• Journal of Communications and Networks
• /
• 제5권4호
• /
• pp.303-308
• /
• 2003

We present a statistical model for the path loss of ultrawideband (UWB) channels in indoor environments. In contrast to our previously reported measurements, the data reported here are for a bandwidth of 6GHz rather than 1.25GHz; they encompass commercial buildings in addition to single-family homes (20 of each); and local spatial averaging is included. As before, the center frequency is 5.0GHz. Separate models are given for commercial and residential environments and, within each category, for lineof sight (LOS) and non-line-of-sight (NLS) paths. All four models have the same mathematical structure, differing only in their numerical parameters. The two new models (LOS and NLS) for residences closely match those derived from the previous measurements, thus affirming the stability of our path loss modeling. We find, also, that the path loss statistics for the two categories of buildings are quite similar.

• 한국소음진동공학회논문집
• /
• 제13권3호
• /
• pp.217-224
• /
• 2003

In this study, the adaptive triangular beam method(ATBM) considering different sound reflection coefficients and angles of a triangular beam on two or more planes as well as diffraction effect is suggested. The ATBM, subdividing a tracing triangular beam into multiple triangular beams on reflection planes, gives reliable and convergent sound-field analysis results without the dependancy on the number of initial triangular beam segmentation to search sound propagation paths from source to receiver. The validity of the method is verified by the comparison of numerical and experimental results for energy decay curve and steady-state sound pressure level of rooms having direct, reflective and diffractive sound paths.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
• /
• pp.306-309
• /
• 1996

This paper presents a method of landmark recognition in indoor environments using a neural-network for an autonomous mobile robot. In order to adapt to image deformation of a landmark resulted from variations of view-points and distances, a multi-labeled template matching(MLTM) method and a dynamic area search method(DASM) are proposed. The MLTM is. used for matching an image template with deformed real images and the DASM is proposed to detect correct feature points among incorrect feature points. Finally a feed-forward neural-network using back-propagation algorithm is adopted for recognizing the landmark.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2001년도 춘계학술대회논문집
• /
• pp.635-641
• /
• 2001

This study introduces the basic concepts of the vibration reducing methods and presents a case study of 'A' apartment construction site which located nearby railroad. The site is only 60m away from the railroad. Therefor much noise and vibration damages could be expected during train or any other transportation's passing. Especially, the first and second floor may suffer much vibration with the low frequency radiation noise from the walls and floors. This study estimates the noise level of indoor area by measuring the vibration of indoor walls and floors. From this result, vibration barrier, as a method to reduce the noise level which exceeds proper standard value, was attempted to protect vibration transmit from the railroad.

• ETRI Journal
• /
• 제34권3호
• /
• pp.319-329
• /
• 2012

Closed-loop transmit diversity is considered an important technique for improving the link budget in the third generation and future wireless communication standards. This paper proposes several transmit diversity algorithms suitable for small wireless terminals and presents performance assessment in terms of average signal-to-noise ratio (SNR) and outage improvement, convergence, and complexity of operations. The algorithms presented herein are verified using data from measured indoor channels with variable antenna spacing and the results explained using measured radiation patterns for a two-element array. It is shown that for a two-element array, the best among the proposed techniques provides SNR improvement of about 3 dB in a tightly spaced array (inter-element spacing of 0.1 wavelength at 2 GHz) typical of small wireless devices. Additionally, these techniques are shown to perform significantly better than a single antenna device in an indoor channel considering realistic values of latency and propagation errors.

• 전기전자학회논문지
• /
• 제26권1호
• /
• pp.67-76
• /
• 2022

In this paper, we propose a new algorithm to improve the accuracy of the Wi-Fi access point (AP) positioning technique. The proposed algorithm based on evaluating the trustworthiness of the signal strength quality of each measurement node is superior to other existing AP positioning algorithms, such as the centroid, weighted centroid, multilateration, and radio distance ratio methods, owing to advantages such as reduction of distance errors during positioning, reduction of complexity, and ease of implementation. To validate the performance of the proposed algorithm, we conducted experiments in a complex indoor environment with multiple walls and obstacles, multiple office rooms, corridors, and lobby, and measured the corresponding AP signal strength value at several specific points based on their coordinates. Using the proposed algorithm, we can obtain more accurate positioning results of the APs for use in research or industrial applications, such as finding rogue APs, creating radio maps, or estimating the radio frequency propagation properties in an area.

• 한국전자파학회논문지
• /
• 제10권5호
• /
• pp.766-776
• /
• 1999

본 논문에서는 실내 전파 환경에서의 편파 다이버시티와 공간 다이버시티의 성능을 분석하기 위하여 영상 법을 기본으로 한 3차원 광선 추적법을 이용하였다. 본 모텔링은 선호강도 뿐만 아니라 채널의 페이딩 특성 을 예측할 수 있기 때문에 편파 및 공간 다이버시티 기법의 성능을 분석하는데 이용될 수 있다. 측정과 시율 레이션 결과로부터 편파 및 공간 다이버시티가 실내 무선 통선 채널의 성능을 향상시킬 수 있음을 확인하였 고, 특히 지향성 안테나를 이용한 편파 다이버시티를 제안하여 기존의 다이폴 안테나를 이용하는 다이버시티 기볍보다 우수한 성능을 가짐을 보였다.

• 한국전자통신학회논문지
• /
• 제15권1호
• /
• pp.15-20
• /
• 2020

본 논문에서는 건물의 실내 환경 전시관과 대회의실에 대한 지연 확산 측정 및 분석하였다. 두 건물의 실내 환경에 대해 시나리오를 작성하였다. 또한, 시스템 구성과 측정 방법을 같은 조건으로 진행하였다. 측정 조건은 중심 주파수인 3 GHz, 6 GHz로 하였고, 분석 대역은 2 GHz로 선정하였다. 측정시스템은 벡터 네트워크 분석기, 전력 증폭기, 무지향성 송·수신 안테나, 전송선로를 구성하였다. 두 건물의 실내 환경 시나리오에 따라 송신 안테나 위치를 기준으로 수신 안테나의 위치를 3개의 구역으로 나누고 각각 18개의 위치에 따라 1 m 간격으로 측정하였다. 두 건물의 전력 지연 프로파일, RMS 지연 확산, K-factor 결과를 비교 분석하였다.

• ETRI Journal
• /
• 제42권1호
• /
• pp.108-117
• /
• 2020

This study proposes a robust range-only beacon mapping method for registering the locations of range-only beacons automatically. The proposed method deals with the multipath propagation of signals from range-only beacons using the range-only measurement association (RoMA) and an unscented Kalman filter (UKF). The RoMA initially predicts the candidate positions of a range-only beacon. The location of the range-only beacon is then updated using the UKF. With the proposed method, the locations of range-only beacons are accurately estimated in a multipath environment. The proposed method also provides the location uncertainty of each range-only beacon. Simulation results using the model for multipath propagation and experimental results in a real indoor environment verify the performance of the proposed method.

• ETRI Journal
• /
• 제38권6호
• /
• pp.1031-1041
• /
• 2016

This paper presents millimeter-wave (mmWave) propagation characteristics and channel model parameters including path loss, delay, and angular properties based on 28 GHz and 38 GHz field measurement data. We conducted measurement campaigns in both outdoor and indoor at the best potential hotspots. In particular, the model parameters are compared to sub-6 GHz parameters, and system design issues are considered for mmWave 5G Giga communications. For path loss modeling, we derived parameters for both the close-in free space model and the alpha-beta-gamma model. For multipath models, we extracted delay and angular dispersion characteristics including clustering results.