• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.4
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• pp.85-90
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• 2014

We realized a wireless multiple integrated laser engagement system composed of personal area network using Zigbee. The wireless laser detector had function of analog signal processor, decoder and wireless communication. However, it should consume low power and be small and light in order to be attached to a soldier's body. The decoder was realized in software to be small and light. We induced low power consumption as reducing the load of system using a narrow band optical filter. The fabricated wireless laser detector functioned well in optically noisy environment. Although the communication to the player unit through the wireless personal area network was dependent on the attachment place it was perfectly worked with transmission power of -40.2dBm or more.

• 한국공간정보시스템학회:학술대회논문집
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• 2005.05a
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• pp.225-233
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• 2005

최근 LBS는 '위치정보의 보호 및 이용에 관한 법률' 제정 및 시행령 준비에 의해 위치정보 이용에 대한 제도적인 안전장치가 마련되었으며 이동통신망, 유선망과 무선망의 결합에 의해 LBS의 범위는 점점 더 확장되고 있어 서비스 또한 고속 통신을 기반으로 매우 개인화되고 다양해지고 있다. 그 중에 위치기반 경보 서비스(Alert based on LBS)기술은 가족안전, 모바일 상거래 등의 Push형 서비스로 이동단말의 인치를 폴링 (Polling)하여 일정 영역이나 특정 조건에 만족하면 통보하거나 기 정의된 서비스를 제공해주는 고부가가치 서비스이다 기존 위치폴링 기술은 일정한 시간간격으로 위치를 획득하여 네트워크 망에 큰 부하를 주고 있다. 본 논문은 위치폴링 기술에 전반적인 이해와 관련 연구를 통해 문제점을 살펴본 후 문제 해결책을 제시한다 또한, 향후에 유무선 통합 환경에서 위치기반 경보 서비스의 중요성을 살펴본다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.7
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• pp.85-92
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• 2010

In this paper, we consider the orthogonal frequency division multiplexing (OFDM) based transmission incoorperating with beam-switching and space-time coding. Specifically, we consider three configurations; (1) the beamforming technique, (2) the spatial diversity technique and (3) their combination and evaluate the performance in wireless personal area network (WPAN) environment. For the beam-forming technique, we consider the beam-switching which is performed at RF front-end with a pre-defined set of beams and for the space-time coding, we consider the Alamauti scheme with antenna selection. For the combined scheme, we divide the antennas used into two group to generate two independent beams and apply the two-antenna Alamauti scheme over the two beams. For these three configurations, performance is evaluated in terms of the SNR gain.

• The Journal of the Korea Contents Association
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• v.9 no.7
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• pp.76-85
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• 2009

UWB signal with high resolution capability can be used to estimate ranging and positioning in wireless personal area network. The node works on its local clock and the frequency differences of nodes have serious affects on ranging algorithms estimating locations of mobile nodes. The low rate UWB, IEEE802.15.4a, describes asynchronous two way ranging methods such as TWR and SDS-TWR working without any additional network synchronization, but the algorithms can not eliminate the effect of clock frequency differences. Therefore, the mechanisms to characterize the crystal difference is essential in typical UWB PHY implementations. In high rate UWB, characterizing of crystal offset with tracking loop is not required. But, detection of the clock frequency offset between the local clock and remote clock can be performed if there is little noise induced jitter. In this paper, we complete related ranging equations of high rate UWB based on TWR with relative frequency offset, and analyze a residual error in the ideal equations. We also evaluate the performance of the relative frequency offset algorithm by simulation and analyze the ranging errors according to the number of TWR to compensate coarse clock resolution. The results show that the relative frequency offset compensation and many times of TWR enhance the performance to converge to a limited ranging errors even with coarse clock resolutions.

• Journal of the Korea Society of Computer and Information
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• v.17 no.10
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• pp.99-105
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• 2012

ZigBee is the low power, low cost and low data rate wireless personal area network(LR-WPAN) standard. The Directed-Messaging is the protocol which improves the energy efficiency through reducing the redundant message transmission by transmitting messages with directional information toward the specified sub-network area in wireless sensor network using broadcasting. In this paper, we design and implement the experimental grid sensor network using ZigBee modified by the Directed-Messaging for the energy efficiency improvement. The experimental sensor network in this paper is configured with Nano24 supporting the ADV message and the routing management module modified to use the directional information. The energy efficiency improvement of the experimental sensor-network by evaluating the experimental results according to transmitting ADV message.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.271-273
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• 2001

