• Journal of Advanced Navigation Technology
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• v.19 no.6
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• pp.552-557
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• 2015

Recent performed by recognizing a user's location, various services have been tailored focus on short-range wireless communication technology. A beacon in which is attracting attention as next-generation technology. Beacon is a terminal by utilizing the frequency of the non-audible area can not be bluetooth and human sending and receiving terminals and information, Apple recently iBeacon like a low-power Bluetooth (BLE; bluetooth low energy) based beacon showing a tendency to rise into the mainstream there. Services using a beacon is basically installs the terminal in a certain place indoor. It is characterized by providing the user the services to catch the user's position, even automatically take a separate action. Various types of location-based service provided by the target interior space began to attract attention. A variety of location-based services are provided in the interior space in order to be successfully deployed and provide guidance to the interior space, the movement route and the like are essentially required to build various types of information. In this paper, for efficient indoor positioning by varying the signal strength of the beacon in such areas were measured and analyzed.

• Journal of Intelligence and Information Systems
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• v.11 no.3
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• pp.25-43
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• 2005

In modern automated container terminals, automated guided vehicle (AGV) systems are considered a viable option for the horizontal tansportation of containers between the stacking yard and the quayside cranes. AGVs in a container terminal move rather freely and do not follow fixed guide paths. For an efficient operation of such AGVs, however, a sophisticated traffic management system is required. Although the flexible routing scheme allows us to find the shortest possible routes for each of the AGVs, it may incur many coincidental encounters and path intersections of the AGVs, leading to collisions or deadlocks. However, the computational cost of perfect prediction and avoidance of deadlocks is prohibitively expensive for a real time application. In this paper, we propose a traffic control method that predicts and avoids some simple, but at the same time the most frequently occurring, cases of deadlocks between two AGVs. More complicated deadlock situations are not predicted ahead of time but detected and resolved after they occur. Our method is computationally cheap and readily applicable to real time applications. The efficiency and effectiveness of our proposed methods have been validated by simulation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.359-367
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• 2005

In order to increase the productivity of container terminals, automation is being considered seriously in nowadays. A yard is usually automated by running autumated RMGs (rail mounted gantries) which may require somewhat a different stacking strategy to archive a better performance. In this paper, we present a simulation model for RMGs and summarize experimental results with two different stacking strategies applied to a horizontal block which has two non-crossable RMGs. The concentrating strategy, which stacks containers belong to a single ship together and dedicateds each RMG to either ship services or external truck services, showed a good performance in ship unloading. In the contrast, the distributing strategy, which partitions a block into two regions and binds each RMG to one of the regions to improve the productivity of ship services by running each RMG alternately, is suggested for blocks of exporting.

• Journal of Intelligence and Information Systems
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• v.14 no.4
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• pp.103-116
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• 2008

This paper proposes quay crane (QC) scheduling algorithms that determine the working sequence of QCs over ship bays in a container vessel in automated container terminals. We propose two scheduling algorithms that examine the distribution of export containers in the stacking yard and determine the sequence of ship bays to balance the workload distribution among the yard blocks. One of the algorithms is a simple heuristic algorithm which dynamically selects the next ship bay based on the entropy of workloads among yard blocks whenever a QC finishes loading containers at a ship bay and the other uses genetic algorithm to search the optimal sequence of ship bays. To evaluate the fitness of each chromosome in the genetic algorithm, we have devised a method that is able to calculate an approximation of loading time of container vessels considering the workloads among yard blocks. Simulation experiments have been carried out to compare the efficiency of the proposed algorithms. The results show that our QC scheduling algorithms are efficient in reducing the turn-around time of container vessels.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.11 s.353
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• pp.149-158
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• 2006

We proposed a method for improving a performance of TCP downstream between a desktop PC as a fixed host and a PDA as a mobile host in a wired and wireless network based on IEEE 802.11x wireless LAN. With data transmission between these heterogeneous terminals a receiving time during downstream is slower than that during upstream by 20% at maximum. The reason is that their congestion window size will be oscillated due to a significantly lower packet processing rate at receiver compared to a packet sending rate at sender. Thus it will cause to increase the number of control packets to negotiate their window size. To mitigate these allergies, we proposed two distinct methods. First, by increasing a buffer size of a PDA at application layer an internal processing speed of a socket receive buffer of TCP becomes faster and then the window size is more stable. However, a file access time in a PDA is kept nearly constant as the buffer size increases. With the buffer size of 32,768bytes the receiving time is faster by 32% than with that of 512bytes. Second, a delay between packets to be transmitted at sender should be given. With an inter-packet delay of 5ms at sender a resulting receiving time is faster by 7% than without such a delay.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.10-18
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• 2013

