• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.12
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• pp.1631-1637
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• 2019

In this paper, we propose a low-complexity robust maximum likelihood (ML) receiver for generalized spatial modulation. The proposed receiver performs the transmit antenna partition to lower the computational loads. After we divide the transmit antenna combinations into two parts, one of which is "the likely TAC part," and the other of which is "the unlikely TAC part", based on the minimum mean square error (MMSE) filtering output. We first perform the maximum likelihood detection only in the likely TAC part. Then we evaluate the reliability of the solution found in the first search, and based its reliability we decide whether we continue the search in the unlikely TAC part. This partitioned search strategy maintains the performance of the conventional robust maximum likelihood receiver and simultaneously lowers computational loads. Through simulation, we found that our newly-proposed receiver achieves considerable gains over the conventional robust ML detector in terms of the computational loads while providing almost the same performance.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.160-162
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• 2005

무선 방송 방식은 부족한 대역폭의 효율적인 활용과 채널을 듣는 모든 사용자를 지원할 수 있다는 효율성 측면에서 각광받고 있다. 위치기반 서비스 중에서도 효율적인 방송기법을 이용하기 위한 연구 및 가장 기본적인 질의 중 하나인 NN 질의를 효율적으로 수행하기 위한 연구가 이루어져 왔다. 그러나 기존의 연구된 기법들은 NN 탐색 시 하나 이상의 방송주기를 필요로 하여 긴 접근 시간을 가진다는 단점이 있다. 이러한 단점을 모바일 환경에서 비효율적으로 자원을 사용한다는 문제를 발생시킨다. 이에 따라 본 논문에서는 한층 효율적인 자원 사용을 위해서 무선 기기에서 무선 방송 채널을 통해 NN 탐색을 수행할 수 있는 새로운 기법을 제안하고자 한다. 기존의 기법들에 비해서 접근 시간과 튜닝 시간을 줄임으로써 본 논문에서는 효율적으로 자원을 사용하고자 한다. 또한, 실험을 통해 본 논문에서 제안한 기법이 기존의 기법보다. 향상된 성능을 보이는 것을 증명한다.

• Journal of Satellite, Information and Communications
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• v.2 no.1
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• pp.1-6
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• 2007

In this paper, we proposed new algorithm that improves the acquisition performance of the PN code searcher used in DS-CDMA systems. Using the mean deviation computed from the correlator output of the PN code searcher, it is possible to estimate received channel environment. To satisfy the required acquisition performance in estimated channel environment, the PN code searcher changes the correlator tap size adaptively. Proposed algorithm shows improved performance compared with conventional algorithm using the fixed correlator tap size.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.277-280
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• 2007

A moving object tracking algorithm for image searching based on specific color detection is proposed in this paper. That is preprocessed for a luminance variation and noise cancellation to be robust system. The motion tracking is used the difference between input image and reference image in R, G, B each channels for a moving image. The proposed method is enhanced to 15% fast in comparison with the contour tracking method and the matching method, and stable.

• Journal of the Korea Society of Computer and Information
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• v.18 no.2
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• pp.69-76
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• 2013

Reader-to-reader interference in RFID system is occurred due to the use of limited number of frequencies, and this is the main cause of read rate reduction in the passive RFID tags. Therefore, in order to maximize the read rate under the circumstances of limited frequency resources, it is necessary to minimize the frequency interference among RFID readers. This paper presents a hybrid FDM/TDM constraint satisfaction problem models for frequency interference minimization problems of the RFID readers, and assigns optimal channels to each readers using conventional backtracking search algorithms. A depth first search based on backtracking are accomplished to find solutions of constraint satisfaction problems. At this moment, a variable ordering algorithm is very important to find a solution quickly. Variable ordering algorithms applied in the experiment are known as efficient in the graph coloring. To justify the performance of the proposed constraint satisfaction problem model, optimal channels for each readers in the passive UHF RFID system are allocated by using computer simulation satisfying various interference constraints.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.8
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• pp.1649-1655
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• 2005

For systems with coexisting cellular and hot-spot cells in broadband orhogonal frequency and code division multiplexing (OFCDM) systems, a suitable cell search algorithm is proposed fur the common pilot channel (CPICH) in the forward link using separated I/Q channel cell specific codes(CSSC), in which the cellular cell specific scrambling code (CCSSC) is assigned to the in-phase (Q) pilot channel of all cellular cells, and the exclusive hot-spot cell specific scrambling code (HSCSSC) group is assigned to the quadrature (Q) pilot channel of all hot-spot cells. Therefore, the proposed algorithm enables a mobile station (MS) to search quickly for the most desirable hot-spot cell due to reducing the effect of CCSSC, when a MS wants to use a mobile internet. The computer simulation results show that the proposed cell search algorithm can achieve faster cell search time performance, compared to conventional cell search methods.

• 한국정보통신설비학회:학술대회논문집
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• 2004.08a
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• pp.27-30
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• 2004

본 논문에서는 무선 랜 환경에서 단말을 사용하는 사용자의 이동으로 인한 서비스영역의 변화에도 끊김 없는 서비스를 제공하기 위한 방식을 제안한다 제안방식은 이동하는 단말이 사용 가능한 채널탐색과정 중 MAC주소를 참조하여 단말의 이동을 알려주는 방식을 사용한다. 기존방식과 제안방식에 대해서 시뮬레이션을 통한 성능분석을 수행하였다. 단말의 이동을 채널탐색과정에서 인식함으로 단말에게 전송되어야 하는 데이터를 버퍼링 한 후 재결합과정이 발생하면 즉시, 전송하는 방식으로 구성되므로 핸드오프 기간 동안에 Throughput 감소가 적게 이루어짐을 확인하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2256-2262
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• 2015

Recently, device-to-device (D2D) communication has been considered as key technology for future cellular system, because it can solve the problem of excessive data traffic increment and can also provide new communication services. Herein, we propose new neighbor discovery for D2D communication and examine its performance. Our proposed scheme is proximity beacon based discovery in which wireless resource for pilot transmission is assigned based on the spatial correlation of wireless channel and sensing period is adjusted according to target accuracy such that power consumption can be reduced. The performance of our propose scheme is analyzed mathematically and verified through computer simulations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.363-364
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• 2015

On the area which is restricted an unauthorized WiFi service, mobile WiFi hotspot causes security problems like leaking and gathering internal data. In this paper, we modify a wireless lan driver and implement a detector that periodically scans the wireless channels.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.5
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• pp.961-971
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• 2019

Isolation between virtual machines in a cloud computing environment is an important security factor. The violation of isolation between virtual machines leads to interferences of shared resources and the implementation of covert channels. In this paper, the structure of Hyper-V hypervisor is analyzed to implement covert channels between virtual machines. Hyper-V uses a mutex technique for mutual exclusion between virtual machines. It indicates that isolation of virtual machines is violated and covert channels can be implemented due to mutex. We implemented several covert channels by designing a method for searching mutex resources applicable to Hyper-V with complex architectures. The mutex-based covert channel is not hardware dependent. If the covert channel is detected or defended, the defensive technique can be avoided by using the other covert channel among several covert channels.