최근들어 블루투스 기술은 정보 기기간의 케이블 통신을 대체하는 저가격의 무선 통신 기술로서 많은 관심을 끌고 있으며 블루투스 칩, 프로토콜 스택 및 응용 제품 개발이 활발히 진행되고 있다. 특히 블루투스는 1개의 마스터와 최대 7개의 슬레이브로 구성되는 피코넷과 다수의 피코넷으로 구성되는 스캐터넷의 형성이 가능하여 이를 이용한 ad hoc PAN 네트워킹에 대한 연구가 시작되고 있다. 블루투스 ad hoc PAN 연구를 위해서는 시뮬레이터의 이용이 필수적이다. 본 논문은 블루투스 피코넷에서의 ad hoc 네트워킹을 위한 Glomosim 기반 시뮬레이터의 설계 및 구현에 관한 내용이다. 이 시뮬레이터는 Glomosim 시뮬레이터의 MAC 계층 모듈에 블루투스 baseband 및 LM 래이어를 추가하여 ad hoc IP 라우팅이 가능하도록 설계되어 있다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.10
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• pp.2121-2128
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• 2009

The application range of IEEE 802.11 wireless LAN has rapidly expanding from campus, enterprise to the public network of Hot Spot area due to the advantages of easiness of construction, mobility of wireless client station, convenience of usage and so on. However the security of WLAN(Wireless LAN) is vulnerable inherently because of using RF as a medium, and so the dangers of infringement of personal information and inside data of enterprises have increased and wardriving attack searching for security vulnerability in wireless LAN has become more serious especially. In this paper, we find out the overview of various procedures and preparatory stages for wardriving attack against wireless LAN, and propose complementary methods to prevent information infringement accidents from wardriving attack in wireless LAN. For this purpose, we make an equipment which is suitable for wardriving in wireless LAN and show security vulnerability of AP(Access Point) operation in WLAN around Yangjae-Dong in Seoul as a result of using the equipment.

• Journal of IKEEE
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• v.11 no.4
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• pp.348-357
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• 2007

Due to the improved performance and cost of personal mobile devices and rapid progress of wireless communication technology, the number of users who utilize these devices is increasing. This trend requires various types of services be available to users. So far, there have been many solutions provided for the shortest path problem. But, technologies which can offer various recommendation services to user depending on user’s current location are focused on Euclidean spaces rather than road network. Thus, in this paper, we extend the previous work to satisfy this requirement on road network database. Our proposed scheme requires pre-computation for the efficient query processing. In the preprocessing step, we first partition the input road network into a fixed number of Voronoi polygons and then pre-compute routing information for each polygon. In the meantime, we select the number of Voronoi polygons in proposition to the scale of road network. Through this selection, the required size of pre-computation is linearly increasing to the size of road network. Using this pre-computated information, we can process queries more quickly. Through experiments, we have shown that our proposed scheme can achieve excellent performance in terms of scheduling time and the number of visited nodes.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.8 s.350
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• pp.25-34
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• 2006

In this paper DynaMoNET is suggested as a novel IPv6-based multi-homed mobile network architecture which is composed of nested mobile ad hoc networks dynamically coming together through wireless personal area networks. Each ad hoc network has a mobile router which may work as a root mobile router instead of fixed mobile routers in a DynaMoNET. A root mobile router provides the reliable Internet connectivity for the entire mobile network. This paper includes a innovative handover protocol for multi-homed mobile networks, network switchover algorithm considering multiple decision factors, root mobile router election process based on token-based algorithm fast root mobile router discovery algorithm and fault avoidance mechanism to support reliable Internet connectivity. Finally the system architecture of a mobile router is given in detail.

• The KIPS Transactions:PartC
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• v.19C no.4
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• pp.239-246
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• 2012

The function of location estimation in WPAN has been studied and specified on the ultra wide band optionally. But the devices based on CSS(Chirp Spread Spectrum) specification has been used widely in the market because of its functionality, cheapness and support of development. As the CSS device uses 2.4GHz for a carrier frequency and the sampling frequency is lower than that of the UWB, the resolution of a timestamp is very coarse. Then actually the error of a measured distance is very large about 30cm~1m at 10 m depart. And the location error in ($10m{\times}10m$) environment is known as about 1m~2m. So for some applications which require more accurate location information, it is very natural and important to develop a sophisticated post processing algorithm after distance measurements. In this paper, we have studied extended Kalman filter with the frequency offsets of anchor nodes, and proposed a novel algorithm frequency offset compensated extended Kalman filter. The frequency offsets are composed with a variable as a common frequency offset and constants as individual frequency offsets. The proposed algorithm shows that the accurate location estimation, less than 10cm distance error, with CSS WPAN nodes is possible practically.