• KIPS Transactions on Computer and Communication Systems
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• v.9 no.6
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• pp.131-136
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• 2020

In vehicular communications environment, content pre-caching can reduce the delay time from the user to the content server. However, the problem of where and how much pre-caching is still not solved. In this paper, based on the movement probability of the vehicle, we propose a method for pre-caching by distributing the optimized amount of content to each base station candidate that the vehicle will move as follows. First, the movement probability of each vehicle was learned using Markov Model. And the amount of content to be distributed and pre-cached was optimized based on the wireless environment. In experiments based on NS-3, the proposed strategy maintained the least delay compared to the existing protocol, leading to the most traffic-saving results.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.1
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• pp.55-68
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• 2010

IEEE WAVE is going through the final standardization process as the wireless access technology which provides drivers in high-speed vehicles with safety-related information and commercial services This paper presents an application-layer protocol for safe driving assistant service and a service system emulator based on this protocol. The safe driving assistant system includes a construction zone information service and a vehicle crash notification service, an emergency vehicle notification service, a probing service and a dilemma zone decision assistant service. Emulator System design for verifying functions of system, The emulator consists of an emulator server that models the movement of all vehicles and road states and a number of clients that models functional units for OBUs, RSUs, and a traffic control center).

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.1015-1016
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• 2015

VANET is a technology for building a robust ad-hoc network between mobile vehicles as well as, between vehicles and RSU. Vehicles are moving and they only stay in the RSU area for a short time. When the number of requests is increased, an important challenge is to implement a suitable scheduling algorithm which serves as more requests as possible. $D^*S$ algorithm uses a priority weight, DS_Value, for selection of a request to get service. Priority weight is influenced only by deadline and data size parameters. We propose a packet scheduling using multilevel queue and show that using this idea leads to higher service ratio compare to previous algorithms.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.1100-1103
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• 2008

VANET(Vehicle Ad-hoc Network) 환경은 도로위의 차량을 노드로 하여 구성하는 애드혹 네트워크로써 최근 들어 그 연구가 활발히 진행되고 있는 분야이다. 일반적인 애드혹 환경과 마찬가지로 VANET 환경에서도 보안적인 문제가 중요한 이슈로 대두되고 있다. VANET 환경에서 가장 중요하게 요구되는 보안요소는 차량의 익명성을 통한 위치 프라이버시와 협력 운전(cooperative driving) 단계에서 사용되는 메시지에 대한 인증, 무결성, 부인방지 등이다. 본 논문에서는 익명 아이디(pseudonym), 그룹화 등을 통해 차량의 위치 프라이버시를 제공하고 또한 이를 이용해 VANET 환경에서 사용할 수 있는 라우팅 프로토콜을 제안하고자 한다. RA(Registration Authority)에서 발급되는 익명 아이디의 집합과 차량의 전송 범위를 고려해서 구성되는 그룹화는 그룹에 속한 차량에 대해 익명성을 제공하고, 또한 그룹리더에 의해 생성되는 그룹키를 통해 효율적인 협력 운전 메시지 전달을 할 수 있게 된다. 그리고 각각의 그룹리더를 라우터로 이용해 전달되는 라우팅 프로토콜은 노드가 매우 유동적으로 움직이는 VANET 환경에서 효과적으로 메시지를 전달할 수 있도록 해줄 것이다.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11b
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• pp.745-748
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• 2003

인터넷과 컴퓨팅 환경의 발전으로 모바일 네트워크 환경이 발전하였다. 본 논문에서는 이동차량에서 실시간 주차정보를 제공 받기 위한 무선 네트워크 환경을 구축하고, 다양한 어플리케이션간에 데이터를 교환하고 공유하기 편리한 XML 데이터를 생성하여, 실시간으로 주차정보를 전달하는 방법을 제시 및 구현한다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2006.11a
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• pp.332-335
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• 2006

최근 건설되고 있는 교량 대부분은 장대교라 명명할 정도로 그 길이가 매우 길게 되어 교량의 노후화, 차량의 증가 및 대형화로 인한 교량의 피로 축적, 예기치 않은 자연재해 등에 의해 붕괴 위험에 노출되어 있다. 따라서 이러한 위험을 사전에 예측하기 위해서는 효율적인 교량모니터링 시스템의 설계가 필수적으로 요구된다. 본 연구에서는 최근 각광을 받고 있는 유비쿼터스 센서 네트워크 기술을 이용한 효율적인 교량 모니터링 시스템을 제안하고 이의 유용성을 확인해 보고자 한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.11a
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• pp.273-276
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• 2020

