• Journal of Communications and Networks
• /
• v.12 no.3
• /
• pp.222-230
• /
• 2010

In this paper, we present a closed-form approximation of the average sum rate of zero-forcing (ZF) beamforming (BF) with semi-orthogonal user selection (SUS). We first derive the survival probability associated with the SUS that absolute square of the channel correlation between two users is less than the orthogonalization level threshold (OLT).With this result, each distribution for the number of surviving users at each iteration of the SUS and the number of streams for transmission is calculated. Secondly, the received signal power of ZF-BF is represented as a function of the elements of the upper triangular matrix from QR decomposition of the channel matrix. Thirdly, we approximate the received signal power of ZF-BF with the SUS as the maximum of scaled chisquare random variables where the scaling factor is approximated as a function of both OLT and the number of users in the system. Putting all the above derivations and order statistics together, the approximated ergodic sum rate of ZF-BF with the SUS is shown in a closed form. The simulation results verify that the approximation tightly matches with the sample average for any OLT and even for a small number of users.

• The Journal of the Acoustical Society of Korea
• /
• v.29 no.2E
• /
• pp.86-99
• /
• 2010

This paper analyzes the performance of various single channel speech enhancement algorithms when they are applied to automatic speech recognition (ASR) systems as a preprocessor. The functional modules of speech enhancement systems are first divided into four major modules such as a gain estimator, a noise power spectrum estimator, a priori signal to noise ratio (SNR) estimator, and a speech absence probability (SAP) estimator. We investigate the relationship between speech recognition accuracy and the roles of each module. Simulation results show that the Wiener filter outperforms other gain functions such as minimum mean square error-short time spectral amplitude (MMSE-STSA) and minimum mean square error-log spectral amplitude (MMSE-LSA) estimators when a perfect noise estimator is applied. When the performance of the noise estimator degrades, however, MMSE methods including the decision directed module to estimate a priori SNR and the SAP estimation module helps to improve the performance of the enhancement algorithm for speech recognition systems.

• ETRI Journal
• /
• v.40 no.1
• /
• pp.26-38
• /
• 2018

To overcome considerable path loss in millimeter-wave propagation, high-gain directional beamforming is considered to be a key enabling technology for outdoor 5G mobile networks. Associated with beamforming, this paper investigates propagation power loss characteristics in two aspects. The first is beamwidth effects. Owing to the multipath receiving nature of mobile environments, it is expected that a narrower beamwidth antenna will capture fewer multipath signals, while increasing directivity gain. If we normalize the directivity gain, this narrow-beamwidth reception incurs an additional power loss compared to omnidirectional-antenna power reception. With measurement data collected in an urban area at 28 GHz and 38 GHz, we illustrate the amount of these additional propagation losses as a function of the half-power beamwidth. Secondly, we investigate power losses due to steering beam misalignment, as well as the measurement data. The results show that a small angle misalignment can cause a large power loss. Considering that most standard documents provide omnidirectional antenna path loss characteristics, these results are expected to contribute to mmWave mobile system designs.

• International journal of advanced smart convergence
• /
• v.4 no.2
• /
• pp.145-153
• /
• 2015

Development of IT technology, in combination with the medical area, a number of developments have been made of the digital advanced medical devices, also increased interest in health, sharing of medical information has become increasingly necessary. Standardization for medical information sharing to satisfy these requirements have been studied. However, the medical information system is to build a system independent hospital itself, is difficult to share and exchange medical data with other medical institutions. In this paper, we provide a medical cloud system that can share medical information. Use DBaaS of cloud services. And is an international standard to have a HL7 share information by forming a meta-schema, each of the data transfer, the format of the document oriented data solves the heterogeneity between hospitals. Extracts the required field name of examination information, to exchange information with each of the local information and mapping. Health diagnostic information in the present study and diagnosis through accurate information sharing and exchange is possible ongoing management.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2015.07a
• /
• pp.39-40
• /
• 2015

