• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.3
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• pp.74-82
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• 2002

본 논문에서는 제한된 전파자원을 가장 효율적으로 사용할 수 있는 유력한 후보로 떠오르고 있는 UWB(Ultra Wide Band)무선기술의 도입을 위한 미국, 유럽 및 국제전기통신연합(ITU)에서의 규제정책 동향을 소개하고자 한다 특히 채근에 미국 FCC에서 제한적 범위의 주파수 사용허가가 이루어진 것을 계기로 UWB 무선기술 상용화가 활발히 이루어질 것이므로 이와 관련하여 FCC의 전파 규제 제도를 분석하여 소개하였다. 또 IEEE산하 802.15.3 working group에서 진행되고 있는 무선 개인 통신(Wireless Personal Communication)방식으로 UWB 시스템을 사용하기 위한 표준화 작업에 관한 최신 동향도 소개하고자 한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.348-353
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• 2008

Despite the increasing popularity of wireless sensor network, indoor positioning using low power IEEE 802.15.4 compliant radio had attracted an interest of many researchers in the last decade. Old fashionable indoor location sensing information has been presented in dull and unpleasant 2D image standard. This paper focused on visualizing high precision 3 dimensional RSSI-based (received signal strength indication) spatial sensing information in an interactive virtual reality on PDA. The developed system operates by capturing and extracting signal strength information at multiple pre-defined reference nodes to provide information in the area of interest, thus updating user's location in 3D indoor virtual map. VRML (Virtual Reality Modeling Language) which specifically developed for 3D objects modeling is utilized to design 3D indoor environment.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.2
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• pp.106-113
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• 2009

Recently, due to many industrial accidents at construction sites, a variety of researches for structural health monitoring (SHM) of buildings are progressing. For real site application of SHM, one of the advanced technologies has blown as wireless sensor networks (WSN). In this paper, we proposed WIVA(WSN Monitoring framework based on 3D Visualization and Augmented Reality in Mobile Devices) system that applies 3D visualization and AR technology to mobile devices with camera based on WSN in order to expand the extent of information can observe. Moreover, we performed experiments to validate effectiveness in 3D and AR mode that utilize WSN data based on IEEE 802.15.4. In real implementation scenario, we demonstrated a fire occurrence test in 3-story building miniature.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.10B
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• pp.639-647
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• 2005

When a DEV associates with an existing WPAN, the PNC checks the capabilities of the new DEV to see if it is more capable to be the PNC of the piconet based on the criteria defined in the IEEE Std 802.15. If the new DEV is more capable and the current security policies allow it, then the PNC has the option of handing over control of the piconet to the DEV that has just joined. And, If the PNC is shutting down or wants to leave the WPAN, it also uses the handover process to give control to another DEV in the piconet. However, IEEE 802.15.3 checks only DEV capability information for more PNC capable. For PNC selection, it should consider the radio coverage of new PNC capable DEVs. So, we propose the method of PNC selection with accessibility check. This method manages PNC candidate list in the current piconet. In this paper, we analyze accessibility problems for PNC selection in section 2. In section 3, we explain CI(Configuration Inquiry) process which is proposed by Sony Corporation and propose PCI(PNC Candidate Inquiry) process. Also, we perform numerical analysis to compare PCI process with CI process in section 4. Finally, we conclude in section 5.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2B
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• pp.117-128
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• 2006

For the legacy IEEE 802.15.3 WPAN protocol, an unpredictable piconet coordinator(PNC) leaving from a piconet without a proper handoff procedure causes an absence of PNC, and thus the piconet gets collapsed. In addition, several beacons from PNCs in adjacent piconets may be collided on a device(DEV) located between those piconets. This beacon collision eventually makes the DEV leave from the piconet. To remedy these two problems, we here propose an Active Seamless Coordinator Switching(ASCS) scheme and a PNC HB based Beacon Alignment(PHBA) one. In the ASCS scheme, a PNC assigns a number of DEVs as next possible PNCs in sequence for provisioning against the abrupt breakdown of the current active PNC. Each nominated DEV proactively sends a probe frame to confirm the operation status of the active PNC. For the case of no response from the PNC, the nominated DEV tries to become a new PNC immediately. In the second PHBA scheme, each PNC is allow to broadcast a special Heart Beat(HB) frame randomly during a superframe period. When a DEV receives a HB frame from other PNC, it promptly sends the related PNCs a special Hiccup Beat(HCB) frame with the superframe information of its associated PNC. As a result, the HCB frame makes both PNCs align their superframe beginning time in order to yield no more beacon collisions. For these two proposed schemes, we show the performance by simulations. We can confirm the enhancement of throughput for each superframe and average frame transfer delay, since each scheme can reduce the duration of piconet collapse. Finally, it is worth while to note that the proposed schemes can be operated with frames those are permitted in the legacy WPAN standard.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.3
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• pp.1213-1237
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• 2019

