• Journal of the Institute of Electronics Engineers of Korea CI
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• v.42 no.6
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• pp.101-108
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• 2005

In this paper, we proposed a new algorithm of pulse generation and detection for the UWB multimedia communication system. The existing UWB systems using Gaussian pulse have some difficulties to cope with bandwidth limitation and frequency transition. In this paper, we introduce a new pulse generation method, which is able to control the bandwidth and center frequency that applies to the frequency modulation method, thus the proposed algorithm could improve the detection performance of receiving. And we proposed the multi channel transmission algorithm which transmits 1 channel synthesized at same time using the wavelet synthesis filter. Because of wavelet filter's perfect reconstruction property, the BER(Bit Error Rate) of transmission data is not changed by the number of accessed user. BER is changed only the property of channel transmission. By the results of simulation, when shift SNR from 2dB to 8dB on AWGN channel, we confirmed that the proposed algerian has $3.9063{\times}10^{-4}$ BER at 4dB SNR(AWGN channel).

• The KIPS Transactions:PartB
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• v.14B no.3 s.113
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• pp.191-198
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• 2007

In this paper, we present a marker detection and recognition method from camera image for a disabled person to interact with a server system which can control appliance of surrounding environment. It converts the camera image to a binary image by using multi-threshold and extracts contours of objects in the binary image. After that, it approximates the contours to a list of line segments. It finds rectangular markers by using geometrical features which are extracted from the approximated line segments. It normalizes the shape of extracted markers into exact squares by using the warping technique. It extracts feature vectors from marker image by using principal component analysis and then recognizes the marker. The proposed marker recognition system is robust for light change by using multi-threshold. Also, it is robust for angular variation of camera by using warping technique and principal component analysis. Experimental results show that the proposed method achieves 100% recognition rate at maximum for 21 markers and execution speed of 12 frames/sec.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.11
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• pp.2866-2879
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• 2012

Among the various security threats in online games, the use of game bots is the most serious problem. Previous studies on game bot detection have proposed many methods to find out discriminable behaviors of bots from humans based on the fact that a bot's playing pattern is different from that of a human. In this paper, we look at the chatting data that reflects gamers' communication patterns and propose a communication pattern analysis framework for online game bot detection. In massive multi-user online role playing games (MMORPGs), game bots use chatting message in a different way from normal users. We derive four features; a network feature, a descriptive feature, a diversity feature and a text feature. To measure the diversity of communication patterns, we propose lightly summarized indices, which are computationally inexpensive and intuitive. For text features, we derive lexical, syntactic and semantic features from chatting contents using text mining techniques. To build the learning model for game bot detection, we test and compare three classification models: the random forest, logistic regression and lazy learning. We apply the proposed framework to AION operated by NCsoft, a leading online game company in Korea. As a result of our experiments, we found that the random forest outperforms the logistic regression and lazy learning. The model that employs the entire feature sets gives the highest performance with a precision value of 0.893 and a recall value of 0.965.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.2
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• pp.550-565
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• 2018

Cognitive radio technology is still the key technology of future mobile communication systems. Previous studies have focused on improving spectrum utilization and less energy consumption. In this paper, we propose an Overhead Reduced Scheme (ORS) for green cooperative spectrum sensing. Compared to traditional cooperative sensing scheme, ORS scheme divides the sensing time into three time slots and selects the best multi-mode user to report decisions. In consideration of reporting channel deviation, we derive closed-form expressions for detection probability and false alarm probability of ORS scheme based on Rayleigh fading channel. Simulation results show that ORS scheme can improve the perception accuracy while reducing the perceived delay and energy consumption in the process of perception, so as to realize the green communication.

• Journal of Korea Society of Industrial Information Systems
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• v.11 no.4
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• pp.40-46
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• 2006

The performance of iterative multiuser detector and turbo decoder is presented to provide high quality multimedia services in WCDMA (wideband code division multiple access) system in this paper. Especially the relationship between the local iteration of turbo decoder and the global iteration of multiuser detector including the turbo decoder is analyzed. As a result, three local iterations and three global iterations are considered to be sufficient to provide satisfactory error performance with resonable complexity. The interference cancellation capability of global iteration is improved when the number of users is increased.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11C
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• pp.1085-1091
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• 2006

