• Journal of the Institute of Electronics Engineers of Korea TC
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• 제46권6호
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• pp.111-117
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• 2009

In the wideband code division access (WCDMA) systems, a pilot channel is used to determine WCDMA network coverage, cell identification, synchronization, timing acquisition and tracking, user-set handoff, channel estimation, and so on. A wireless repeater, which is deployed in the urban area for the WCDMA system to meet the growing demand on wireless communication services, has the possibility to receive several pilot signals from a large number of base stations, however, cannot distinguish its service base station's signal among them. This pilot interference results in frequent handoffs in the user equipment, which degrades the radio reception, transmission efficiency, quality of service, and channel capacity and increases the unwanted power consumption. In this paper, thus, we propose a pilot pollution interference cancellation scheme using one of the adaptive estimation algorithms, normalized least mean square (NLMS), which is applicable to a wireless repeater. We carried out link-level and network-level computer simulations to evaluate the performance of the proposed scheme in a wireless repeater. The simulation results verify the bit error rate (BER) improvement in the link level and the call drop probability improvement in the network level.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제16권12호
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• pp.8370-8377
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• 2015

In spatial data stream management systems, it is needed appropriate load shedding algorithm because real-time input spatial data streams could exceed the limitation of main memory. However previous researches, lack regard for input ratio and spatial utilization rates of spatial data streams, or the characteristics of data source which generates data streams with spatial information efficiently, can lead to decrease the performance and accuracy of spatial data stream query. Therefore, multi-level load shedding scheme for spatial data stream management systems is proposed to increase the spatial query performance and accuracy. This proposed scheme limits overloads in relation to the input rate and the characteristics of data source first, and then, if needed, query data representing low query participation probability based on spatial utilizations are dropped relatively. Our experiments show that the proposed method could decrease load shedding frequency for previous researches by more than 11% despite query results accuracy and query performance are superior at 0.04% and 3%.

• Journal of the Institute of Electronics Engineers of Korea SC
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• 제45권6호
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• pp.149-156
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• 2008

SLAM(Simultaneous Localization and Mapping) system is to find a global position and build a map with sensing data when an unmanned-robot navigates an unknown environment. Two kinds of system were developed. One is used distance measurement sensors such as an ultra sonic and a laser sensor. The other is used stereo vision system. The distance measurement SLAM with sensors has low computing time and low cost, but precision of system can be somewhat worse by measurement error or non-linearity of the sensor In contrast, stereo vision system can accurately measure the 3D space area, but it needs high-end system for complex calculation and it is an expensive tool. In this paper, we implement the SLAM system using a single camera image and a PSD sensors. It detects obstacles from the front PSD sensor and then perceive size and feature of the obstacles by image processing. The probability SLAM was implemented using the data of sensor and image and we verify the performance of the system by real experiment.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제36권5B호
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• pp.539-548
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• 2011

We propose an efficient cooperative ARQ (Automatic Repeat reQuest) scheme for single-hop and multi-hop underwater acoustic communications, in which cooperative nodes are used to provide more reliable alternative paths for a specific source-to-destination connection. This alternative path has higher channel quality than that of the direct source-destination path. In addition, during a packet-relay through multiple hops, the typical acknowledgement (ACK) signal is replaced with overhearing data packet returned back from the next hop. The usage of overhearing as an ACK improves the system performance. In this paper, we evaluate the proposed scheme by comparing it with a conventional S&W ARQ in terms of throughput efficiency. Computer simulation results show that the proposed cooperative retransmission scheme can significantly improve the throughput by increasing the probability of successful retransmission.

• Journal of the Institute of Electronics Engineers of Korea CI
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• 제47권6호
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• pp.103-112
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• 2010

A study on network traffic analysis and modeling has been exclusively done due to its importance. However, conventional studies on network traffic analysis and modeling only focus on transmitting simple packet stream or traffic features of specific application, such as HTTP. In this paper, we propose a network traffic generator, which reflects the characteristics of multimedia data. To analyze the traffics of online game, which is one of the most popular multimedia contents, we modeled the distribution according to the time between packets and packet size random variable and designed the traffic generator which has the model for input. We generated the traffics of L4D(Left4Dead), WoW(World of Warcraft) with proposed network traffic generator and we found that the generated traffics have similar distributions with real data.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 한국산업정보학회 1999년도 추계공동학술대회 논문집:21세기지식경영과 정보기술
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• pp.315-323
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• 1999

