• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.5A
• /
• pp.267-275
• /
• 2003

In UMTS terminal modem uses 3 step search procedure for initial cell search, which comprises 1) slot synchronization, 2) code group identification and frame synchronization, and 3) scrambling-code identification. The performance of initial cell search procedure depends on search parameters like observation time and threshold. The purpose of this paper is to get the optimal observation time and threshold of each step for minimum mean acquisition time. In this paper we induce mean detection time of each step and mean acquisition timefrom the model of 3 step search procedure using state diagram. Also we propose initial cell search algorithm which utilize window search method against initial oscillator error, and select an appropriate observation time and threshold of each step by the analysis of simulation and induced result. It is shown that the mean acquisition time in multipath fading channel can be shorter than 500ms by using the determined observation time and threshold of each step.

• Proceedings of the Korean Information Science Society Conference
• /
• 2002.04a
• /
• pp.1-3
• /
• 2002

본 논문에서는 상위 단계 합성(high-level synthesis)에서의 메모리 탐색(exploration) 문제를 푸는 데 있어, 현존하는 메모리 합성 시스템들이 간과했던 한 가지 중요한 성질인 메모리 탐색에서의 스케줄링 효과(scheduling effect)를 말하고자 한다. 그리고 이 성질을 충분히 활용할 수 있는 새로운 형태의 통합된 알고리즘을 제안한다. 이 알고리즘은 메모리 구성(configuration)과 스케줄을 동시에 고려한다는 것을 가장 큰 특징으로 하는데, 몇 개의 벤치마크 필터 회로에 대한 실험을 통해 제안된 탐색 기법이 빠른 시간 안에 최적에 가까운 메모리 구성을 찾는다는 것을 보일 수 있었다.

• KIPS Transactions on Computer and Communication Systems
• /
• v.5 no.7
• /
• pp.159-172
• /
• 2016

This paper presents a novel algorithm for searching evacuation paths in indoor disaster environments. The proposed method significantly improves the time complexity to find the paths to the evacuation exit by introducing a light-weight Disaster Evacuation Graph (DEG) for a building in terms of the size of the graph. With the DEG, the method also considers load balancing and bottleneck capacity of the paths to the evacuation exit simultaneously. The behavior of the algorithm consists of two phases: horizontal tiering (HT) and vertical tiering (VT). The HT phase finds a possible optimal path from anywhere of a specific floor to the evacuation stairs of the floor. Thus, after finishing the HT phases of all floors in parallel the VT phase begins to integrate all results from the previous HT phases to determine a evacuation path from anywhere of a floor to the safety zone of the building that could be the entrance or the roof of the building. It should be noted that the path produced by the algorithm. And, in order to define the range of graph to process, tiering scheme is used. In order to test the performance of the method, computing times and evacuation times are compared to the existing path searching algorithms. The result shows the proposed method is better than the existing algorithms in terms of the computing time and evacuation time. It is useful in a large-scale building to find the evacuation routes for evacuees quickly.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
• /
• v.7 no.3
• /
• pp.329-337
• /
• 2017

This paper proposes a search method that explores parameters C and σ values of support vector machines (SVM) to improve performance while maintaining search accuracy. A traditional grid search method requires tremendous computational times because it searches all available combinations of C and σ values to find optimal combinations which provide the best performance of SVM. To address this issue, this paper proposes a deep search method that reduces computational time. In the first stage, it divides C-σ- accurate metrics into four regions, searches a median value of each region, and then selects a point of the highest accurate value as a start point. In the second stage, the selected start points are re-divided into four regions, and then the highest accurate point is assigned as a new search point. In the third stage, after eight points near the search point. are explored and the highest accurate value is assigned as a new search point, corresponding points are divided into four parts and it calculates an accurate value. In the last stage, it is continued until an accurate metric value is the highest compared to the neighborhood point values. If it is not satisfied, it is repeated from the second stage with the input level value. Experimental results using normal and defect bearings show that the proposed deep search algorithm outperforms the conventional algorithms in terms of performance and search time.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.1B
• /
• pp.167-174
• /
• 2000

The three-step search(TSS) algorithm, a simple and gradual motion estimation algorithm, has been widely used in some low bit-rate video compression. We propose a new fast block motion estimation algorithm using the characteristics of motion in search region. Most of motion vectors exist in the center region of search area, so the notion in that region is examined more closely than TSS in this paper. Also in a search step, motion vector is estimated in the local area which is not overlapped with the search area in previous step, considering the all possible direction of motion. Therefore, we get the better motion estimation and reduce computational time in compared with the conventional methods.

