• 제25권3A호
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• pp.325-333
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• 2000

The proposed RPSS(Reference Picture Segment Selection) mode is the RPS mode in picture segment of the ISD mode. The RPS mode has the weakness that it has to change the whole reference picture even if transmission error occurs only in the small part of picture. If the RPS mode is applied only to an error-occurred part and a conventional coding scheme is applied to an error-free part, the higher coding efficiency can be obtained. Simulation results show that there is the optimal number of segment which provides that best performance with given environment such as the BER(Bit Error Rate) of wireless channels, the characteristics of imput sequence, what kind of RPSS mode is used, etc. To apply the channel-adoptive RPSS mode later, the scheme which can change the number of segment without INTRA refresh and spatial error propagation is proposed in this paper.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권11호
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• pp.5209-5228
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• 2016

Device-to-device (D2D) communication underlaying cellular networks can bring significate benefits for improving the performance of mobile services. However, it hinges on elaborate resource sharing scheme to coordinate interference between cellular users and D2D pairs. We formulate a joint mode selection, link allocation and power control optimization problem for D2D communication sharing uplink resources in a multi-user cellular network and consider the efficiency and the fairness simultaneously. Due to the non-convex difficulty, we propose a three-step scheme: firstly, we conduct mode selection for D2D pairs based on a minimum distance metric after an admission control and obtain some cellular candidates for them. And then, a cellular candidate will be paired to each D2D pair based on fairness. Finally, we use Lagrangian Algorithm to formulate a joint power control strategy for D2D pairs and their reused cellular users and a closed-form of solution is derived. Simulation results demonstrate that our proposed algorithms converge in a short time. Moreover, both the sum rate of D2D pairs and the energy efficiency of cellular users are improved.

• 대한의용생체공학회:의공학회지
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• 제20권3호
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• pp.265-274
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• 1999

본 논문에서는 3차원 의료 영상에 적합한 interframe 부호화 알고리즘을 제안하였다. 제안된 알고리즘은 움직임 추정/보상과 변환 부호화를 사용하는 동영상 압축 방법에 기초를 두고 있다. 이 알고리즘에서는 움직임 추정을 위해 와핑 방법이 채택되었다. 그리고, 부호화 효율을 향상시키기 위해 적응적 모드 선택을 사용하여 웨이블릿 변환 영역에서 움직임 조상된 오차 영상과 원 영상을 혼합한다. 이렇게 혼합된 영상은 제로트리 부호화 기법에 의해 압축된다. 본 논문은 제안된 방법이 3차원 의료 영상의 부호화에 매우 유용함을 증명하였다. 모의실험결과는 제안된 방법이 슬라이스 간의 간격과 무관하게 항상 좋은 결과를 얻을 수 있도록 하고, 그럼으로써 3차원 의료 영상 압축에 매우 바람직하다는 사실을 보여준다.

• 한국통신학회논문지
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• 제34권8C호
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• pp.790-800
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• 2009

H.264/AVC 부호화 표준은 부호화 효율을 높이기 위해 1/4 화소 단위의 움직임 추정, 다중 참조 프레임, 인트라 예측, 루프 필터, 다양한 블록 크기의 지원 등과 같은 새로운 부호화 도구들을 사용한다. 이를 통해 이전의 비디오 부호화 표준들에 비해 율-왜곡(率-歪曲) 관점에서 높은 성능을 보이지만 그로 인해 부호기의 복잡도는 크게 증가하였다. 본 논문은 부호기 복잡도의 증가를 초래하는 주요 부호화 도구들 중 인트라 매크로블록 모드 선택의 복잡도 감소에 주안(主眼)점을 두며, 이에 대한 복잡도 감소 알고리즘을 제시한다. 고속 인트라 모드 선택을 위한 제안하는 방법은 변환 영역에서 에지 활동도를 산출효과 이를 이용하여 intra4x4 및 색차블록에 대한 예측모드를 고속으로 선택함으로써 H.264/AVC 인트라프레임에 대한 고속 부호화를 수행한다. 실험 결과 제안하는 알고리즘은 참조소프트웨어와 비교하여 QCIF 및 CIF 영상에 대해서 각각 59.76% 및 65.03%의 속도향상을 가져오는 반면 비트율 증가 및 PSNR 감소는 매우 미미한 것으로 나타났다.

• Journal of Mechanical Science and Technology
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• 제19권10호
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• pp.1846-1855
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• 2005

This paper presents a new stochastic controller applied on the vibration control system under irregular disturbances based on the mode selection scheme. Measured displacement and frequency characteristics are simultaneously used in designing a mode selecting controller. This technique is validated by applying to the suppression problem of a flexible beam with randomly vibrated circumstances. The presented method, called Mode Selecting Stochastic Controller, uses the frequency measurement of the flexible system based on a Fast-Fourier transformation algorithm. This controller is constructed by combining mode selection method with previous known Stochastic Controller in real time: Numerical simulations and several experiments are conducted to validate the proposed method. The performance of the proposed method is compared with a stochastic controller developed recently. This method was improved compared with previous one.