The measuring systems of auto-parts are most of greater part very expensive. This paper tries to study to make a low-cost measuring equipment. There's several kinds of parts in automobile. In this study, we take aircon-switch called magnet coil-housing as the object of measurements. The measurements of this product is currently in difficult situations at factory. In the case of the mesuring objects being big sizes and camera sensor having under 410000 pixels, the key point is the number of pixels not to be changed whenever the same object is measured under the same position. We modified and used fuzzy c-means algorithm to get mostly without the change of the numbers of pixels exactly. Also, the standardized ruler is necessary to measure the length of the object but it is not easy to get the precised ruler. Therefore, the standard length has been taken as the mean value of the pixels in the previous passed objects manually obtained at factory. The results are displayed on monitor and transferred these signals to the microprocessor through RSC-232 port to determine a good or bad of products.

• The Journal of the Korea Contents Association
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• 제10권9호
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• pp.97-106
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• 2010

Various time series representation methods have been suggested in order to process time series data efficiently and effectively. SAX is the representative time series representation method combining segmentation and discretization techniques, which has been successfully applied to the time series classification task. But SAX requires a large number of segments in order to represent the meaningful dynamic patterns of time series accurately, since it loss the dynamic property of time series in the course of smoothing the movement of time series. Therefore, this paper suggests a new time series representation method that combines PIPs detection and Persist discretization techniques. The suggested method represents the dynamic movement of high-diemensional time series in a lower dimensional space by detecting PIPs indicating the important inflection points of time series. And it determines the optimal discretizaton ranges by applying self-transition and marginal probabilities distributions to KL divergence measure. It minimizes the information loss in process of the dimensionality reduction. The suggested method enhances the performance of time series classification task by minimizing the information loss in the course of dimensionality reduction.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• 제9권6호
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• pp.584-590
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• 2016

This paper proposed "Priority Scheduling and MultiPath Routing Protocol (RRPS) for preventing communication disruption in the urban environment" to minimize the disconnection or disruption of V2I and V2V communication in the urban environment where communication is frequently disconnected according to density. The flow of the RRPS is explained as follows. RSU Request Priority Scheduling (RRPS) is used to apply the priority of the request message prior to reaching the end line by using the Start Line and End Line, which are the management areas of the RSU). This paper also proposed MPRP (Multi Path Routing Protocol) design to set up the multipath to the destination. As a result, the proposed RRPS improves the processing efficiency of V2I by applying priority scheduling to the message of the vehicle requesting the information in the RSU, and can prevent the communication disconnection. Thereby, it is improved the transmission success probability.

• Journal of the Korean Society for information Management
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• 제19권4호
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• pp.258-296
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• 2002

This study is to consider varying factors of jnternal/external informational and operational environments in libraries, and develop a new evaluation indicators for university libraries in digital environments. The main research results are as follows. First, the results through the Delphi method that was to adopted to verify evaluation items and indicators determined by the literature review show that the repressed values for each evaluation category is greater than 3.00, overall average is 4.02, and standard deviation is ranged from 0.40 to 0.62 for each category. This means that the evaluation indicators are valid. Second, the factor analysis was performed to verify .the construct validity of evaluation indicators. As a result, the cumulative variance of evaluation indicators consisting of 11 dimensions per factor is 72.733%. In turn, this result shows that the validity of these indicators is very reliable. Third, t-test and one-way ANOVA are performed within significance probability 0.05 in order to verify differences in each librarians point of views for the degree of importance in evaluation indicators. Based on the Delphi study and our own analysis, we developed a new evaluation indicators that consists of 7 evaluation categories, 35 evaluation items, and 92 evaluation indicators.

• Journal of Satellite, Information and Communications
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• 제12권1호
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• pp.76-80
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• 2017

With the fast growing popularity of small UAVs (Unmanned Aerial Vehicles), recent UAV systems have been designed and utilized for the various field with their own specific purposes. UAVs are opening up many new opportunities in the fields of electronics, sensors, camera, and software for pilots. Increase in awareness and mission capabilities of UAVs are driving innovations and new applications driven with the help of low cost and its capability in undertaking high threat task. In particular, small unmanned aerial vehicles should fly in environments with high probability of unexpected sudden change or obstacle appearance in low altitude situations. In this paper, current researches regarding techniques of autonomous flight of smal UAV systems are introduced and we propose a draft idea for planning paths for small unmanned aerial vehicles in adversarial environments to arrive at the given target safely with low cost sensors.