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Jaeyoung Song,TaeHyeong Jeon,Gimin Kim,Sang Hyun Park,Sul Gee Park 사단법인 항법시스템학회 2023 Journal of Positioning, Navigation, and Timing Vol.12 No.3
The International Maritime Organization (IMO) states that the recommended horizontal accuracy for coastal and offshore areas is 10 m, the Alert Limit (AL) is 25 m, the time to alert is 10 seconds, and the integrity risk (IR) is 10-5 per three hours. For operations requiring high accuracy, such as tugs and pushers, icebreakers, and automated docking, the IMO dictates that a high level of positioning accuracy of less than one meter and a protection level of 0.25 meters (for automated docking) to 2.5meters should be achieved. In this paper, we analyze a method of calculating the user-side protection level of the centimeterlevel precision Global Navigation Satellite System (GNSS) that is being studied to provide augmentation information for the precision Positioning, Navigation and Timing (PNT) service. In addition, we analyze standardized integrity forms based on RTCM SC-134 to propose an integrity information form and generate a centimeter-level precise PNT service plan.
Minimum Cache Size and Backhaul Capacity for Cache-Enabled Small Cell Networks
Song, Jaeyoung,Choi, Wan IEEE 2018 IEEE wireless communications letters Vol.7 No.4
<P>In cache enabled networks, either memory or backhaul is used to deliver files from a core network to a transmitter. To support a high level of wireless quality of service (QoS), network resources including small base stations, memory, and backhaul are required. In this letter, while satisfying a wireless QoS constraint, memory, and backhaul for the whole network are minimized. For a given density of small base stations, optimal memory size is found in closed-form. Also, the optimal density of SBSs is numerically obtained to minimize the total memory and backhual required to satisfy the QoS.</P>
Optimal Content Placement for Wireless Femto-Caching Network
Song, Jaeyoung,Song, Hojin,Choi, Wan IEEE 2017 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.16 No.7
<P>This paper investigates optimal content placement for wireless femto-caching network. The average bit error rate (BER) is formulated as a function of content placement under wireless fading. To minimize the average BER, we propose a greedy algorithm finding optimal content placement with low-computational complexity. Exploiting the property of the optimal content placement which we derive, the proposed algorithm can be performed over considerably reduced search space. Contrary to the optimal content placement without consideration of wireless fading aspects, we reveal that optimal content placement can be reached by balancing a tradeoff between two different gains: file diversity gain and channel diversity gain. Moreover, we also identify the conditions that the optimal placement can be found without running the proposed greedy algorithm and derive the corresponding optimal content placement in closed form.</P>
정보의 신선도 유지를 위한 게이트웨이 스케쥴링 기법 연구
송재영(Jaeyoung Song) 한국정보통신학회 2024 한국정보통신학회논문지 Vol.28 No.2
This paper examines the performance evaluation of a status updating system utilizing a network with two gateways. Multiple sensors are connected to multiple servers via two gateways. These gateways are responsible for scheduling sensor sampling and server updates. At each time slot, each gateway can choose different physical processes that each sensor observes to update. Due to limited communication resources, the number of selected physical processes is bounded. We consider the case where the number of selection is strictly less than the total number of sensors or servers. In this system, depending on the decisions at two gateways, the time elpased since generation status of information can vary. In this paper, we consider how freshness of information is changed depending on the scheduling at two gateways. We define the age-of-information(AoI) to measure freshness information. Based on the definition, we formulate minimization of AoI and solve by proposing proper scheduling at two gateways. We verify the proposed algorithm through numerous simulations.
송재영(Jaeyoung Song),임정빈(Jeong-Bin Yim) 한국항해항만학회 2020 한국항해항만학회 학술대회논문집 Vol.2020 No.춘계
선박이 점유하는 영역은 다양한 환경의 영향을 받아 형성된다. 선박이 점유하는 영역은 선박의 안전을 확보할 수 있는 중요한 요소이므로 정확한 추정이 필요한 실정이다. 기존의 연구는 선박이 점유하는 영역을 확정된 수치로 제시하여 주변 환경의 영향을 받는 가변성을 띄지 못하는 문제가 있다. 이 문제에 대하여 최근 확률론적 선박 점유영역의 개념이 제안되었다. 하지만 선박 대 선박만을 고려하였기에 선박점 유영역이 물표 또는 장해물을 침범하는 한계가 있었다. 본 연구에서는 확률론적 선박점유영역의 개념을 적용해 제한수역 내에서 장해물과 상호작용하여 가변성을 띄는 선박점유영역의 개념을 소개한다. 제안되는 모델은 1)항적기반의 확률공간, 2)위험성 평가로 구성된다. 본 모델은 장해물에 영향을 받아 가변되는 선박점유영역을 수치화 하여 정의할 수 있고, 리스크 팩터 분석을 통해 점유영역의 특성을 추정하는데 용이할 것으로 기대된다. Ship’s domain is formed under the influence of various environments. Ship’s domain is an important factor for securing safety of ships, so accurate estimates are needed. Previous studies have the problem of presenting the domains in fixed figures, thus failing to produce variability affected by the surrounding environment. The concept of probability-based ship’s domain has recently been proposed for this issue. However, considering ship by ship situation the domain has limited to encroaching on seals or obstacles. In this study, the concept of probability-based ship’s domain is applied to introduce the concept of variable domain by interacting with obstacles within the restricted area. The proposed model consists of 1) probability space on the basis of antibodies, 2) risk assessment. This model can be defined by numerical method the variable domain affected by the obstacles, and it is expected to be simple to estimate the characteristics of the domain through risk factor analysis.
Cho, Jaeyoung,Kim, Yongtae,Song, Jeongwoo,Lee, Tae Kyung,Song, Han Ho Elsevier 2018 ENERGY Vol.147 No.-
<P><B>Abstract</B></P> <P>We developed a plant model and model-based controller for a heat recovery system with a swirling flow incinerator located in South Korea. First, a plant model was designed to understand the dynamic characteristics of the system. The system was divided into three parts: incinerator, boiler, and steam drum. Then, each part was modeled with a multi-zone, zero-dimensional modeling scheme. Consequently, we found that the plant model followed the dynamic behavior of the target system, particularly for the seven important variables: boiler inlet temperature, superheater inlet temperature, boiler outlet temperature, oxygen mole fraction, steam production rate, steam pressure, and steam temperature. Then, we designed a multi-input multi-output controller for the system with a nonlinear control model. In the controller design, input variables were selected as air flow rate, fuel supply rate and steam valve opening area; while output variables were oxygen mole fraction of exhaust gas, steam production rate and steam pressure. A nonlinear control model was constructed by reducing the plant model. Then a linear quadratic regulator was applied while evaluating control gain at each time step. Finally, we validated the controller on the plant model, which adequately suppressed the disturbance on fuel composition and adjusted the steam production rate.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Plant model was built to simulate heat recovery system with a waste incinerator. </LI> <LI> Multi-input multi-output controller was designed for the system. </LI> <LI> The controller could efficiently suppress disturbance and adjusts load variation. </LI> </UL> </P>