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Kyunghwi Kim,Jeongbeen Lee,Wonjun Lee IEEE 2013 IEEE transactions on intelligent transportation sy Vol.14 No.3
<P>The development of vehicular communication technology can make more intelligent transportation systems (ITSs) by enabling a large number of potential applications. In particular, infrastructure-to-vehicle (I2V) communication will support ITS applications and provide inexpensive high-rate Internet access as well. Thus, a study on I2V communications may improve the quality of experience of end users in vehicles, such as drivers and passengers. To this end, we propose a medium access control (MAC) protocol for I2V communications to improve the fairness of node throughput while maximizing the expected system throughput. We derive the way of estimating road traffic to precisely control the transmission probability of vehicles for maximizing system throughput. The estimation is performed by utilizing the spacing distribution model in transportation systems. Furthermore, we present a threshold to limit the number of transmitted packets for the fairness of the vehicles. The threshold is set based on the achievable node throughput and the estimated sojourn time. Through extensive simulations based on the empirical vehicular trajectory data, we demonstrate the improved performance of the proposed MAC protocol. The test results show that the expected system throughput is increased by more than 21.3% and that Jain's fairness index with regard to the number of transmitted packets among the nodes is close to 1.</P>
노변기지국과 차량 간 통신을 위한 실제 경로 데이터 기반 EDCA 성능 분석
김경휘(Kyunghwi Kim),이정빈(Jeongbeen Lee),이원준(Wonjun Lee) 한국정보과학회 2013 정보과학회논문지 : 정보통신 Vol.40 No.4
본 논문에서는 실제 차량들의 경로 데이터를 활용하여 차량 네트워크에서의 노변기지국과 차량 간 통신성능분석 연구를 수행한다. 해당 네트워크 통신 관련 표준인 IEEE 802.11p에서는 EDCA(Enhanced Distributed Channel Access)를 이용하여 차량들의 통신 접근을 제어하며, 우리는 여러 가지 전송 차량의 비율을 사용하고 주어진 AC(Access Category; 접근범주)에 따른 사용 비율을 다양하게 하여 전체 시스템의 성능과 카테고리별 차량들의 성능을 비교/분석한다. 10MHz 사용에 따른 다중 전송률의 영향을 고려하였으며, 기존 EDCA 세팅에 따른 성능 악화를 피하기 위해 매개변수(parameter) 조절에 따른 성능 변화도 보인다. 성능 평가 결과에 따르면 전송 노드 수에 따른 매개변수 조절이 필요하고, 높은 우선순위를 갖는 AC의 CW(Contention Window) 값 조절이 통신 성능에 결정적 역할을 나타냄을 알 수 있다. We conduct the network performance analysis for infrastructure-to-vehicle communications with the empirical trajectory data from NGSIM (Next Generation Simulation), and the default parameters from IEEE 802.11p standard are applied for EDCA (Enhanced Distributed Channel Access) setup. Different contending node ratios for ACs (Access Categories) are considered, and we analyze the network performance in terms of the average network system throughput and the expected node throughput at the access categories. We use multiple data rates for 10MHz channel, and simulation results include the network performance with modified parameter values. Simulation results show that the parameter should be controlled based on the number of contending nodes and the setup of CW (Contention Window) of high priority AC is the critical factor with regard to the transmission performance.
Optimal transmission policies for MOT in T-DMB
Donghwan Lee,Jihoon Choi,Kyunghwi Kim,Wonjun Lee,Choonhwa Lee IEEE 2007 IEEE communications letters Vol.11 No.12
<P>The Multimedia Object Transfer (MOT) protocol in Terrestrial Digital Multimedia Broadcasting (T-DMB) systems inherently does not facilitate return paths in data transmission and therefore additional policies are required to envision further efficient reliable media broadcasting. This letter proposes novel optimal transmission policies for MOT standard definition in T-DMB. The proposed broadcasting policies drastically enhance the capability of conventional MOT protocol.</P>
분할-전이 기법을 통한 다중 전송률 지원 무선랜 게이트웨이 배치 연구
정철훈(Cheoulhoon Jung),김경휘(Kyunghwi Kim),이원준(Wonjun Lee) 한국정보과학회 2012 정보과학회 컴퓨팅의 실제 논문지 Vol.18 No.6
본 논문에서는 다중 전송률을 지원하는 게이트 웨이를 무선랜과 같이 주어진 네트워크 환경에서 보다 효과적으로 배치시키는 기법에 대해 연구한다. 본 논문을 통해 주어진 네트워크 상의 각 노드들이 최대 처리량을 형평성 있게 달성할 수 있는 재귀적 분할-전이 기법을 제안한다. 분할-전이 기법은 게이트웨이들의 위치 선정 과정이 기존의 연구들에 비해 쉽고 간편하며, 보다 낮은 시간 복잡도를 제공함으로써 노드의 수, 이동성 등을 고려하는 복합적인 상황에서 실시간으로 배치 위치를 계산해 낼 수 있다. 자신이 이동할 방향과 거리를 결정하는 분할 단계와 최대 성능 향상을 제공하는 위치로 이동하는 전이 단계를 통해 기법이 동작한다. 본 논문에서는 정적인, 또는 이동성을 갖는 노드들이 존재하는 네트워크 상황을 상정하여, 시뮬레이션을 통한 분할-전이 기법의 성능을 평가한다. In this paper, we deal with an effective gateway placement scheme in multi-rate wireless networks. The proposed scheme utilizes the recursive partition-shift that makes each node be able to achieve its throughput through the maximization of the utility function of each gateway with the consideration of fairness. The partition-shift scheme provides the simple and easy way to choose the intended positions for the gateways by the decision of moving direction and length (partition) and the movement to the selected position maximizing the utility improvement (shift). Since the proposed scheme has low time-complexity, it is more applicable for complex situations such that the number of nodes and their mobility must be jointly considered. In this paper, we show the feasibility of the proposed scheme by the simulation considering static or mobile nodes.
홍영지(YoungJee Hong),태경휘(KyungHwi Tae),박진우(JinWoo Park) 한국경영과학회 2010 經營 科學 Vol.27 No.3
Real-time supply chain environments based on RFID will be an important topic in future society; Nevertheless, adopting RFID in real industry SCM is still in its infancy. The aim of this paper is to develop the physical framework of a fully adopting RFID system from manufacturing to recycle phase and measure the effect. So, we built a simulation station with fully appling RFID and analyzed benefits with mathematic model. Then, specifying the advantages and improvement scheme for real industry limitations were suggested. This work concluded that fully appling RFID in SCM gives improvement of quality and service to both production and consumer.