Frequency-Dependent UWB Channel Characteristics in Office Environments

This paper reports frequency-dependent ultrawideband (UWB) channel characteristics. Measurements were performed in 103 receiver locations of six different office environments. From the measured data, the effect of frequency on the pathloss properties of a UWB signal is analyzed. After analyzing the pathloss behavior to propagation environments, the pathloss exponent variation models are developed in various environments as a function of frequency. Based on these models, pathloss prediction is performed, and the accuracy of the prediction is compared with those of existing pathloss models. In addition, the frequency-dependent UWB channel correlation characteristics are investigated. For the frequency correlation statistics of the UWB channel, double-slope models representing correlation coefficients are established with and without line-of-sight (LOS) paths. Using these correlation models, a channel gain estimation algorithm is proposed. The performance of the proposed estimation algorithm is evaluated with estimation parameters, and it is confirmed that the proposed estimation algorithm has better performance than the conventional algorithm using a linear interpolation algorithm.Brain Korea 21 Project IT R&D Program of the Ministry of Knowledge Economy/Institute for Information Technology Advancement under Grant 2008-F-007-01, Intelligent Wireless Communication Systems in 3 Dimensional Environmen

Performance Evaluation of Positioning Techniques Based on UWB Radio

In this paper, performances of positioning techniques based on UWB radio are evaluated. The positioning techniques for UWB systems, SS, and time based algorithms, TOA and TDOA, are the target ones to be analyzed. Using the reported CRLB of each algorithm, the location estimation error is obtained. The estimation error variation to the number of base stations is reported also.This work is supported in part by ITRC and Seoul R&BD Program (10544)

Analysis Technique on Water Permeability in Concrete with Cold Joint considering Micro Pore Structure and Mineral Admixture

Cold joint in concrete due to delayed concrete placing may cause a reduced shear resistance and increased water permeation. This study presents an analytical model based on the concept of REV (Representative Element Volume) to assess the effect of water permeability in cold joint concrete. Here, OPC (Ordinary Portland Cement) concrete samples with cold joint are prepared and WPT (Water Permeability Test) is performed on the samples cured for 91 days. In order to account for the effect of GGBFS (Granulated Ground Blast Furnace Slag) on water permeability, concrete samples with the same W/B (Water to Binder) ratio and 40% replacement ratio of GGBFS are tested as well. Utilizing the previous models handling porosity and saturation, the analysis technique for equivalent water permeability with effective cold joint width is proposed. Water permeability in cold joint increases to 140.7% in control case but it decreases to 120.7% through GGBFS replacement. Simulation results agree reasonably well with experimental data gathered for sound and cold joint concrete

The Practice of Korean Medicine: An Overview of Clinical Trials in Acupuncture

Acupuncture, one of the Oriental medical therapeutic techniques that can be traced back at least 2500 years, is growing in popularity all over the world. Korea has continued to develop its own unique tradition of medicine throughout its long history, and has formed different types of acupuncture methods. The purpose of this review is to summarize clinical case studies in acupuncture and related therapies, such as acupressure, electric acupuncture, auricular acupuncture and moxibustion in Korea. A survey of Korean journals revealed that a total of 124 studies were published from 1983 to 2001. Results obtained from the survey showed that most clinical studies using acupuncture, electric acupuncture, moxibustion and other traditional therapies could alleviate a relatively broad range of medical problems. However, it should be emphasized that almost all clinical case studies published in various local journals did not follow the ‘good clinical practice’ with respect to regulatory aspects. Since they were not conducted using the randomized double-blinded controls with a large sample size, all the results should be considered as therapeutic indications. This review is an attempt to show the scope of acupuncture in our country and the kind of diseases, after many years of clinical experience, that were deemed valid targets for clinical trials

Crystal structure of xenotropic murine leukaemia virus-related virus (XMRV) ribonuclease H

RNase H (retroviral ribonuclease H) cleaves the phosphate backbone of the RNA template within an RNA/DNA hybrid to complete the synthesis of double-stranded viral DNA. In the present study we have determined the complete structure of the RNase H domain from XMRV (xenotropic murine leukaemia virus-related virus) RT (reverse transcriptase). The basic protrusion motif of the XMRV RNase H domain is folded as a short helix and an adjacent highly bent loop. Structural superposition and subsequent mutagenesis experiments suggest that the basic protrusion motif plays a role in direct binding to the major groove in RNA/DNA hybrid, as well as in establishing the co-ordination among modules in RT necessary for proper function.Molecular and Cellular Biolog

Frequency correlation property of Ultra Wideband Channel in Office environments

본 논문은 사무실 환경에서 측정된 초광대역 통신채널의 주파수 응답 사이의 상관관계를 모델링하고 있다. 측정은 주파수 영역에서 회로망 분석기를 바탕으로 한 측정시스템을 통해 이루어졌으며 3개의 서로 다른 사무실 환경의 46개 송, 수신지점에서 총 23,000개의 채널응답이 얻어졌다. 주파수에 따른 채널 이득사이의 상관관계를 나타내는 변수로는 상관계수 (Correlation Coefficient)가 사용되어, 주파수 이격에 따른 상관계수 값의 변화를 가시경로의 존재 유무에 따라 선형 모델로 모델링하였다. 아울러 역푸리에 변환 (Inverse Fast Fourier Transform, IFFT)을 통해 얻어낸 시간영역의 채널응답을 바탕으로 지연함수 값을 얻어내고 그에 따른 연관대역폭 (Coherence bandwidth)을 산출하여 그 결과값을 주파수 영역에서의 결과 값과 비교하였다