• 한국통신학회논문지
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• 제24권7A호
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• pp.996-1004
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• 1999

본 논문에서는 레일레이 다중경로 페이딩 채널 환경하에서 직교 확산 방식과 레이크 수신를 채용하는 역방향 링크 동기화 (synchronous) DS-CDMA 시스템의 성능을 분석하고 이를 비동기 (asynchronous) 전송 시스템과 비교하고자 한다. 이상적인 이진 부호화 변조라 가정할 때, 시스템 성능은 평균비트오율과 수용용량으로 계산되어진다. 본 논문에서는 주로 다중경로 강도 프로파일 (MIP) 모양과 레이크 탭의 수가 동기화 전송 시스템의 성능에 미치는 영향을 분석하고자 한다. 분석 결과 경로간 간섭이 존재하는 경우일지라도, 비동기 DS-CDMA 시스템보다 역방향 링크 동기화 DS-CDMA시스템이 우월한 성능을 가짐을 확인할 수 있었다.

• 한국통신학회논문지
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• 제23권7호
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• pp.1659-1666
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• 1998

IMT-2000 시스템을 위한 전송 방식으로 활발히 연구되고 있는 다중부호 부호분할 다원접속 시스템은, 고속 데이터를 다수의 저속데이터로 병렬변환하고 이들 변환 신호를 직교 부호를 이용하여 구분한 뒤 동시 전송하는 방법이다. 이 논문에서는 부호율 r=1/2인 길쌈 부호와 이원 직교 부호를 이용함으로써, 기존의 시스템과 동일한 데이터 전송율과 처리이득을 유지하면서도 비트오율 성능을 월등히 개선하는 새로운 방식을 제안한다. 부가성 백색 정규 잡음 채널과 다중 경로 감쇄 채널에서 최대비 결합 갈퀴 수신기를 이용하는 동기식 시스템에 대한 모의 실험을 통해서 월등한 성능 향상이 가능함을 확인하였다.

• 제어로봇시스템학회논문지
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• 제22권11호
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• pp.967-976
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• 2016

This paper presents a 3D carrier-smoothed GNSS/DR (Global Navigation Satellite System/Dead Reckoning) integrated system for precise ground-vehicle trajectory estimation. For precise DR navigation on sloping roads, the AHRS (Attitude Heading Reference System) methodology is employed. By combining the integrated carrier phase of GNSS and DR sensor measurements, a vehicle trajectory with an accuracy of less than 20cm is obtained even when cycle slip or change of visibility occur. In order to supplement the weak GNSS environment with DR successfully, the DR sensor is precisely compensated for using GNSS Doppler measurements when GNSS visibility is good. By integrating a multi-GNSS receiver with low-cost IMU, a precise 3D navigation system for land vehicles is proposed in this paper. For real-time implementation, a decoupled Kalman filter is employed in the integrated system. Through field experiments, the performance of the proposed system is verified in various road environments, including sloping roads, good-visibility areas, high multi-path areas, and under-ground parking areas.

• ETRI Journal
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• 제42권5호
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• pp.773-780
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• 2020

A 40 nm complementary metal oxide semiconductor carrier-aggregated drive amplifier with high linearity is presented for sub-GHz Internet of Things applications. The proposed drive amplifier consists of two high linear amplifiers, which are composed of five differential cascode cells. Carrier aggregation can be achieved by switching on both the driver amplifiers simultaneously and combining the two independent signals in the current mode. The common gate bias of the cascode cells is selected to maximize the output 1 dB compression point (P1dB) to support high-linear wideband applications, and is used for the local supply voltage of digital circuitry for gain control. The proposed circuit achieved an output P1dB of 10.7 dBm with over 22.8 dBm of output 3rd-order intercept point up to 0.9 GHz and demonstrated a 55 dBc adjacent channel leakage ratio (ACLR) for the 802.11af with -5 dBm channel power. To the best of our knowledge, this is the first demonstration of the wideband carrier-aggregated drive amplifier that achieves the highest ACLR performance.

• 대한조선학회논문집
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• 제45권6호
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• pp.646-655
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• 2008

A main issue about production management of shipyards is to efficiently manage the work in process and logistics. However, so far the management of a transporter for moving building blocks has not been efficiently performed. To solve the issues, optimal block transporting scheduling system is developed for minimizing of the travel distance without overload of a transporter. To implement the developed system, a hybrid optimization algorithm for an optimal block transportation scheduling is proposed by combining the genetic algorithm and the ant algorithm. Finally, to evaluate the applicability of the developed system, it is applied to a block transportation scheduling problem of shipyards. The result shows that the developed system can generate the optimal block transportation scheduling of a transporter which minimizes the travel distance without overload of the transporter.

