• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2006.11a
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• pp.223-227
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• 2006

본 논문에서는 이동 환경에서 지상파DTV의 Delay Profile의 도출을 위하여 이동 상태에서 필드테스트로 측정된 수신데이터에 포함되어 있는 PN 511(Psuedo Noise)코드를 이용하여 다양한 이동환경에서의 ACF(Auto Correlation Function)값을 도출하였다. 또한, 지역별 대표적인 LOS지역, NLOS지역, 중간지역으로 구분되는 대표적인 세 곳을 선정하여 다양한 이동속도에서의 도출된 ACF값을 통해 최대지연, 평균지연, RMS 지연을 도출하여 이동환경에서의 지상파 DTV의 Delay Profile을 제시하였다.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.43-44
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• 2006

In this paper modeled UWB system transmission channel in apartment environment while furniture and household electric appliance etc. existed. We measured from 10MHz to 16.01GHz by using method of CIR and CTF in both LOS and NLOS environment. Also we design channel model simulator by MATLAB. The Result of Simulation shows BER characteristics by SNR.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.3
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• pp.648-653
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• 2011

We propose a new frequency offset estimation technique for multiband orthogonal frequency modulation (MB-OFDM) based ultra wideband (UWB) systems. The proposed frequency offset estimation technique is related to the scheme of Schmidl for channel model 1 (4-1Om NLOS, rms. delay =14.3ns.) using more than two symbols and with alternate symbols. Variance of frequency offset estimate obtained from the proposed frequency offset estimation technique approaches very nearing to Cramer Rao Lower Bound (CRLB) in an AWGN channel. BER performance of the proposed technique is also presented.

• Journal of information and communication convergence engineering
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• v.10 no.3
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• pp.269-275
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• 2012

In this paper, we proposed a novel location estimation algorithm based on the concept of space-time signature matching in a moving target environment. In contrast to previous fingerprint-based approaches that rely on received signal strength (RSS) information only, the proposed algorithm uses angle, delay, and RSS information from the received signal to form a signature, which in turn is utilized for location estimation. We evaluated the performance of the proposed algorithm in terms of the average probability of error and the average error distance as a function of target movement. Simulation results confirmed the effectiveness of the proposed algorithm for location estimation even in moving target environment.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.11a
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• pp.551-552
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• 2009

조선산업에서 선박의 건조 과정 중 탑재 공정은 작업자 간의 긴밀한 통신을 필요로 하며 매우 위험한 작업이다. 이러한 작업을 음성 품질이 매우 열악한 무전기나 호접속 지연이 많은 주파수 공용통신(TRS)를 이용하여 통신을 하고 있어 매우 위험하다. 따라서, 이러한 기존 통신방식을 대체하는 IP 기반 그룹통신 시스템과 이에 대한 품질 측정 및 평가가 필요하다. 본고에서는 IP 멀티미디어 시스템의 최초의 서비스인 PoC(PTT over Cellular) 서비스를 기반으로 조선산업에서 통합통신(Unified Communication)을 지향하기 위하여, 강재로 인한 매우 열악한 비가시 거리(NLOS)를 극복하고, 효율적인 통신 서비스를 제공하기 위한 엔터프라이즈 PoC을 기반으로 그룹통신의 품질을 측정하고 평가하였다. WiBro 기반 엔터프라이즈 PoC 서비스는 실제적으로 적용이 가능할 뿐 아니라, 실제의 작업자가 통신할때 지연이 느껴지지 않는 1초 이내의 그룹통신 지연시간에 대해 상기 서비스를 분석하였으며, 이론 상으로는 충분히 제공 가능함을 보이고 있다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.5 s.108
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• pp.430-439
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• 2006

This paper presents the a measured path-loss characteristics for mobile communications beyond 3G in microcellular residential area and street microcell at 3.4, 5.3, and 6.4 GHz band signals. The residential area is divided into two sections, one of which is composed of fifteen-story appartment buildings. The other section comprises four-story houses. The street microcell is classified line-of-sight(LOS) and nonline-of-sight(NLOS) areas. Both residential areas have standard deviations independent of the residential area classification, whereas the path loss exponents in the apartments is higher than those in area for same frequencies. A two-ray model is applied to analyse the path-loss charateristics in LOS areas. In LOS areas, an empirical breakpoint, whose distance is 6 percent shorter than a theorical breakpoint, is founded. Further, a sudden power level drop occurs at a transition point from LOS region to NLOS area. Path loss exponent is found to be significantly higher for non-LOS region than for LOS region. The power level drop due to corner loss and path-loss exponents both increase as the distance between the transmitter and the corner increases.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.254-260
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• 1999