The major goal of this paper is to develop a practically implemental radial basis function (RBF) neural network based multi-user detector (MUD) for direct sequence (DS)-CDMA system. This work is expected to provide an efficient solution for RBF based MUD by quickly setting up the proper number of RBF centers and their locations required in training. The basic idea in this research is to estimate all the possible RBF centers by using supervised ${\kappa-means$ clustering technique, and select the only centers which locate near seemingly decision boundary between centers, and reduce further by grouping the some of centers adjacent each other. Therefore, it reduces the computational burden for finding the proper number of RBF centers and their locations in the existing RBF based MUD, and ultimately, make its implementation practical.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.142-146
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• 2002

직접 대역 확산 통신 방식에서 처리 이득에 비해 강한 협대역 간섭 신호가 존재 할 때 성능 향상을 위하여 다중 사용자 탐지 기술(MUD)을 사용하여 간섭 신호 제고를 위한 신호 검출을 하였으며, 적응 접속 채널 배열 응답과 다중 사용자 검출을 하기 위하여 BISP 알고리즘을 제안하였다. 또한 CDMA 채널에서 MAI와 ISI 검출에 BISP 알고리즘 신호 흐름 형태를 파악하여, 신호대 간섭 비율(SIR)과 신호대 잡음비율(SNR)에서 시간에 따른 비트율를 평가 하였다. 제안한 BISP 알고리즘은 방사 특성에 시간 지연 효율이 절반 이상 차이가 나지만 채널 특성 따라서 입력 신호를 조정 할 수 있다. 그리고 매치 필터를 통과하면서 각 채널간의 간섭을 억제하고, 사용자 검출을 용이하게 처리할 수 있다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.2
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• pp.56-63
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• 2003

We investigate some implementation factors that affect the performance of multi-rate parallel interference cancellers (PICs) for the international mobile telecommunications-2000 (IMT-2000) 3rd-generation partnership project (3GPP) system. We consider the simple multi-rate PIC [1,2] that can remove effectively multiple access interference (MAI) through block-based detection and sample-based cancellation in asynchronous user environments. The PIC structure has significantly lower complexity as compared with that of the existing scheme, especially as the number of users increases. We analyze the effects of timing error, oversampling rate, unsynchronized users and/or outer-cell interference, and the number of Quantization bits on the PIE performance through extensive computer simulations. The models for such factors and the optimum parameters are drawn. Finally, we evaluate the receiver complexities of the PIC receivers employing using the advanced removal scheme.

• Journal of the Korea Society of Computer and Information
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• v.20 no.2
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• pp.99-112
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• 2015

Datum point for displaying location and altitude of point has being advantage usefully in various measurement parts. However, datum point has been increasing loss cases owing to weather changes and stratum changes and neglecting meaninglessly. In this paper, we design and implement a multi electronic measurement system monitoring software with functions such as include maximize utilization of existing measurement datum system as well as collected various environment data and detection stratum changes of surround area. Proposed software is implemented to support that reusability and extensibility of software using object oriented modeling method. Our software supports a GUI for electronic measurement datum point administrator as well as for web user and mobile user. Our system can support a graph GUI for various data analysis and reposition in realtime to database that measured location information and various sensing information to prevent loss of electronic measurement datum point and to detected stratum changes. In addition, we include a QR code and RFID recognition function. Finally, we suggest performance evaluation result to confirm stratum changes detection and GPS location error rate.

• 한국지형공간정보학회:학술대회논문집
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• 2002.11a
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• pp.117-122
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• 2002

Change detection is a useful technology that can be applied to various fields, taking temporal change information with the comparison and analysis among multi-temporal satellite images. Especially, change detection that utilizes high-resolution satellite imagery can be implemented to extract useful change information for many purposes, such as the environmental inspection, the circumstantial analysis of disaster damage, the inspection of illegal building, and the military use, which cannot be achieved by lower middle-resolution satellite imagery. However, because of the special characteristics that result from high-resolution satellite imagery, it cannot use a pixel-based method that is used for low-resolution satellite imagery. Therefore, it must be used a feature-based algorithm based on the geographical and morphological feature. This paper presents the system that builds the change map by digitizing the boundary of the changed object. In this system, we can make the change map using manual or semi-automatic digitizing through the user interface implemented with a floating window that enables to detect the sign of the change, such as the construction or dismantlement, more efficiently.