With advancing of mobile communication services and commercializing of VoLTE (Voice of LTE), it is getting to pay attention on QoS of VoLTE. This paper proposes an integrated E-model in which some factors influenced to service quality of VoIP and VoLTE based voice communication system are considered in calculating the voice quality of Wideband Codec. The model aims to calculate R value which reflects the situations of access network, network characteristics, terminals' usage and mobility. We mainly deal with the integrated E-model's structure, related algorithms and optimal parameters for VoLTE. Some experiments show that the voice quality difference between VoIP and VoiceChecker, and VoLTE and POLQA, is below 10%. With the proposed model, we can calculate the voice quality by making use of the factors directly affected to service quality and the environment of VoLTE terminal and network. As a result, we can estimate the service quality in advance, without measuring it in real wireless environment.

• The KIPS Transactions:PartC
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• v.9C no.3
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• pp.385-398
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• 2002

To accommodate the increasing number of mobile terminals in the limited radio spectrum, wireless systems have been designed as micro/picocellular architectures for a higher capacity. This reduced coverage area of a cell has caused a higher rate of hand-off events, and the hand-off technology for efficient process becomes a necessity to provide a stable service. Population-based Bandwidth Reservation(PBR) Scheme is proposed to provide prioritized handling for hand-off calls by dynamically adjusting the amount of reserved bandwidth of a cell according to the amount of cellular traffic in its neighboring cells. We analyze the performance of the PBR scheme according to the changes of a fractional parameter, f, which is the ratio of request reservation to the total amount of bandwidth units required for hand-off calls that will occur for the next period. The vague of this parameter, f should be determined based on QoS(Quality of Service) requirement. To meet the requirement the value of Parameter(f) must be able to be adjusted dynamically according to the changing traffic conditions. The best value of f can be determined by a function of the average speed of mobile stations, average call duration, cell size, and so on. This paper considers the average call duration and the cell size according to the speed of mobile stations. Although some difference exists as per speed, in the range of 0.4 $\leq$ f $\leq$ 0.6, Blocking Probability, Dropping Probability and Utilization show the best values.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.12
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• pp.1336-1347
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• 1991

In this paper, The PC interface for packet terminal of ISDN is designed and implemented in order to build packet communication networks which share computer resources and exchange informations between computer in the ISDN environment. The PC interface for packet terminal of ISDN constitutes S interface handler part which controls functions of ISDN layer1 and layer 2, constitutes packet handler part which controls services of X.25 protocol in the packet level.Where, The function of ISDN layer1 provides rules of electrical and mechanical characteristics, services for ISDN layer 2. The function of ISDN layer 2 provides function of LAPD procedure, services for X.25 The X.25 specifies interface between DCE and DTE for terminals operrating in the packet mode. The S interface handler part is orfanized by Am 79C30 ICs manufactured by Advanecd Micro Devices. ISDN packet handler part is organiged by AmZ8038 for FIFO for the purpose of D channel. The common signal procedure for D channel is controlled by Intel's 8086 microprocessor. The S interface handler part is based on ISDN layer1,2 is controlled by mail box in order to communicate between layers. The ISDN packet handler part is based on module in the X.25 lebel. The communication between S interface handler part and ISDN packet handler part is organized by interface controller.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.10
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• pp.967-973
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• 2014

WAVE (Wireless Access in Vehicular Environments) communications is the core technology for C-ITS (Cooperative-Intelligent Transportation System) which communicates with the road infrastructure and other vehicles to exchange traffic information and service while driving. In this paper, to analyze the performance degradation according to the distance between WAVE communication terminals, we derived the formulas for the locations of down-fade and up-fade points by using the two-ray ground reflection model, and verified these theoretical results by comparing with those of RSSI (Receiver Signal Strength Indicator) measurements. In addition, to solve the problem of down-fade, we suggested the WAVE communication with the antenna diversity and experimentally confirmed the performance improvement in the highway LOS (Line Of Sight) environments.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.4
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• pp.139-145
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• 2016

On the ICT healing platform designed to issue early disease alerts, TOS connected between the provider of personal health-related data and the service provider and relayed personalized health data. In the previous study, TOS proposed how to monitor the retrieval and management of document/measurement resources by taking mobile devices into account. Recently the healthcare field, however, defined the standard items needed for communication and data exchanges with a mobile device through HL7 FHIR. This study designed a data grid model between TOS and FHIR to provide personal health resources relayed through TOS in FHIR bundle search sets. The proposed design was organized as follows: first, it stated similarities between the method of TOS resource request and that of FHIR observation request. Then, it designed an eventbus module to process a retrieval request for FHIR service based on the imdb and cluster technologies. The proposed design can be used to expand the old service terminals of ICT healing platform to mobile health devices capable of using FHIR resources.