• 제어로봇시스템학회논문지
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• 제16권2호
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• pp.101-106
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• 2010

Researches on air-ground robot cooperating system has been made recently. The cooperation among homogeneous robots focused on the architecture of the system, quality and influence of the communication. In contrast, the cooperation among heterogeneous robots such as aerial vehicle and ground vehicle robots has not been much handled. There are a couple of main points for those air-ground cooperating robots. One is using UAV (Unmanned Aerial Vehicle) as an extra sensor of UGV (Unmanned Ground Vehicle). This kind of application is usually used in situations such as guiding UGV to an appropriate path which could be better determined from the eye in the sky as UAV. The other main application of air-ground cooperating robot system is the localization. By combining sensor information from both UAV and UGV, the robot system as a whole can localize a target object or find features in the environment with better performance than UGV or UAV alone. Although these applications are recently studied in many different ways and devices, there are still a lot of possibilities in the field of air-ground cooperating robot systems. We introduce those research fields in this paper.

• 정보처리학회논문지C
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• 제12C권2호
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• pp.223-228
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• 2005

현재 디지털 이동통신에서 사용되고 있는 DS(direct sequence)/CDMA 방식은 멀티미디어 통신과 같은 고속 데이터 전송에 적용할 경우 다중경로 페이딩 채널하에서 인접심볼간 간섭 및 다중접속간섭이 심해지는 문제점을 갖고 있다. 이러한 문제들을 보완하기 위해, 본 논문에서는 다원 접속 간섭을 억제하는 멀티코드 시스템에 인접 심볼간 간섭을 줄여주는 하이브리드 DS/FH(frequency hopping) SS(spread-spectrum)기술을 접목하여 멀티코드 하이브리드 DS/FH SS 시스템을 고안하였고, 기존의 멀티펀드 시스템이 가지는 문제점을 해결하고자 sub-code 기술을 이용하여 sub-code멀티코드 하이브리드 DS/FS SS 시스템을 제안하였다. 제안한 시스템의 성능을 분석하고자 다양한 채널 환경 하에서 컴퓨터 시뮬레이션을 실시하였다.

• Journal of Information Processing Systems
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• 제10권4호
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• pp.602-617
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• 2014

The performance of a cognitive radio network (CRN) solely depends on how precisely the secondary users can sense the presence or absence of primary users. The incorporation of a spatial false alarm makes deriving the probability of a correct decision a cumbersome task. Previous literature performed this task for the case of a received signal under a Normal probability density function case. In this paper we enhance the previous work, including the impact of carrier frequency, the gain of antennas on both sides, and antenna heights so as to observe the robustness against noise and interference and to make the correct decision of detection. Three small scale fading channels: Rayleigh, Normal, and Weibull were considered to get the real scenario of a CRN in an urban area. The incorporation of a maximal-ratio combining and selection combing with a variation of the number of received antennas have also been studied in order to achieve the correct decision of spectral sensing, so as to serve the cognitive users. Finally, we applied the above concept to a traffic model of the CRN, which we based on a two-dimensional state transition chain.

• 통합자연과학논문집
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• 제2권4호
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• pp.243-251
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• 2009

This paper surveys some researches to accomplish on bioinformatics. These researches wish to propose a database architecture combining a general view of bioinformatics data as a graph of data objects and data relationships, with the efficiency and robustness of data management and query provided by indexing and generic programming techniques. Here, these invert the role of the index, and make it a first-class citizen in the query language. It is possible to do this in a structured way, allowing users to mention indexes explicitly without yielding to a procedural query model, by converting functional relations into explicit functions. In the limit, the database becomes a graph, in which the edges are these indexes. Function composition can be specified either explicitly or implicitly as path queries. The net effect of the inversion is to convert the database into a hyperdatabase: a database of databases, connected by indexes or functions. The inversion approach was motivated by their work in biological databases, for which hyperdatabases are a good model. The need for a good model has slowed progress in bioinformatics.

• 대한수학회보
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• 제58권5호
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• pp.1279-1300
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• 2021

Let P be a finite point set in ℝ² with the set of distance n-chains defined as ∆_n(P) = {(|p₁ - p₂|, |p₂ - p₃|, …, |p_n - p_n+1|) : p_i ∈ P}. We show that for 2 ⩽ n = O_|P|(1) we have ${\mid}{\Delta}_n(P){\mid}{\gtrsim}{\frac{{\mid}P{\mid}^n}{{\log}^{\frac{13}{2}(n-1)}{\mid}P{\mid}}}$. Our argument uses the energy construction of Elekes and a general version of Rudnev's rich-line bound implicit in [28], which allows one to iterate efficiently on intersecting nested subsets of Guth-Katz lines. Let G is a simple connected graph on m = O(1) vertices with m ⩾ 2. Define the graph-distance set ∆_G(P) as ∆_G(P) = {(|p_i - p_j|)_{i,j}∈E(G) : p_i, p_j ∈ P}. Combining with results of Guth and Katz [17] and Rudnev [28] with the above, if G has a Hamiltonian path we have ${\mid}{\Delta}_G(P){\mid}{\gtrsim}{\frac{{\mid}P{\mid}^{m-1}}{\text{polylog}{\mid}P{\mid}}}$.