• 한국통신학회논문지
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• 제31권3C
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• pp.271-278
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• 2006

비트율-왜곡 최적화 기법은 H.264/AVC(Advance Video Coding)의 부호화 효율을 높이기 위한 방법이긴 하나 모드 결정 과정 중 부호화기의 복잡도를 높아지는 단점이 있다. 많은 고속화 모드결정 연구들이 모드결정의 복잡도를 줄이기 위하여 제안되어져 왔었다. 본 논문에서는 H.264/AVC의 모드결정의 전체적인 복잡도를 줄이기 위하여 다중 참조 영상 선택 고속화 알고리즘과 선택적인 인트라 모드 선택 알고리즘의 두 가지 고속화 알고리즘을 제안한다. 참조영상 선택 고속화 알고리즘은 인터 모드 결정에 효과적이며, 선택적인 인트라 모드 선해 알고리즘은 과도한 인트라 모드 결정의 계산량을 효율적으로 감소시켰다. 제안된 알고리즘을 실험한 결과로 평균 44.63%의 부호화 시간 감소비를 보이면서 영상의 열화와 같은 부호화 효율 감소는 거의 눈에 띄지 않았다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권3호
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• pp.950-975
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• 2016

Device-to-Device (D2D) communication underlaying cellular networks is a promising add-on component for future radio communication systems. It provides more access opportunities for local device pairs and enhances system throughput (ST), especially when mobile relays (MR) are further enabled to facilitate D2D links when the channel condition of their desired links is unfavorable. However, mutual interference is inevitable due to spectral reuse, and moreover, selecting a suitable transmission mode to benefit the correlated resource allocation (RA) is another difficult problem. We aim to optimize ST of the hybrid system via joint consideration of mode selection (MS) and RA, which includes admission control (AC), power control (PC), channel assignment (CA) and relay selection (RS). However, the original problem is generally NP-hard; therefore, we decompose it into two parts where a hierarchical structure exists: (i) PC is mode-dependent, but its optimality can be perfectly addressed for any given mode with additional AC design to achieve individual quality-of-service requirements. (ii) Based on that optimality, the joint design of MS, CA and RS can be viewed from the graph perspective and transferred into the maximum weighted independent set problem, which is then approximated by our greedy algorithm in polynomial-time. Thanks to the numerical results, we elucidate the efficacy of our mechanism and observe a resulting gain in MR-aided D2D communication.

• 한국소음진동공학회논문집
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• 제25권4호
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• pp.232-237
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• 2015

Complex dynamic systems are composed of several subsystems. Each subsystems affect the dynamics of other subsystems since they are connected to each other in the whole system. Theoretically, we can derive the exact mass and stiffness matrix of a system if we have the natural frequencies and mode shapes of that system. In real situation, the modal parameters for the higher modes are not available and the number of degree of freedom concerned are not so high. This paper shows a simple method to derive the mass and stiffness matrix of a system considering the connecting points of subsystems. Since the accuracy of reconstructed structure depends on the selection of node and mode, the rule for selection of node and mode are derived from the numerical examples.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권12호
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• pp.5347-5360
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• 2016

In decode and forward relay systems, choosing the duplex mode is an important factor to the performance. To satisfy the performance requirement, self-interference must be mitigated for the full-duplex relay (FDR), and the resource efficiency must be increased for the half-duplex ratio (HDR). Therefore, if a wise scheme to consider these two factors exists, decode and forward relay systems are used more effectively. This study proposes a new duplex selection scheme for decode and forward relay systems. The proposed duplex selection scheme chooses the better duplex mode according to the channel statistical conditions with optimal power allocation. The simulation results show that the proposed duplex scheme with optimal power allocation has lower outage probability than the FDR and the HDR.

• 전자공학회논문지S
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• 제35S권5호
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• pp.94-102
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• 1998

In this paper, we proposed a dynamic selection scheme of advnaced prediction mode(DAPM), which reduces computational cost and improves coding efficiency. We can select the mode between default prediction mode (DPM) and advanced prediction mode (APM) according to motion componenets in a frame dynamically. For this purpose, we defined error distribution of motion estimation (EDME) as sum of absolute difference(SAD) for each searching points. This distribution region is divided to four subregions. We calculate minimum values in each subregions and then, we determine whether block motion estimation is performed or not depending on the results. As a result, we reduced computational complexity to 30% without degradation of image quality compared to fixed APM(FAPM) by selecting DPM for linear movement.