본 논문에서는 대용량의 영상을 빠르고 정확하게 편집해야 하는 방송 환경에서 오픈 소스를 활용한 방송용 영상 편집 시스템과 편집 결과를 신속히 통보하는 다기능 알람 시스템에 대하여 다루었다. 디지털 방송에서 사용하는 영상은 매우 고품질이면서 동시에 매우 큰 데이터 용량을 가지고 있으며, 또 방송이라는 매체의 성격상 방송 시간에 맞춰 영상 편집을 완료해야 하는 시간적 부담이 있다. 본 논문에서 제안하는 방송 편집 시스템은 갈수록 그 기능이 다양하고 좋은 성능을 보여주는 오픈 소스 영상 처리 소프트웨어를 활용하는 동시에, 분산 처리 시스템을 도입하여 영상의 빠른 편집 기능을 저렴한 도입 비용으로 가능하도록 하였다. 오픈 소스 영상 처리 소프트웨어는 백엔드 모듈로 동작하며, 영상의 다양한 편집 기능들, 예를 들어 영상의 구간 자르기, 붙이기, 자막넣기, 로고 넣기, 비디오/오디오 포맷 변환 등을 수행한다. 사용자 편의성을 위한 프론트엔드 시스템은 자바 기반의 프레임워크를 사용하였으며, 비디오 편집 기능 결과 및 과정에 대한 다기능 알람 기능을 첨가하여 방송 종사자들의 업무 편리를 도모하였다. 본 시스템은 기존의 고가 방송 편집 장비와 비교하여 매우 저렴하면서도 안정된 성능을 보장하여 디지털 방송 시대에 활용 가능성이 매우 높다고 할 수 있다.

• Journal of the Korean Society of Earth Science Education
• /
• v.8 no.2
• /
• pp.114-127
• /
• 2015

The nature of science has been recognized in a great deal in the field of science education. However, Most of the papers were going to study of teachers and students. to improve their recognition of the nature of science. The current study describes and analyzes Weather-Forecaster's understandings of the nature of science (NOS). Data used in this study were collected from 3 Weather-Forecasters using an semi-structured interview. The results of this study were as follows. First, the participants recognized that science has explored the phenomenon of unknown facts or observations and they were careful inductive perspective. Second, participants felt that science and society are associated with each other. Also, all participants were judged science verification process is required. Third, they are showed that science and technology interact closely with social relationships.

• Journal of Broadcast Engineering
• /
• v.8 no.2
• /
• pp.109-115
• /
• 2003

In this paper we propose an efficient method to broadcast digital television signals using Single Frequency Networks (SFNs) in the Advanced Television Systems Committee (ATSC) transmission systems. Since the proposed schemes to synchronize multiple transmitters minimize the changes from the conventional ATSC system, the hardware complexity for the changes is very low. Our simulation results show that the proposed scheme makes less than 0.1 dB degradation at the threshold of visibility (TOV： BER= 3$\times$$10^{-6}$) in the additive white Gaussian noise (AWGN) channel. It is possible to reduce the performance degradation by increasing an initialization period of the proposed scheme.

• Journal of Broadcast Engineering
• /
• v.15 no.1
• /
• pp.99-111
• /
• 2010

In this paper as a follow-up to Paper I, the required fade margin derived in Paper I to preserve the same service quality has been examined by analyzing system and propagation characteristics as well as measured data. The comparison of the fade margin between simulated and measured results is also performed for the actual operating line-of-sight(LOS) and non-LOS links, and practical usefulness as an analysis tool is revealed by checking service quality of M/W system relevant to frequency reallocation. According to simulated and measured results, there was a little difference for LOS link between Mt. Moodung and Mt. Mangun, but a fairly good agreement was reached for non-LOS link between Andong KBS and transmitter site.

• Journal of Broadcast Engineering
• /
• v.23 no.2
• /
• pp.293-301
• /
• 2018

In ISDB-T, which is Japanese digital terrestrial TV specification based on OFDM technology, 6MHz bandwidth is divided into 13 segments. Twelve segments (full-seg) are used for high definition broadcasting for fixed receivers and one segment (one-seg) for mobile receivers. Though one-seg supports high speed mobility by using QPSK modulation, it is not suitable for large display mobile devices because of its low data rate. Full-seg using 64QAM modulation also suffers from its low mobile performance. In this paper, mobile performance of ISDB-T full-seg receiver is evaluated by applying sub-carrier interference removing scheme, high speed mobile channel estimation scheme and antenna diversity scheme.

• Journal of Broadcast Engineering
• /
• v.24 no.6
• /
• pp.974-982
• /
• 2019

Real-time 360 VR (Virtual Reality) stereo image acquisition technique based on game engine was proposed. However, GPU (Graphics Processing Unit) resource is not fully utilized due to bottlenecks. In this paper, we propose an improved GPU scheduling technique to solve the bottleneck of the existing technique and measure the performance of the proposed technique using the sample games of the commercial game engine. As a result, proposed technique showed an improvement of performance up to 70% and usage of GPU resources more evenly compared existing technique.