Meteor Burst Communication can provide effective and economical means of communication where long distance VHF NLOS data transmission is needed; often ranges more than 1000 km. It has been, however, so far considered unsuitable for short distance application because of phenomenal decrease in burst durations, which leads to decreation of total duty rate of the system. This paper extensively analyzes characteristics of shot distance MB(Meteor Burst) path and shows the low duty rate may be improved by increasing burst rate through adapting antenna beam width to cover entire hot-spot region in the space and, by compensating effective burst length through cutting down man-made noises introduced by antenna. Based on the analysis, we are developed a small-opening-cavity antenna, especially designed for short distance MB path. In operation, the antenna is to be buried under ground surface so as to improve directivity and reduces noise introduction. The antenna exhibits power gain of 3 dB with 90 degree beam width and thus enables to illuminate entire hot-spot regions with the elevation angle of 8-90 degree which is the case of transmission less than 100 km. Directivity horizontal to earth surface is suppressed to minimum which enables to cut man-made noises from near-by sources down to more than 3 dB from the level reported with conventional 4 element Yagi. A series of experiments performed on 100 km MB paths have conformed that, with the antenna installed at receiving site, the burst rate and duration time have been noticed to increase by 10 and 20 percent respectively from the values obtained by conventional 4-element Yagi antenna under same testing condition.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.4
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• pp.86-94
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• 2009

Currently, positioning methods for LBS(Location Based Service) are GPS and network-based positioning techniques that use mobile communication networks. In these methods, however, the accuracy of positioning decreases due to the propagation delay caused by the non-line-of-sight(NLOS) effect and the repeater. To address this disadvantage, the CDMA system uses Pattern Matching algorithm. The Pattern Matching algorithm constructs a database of the propagation characteristics of the RF signals measured during the GPS positioning along with the positioned locations, so that the location can be provided by comparing the propagation characteristics of the received signals and the database, upon a user's request. In the area where GPS signals are not received, however, a database cannot be constructed. There are problem that the accuracy of positioning decreases due to the area without a database Because Pattern Matching algorithm depend on database existence. Therefore, this paper proposed a pilot signal strength prediction algorithm to enable construction of databases for areas without databases, so as to improve the performance of the Pattern Matching algorithm. The database was constructed by predicting the pilot signals in the area without a database using the proposed algorithm, and the Pattern Matching algorithm analysed positioning performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.6
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• pp.788-801
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• 1998

Meteor Burst Communication can provide effective and economical means of communication where long distance VHF NLOS data transmission is needed ; often ranges more than 1000 km. It has been, however, so far considered unsuitable for short distance application because of phenomenal decrease in burst durations, which leads to decreation of total duty rate of the system. This paper extensively analyzes characteristics of shot distance MB(Meteor Burst) path and shows the low duty rate may be improved by increasing burst rate through adapting antennal beam width to cover entire hot-spot region in the space and, by compensating effective burst length throughcutting down man-made noises introduced by antennal. Based on the analysis, we are developed a small-opening-cavity antennal, especially designed for short distance MB path. In operation, the antenna is to be buried under ground surface so as to improve directivity and reduces noise introduction. The antennal exhibits power gain of 3 dB with 90 degree beam width and thus enables to illuminate entire hot-spot regions with the elevation angle of 8-90 degree which is the case of transmission less than 100 km. Directivity horizontal to earth surface is suppressed to minimum which enables to cut man-made noises from near-by sources down to more than 3 dB from the level reported with conventional 4 element Yagi. A series of experiments performed on 100km MB paths have conformed that, with the antenna installed at receiving site, the burst rate and duration time have been noticed to increase by 10 and 20 percent respectively from the values obtained by conventional 4-element Yagi antennal under same testing condition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10A
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• pp.1014-1019
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• 2006

The research deals with the measurement of electromagnetic wave propagation in subway tunnels at 2.65GHz. Measurements have been conducted in 4 different types of tunnel courses, a straight tunnel, two curved tunnels, with 245m and 500m radius of curvature, and a tunnel that has both straight and curved sections. we found that the path loss exponent for the line-of-sight(LOS) region inside all the tunnels is $1.31{\sim}2.19$. The path loss exponents for LOS regions in the tunnel is lower than $(3{\sim}4)$, which corresponds to the path loss exponent factor for outdoor cellular environments. The path loss exponents of the straight tunnel, two curved tunnels with 245m and 500m radius of curvature are 1.94, 2.92, and 4.34, respectively. This indicates that a smaller radius of curvature in tunnel results in a higher path loss exponent for nonline-of-sight(NLOS) region. The path loss exponents for the NLOS region in the combined and curved tunnel, which have the same radii of cuvature, are 5.88 and 4.34, respectively. Therefore, it can be concluded that the path loss characteristics in tunnel environments are infulenced by the radii of curvature as well as the LOS distance.