• Proceedings of the Korean Information Science Society Conference
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• 2007.10b
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• pp.313-318
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• 2007

위치기반서비스에서 사용자의 정확한 위치가 요구되면서 측위와 추적에 대한 연구가 활발히 진행되고 있다. 측위 방법에는 위성기반 방법[1, 2], 로컬네트워크기반 방법[3-6], 센서기반 방법[1, 7, 8, 9]등이 있다. 본 연구에서는 로컬네트워크 중 WLAN (Wireless Local Area Network) 환경의 옥내에서 사용자의 위치를 추적하는 기존의 방법의 정확성을 제고하는 방안을 제안한다. 제안하는 방법은 WLAN 환경에서 RSS를 측정하여 K-NN방식으로 현재 위치를 판단한 다음, 칼만필터를 사용하여 사용자의 위치와 이동경로를 예측한다는 점에서 기존의 방법과 비슷하다. 제안하는 방법의 특징은 도면 정보를 이용하는 것이다. 제안하는 방법은 도면정보로부터 갈림길 영역을 파악하고, 갈림길 영역에서는 측정치에 가중치를 두고 갈림길이 아닌 지역에서는 시스템 모델에 가중치를 두도록 파라메타의 값을 조절한다. 제안하는 방법의 효율성을 실험적으로 증명하기 위한 실험 결과와 분석 내용도 제시한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2022.06a
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• pp.146-149
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• 2022

기존 RDO(Rate Distortion Optimization) 기반 압축 방식은 압축 성능에 초점을 두기 때문에 영상 내 인지 특성이 무시될 수 있다. 따라서 RoI(Region of Interest)을 기반으로 압축률을 조절하는 연구가 고안[1, 2, 3, 4] 되었으며, HVS(Human Visual System) 관점에서 영상 내 중요한 부분에 대해 더 높은 품질로 영상을 압축하는 연구가 대부분이다. 최근 인공지능 기술이 발전함에 따라 지능형 영상 분석에 대한 수요가 증가하고 있으며, 이에 따라 머신 비전을 위한 영상 부호화 및 효율적인 전송에 대한 필요성이 대두되고 있다. 본 논문에서는 VVC(Versatile Video Coding)의 dQP(delta Quantization Parameter)를 활용하여 RoI(Region of Interest) 기반압축 방법을 제안하고, 두가지의 RoI 추출 방식을 소개한다. Detectron2 Faster R-CNN X101-FPN [5]의 첫번째 탐지기를 통해 후보 영역 기반 RoI 을 추출하고, 두번째 탐지기를 통해 객체 기반 RoI 을 추출하여, 영상 내 객체 부분과 비객체 부분으로 나누어 서로 다른 압축률로 압축을 수행하였으며, 이에 따른 성능을 비교하고자 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.11
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• pp.2205-2217
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• 2015

Bio-inspired routing protocol uses a principle of swarm intelligence, which finds the optimal path to the destination in a distributed and autonomous way in dynamic environments, so that it can maximize routing performances, reduce control overhead, and recover a path failure quickly according to the change of network topology. In this paper, we propose a bio-inspired routing protocol for mobile ad hoc networks. The proposed scheme uses a function of overhearing via wireless media in order to obtain the routing information without additional overhead. Through overhearing, the pheromone is diffused around the shortest path between the source and destination. Based on this diffused pheromone, a probabilistic path exploration is executed and the useful alternative routes between the source and destination are collected. Therefore, the proposed routing protocol can ensure the up-to-date routing information while reducing the control overhead. The simulation results show that the proposed scheme outperforms the typical AODV and AntHocNet protocols in terms of routing performances and significantly decreases the routing overhead against the AntHocNet.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4B
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• pp.227-235
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• 2012

Holes that generated by the unpredictable and harsh nature application environment or uneven energy consumption are an inevitable phenomenon in wireless sensor networks. Most of the existing schemes for this hole problem tend to use a static detour path to bypass a hole. The static detour path may lead to uneven energy consumption of the nodes on the boundary of the hole, thus it may enlarge the region of holes. At the same time, traffic would concentrate on the nodes on the boundary of the hole and tend to be depleted quickly. To solve this problem, we introduce energy-efficient grid-based geographic routing and hole-detouring scheme by taking advantage of grid anchor point in wireless sensor network with holes. The location of hole detour anchor node is dynamically shifted in grid cell. just generating dynamic hole detour paths to reduce total energy consumption. Simulation results are provided to validate the claims.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.12
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• pp.1394-1400
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• 2010

In this paper, we analyze performance of PSPM(Phase Shift Position Modulation) modulation scheme in multi-path channel. A PSPM modulation method transmits the information data by both PSK symbol data and symbol position data, so that we can significantly improve the power efficiency. The bandwidth efficiency of PSPM is quarter than PSK but improve BER performance, because increasing symbol hamming distance. In this results, a PSPM scheme is bandwidth efficiency better than FSK and power efficiency better than PSK. This characteristic can be useful in WBAN and wireless sensor networks also PSPM modulation method can be expected high throughput than existing FSK. In this paper, we compare PSPM, PSSK and PSK regard to BER performance and throughput in multi-path channel.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10c
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• pp.439-441
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• 1999

