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단일 및 이중명령을 수행하는 자동창고 시스템의 성능분석
남진규(Jin-Gyu Nam),허선(Hur Sun),정석윤(Seok-Yun Jeong),김정기(Jeong-Kee Kim) 한국산업경영시스템학회 2004 한국산업경영시스템학회지 Vol.27 No.3
We consider an AS/RS(Automated Storage/ Retrieval System) which performs both of single and dual commands. The service times of single and dual commands are assumed to be differently distributed. Steady-state probabilities at the service completion epochs are calculated. Then, we transform the arrival rates of storage and retrieval commands into those of single and dual commands. Using this, we propose a non-preemptive queueing model with priority for the performance analysis of an AS/RS, and obtain approximated means of queue lengths and waiting times.
상황인지 컴퓨팅 환경에서 복합서비스를 제공하는 서비스시스템의 성능분석
남진규(Jingyu Nam),주국선(Kuksun Joo),신동민(Dongmin Shin),허선(Sun Hur) 대한산업공학회 2009 대한산업공학회지 Vol.35 No.1
There are a variety of users and devices in a context-aware computing environment. In this environment, the service provided to a user may be the composition of diverse services rather than one independent service. Before user’s devices provide the composite service to the user, they should perceive user’s needs by gathering related information segments from other surrounding devices and/or sensors. We consider a context-aware computing environment providing composite and adapted service to users and propose an information processing model that characterizes the device where the collected data should be processed through services and/or applications. Based on this model, we provide an analytical tool to obtain some performance measures of the context-aware computing environment.
유비쿼터스 환경에서 커뮤니티 컴퓨팅 지원을 위한 코디네이터 개발
남진규(Jingyu Nam),김현우(Hyunwoo Kim),신동민(Dongmin Shin),박재일(Jaeil Park),허선(Sun Hur) 한국산업경영시스템학회 2008 한국산업경영시스템학회지 Vol.31 No.3
Recent advances in mobile computing technologies and platform-independent information systems have enabled to realize a ubiquitous environment. Community computing has been developed as a useful tool for realizing collaborative services in a ubiquitous environment. In this paper, we present a formal model of a ubiquitous space that takes community concept into consideration and propose two management frameworks that prevent conflicts among communities. To demonstrate the validity of the proposed frameworks, an example for coordinating two communities is provided.
IEEE 802.16e 시스템에서 망 지원을 이용한 효율적인 펨토셀 스캐닝 방안
최재인(Jae-In Choi),남진규(Jin-Kyu Nam),서원경(Won-Keyong Seo),조유제(You-Ze Cho) 한국통신학회 2011 韓國通信學會論文誌 Vol.36 No.1
본 논문에서는 IEEE 802.16e 기반의 펨토셀 환경에서 이동단말이 매크로셀에서 펨토셀로 핸드오버를 수행할 때 발생하는 긴 스캐닝 지연 시간과 큰 배터리 소모를 줄이고자 한다. IEEE 802.16e 시스템에서는 이동단말이 핸드오버를 수행할 때 인접한 기지국들을 스캐닝 해서 적절한 후보 기지국들을 선정하는데, 펨토셀이 도입되면 인접한 펨토셀의 수만큼 추가적으로 스캐닝 동작을 수행하여야 한다. 따라서 이동단말의 스캐닝 지연 시간 및 배터리 소모가 증가하는 문제가 발생한다. 이러한 문제를 해결하기 위해 본 논문에서는 삼각 측위법과 펨토셀의 모니터링 메커니즘을 이용하여 이동단말의 위치로부터 가장 근접한 하나의 펨토셀을 찾는 방안을 제안한다. 이동단말은 선정된 하나의 펨토셀에 대해서만 스캐닝 동작을 수행하기 때문에 스캐닝 지연 시간 및 배터리 소모를 줄일 수 있다. 시뮬레이션을 통해 제안 방안으로 동작할 경우 실제 이동단말의 위치에서 가장 근접한 펨토셀을 찾을 수 있는 확률이 높음을 확인하였으며 스캐닝 대상 펨토셀을 줄임으로써 기존 방안보다 스캐닝 지연 시간이 현저히 줄어들었음을 확인하였다. The femtocell is a miniaturized Base Station (BS) with low-cost and low-power using general broadband access network as backhaul. It is expected not only to improve indoor coverage but also to reduce a service charge. However, in IEEE 802.16e femtocells, when the Mobile Station (MS) scans neighbor BSs for handover, it takes a long time due to too many number of femto BSs. Also the size of the neighbor advertisement message that will be periodically sent by a serving BS is increased as the number of target femto BSs for scanning increases. In this paper, we proposed an efficient femtocell scanning scheme, using a triangulation mechanism and a femto BS monitoring scheme to reduce the number of scanning operations and the size of the neighbor advertisement messages. The proposed scheme can avoid wasting air resources and reduce scanning overheads by minimal scanning operation. The simulation results showed that the proposed scheme could improve scanning performance and avoid wasting air resources, compared with the conventional scheme of the IEEE 802.16e system.
