• KEPCO Journal on Electric Power and Energy
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• 제6권1호
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• pp.59-64
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• 2020

Scheduling of electric vehicles and optimizing for charging waiting time have been critical. Meanwhile, it is challengeable to exploit the fluctuating data from electric vehicles in real-time. We introduce an optimal routing algorithm and a simulator with electric vehicles obeying the Poisson distribution of the observed information about time, space and energy-demand. Electric vehicle routing is updated in every cycle even it is already set. Also, we suggest an electric vehicle routing algorithm for minimizing total trip time, considering a threshold of the waiting time. Total trip time and charging waiting time are decreased 34.3% and 86.4% respectively, compared to the previous algorithm. It can be applied to the information service of charging stations and utilized as a reservation service.

• 한국통신학회논문지
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• 제35권7A호
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• pp.706-714
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• 2010

무선 센서 망에서, 전형적인 실시간 데이터 전송기법들은 각 센서의 1-홉 안에 존재하는 노드들의 전송속도를 조회하여 임계속도보다 높은 노드를 선택하는 기법이었다. 최근 이러한 기법들의 성능을 높이기 위해 2-홉 전송속도를 예측하는 기법이 제시되었다. 그러나 이 연구는 전달해야 할 데이터의 유무와 상관없이 망의 모든 센서가 미리 2-홉의 전송정보를 모두 공유하는 방법을 사용하여 불필요한 메시지를 교환하는 오버헤드(overhead)를 발생시킨다. 또한 2-홉 이상의 멀티-홉 정보를 조회 할 경우 더 높은 실시간 전송률을 제공 할 수 있음에도 불구하고, 연산의 복잡도와 통신오버헤드 때문에 단순하게 2-홉 정보만을 채택했다. 본 논문에서는 실시간 데이터 전송률을 높이고자 제한적 멀티-홉 정보 예측 기법을 제시한다. 이 기법은 오직 데이터가 전달되는 경로 상에서 제한된 지역 안의 멀티-홉 속도정보를 조회한다. 시뮬레이션을 통해 제안기법이 실시간 데이터 전달 성공률, 네트워크 수명, 데이터 전달시 필요한 통신비용면에서 우수함을 보였다.

• ETRI Journal
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• 제44권2호
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• pp.220-231
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• 2022

Building smart transportation services in urban cities has become a worldwide problem owing to the rapidly increasing global population and the development of Internet-of-Things applications. Traffic congestion and environmental concerns can be alleviated by sharing mobility, which reduces the number of vehicles on the road network. The taxi-parcel sharing problem has been considered as an efficient planning model for people and goods flows. In this paper, we enhance the functionality of a current people-parcel taxi sharing model. The adapted model analyzes the historical request data and predicts the current service demands. We then propose two novel online routing algorithms that construct optimal routes in real-time. The objectives are to maximize (as far as possible) both the parcel delivery requests and ride requests while minimizing the idle time and travel distance of the taxis. The proposed online routing algorithms are evaluated on instances adapted from real Cabspotting datasets. After implementing our routing algorithms, the total idle travel distance per day was 9.64% to 12.76% lower than that of the existing taxi-parcel sharing method. Our online routing algorithms can be incorporated into an efficient smart shared taxi system.

• 산업공학
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• 제15권4호
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• pp.374-381
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• 2002

In this paper, we design and implement a real-time route guidance system(RGS) in large-scale networks. Coupled with the well-known mathematical routing algorithms, we devise an RGS for knowledge aquisition and self-learning ability within the framework of the expert system. Through off-line construction of database, on-line treatment of unexpected traffic accidents, etc., the developed RGS can provide drivers with good quality real-time routing information. The practical effectiveness of the proposed system is demonstrated in terms of response time and route appropriateness.

• 산업경영시스템학회지
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• 제42권4호
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• pp.16-22
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• 2019

After Dantzig and Rasmer introduced Vehicle Routing Problem in 1959, this field has been studied with numerous approaches so far. Classical Vehicle Routing Problem can be described as a problem of multiple number of homogeneous vehicles sharing a same starting node and having their own routes to meet the needs of demand nodes. After satisfying all the needs, they go back to the starting node. In order to apply the real world problem, this problem had been developed with additional constraints and pick up & delivery model is one of them. To enhance the effectiveness of pick up & delivery, hub became a popular concept, which often helps reducing the overall cost and improving the quality of service. Lots of studies have suggested heuristic methods to realize this problem because it often becomes a NP-hard problem. However, because of this characteristic, there are not many studies solving this problem optimally. If the problem can be solved in polynomial time, optimal solution is the best option. Therefore, this study proposes a new mathematical model to solve this problem optimally, verified by a real world problem. The main improvements of this study compared to real world case are firstly, make drivers visit every nodes once except hub, secondly, make drivers visit every nodes at the right time, and thirdly, make drivers start and end their journey at their own homes.