기존의 물리 센서를 활용한 주차 감지는 주차장 규모가 클수록 큰 비용이 필요하고 이미지 기반의 분석은 개별 주차장에 대한 데이터 라벨링과 학습의 노력이 필요했다. 본 논문은 LoRa(Long Range) 네트워크와 마이크로프로세서를 활용한 IoT기반의 시스템으로 영상데이터를 서버로 전송하고 COCO(Common Object in context) 데이터셋으로 학습된 Mask R-CNN 기반의 모델을 활용한 주차장 내 차량점유 감지 알고리즘을 통해 개별 주차장에 대한 학습 또는 라벨링 없이 주차장 내 주차상태를 식별하고 사용자에게 인터페이스를 통해 실시간으로 주차정보를 제공하는 시스템을 구현한다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.5
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• pp.343-351
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• 2015

It is well-known that even the DGNSS (Differential Global Navigation Satellite System) technique in navigation for ground vehicles can only provide several meters of accuracy, such that it is suitable for simple guidance. On the other hand, centimeter to millimeter level accuracy can be obtained by using carrier phase observables in the field of precision geodesy/surveying. In this study, a preliminary study was conducted to apply NRTK (Network-RTK) by NGII (National Geographic Information Institute) to ground vehicle navigation. Onboard GNSS receivers were used for NRTK throughout the country, and the applicability of NRTK on navigation was analyzed based on NRTK surveying results. The analysis shows that the overall ambiguity fixing rate of NRTK is high and is therefore possible to apply it for navigation. In urban areas, however, the fixing rate decreases sharply, therefore, it needs to employ a method to minimize the effect of the float solutions, which can reach up to 10 meters. It is still feasible to obtain a centimeter level of accuracy in some area using NRTK under certain conditions. But, the ambiguity fixing rate of FKP falls down to 55% for high speed vehicles, and so the surveying accuracy should be determined by considering various factors of surveying environments. In addition, it is difficult to fix ambiguities using single-frequency GPS receivers. Finally, several suspicious NRTK(FKP) connection problems occurred during atmospheric disturbances (phase two or up), which should be investigated further in upcoming research.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.5
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• pp.71-82
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• 2016

Information System for rear-end collision avoidance is a unit service of C-ITS pilot project. Road environment that the number of vehicles at the same driving high-speed has a possibility that the communication delay or failure caused by heavy load of vehicle to vehicle communication. In this study, effects of the road network about a communication failure rate of information system for rear-end collision avoidance was analyzed quantitatively with micro traffic simulation. The simulation was carried out in situation that crash of two vehicles are occurred at merging area with speed limit 80km/h and information of collision is prvoided to the rear vehicle. From simulation results, it can confirm the trend of the increasing 14% of potential conflict according to 10% increasing of the communication failure rate. C-ITS service has a goal of increasing safety. The coommunication failure rate increases due to heavy load of vehicle causes a fatal result in road safety administrator position. For the success of C-ITS project, a communication system developers side should perform the effort to reduce the communication failure rate.

• Journal of Korean Society of Transportation
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• v.26 no.5
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• pp.63-72
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• 2008

Signalized intersections are operated without a signal preemption control strategy in Korea, thus there is no priority treatment for an emergency vehicle passing through the intersections. In this paper, a signal preemption control strategy is introduced to improve the safety and operational efficiency of an emergency vehicle. Using the micro simulation tool, the effects on delay and travel speed of the signal preemption control strategy are analyzed for various traffic conditions to identify the general performance trends. Then, another simulation analysis is performed to verify the feasibility of the control strategy using real network data collected from field study. Results show that the preemption control strategy provides the positive impact on emergency vehicles' operation, but the positive impact is reduced as the v/c ratios increase. As expected, the average delays of the normal vehicles are slightly increased, but the magnitude is not significant. Therefore, it is expected that the introduction of the preemption control strategy in Korea would produce the positive social benefits.