무선 환경 하에서 Slotted ALOHA 방식의 다중채널 경쟁에 대한 지연시간분석
허선(Sun Hur),김정기(Jeong-Kee Kim),남진규(Jin-Gyu Nam) 한국산업경영시스템학회 2005 한국산업경영시스템학회지 Vol.28 No.1
Slotted ALOHA(S-ALOHA) is widely used in local wireless network. We analyze the performance of contention-based model in wireless LAN using S-ALOHA protocol. We analyze the performance of binary exponential backoff (BEB) algorithm under the slotted ALOHA protocol : whenever a node's message which tries to reserve a channel is involved in a collision for the ith time, it chooses one of the next 2^i frames with equal probability and attempts the reservation again. We derive the expected access delay and throughput which is defined as the expected number of messages that reserve a channel in a frame. A simulation study is performed to verify our method.
정석윤(Seo-Kyun Jeong),허선(Sun Hur),남진규(Jin-Gyu Nam) 한국산업경영시스템학회 2006 한국산업경영시스템학회지 Vol.29 No.1
In mobile ad-hoc networks(MANETs), nodes are mobile and network topology changes very frequently. The mobility of nodes does affect the system performance. There has been considerable attention on the mobility models, however, most work is confined to the simulation or test-bed. In this paper, we propose an analytical method to evaluate the performances of MANETs such as the average radio range dwell time of mobile nodes, link holding time, and transmission failure probability considering the node"s mobility. In the proposed model, MANETs consist of the multi-hop and multicasting routing paths. A simulation is done to validate our proposed analytical model.
허선(Hur, Sun),신동민(Shin, Dong Min),남진규(Nam, Jin gyu),이현(Lee, Hyun),김현우(Kim, Hyun Woo) 인하대학교 정석물류통상연구원 2008 인하대학교 정석물류통상연구원 연구총서 Vol.- No.-
Ubiquitous means integration of different networks and under which all operations should be processed in real time and prediction of data generation is not available. In ubiquitous environments, the types of information are vast and their forms are complex. Collection of these data may cause queuing situation and it affects system performances. In addition, most data generated in ubiquitous environments have time constraints, by which they become obsolete as time elapses. Therefore, it is essential to establish systems which accommodate the time constraints as the systems become more complicated. In this paper, we consider the characteristics of information in ubiquitous environments and build an analytical model to provide system performance measures which are required to compose and plan a system. We build a time constrained information processing model which deals with more than one types of information. We also analyze parameters which decide information processing time as one of the system measures and provide a method which satisfies the required level of it. Several numerical computations are given to illustrate the extent of effect that the parameters have on the system.
차세대 통신네트워크에서 이동단말의 효율적인 동적제어 정책
김상용(Sang-Yong Kim),손재동(Jae-Dong Son),남진규(Jin-Gyu Nam) 대한산업공학회 2009 대한산업공학회 추계학술대회논문집 Vol.2009 No.10
Next generation communication systems are proposed in order to serve integrated multimedia services on heterogeneous networking environment. Supporting multimedia services with different quality of service (QoS) requirements in highly heterogeneous networking environment is very challenging and difficult task, and an optimal policy of unified call admission control (CAC) is needed to utilize the wired and wireless resources efficiently. In this paper, we propose a dynamic optimization on call admission control for next generation network. We consider three types of mobile stations (MSs) entering a network domain, namely, a new MS, a vertical hand-off MS, and a horizontal hand-off MS. If the MSs are moving between homogeneous systems, horizontal hand-off calls occur. On the other hand, if the MSs are moving between heterogeneous systems, vertical hand-off calls occur. We impose different costs on rejection of requests from these MSs, since the forced termination of an ongoing communication causes greater pain to a user than blocking a new MS. An optimal admission policy is obtained from a semi-Markov decision process with respect to the number of MSs present in a system cell domain. Based on this optimal policy, we calculate the probabilities of blocking each type of MS.