• Journal of Communications and Networks
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• 제6권4호
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• pp.387-396
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• 2004

One of the main problems associated with MANETs is that mobility and the associated route discovery and maintenance procedures of reactive routing protocols cause severe interruptions on real-time video streams. Some of these interruptions are too large to be concealed using any sort of video technology, resulting in communications breaks unpleasant for the final end user. We present a solution for enhanced video transmission that increases route stability by using an improved route discovery process based on the DSR routing protocol, along with traffic splitting algorithms and a preventive route discovery mechanism. We also present some video adaptative mechanisms that improve the overall performance of multipath routing in terms of video data replication and video packet splitting strategies. Combining our proposals, we achieve up to 97% less interruptions on communication with high mobility and over 1.2 dB of improvements in terms of video distortion.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.3-6
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• 1998

This paper considers the analysis of QoS(Quality of Service) routing mechanisms to support the NGIs(Next Generation Internets). NGIs are constructing high-speed IP layer networks to support all data services. To support real time multimedia services on NGIs, it is important to satisfy the required QoS parameters on networks. To support QoS requirements for NGI networks, new QoS routing methods are essential. In this paper, serveral new QoS routing algorithms are explained. Some problems for the high speed QoS routing will be explained and possible solutions are suggested.

• International Journal of Computer Science & Network Security
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• 제23권8호
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• pp.85-90
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• 2023

The Ant Colony System (ACS) is a variant of Ant colony optimization algorithm which is well-known in Traveling Salesman Problem. This paper proposed a hybrid method based on genetic algorithm (GA) and ant colony system (ACS), called GACS, to solve traffic routing problem. In the GACS, we use genetic algorithm to optimize the ACS parameters that aims to attain the shortest trips and time through new functions to help the ants to update global and local pheromones. Our experiments are performed by the GACS framework which is developed from VANETsim with the ability of real map loading from open street map project, and updating traffic light in real-time. The obtained results show that our framework acquired higher performance than A-Star and classical ACS algorithms in terms of length of the best global tour and the time for trip.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제2권5호
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• pp.191-198
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• 2013

이동하는 베이스 노드를 가진 무선 센서 네트워크(WSN)에서 실시간 침입탐지를 위해서는 침입을 탐지한 센서로부터 베이스 노드까지의 정보 전달이 짧은 라우팅 경로를 통해 이루어져야 한다. 센서 네트워크에서 최소 Wiener수 신장트리(MWST)기반 라우팅 방법은 최소 신장트리(MST)기반 라우팅 방법에 비해 작은 홉 수를 보장하고 있어서 실시간 침입탐지에 적합함이 알려져 있다. 하지만 주어진 네트워크로부터 최소 Wiener 수 신장트리를 찾는 문제는 NP-hard이고 특정 노드에 대한 의존성이 커서 최소 신장 트리 기반 라우팅 방법에 비해 짧은 네트워크 수명을 갖는 단점이 있다. 본 논문은 실시간 침입탐지를 위해 최소 Wiener수 신장트리를 개선해 작은 홉 수와 긴 네트워크의 수명을 동시에 보장하는 라우팅 트리를 찾는 다목적 개미 군집 최적화 알고리즘을 제안한다. 그리고 제안한 라우팅 트리의 성능을 패킷의 평균 전송 홉 수 및 네트워크 전력 소모, 네트워크의 수명 측면에서 최소 신장트리기반 라우팅 방법 및 최소 Wiener수 신장트리기반 라우팅 방법과 비교한다.

• 한국경영과학회지
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• 제22권2호
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• pp.79-97
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• 1997

Many dispatching rules have been developed for the on-line control of product flow in a job shop. The introduction of a flexible manufacturing system (FMS) has added a new requirement to classical job shop control problem : the selection of machines by parts of different types. An FMS can keep a great deal of information on the status of the system, such as information on what is scheduled in the near future, with great accuracy. For example, the knowledge of the time when the next part will arrive at each machine can be neneficial for the routing. This paper tests the effects of the use of this knowledge for part routing on the parts flow time (sum of the time for waiting and service) under a simple routing procedure- a look-ahead routing procedure. A test under many operating conditions shows that the reduction of part flow time from the cases without using this information is between 1% and 11%, which justifies more study on this routing procedure at real production sites when machine capacity is a critical issue. The test results of this paper are also valid for other highly automated systems such as the semi-conductor fabrication plants for routing when the arrivals of parts in the near future are known.