트리 기반 신뢰적 멀티캐스트에서 효율적이고 확장성 있는 손실 복구를 하기 위한 RTE(Routing Tree Estimation) 기법을 제안한다. 에러 비트맵(error bitmap) 정보를 통하여 멀티캐스트 라우팅 트리와 유사한 논리적 트리(logical tree)를 구성함으로써 멀티캐스트 라우팅 트리에서 상위에 위치하는 수신자들이 재전송을 요청한 수신자의 신뢰성을 책임지도록 보장한다. 논리적 트리는 세션 멤버쉽이나 멀티캐스트 경로의 변화에 따라 적응적으로 재구성되는데 이는 멀티캐스트 세션 진행동안 논리적 트리와 멀티캐스트 라우팅 트리 사이에 불일치를 최소화함으로써 멤버십과 경로가 변하는 상황에서도 implosion과 exposure를 감소시키는 장점을 지닌다. 제안한 기법과 정적 트리기반의 신뢰적 멀티캐스트 프로토콜의 시뮬레이션 결과는 세션의 크기가 커짐에 따라 제안한 적응형 트리 기반의 복구방식의 효율성을 입증한다.

• Journal of the Korea Society of Computer and Information
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• v.20 no.1
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• pp.85-92
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• 2015

As computer game maps get more elaborate, path-finding by using $A^*$ algorithm in grid-based game maps becomes bottlenecks of the overall game performance. It is because the search space becomes large as the number of nodes increases with detailed representation in cells. In this paper we propose an efficient pathfinding method in which the computer game maps in a regular grid is converted into the polygon-based representation of the list of vertices and then the visibility information about vertices of polygons can be utilized. The conversion to the polygon-based map does not give any effect to the real-time query process because it is preprocessed offline. The number of visited nodes during search can be reduced dramatically by designing heuristics using visibility information of vertices that make the accuracy of the estimation enhanced. Through simulations, we show that the proposed methods reduce the search space and the search time effectively while maintaining the advantages of the grid-based method.

• Journal of KIISE:Databases
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• v.31 no.2
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• pp.183-194
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• 2004

As XML is a do facto standard for a data exchange language, there have been several researches on efficient processing XML queries. The most important thing to consider when processing XML queries is how efficiently we can process path expressions in queries. Some previous works make results by performing a sequence of join operations on all records corresponding to labels in the path expression. Others works check the existence of paths in the query using an RDBMS's string comparison operator and make results by extracting the records corresponding to the paths. In this paper we suggested a new query planning algorithm based on path containment relationships and two join operators supporting the planning algorithm. The join operators use only the records related to the paths in a query as input data, scan them only once, and generate result data using a pipelining mechanism. By analysis and experiments, we confirmed that our techniques(a new query planning algorithm and two join operators) achieved significantly higher performance than other previous works.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.9
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• pp.830-835
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• 2016

With the relaxation of regulations on unmanned aerial vehicles (UAVs) in the USA, the development of related industries is expected. Hence, it is anticipated that the number the UAVs will reach approximately 600,000 in the USA in 2017. However, automated flights of commercial UAVs are restricted owing to concerns about accidents. To deal with the possibility of collisions, several studies on collision prevention and the routing of UAVs have been conducted. However, these studies do not deal with various situations dynamically or provide efficient solutions. Therefore, we propose a centralized routing method for the UAV that uses vehicular networks. In the proposed scheme, vehicular networks regard UAVs as data packets to be routed. Accordingly, the proposed method reduces UAV processing power required for route searches. In addition, the routing efficiency for UAV flight paths can be improved since congestion can be minimized by using a vehicular network.

• The Transactions of the Korea Information Processing Society
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• v.7 no.8S
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• pp.2608-2619
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• 2000

This paper proposes the Handover Scheme for the mobile and describes the result of the performance analysis. In the conventional scheme of handover request, the withdrawal of terminal may occur because handover request is performed based on fixed signal level without considering network load and terminal mobility. The proposed scheme offers the minimization of withdrawal and handover blocking probability by means of the handover request of terminal based on the network load and terminal mobility. Conventional handover scheme has the sequential procedure that network performs resource check and path rerouting on the handover by MT(Mobile Terminal). Proposed handover scheme pre-processes the resource check before the handover request by predicting the handover request timo so that handover latency can be reduced. Moreover, path optimization is executed after the completion of handover in order to reduce handover latency. The rdduction of handover latency prevents the dropping of service by minimizing backward handover blocking. In summary, we propose the prediction of handover request time and decision method based on terminal, validating the performance of proposed scheme considering various cases of simulation.