• Journal of Advanced Navigation Technology
• /
• v.12 no.2
• /
• pp.146-153
• /
• 2008

Due to the extremely short pulse in the Ultra-Wideband (UWB) technology, the accurate synchronization acquisition method is very important for both high data-rate WPAN and low data-rate WPAN. In this paper, we propose the synchronization acquisition algorithm based on two-step signal search method to acquire the synchronization in the UWB multi-path channel. At the first step, the search window is divided by two and the window that has higher power is chosen as a next search window. This operation is repeated until the measure power of the search window is smaller than the threshold value. At the second step, we employ Linear Search algorithm to the search window obtained at the first step for fine search. The proposed algorithm is proved that the synchronization acquisition is faster than the parallel search algorithm and it shows good performance in environment of the SNR extreme changes by the simulation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.8C
• /
• pp.742-753
• /
• 2005

In this paper, we propose a rapid and reliable signal acquisition scheme for UWB (Ultra Wide Band) systems in typical indoor wireless channels. The proposed scheme is a two-step search with different thresholds and search window applied to a single correlator, where each step utilizes the single-dwell search with the bit reversal. Simulation results in IEEE 802. I5 Task Group .3a UWB indoor wireless channel show that the proposed scheme for the LHWB signals can achieve significant reduction of the required mean acquisition time as compared to the conventional single-dwell bit reversal search and double-dwell bit reversal search with more complex structure employing two correlators for various threshold levels. In addition, it is also observed that the proposed scheme can achieve much faster and reliable signal acquisition in noisy environments.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.1B
• /
• pp.128-140
• /
• 2000

In this paper, we propose a fast block matching algorithm using the mean absolute error (MAE) of neighbor search point and search region reduction. The proposed algorithm is composed of two stages. At the first stage,the search region is divided into nonoverlapped 3$\times$3 areas and MAE of the center point of each area iscalculated. The minimum MAE value of all the calculated MAE's is determined as reference MAE. At thesecond stage, because the possibility that final motion vector exist near the position of reference MAE is veryhigh, we use smaller search region than first stage, And, using the MAE of center point of each area, the lowerbound of rest search point of each area is calculated and block matching process is performed only at the searchpoints that the lower bound is smaller than reference MAE. By doing so, we can significantly reduce thecomputational complexity while keep the increasement of motion estimation error small.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.26 no.6A
• /
• pp.1107-1116
• /
• 2001

고속 IP 주소 룩업(lookup)은 고속 인터넷 라우터의 성능을 좌우하는 주요 요소이다. LPM(longest prefix matching) 탐색은 IP 주소 룩업에서 가장 시간이 많이 걸리는 부분이다. PICAM은 고속 LPM 탐색을 위한 파이프라인 CAM 구조로서, 기존 CAM(content addressable memory, 내용 주수화 메모리)을 이용한 방법보다 룩업 테이블의 갱신속도가 빠르면서도 LPM 탐색율이 높은 CAM 구조이다. PICAM은 3단계의 파이프라인으로 구성된다. 단계 1 및 단계 2의 키필드분할수 및 매칭점의 분포에 따라 파이프라인의 성능이 좌우되며, LPM 탐색율이 달라질 수 있다. 본 논문에서는 PICAM의 파이프라인 성능모델을 제시하고, 이산사건 시뮬레이션(discrete event simulation)을 수행하여, 최적의 PICAM 구조를 도출하였다. IP version 4인 경우 키필드분할수를 8로 하고, 부하가 많이 걸리는 키필드블록을 중복 설치하는 것이 최적구조이며, IP version 6인 경우 키필드블록의 개수를 16으로 하는 것이 최적구조다.

• Journal of Fisheries and Marine Sciences Education
• /
• v.19 no.3
• /
• pp.415-428
• /
• 2007

본 연구는 인지양식이 온라인 학습의 성취도에 영향을 미치는 요인중의 하나라는 선행연구 결과들을 토대로, 인지양식이 온라인 정보탐색능력에도 영향을 미치는지 그리고 어떤 다른 개인적인 특성들이 온라인 정보탐색행위와 연관성이 있는지 고찰 하였다. 연구 대상은 대학원 석사과정과 박사과정에 재학중인 학생 36명이었으며, 인지양식검사와 Ellis와 Haugan (1997)의 정보탐색행위 모델에 근거하여 연구자에 의해 제작된 설문조사를 실시하였다. 학생들에게 연구 주제를 주고 온라인상에서 정보를 탐색하도록 시켰으며, 이들의 정보탐색행위 과정과 특성을 관찰하고 기록하였다. 인지양식검사 결과와 설문조사 결과를 양적 분석하고, 정보탐색행위 과정과 특성에 관한 질적 분석한 결과에 의하면, 개인의 인지양식과 온라인시스템을 이용한 정보탐색능력과는 아무런 상관관계가 없었다. 반면에, 정보탐색행위는 컴퓨터 이용 능력, 온라인 도서관 시스템 사용경험/능력과 상관관계를 보였다. 또한 검색한 정보에 대한 만족도는 정보탐색에 보내는 시간과 반비례 상관관계를 가지며, 대부분의 학습자들이 총 8단계의 정보탐색과정 중 " Browsing" 단계에 대부분의 시간을 보내는 것으로 관찰 되었다. 끝으로 대부분의 학생들이 도서관 시스템 사용능력에 높은 효능감을 보였지만, 학교 온라인도서관 시스템이 사용하기 편리하지 않도록 설계되어있다고 대답했으며, 자신들의 연구를 위해서 인터넷 검색엔진보다는 도서관 데이터베이스를 더 자주 사용하고 있는 것으로 나타났다.