Vehicular Ad-hoc Network (VANET) facilities envision future Intelligent Transporting Systems (ITSs) by providing inter-vehicle communication for metrics such as road surveillance, traffic information, and road condition. In recent years, vehicle manufacturers, researchers and academicians have devoted significant attention to vehicular communication technology because of its highly dynamic connectivity and self-organized, decentralized networking characteristics. However, due to VANET's high mobility, dynamic network topology and low communication coverage, dissemination of large data packets (e.g. multimedia content) is challenging. Clustering enhances network performance by maintaining communication link stability, sharing network resources and efficiently using bandwidth among nodes. This paper proposes a mobility-based, multi-hop clustering algorithm, (MBCA) for multimedia content broadcasting over an IEEE 802.11p-LTE-enabled hybrid VANET architecture. The OMNeT++ network simulator and a SUMO traffic generator are used to simulate a network scenario. The simulation results indicate that the proposed clustering algorithm over a hybrid VANET architecture improves the overall network stability and performance, resulting in an overall 20% increased cluster head duration, 20% increased cluster member duration, lower cluster overhead, 15% improved data packet delivery ratio and lower network delay from the referenced schemes [46], [47] and [50] during multimedia content dissemination over VANET.

• Journal of Digital Convergence
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• v.12 no.11
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• pp.273-279
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• 2014

In this paper, we propose a novel algorithm for three dimensional positioning system and implement a system over indoor wireless channel. A commercial modules are used for mobile and fixed nodes which are product of German company Nanotron Co. This module adopts chirp spread spreading scheme as modulation method to improve the ranging resolution and the module satisfies the IEEE standard 802.15.4a. The distance computation is based on received signal strength(RSS) levels and trilateration method. A testbed was set up to measure and compare the positioning estimation error of the proposed algorithm. The experiments results showed that the accuracy of location estimation was sufficiently good as much as 1m distance error in a wireless environment in an office building.

• Journal of electromagnetic engineering and science
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• v.4 no.3
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• pp.124-127
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• 2004

A novel printed inverted-F antenna for dual-band WLAN is presented. The proposed design is based on the folded quarter-wave antennas, which have a conductor plate having two arms. An extremely thin prototype antenna is fabricated according to the simulation result. The obtained antenna can perform in IEEE802.11a, b(2.4～2.484 GHz and 5.15～5.35 GHz bands) and be adopted for laptop applications. All the measurements are performed in the actual test fixture.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.87-89
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• 2006

U-물류/유통, U-항만에 핵심적인 기술이 될 Ultra-Wide(UWB)통신을 위한 광대역 안테나를 설계, 개발하였다. 설계된 안테나는 UWB 주파수 대역인 3.1$^{\sim}$11.7GHz 대역에서 안테나 특성을 만족하고, IEEE 802-11a와HIPERLAN/2에 의해 사용이 제한된 5.15${\sim}$5.825GHz 대역에서 주파수 저지 대역을 가지기 위하여 U모양의 얇은 슬롯을 복사 패치 위에 구현 하였다. 제작한 안테나는 5${\sim}$595GHz 대역을 제외하고는 안테나의 특성을 만족한다.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.27-30
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• 2003

무선 통신 서비스에 대한 수요가 급격히 증가하면서 높은 데이터 전송율을 갖는 무선 통신에 대한 연구가 활발히 진행되고 있다. UWB는 (Ultra Wide Band) 이러한 문제점을 해결할 수 있는 통신 방법 중의 하나로 이 논문에서는 현재 IEEE 802.15.TG3a 표준화 위원회에서 제시하고 있는 채널 모델에 대해서 알아보고, 제시된 채널 모델에 LS (Least Square) 방법을 적용하여 채널의 임펄스 응답을 (Channel Impulse Response) 추정한다. 채널 추정의 성능 지표로 Preamble의 크기에 따른 MSE와 (Mean Square Error) 각각의 채널에 대한 비트 에러율을 사용하여 모의 실험을 본 논문에서 다루는 추정 기법의 성능을 분석한다.